Home Tutorials Training Consulting Products Books Company Donate Contact us









NOW Hiring

Quick links

Share

This tutorial describes how to create Android applications. It is based on the latest and greatest Android and Android Studio release.

1. High-level overview of Android development

1.1. The Android operating system

Android is an operating system based on the Linux kernel. Android is developed in the Android Open Source Project (AOSP). This project is lead by Google.

The Android operating system can be divided into the four areas as depicted in the following graphic. An Android application developer typically works with the two layers on top to create new Android applications.

Android software layers

The levels can be described as:

  • Applications - Contains the applications, like the Browser, Camera, Gallery, Music and Phone

  • Application framework - An API which allows high-level interactions with the Android system

  • Libraries and runtime - The libraries for many common framework functions, like graphic rendering, data storage, web browsing. Also contains the Android runtime, as well as the core Java libraries for running Android applications.

  • Linux kernel - Communication layer for the underlying hardware.

1.2. Android versions

The Android operating system is published in different versions. The following table gives an overview of the available versions.

Table 1. Android versions
Code name Version API level

Oreo

8.0

26

Nougat

7.0 – 7.1.1

24 -25

Marshmallow

6.0

23

Lollipop

5.1

22

Lollipop

5.0

21

KitKat

4.4 - 4.4.4

19

Jelly Bean

4.1.x - 4.3.x

16 - 18

Ice Cream Sandwich

4.0.1 - 4.0.4

14 - 15

Honeycomb

3.2.x

13

Honeycomb

3.0 - 3.1

11 - 12

Gingerbread

2.3 - 2.3.7

9-10

Froyo

2.2.x

8

Eclair

2.1

7

Eclair

2.0 - 2.0.1

5 -6

Donut

1.6

4

Cupcake

1.5

3

(no code name)

1.1

2

(no code name)

1.0

1

1.3. Android application

An Android application (app) is a single installable unit which can be started and used independently. An Android application consists of configuration files, Java source and resource files. You can define the following components in your configuration files:

Table 2. Android application components
Component Description

Application

An Android application can have one Application class which is instantiated before any other Android component. It is the last component which is stopped during application shutdown.

If not explicitly defined, Android creates a default application object for your application.

Activity

An activity is the visual representation of an Android application. An Android application can have several activities.

Activities use views and fragments to create their user interface and to interact with the user.

Service

A service performs tasks without providing an user interface. They can communicate with other Android components and send notifications to the user. For example, a broadcast receiver can notify the user via the notification framework in Android.

Broadcast receiver (short: receiver)

A receiver can be registered to listen to system messages and intents. A receiver gets notified by the Android system if the specified event occurs.

For example, you can register a receiver for the event that the Android system finished the boot process. Or you can register for the event that the state of the phone changes, e.g., someone is calling.

Content provider (short: provider)

A provider defines a structured interface to application data. A provider can be used for accessing data within one application, but can also be used to share data with other applications.

Android contains an SQLite database which is frequently used in conjunction with a content provider. The SQLite database would store the data, which would be accessed via the provider.

1.4. Configuration via the manifest file

The components, settings and metadata of an Android application are described in the AndroidManifest.xml file. This file is known as the manifest file or the manifest. The manifest is read by the Android system during installation of the application. The Android system evaluates it and determines the capabilities of the application.

Activities, services and content provider components of the application must be statically declared in this file. Broadcast receiver can either defined here or registered dynamically at runtime.

The Gradle build system can modify the manifest file at build time. For example, the application version is typically supplied by the Gradle build file.

The following listing shows an example for a simple Android manifest file.

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.android.rssreader"
    android:versionCode="1"
    android:versionName="1.0" >
    <uses-permission android:name="android.permission.INTERNET" />

    <application
        android:name="RssApplication"
        android:allowBackup="false"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name="RssfeedActivity"
            android:label="@string/title_activity_main" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <activity
            android:name=".DetailActivity"
            android:label="Details" >
        </activity>
        <activity android:name="MyPreferenceActivity" >
        </activity>

        <service android:name="RssDownloadService" >
        </service>
    </application>

</manifest>

2. Using Android devices for testing

2.1. Using a real Android device for testing

To use a normal Android device, connect your device to your development machine (via USB). On your Android device turn on USB Debugging. Select Settings ▸ Development Options, then enable the USB-Debugging option.

You may also need to install the driver for your mobile phone. Linux and Mac OS usually work out of the box while MS Windows typically requires the installation of a driver.

The minimum Android version of your Android application needs to fit to the Android version on your device.

If you have several devices connected to your computer, you can select which one should be used. If only one device is connected, the application is automatically deployed on this device.

2.2. Using the Android emulator and Android Virtual Device

The Android tooling contains an Android device emulator. This emulator can be used to run an Android Virtual Device (AVD).

These AVDs allow you to test your applications on selected Android devices without access to the real hardware. Virtual devices give you the possibility to test your application for selected Android versions and a specific configurations. Even if you have a physical Android device available, you should get familiar with the creation and usage of AVDs.

During the creation of your AVD you define the configuration for the virtual device. This includes, for example, the resolution, the Android API version and the density of your display.

You can define multiple AVDs with different configurations and start them in parallel.

If you stop and AVD during startup process the AVD might get corrupted. The first start may take long, e.g., several minutes on an older machine. On a modern machine it typically takes less than a minute for a new AVD to start.

After the AVD has started, you can control the GUI with the mouse. The emulator also provides access to the phone buttons via a menu on the right side of the emulator.

Once started, don’t stop the AVD during your development. If you change your application and want to test a new version, you simply re-deploy your application on the AVD.

An AVD created for Android contains the programs from the Android Open Source Project. An AVD created for the Google API’s contains additional Google specific code. AVDs created for the Google API allow you to test applications which use Google Play services, e.g., the new Google maps API or the new location services.

During the creation of an emulator you can choose if you either want Snapshot or Use Host GPU enabled. If you select the Snapshot option, the second time you start the device it is started very fast, because the AVD stores its state if you close it. If you select Use Host GPU the AVD uses the graphics card of your host computer directly which makes the rendering on the emulated device much faster.

Startup options of the emulator
Using ARM CPU or Intels CPU architecture

If possible, select an AVD with an image based on the ARM CPU architecture or based on the Intel CPU architecture.

An Android virtual device which uses the Intel system image is much faster in execution. Intel based images sometimes do not work on certain machines, in this case try an ARM based system image. ARM based system image tend to work on more computers.

Intel emulator

3. Android Studio overview and installation

3.1. Android Developer Tools and Android Studio

The Android Software Development Kit (Android SDK) and the Gradle tooling contains the necessary tools to Compile, package, deploy and start Android application.

Google also provides an IDE called Android Studio to perform development tasks.

The Android SDK contains the Android debug bridge (adb). adb is a tool that allows you to connect to a virtual or real Android device. This allows managing the device or debugging your application.

3.2. System requirements

Development for Android can be done on a reasonably sized computer. For a nice experience a modern computer is recommended, for example, a 2.6 GHz CPU with at least 8 GB of memory. An SSD speeds up the start of the Android emulator significantly.

The Android SDK is 32-bit, therefore on a 64-bit Linux system you need to have the package ia32-libs installed. For Ubuntu you can do this via the following command.

apt-get install ia32-libs

Please check your distribution documentation, if you are using a different flavor of Linux.

3.3. Download and installation of Android Studio

Download Android Studio from the Android Studio Website.

The download comes in two flavors, SDK Tools only and Android Studio Packages. You want to download the Android Studio Package for your operation system.

Installation of Android Studio

Installation for Windows is simple, just launch the .exe you downloaded. On Max OSX drag and drop Android Studio into the Applications folder.

On Linux unpack the downloaded ZIP file into an appropriate location for your applications. To launch Android Studio, navigate to the android-studio/bin/ directory in a terminal and execute studio.sh.

The first time you start a new Android Studio installation, you have the option to import your existing settings.

Configuration wizard of Android Studio

Afterwards click through the setup guide.

Configuration wizard of Android Studio
Configuration wizard of Android Studio
Configuration wizard of Android Studio

Once you reach the last page, press the Finish button.

Configuration wizard of Android Studio

3.3.1. Installation of the Intel emulator on Windows

At the time of this writing your also need to download and install extra drivers for MS windows.

Intel emulator

After the download you find the driver in your Android installation directory in the extras/intel folder.

You need to install the drivers by running the .exe file.

This additional installation step is required on Window to accelerate the Intel emulator. Only downloading the driver via the Android does not make a difference.

After the installation, you can create a new AVD based on the Intel emulator. The emulator does start faster and is way faster during the execution of your Android application.

3.3.2. Installation of the Intel emulator on Linux

Linux requires a more complex setup. For a detailed installation description see the Intel emulator installation guide which also includes detailed instructions for Windows.

3.4. Installation of Android SDKs

The Android SDK manager allows you to install and delete specific Android OS versions.

Select Tools ▸ Android ▸ SDK Manager or the SDK Manager icon in the toolbar of Android Studio to open the Android SDK manager.

Android SDK manager in Android Studio

In the Android SDK manager select the version of desired Android version the tree and press the Install button. The following screenshot shows the selection for the API 18 version of Android.

Install Android API

Press the OK button to start he installation.

The SDK Platforms tab is used to install API versions, which the SDK Tools is used to install the development tools.

4. Exercise: Getting started with Android Studio

In this exercise, you create an Android project and start it on an Android virtual device.

4.1. Create a new Android project

Press the Start a new Android Studio project link to get started. Alternatively you can select the File ▸ New Project…​ entry from the menu, if you already created a project earlier.

Creating a new Android Studio project

Use the following data of input for your project. Project location and package name are derived from your input. If you want another package name, press the small Edit hyperlink.

Table 3. Setting for your Android project
Property Value

Application name

Test App

Company Domain

android.vogella.com

Package Name

com.vogella.android.testapp

API (Minimum, Target, Compile with)

Latest

Template

Empty Activity

Creating a new Android Studio project
Creating a new Android Studio project

Android Studio automatically downloads required SDK versions. Depending on your installation, you may see additional dialogs.

Afterwards select the Empty Activity template.

Creating a new Android Studio project
Creating a new Android Studio project

4.2. Review the generated project

Review the generated project structure and files.

as first70

4.3. Create a virtual device (AVD)

Define a new Android Virtual Device (AVD) by opening the AVD Manager via Tools ▸ Android ▸ AVD Manager. Afterwards press the Create Virtual Device…​ button.

Select values similar to the following screenshots.

Settings for a new AVD

On the next screen select the latest API level for your AVD. You may need to select the option for additional images as highlighted in the following screenshot.

Settings for a new AVD
Settings for a new AVD

Afterwards press the Finish button. This will create the AVD configuration and display it under the list of available virtual devices.

4.4. Start the application on your virtual device

Select your new virtual device and press the Play button.

Settings for a new AVD

Select Run ▸ Run 'app' to start your application. This opens a dialog in which you can select your device to deploy your application to.

Settings for a new AVD

After a while your application should start on the virtual device.

First running android app

5. Using views and view groups to design the user interface

5.1. Views - The widgets in Android

A view in Android represents a widget, e.g., a button, or a layout manager. All views in Android extend the android.view.View class.

The Android SDK provides standard views, for example the Button, TextView and EditText classes.

The main packages for views are:

  • android.view for all base classes

  • android.widget for the default widgets

Additional libraries provide more complex widgets, for example, RecyclerView.

===View groups - Layout manager for layouting views

A layout manager is responsible for the layout of itself and its child views. The base class for these layout managers is the android.view.ViewGroup class.

Layout managers can be nested to create complex layouts.

The most relevant layout managers in Android are:

  • ConstraintLayout - provided by an extra library

  • LinearLayout

  • FrameLayout

  • RelativeLayout

  • GridLayout

All layout manager can be configured via attributes. Children can also define attributes which may be evaluated by their parent layout.

Children can specify their desired width and height via the following attributes.

  • android:layout_width - Defines the width of the widget.

  • android:layout_height - Defines the height of the widget.

Views can define their size. This can be done in units of measurement or via pre-defined layout values. For example, as 100dp.

The match_parent value tells the application to maximize the widget in its parent. The wrap_content value tells the layout to allocate the minimum amount so that the widget is rendered correctly. The effect of these elements is demonstrated in the following graphics.

Layout with wrap_content
Layout with match_parent

5.2. Overview of Android layout managers

5.2.1. ConstraintLayout

ConstraintLayout is provided by an external library. It allows you to use a flat view hierarchy and has great performance. Also the design tools support constraint layout very well. New projects should prefer the usage of constraint layout. ConstraintLayout allows you to define constraints for views.

The following xml file shows an example how to use the ConstraintLayout

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <TextView
        android:id="@+id/text"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="16dp"
        android:text="TextView1"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="16dp"
        android:text="TextView2"
        app:layout_constraintLeft_toLeftOf="@id/text"
        app:layout_constraintRight_toRightOf="@id/text"
        app:layout_constraintTop_toBottomOf="@id/text" />

</android.support.constraint.ConstraintLayout>

In the Layout Editor this is shown as follows

constraintlayout

Using the above constraints for TextView1 its left, right and top edges are aligned to their respective parent edge. By setting the width of TextView1 to 0dp the view expands to fulfill its horizontal constraints.

The position of TextView2 is dependent on the position of TextView1 but in contrast to TextView1, TextView2 only expands to fit its contents (using wrap_content).

In ConstraintLayout the use of match_parent is not recommended. Instead use 0dp to make the view fulfilling its constraints.

There are several attributes in ConstraintLayout to define the size or position of a view.

  • ratio: To size elements you can define an aspect ratio (e.g., 16:9). To define an aspect ratio one dimension has to be set to 0dp (match constraints). In xml you can use app:layout_constraintDimensionRatio.

  • barriers: To align elements which size change dynamically you can define a barrier.

  • chains: To position multiple elements at once you can define a chain. A chain groups multiple elements.

5.2.2. FrameLayout

FrameLayout is a layout manager which draws all child elements on top of each other. This allows to create nice visual effects.

The following screenshot shows the Gmail application which uses FrameLayout to display several button on top of another layout.

FrameLayout

5.2.3. LinearLayout

LinearLayout puts all its child elements into a single column or row depending on the android:orientation attribute. Possible values for this attribute are horizontal and vertical. horizontal is the default value.

If horizontal is used, the child elements are layouted as indicated by the following picture.

linearlayout20

Vertical would result in a layout as depicted in the following picture.

linearlayout10

LinearLayout can be nested to achieve more complex layouts.

LinearLayout supports assigning a weight to individual children via the android:layout_weight layout parameter. This value specifies how much of the extra space in the layout is allocated to the corresponding view. If, for example, you have two widgets and the first one defines a layout_weight of 1 and the second of 2, the first will get 1/3 of the available space and the other one 2/3. You can also set the layout_width to zero to always have a certain ratio.

5.2.4. RelativeLayout

RelativeLayout allows positioning the widget relative to each other. This can be used for complex layouts. RelativeLayout is a complex layout manager and should only be used if such a complex layout is required, as it performs a resource intensive calculation to layout its children.

A simple usage for RelativeLayout is if you want to center a single component. Just add one component to the RelativeLayout and set the android:layout_centerInParent attribute to true.

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" >

    <ProgressBar
        android:id="@+id/progressBar1"
        style="?android:attr/progressBarStyleLarge"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerInParent="true"
         />

</RelativeLayout>

5.2.5. GridLayout

GridLayout allows you to organize views into a grid / table. GridLayout separates its drawing area into: rows, columns, and cells.

You can specify how many columns the grid should have. For each view you can specify in which row and column it should be placed and how many columns and rows it should use. If not specified, GridLayout uses defaults, e.g., one column, one row and the view position depends on the order of the declaration.

The following layout file defines a layout using GridLayout.

<?xml version="1.0" encoding="utf-8"?>
<GridLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/GridLayout1"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:columnCount="4"
    android:useDefaultMargins="true" >

    <TextView
        android:layout_column="0"
        android:layout_columnSpan="3"
        android:layout_gravity="center_horizontal"
        android:layout_marginTop="40dp"
        android:layout_row="0"
        android:text="User Credentials"
        android:textSize="32dip" />

    <TextView
        android:layout_column="0"
        android:layout_gravity="right"
        android:layout_row="1"
        android:text="User Name: " >
    </TextView>

    <EditText
        android:id="@+id/input1"
        android:layout_column="1"
        android:layout_columnSpan="2"
        android:layout_row="1"
        android:ems="10" />

    <TextView
        android:layout_column="0"
        android:layout_gravity="right"
        android:layout_row="2"
        android:text="Password: " >
    </TextView>

    <EditText
        android:id="@+id/input2"
        android:layout_column="1"
        android:layout_columnSpan="2"
        android:layout_row="2"
        android:inputType="textPassword"
        android:ems="8" />

    <Button
        android:id="@+id/button1"
        android:layout_column="2"
        android:layout_row="3"
        android:text="Login" />

</GridLayout>

This creates a user interface similar to the following screenshot.

GridLayout Activity result

5.3. ScrollView

The ScrollView or the HorizontalScrollView class is useful to make views available, even if they do not fit onto the screen. A scroll view can contain one view, e.g., a layout manager containing more views. If the child view is too large, scroll view allows scrolling the content.

Scroll view

The following code shows an example layout file which uses a ScrollView.

<?xml version="1.0" encoding="utf-8"?>
<ScrollView xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:fillViewport="true"
    android:orientation="vertical" >

    <TextView
        android:id="@+id/TextView01"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:paddingLeft="8dip"
        android:paddingRight="8dip"
        android:paddingTop="8dip"
        android:text="This is a header"
        android:textAppearance="?android:attr/textAppearanceLarge" >
    </TextView>

</ScrollView>

The android:fillViewport="true" attribute ensures that the scrollview is set to the full screen even if the elements are smaller than one screen.

6. Resources

6.1. Resource files

Static resources like images and XML configuration files are used in Android applications.

Resource files must be placed in the /res directory of your application in a predefined sub-folder. The specific sub-folder depends on type of resource which is stored. You can also append additional qualifiers to the folder name. These are called resource qualifiers. These qualifiers indicate that the related resources should be used for special device configurations. For example, you can specify that a layout file is only valid for a certain screen size.

The following table gives an overview of the supported resources and their standard folder prefixes.

Table 4. Resources
Resource Folder Description

Drawables

/res/drawables

Images (e.g., png or jpeg files)or vector drawables or XML files which scale automatically with the density of the Android device

Simple Values

/res/values

Used to define strings, colors, dimensions, styles and static arrays of strings or integers via XML files. By convention each type is stored in a separate file, e.g., strings are defined in the res/values/strings.xml file.

Layouts

/res/layout

XML files with layout descriptions are used to define the user interface for activities and fragments.

Styles and themes

/res/values

Files which define the appearance of your Android application.

Animations

/res/animator

Defines animations in XML for the animation API which allows to animate arbitrary properties of objects over time.

Raw data

/res/raw

Arbitrary files saved in their raw form. You access them via an InputStream object.

Menus

/res/menu

Defines the actions which can be used in the toolbar of the application.

For example, the following values.xml file in the /res/values folder defines several resources. It defines a few String constants, a String array, a color and a dimension.

<?xml version="1.0" encoding="utf-8"?>
<resources>

    <string name="app_name">Test</string>
    <string name="action_settings">Settings</string>
    <string name="hello_world">Hello world!</string>

    <string-array name="operationsystems">
        <item>Ubuntu</item>
        <item>Android</item>
        <item>Microsoft Windows</item>
    </string-array>

    <color name="red">#ffff0000</color>

    <dimen name="mymargin">10dp</dimen>

</resources>

6.2. Resource files and R.java

Every relevant resource in the res folder, gets an ID assigned by the Android build system. The Android tooling generates a R.java file which contains the generated values. These references are static integer values.

If you add a new resource file, the corresponding reference is automatically created in a R.java file. Manual changes in the R.java file are not necessary and are overwritten by the tooling. The Android system provides methods to access the corresponding resource files via these IDs.

For example, to access a String with the R.string.yourString ID you would use the getString(R.string.yourString) method. This method is defined via the Context class.

6.3. Layout files

Android activities define their user interface with views (widgets) and fragments. This user interface can be defined via XML layout resource files in the <filename class="filename">/res/layout_ folder or via Java code. You can also mix both approaches.

Defining layouts via XML layout files is the preferred way. This separates the programming logic from the layout definition. It also allows the definition of different layouts for different devices.

A layout resource file is referred to as layout. A layout specifies the ViewGroups, Views, their relationship and their attributes via an XML representation.

The following code is an example for a simple layout file.

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
     >

    <TextView
        android:id="@+id/mytext"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/hello_world" />

</RelativeLayout>

A layout is assigned to an activity via the setContentView() method calls, as demonstrated in the following example code.

package com.vogella.android.first;

import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;

public class MainActivity extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }

}

6.4. Performance considerations with layouts

Calculating the layout and drawing the views is a resource intensive operation. You should use the simplest layout possible to achieve good performance. For example, you should avoid nesting layout managers too deeply or avoid using complex layout managers in case a simple layout manager is sufficient.

6.5. Good practices for resources IDs

If a view needs to be accessed via Java or XML code, you have to give the view a unique ID via the android:id attribute. To assign a new ID to a view use the android:id attribute of the corresponding element in the layout file.

The Android SDK uses the camelCase notation for most of its IDs, e.g., buttonRefresh. It is good practice to follow this approach.

The following shows an example in which a button gets the button1 ID assigned via the android:id="@+id/button1" parameter. By conversion this statement creates a new ID if necessary in the R.java file and assigns the defined ID to the corresponding view.

<Button
    android:id="@+id/button1"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Show Preferences" >
</Button>

It is possible to define IDs in one central configuration file. This is typically called ids.xml and placed in the /res/values folder. This allows you to use the predefined ID in your layout file. If you want to define the id in a separate file, you first need to remove the @+id entries in your layout files, otherwise you get an error messages that these files have already been created. The following listing shows an example for such a file.

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <item name="button1" type="id"/>
</resources>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity" >

    <Button
        android:id="@id/button1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerHorizontal="true"
        android:layout_centerVertical="true"
        android:layout_marginRight="27dp"
        android:text="Button" />

</RelativeLayout>

6.6. System resources

Android also provides resources. These are called system resources. System resources are distinguished from local resources by the android namespace prefix. For example, android.R.string.cancel defines the platform string for a cancel operation.

6.7. References to resources in code

The Resources class allows to access individual resources. An instance of the Resources class can be retrieved via the getResources() method of the Context class. As activities and services extend the Context class, you can directly use this method in implementations of these components.

An instance of the Resources class is also required by other Android framework classes. For example, the following code shows how to create a Bitmap file from a reference ID.

// BitmapFactory requires an instance of the Resource class
BitmapFactory.decodeResource(getResources(), R.drawable.ic_action_search);

6.8. Accessing views from the layout in an activity

In your activity (and fragment) code you frequently need to access the views to access and modify their properties.

In an activity you can use the findViewById(id) method call to search for a view in the current layout. The id is the ID attribute of the view in the layout. The usage of this method is demonstrated by the following code.

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    TextView textView = (TextView) findViewById(R.id.mytext);

    // TODO do something with the TextView
}

It is also possible to search in a view hierarchy with the findViewById(id) method, as demonstrated in the following code snippet.

// search in the layout of the activity
LinearLayout linearLayout = (LinearLayout) findViewById(R.id.mylayout);

// afterwards search in linearLayout for another view
TextView textView = (TextView) linearLayout.findViewById(R.id.mytext);

// note, you could have directly searched for R.id.mytext, the above coding
// is just for demonstration purposes

You could also build a utility method which makes access to views easier.

package com.example.android.test;

import android.app.Activity;
import android.view.View;

public class UiUtils {
   public static <T extends View> T findView(View root, int id)      {
      return (T) root.findViewById(id); }

   public static <T extends View> T findView(Activity activity, int id)      {
      return (T) activity.getWindow().getDecorView().getRootView().findViewById(id); }
}

This would allow you to find the view without explicit cast in your view hierarchy.

Button button = UiUtils.findView(this, R.id.button);

6.9. Reference to resources in XML files

In your XML files, for example, your layout files, you can refer to other resources via the @ sign.

For example, if you want to refer to a color, which is defined in an XML resource, you can refer to it via @color/your_id. Or if you defined a String with the "titlepage" key in an XML resource, you could access it via @string/titlepage

To use an Android system resource, include the android namespace into the references, e.g., android.R.string.cancel.

6.10. Using assets?

The res directory contains structured values which predefined semantics for the Android platform. The assets directory can be used to store any kind of data. You can access files stored in this folder based on their path. The assets directory also allows you to have sub-folders.

You could also store unstructured data in the /res/raw folder. But it is considered good practice to use the assets directory for such data.

You access this data via the AssetsManager which you can access via the getAssets() method from an instance of the Context class.

The AssetsManager class allows you to read a file in the assets folder as InputStream with the open() method. The following code shows an example for this.

// get the AssetManager
AssetManager manager = getAssets();

// read the "logo.png" bitmap from the assets folder
InputStream open = null;
try {
    open = manager.open("logo.png");
    Bitmap bitmap = BitmapFactory.decodeStream(open);
    // assign the bitmap to an ImageView in this layout
    ImageView view = (ImageView) findViewById(R.id.imageView1);
    view.setImageBitmap(bitmap);
    } catch (IOException e) {
        e.printStackTrace();
    } finally {
        if (open != null) {
            try {
                open.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
}

7. Exercise: Your first view interaction

7.1. Review generated layout

Continue to use your project which you created earlier with the com.vogella.android.testapp package. Open the activity_main.xml layout file located in the res/layout folder.

Investigate the XML layout in the visual editor as well in as the XML structure.

7.2. Adjust views

Remove all views, except the top level entry which is the layout manager. In the visual design mode you can remove a view by right-clicking it and by selecting the Delete entry for the context menu.

If necessary, change the layout manager to RelativeLayout. The result layout file should look similar to the following file.

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    >


</RelativeLayout>

Android Studio changes its templates very frequently, so your layout file might look at bit different. For the purpose of the exercises, the layout file must not be exactly the same, as long as the result looks similar.

Add a TextView, a Plain Text (EditText) and a Button to your layout. The easiest way is to find these elements in the Palette and drag and drop them into your layout.

Use the text (XML) editor to change the ID of the new EditText field to username. In the XML file this looks like @+id/username.

Change the button text to Create via the android:text property in your layout file. Assign the name onClick to the android:onClick property of your Button.

This defines that a public void onClick (View view) method is be called in the activity once the button is pressed. This method is implemented in the next step.

After these changes your layout file should be similar to the following code.

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
                xmlns:tools="http://schemas.android.com/tools"
                android:layout_width="match_parent"
                android:layout_height="match_parent"
    >

    <TextView
        android:id="@+id/userlabel"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_margin="16dp"
        android:text="User"
        android:textSize="24sp"
        />

    <EditText
        android:id="@+id/username"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignStart="@+id/userlabel"
        android:layout_below="@+id/userlabel"
        android:ems="10"
        android:inputType="textPersonName"
        android:text=""
        android:textSize="36sp"
        />

    <Button
        android:id="@+id/createUserButton"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentEnd="true"
        android:layout_margin="16dp"
        android:layout_below="@+id/username"
        android:text="Create"
        android:onClick="onClick"
        />

</RelativeLayout>

You see some warning messages in the editor, e.g., because you used hard-codes strings. These can be ignored for small demo applications.

If you run your application and press the button your application crashes because you still need to adjust your activity.

7.3. Display text from your user field as a popup

In your MainActivity class implement the public void onClick (View view) method. Use the findViewById(id) method with the correct id and cast the returned object into EditText.

EditText text = (EditText) findViewById(id)

You can get the right id via the R class. It should be stored under ID and called main_input.

Use the text.getText().toString() method to read the string in the editor field and add the text to your Toast message.

package com.vogella.android.first;

import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.EditText;
import android.widget.Toast;

public class MainActivity extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }

    public void onClick(View view) {
        EditText input = (EditText) findViewById(R.id.username);
        String string = input.getText().toString();
        Toast.makeText(this, "User " + string + " created.", Toast.LENGTH_LONG).show();
    }
}

7.4. Validate popup message

Start your application and ensure that the message displays the text which the text field contains.

Final layout

8. Exercise: Adding radio buttons

Continue to use your project which you created in the Exercise: Getting started with Android Studio exercise. In this exercise you add radio buttons. This application was extended in Exercise: Your first view interaction. Depending on the user selection the radio button arrangement will change from horizontal to vertical.

8.1. Add radio group and radio buttons to your layout

Open your layout file and add a radio group with two radio buttons to your layout.

Assign IDs to them, based on the following table.

Table 5. ID Assignment
ID View

gender

Radio Group

male

First radio button

female

Second radio button

The resulting layout file should be similar to the following listing.

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
                xmlns:tools="http://schemas.android.com/tools"
                android:layout_width="match_parent"
                android:layout_height="match_parent"
    >

    <TextView
        android:id="@+id/userlabel"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_margin="16dp"
        android:text="User"
        android:textSize="24sp"
        />

    <EditText
        android:id="@+id/username"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignStart="@+id/userlabel"
        android:layout_below="@+id/userlabel"
        android:ems="10"
        android:inputType="textPersonName"
        android:text=""
        android:textSize="36sp"
        />

    <RadioGroup
        android:id="@+id/gender"
        android:layout_below="@id/username"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_alignLeft="@id/userlabel"
        android:layout_marginTop="16dp">

        <RadioButton
            android:id="@+id/male"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:checked="true"
            android:text="Male" >
        </RadioButton>

        <RadioButton
            android:id="@+id/female"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Female" >
        </RadioButton>
    </RadioGroup>
    <Button
        android:id="@+id/createUserButton"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentEnd="true"
        android:layout_margin="16dp"
        android:layout_below="@+id/gender"
        android:text="Create"
        android:onClick="onClick"
        />

</RelativeLayout>

The RadioGroup part is new. Also the layout reference of the button has changed. The rest should already be there from previous exercises.

The resulting layout should look like the following screenshot.

Show the layout

8.2. Add the selected button to your Toast

Add the selected button to the text of your toast.

RadioGroup allows you to add a RadioGroup.OnCheckedChangeListener via the setOnCheckedChangeListener() method. This listener is notified if the selection of the radio group changes.

You can use the following code as template to implement the listener.

boolean male = true;

// more code

final RadioGroup group1 = (RadioGroup) findViewById(R.id.gender);
group1.setOnCheckedChangeListener(new RadioGroup.OnCheckedChangeListener() {
    @Override
    public void onCheckedChanged(RadioGroup group, int checkedId) {
        switch (checkedId) {
            case R.id.male:
                male = true;
                break;
            case R.id.female:
                male = true;
                break;
        }
    }
});

8.3. Validating

Run your application and select the different radio button. Display your Toast and ensure the correct data (user name and gender) is displayed.

9. Exercise: Using resources in XML files and in code

9.1. Add images to your application

In this exercise you continue to extend the application you created in Exercise: Getting started with Android Studio. Add to images to your project called maleprofile and femaleprofile.

For this exercises, it does not matter which image you are using. Use for example Android Studio to create two new vector grapics and use them.

9.2. Add widgets to display images to your layout

Open your layout file and add a new ImageView to it. Assign the maleprofile image to your ImageView, via your layout file as demonstrated in the following XML snippet.

 <!--
        NOTE: More attributes are required
        for the correct layout of the ImageView. These are left
        out for brevity
    -->

<ImageView
  android:id="@+id/userimage"
  android:scaleType="fitCenter"
  android:background="@android:color/transparent"
  .... more attributes
  android:src="@drawable/maleprofile" />

9.3. Replace images via radio button selection

Use findViewById() in your onCreateMethod to search for the ImageView.

If your different radio buttons are clicked, use the setImageResource() method of ImageView to assign the correct png file to your ImageView. The parameter of the setImageResource() method is the R reference to your file, e.g., R.drawable.your_png_file.

9.4. Validating

Ensure that if you change your radio button selection, the displayed image is replaced.

10. Exercise: Create a temperature converter

In this exercise you learn how to create and consume Android resources.

This application is available on Google Play under the following URL: http://play.google.com/store/apps/details?id=de.vogella.android.temperature

You can also scan the following barcode with your Android phone to install it via the Google Play application.

QR Code to install the Android Temperature converter

10.1. Create Project

Create a new Android project with the following data.

Table 6. New Android project
Property Value

Application Name

Temperature Converter

Package name

com.vogella.android.temperatureconverter

Minimum SDK

Latest Android release

Template

Empty Activity

Activity

MainActivity

Layout

activity_main

Backwards Compatibility (AppCompat)

false (not selected)

10.2. Create attributes

Select the res/values/strings.xml file to open the editor for this file. Add the Color and String definitions to the file as described by the following table.

Table 7. New attributes to add
Type Name Value

Color

myColor

#F5F5F5

String

celsius

to Celsius

String

fahrenheit

to Fahrenheit

String

calc

Calculate

Afterwards the file should look similar the following.

<?xml version="1.0" encoding="utf-8"?>
<resources>

    <string name="app_name">Temperature Converter</string>
    <string name="action_settings">Settings</string>
    <string name="hello_world">Hello world!</string>
    <color name="myColor">#F5F5F5</color>
    <string name="celsius">to Celsius</string>
    <string name="fahrenheit">to Fahrenheit</string>
    <string name="calc">Calculate</string>

</resources>

10.3. Creating the layout

Open the res/layout/activity_main.xml file.

Remove any existing view from your layout, either directly from the XML source or via the graphical editor.

Afterwards add a LinearLayout with one EditText as child. Afterwards add a RadioGroup with two radio buttons and a button to your layout. Do this either directly in the XML file or via the graphical editor. A simple way of organizing the components is to drag and drop them onto the Component Tree view.

The result should look like the following screenshots. The first one shows the component view the second one the preview.

Component view
Current layout of activity_main.xml

Switch to the XML tab of your layout file and verify that the file looks similar to the following listing.

The Android tools team changes the generated code from time to time, so your XML might look slightly different.

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:background="@color/myColor">


    <EditText
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/editText1" />

    <RadioGroup
        android:id="@+id/radioGroup1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignStart="@+id/editText1"
        android:layout_below="@+id/editText1">

        <RadioButton
            android:id="@+id/radio0"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:checked="true"
            android:text="RadioButton" />

        <RadioButton
            android:id="@+id/radio1"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="RadioButton" />
    </RadioGroup>

    <Button
        android:id="@+id/button1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignStart="@+id/radioGroup1"
        android:layout_below="@+id/radioGroup1"
        android:layout_marginTop="22dp"
        android:text="Button" />

</LinearLayout>

You see some warning messages. You fix these in the following section of this exercise.

10.4. Edit view properties

Switch to the XML representation of the file and assign the @string/celsius value to the android:text property of the first radio button. Assign the fahrenheit string attribute to the text property of the second radio button.

Change the text property of the radio button

Ensure that the checked property is set to true for the first RadioButton.

Assign @string/calc to the text property of your button and assign the value onClick to the onClick property.

Set the inputType property to numberSigned and numberDecimal on the EditText. As an example you can use the last line in the following XML snippet. Also change its ID to "inputValue".

<EditText
  android:id="@+id/inputValue"
  android:layout_width="match_parent"
  android:layout_height="wrap_content"
  android:layout_alignParentEnd="true"
  android:layout_below="@+id/textView"
  android:ems="10"
  android:inputType="numberSigned|numberDecimal" />

All your user interface components are contained in a layout. Assign the background color to this Layout.

Select Color and then select myColor in the dialog. As an example, you can use the last line in the following XML snippet.

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:background="@color/myColor">

Afterwards the background should change to the whitesmoke color. It might be difficult to see the difference.

Switch to the activity_main.xml tab and verify that the XML is correct.

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:background="@color/myColor">


    <EditText
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/inputValue"
        android:inputType="numberSigned|numberDecimal"/>

    <RadioGroup
        android:id="@+id/radioGroup1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignStart="@+id/editText1"
        android:layout_below="@+id/editText1">

        <RadioButton
            android:id="@+id/radio0"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:checked="true"
            android:text="@string/celsius" />

        <RadioButton
            android:id="@+id/radio1"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@string/fahrenheit" />
    </RadioGroup>

    <Button
        android:id="@+id/button1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignStart="@+id/radioGroup1"
        android:layout_below="@+id/radioGroup1"
        android:layout_marginTop="22dp"
        android:text="@string/calc"
        android:onClick="onClick"/>

</LinearLayout>

10.5. Create utiliy class

Create the following utility class to convert from celsius to fahrenheit and vice versa.

package com.vogella.android.temperatureconverter;

public class ConverterUtil {
    // converts to celsius
    public static float convertFahrenheitToCelsius(float fahrenheit) {
        return ((fahrenheit - 32) * 5 / 9);
    }

    // converts to fahrenheit
    public static float convertCelsiusToFahrenheit(float celsius) {
        return ((celsius * 9) / 5) + 32;
    }
}

10.6. Change the activity code

Change the MainActivity to the following

package com.vogella.android.temperatureconverter;

import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.EditText;
import android.widget.RadioButton;
import android.widget.Toast;

public class MainActivity extends Activity {
  private EditText text;

  @Override
  public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    text = (EditText) findViewById(R.id.inputValue);

  }

  // this method is called at button click because we assigned the name to the
  // "OnClick" property of the button
  public void onClick(View view) {
    switch (view.getId()) {
    case R.id.button1:
      RadioButton celsiusButton = (RadioButton) findViewById(R.id.radio0);
      RadioButton fahrenheitButton = (RadioButton) findViewById(R.id.radio1);
      if (text.getText().length() == 0) {
        Toast.makeText(this, "Please enter a valid number",
            Toast.LENGTH_LONG).show();
        return;
      }

      float inputValue = Float.parseFloat(text.getText().toString());
      if (celsiusButton.isChecked()) {
        text.setText(String
            .valueOf(ConverterUtil.convertFahrenheitToCelsius(inputValue)));
        celsiusButton.setChecked(false);
        fahrenheitButton.setChecked(true);
      } else {
        text.setText(String
            .valueOf(ConverterUtil.convertCelsiusToFahrenheit(inputValue)));
        fahrenheitButton.setChecked(false);
        celsiusButton.setChecked(true);
      }
      break;
    }
  }

}

10.7. Start the application

Start your Android application and type in a number, select your conversion and press the button. The result should be displayed and the other option should get selected.

Change the text property of the radio button

11. Deployment

11.1. How to deploy

In general there are restrictions how to deploy an Android application to your device. You can deploy the application via USB in test mode onto your device, email yourself the application or use one of the many Android markets to install the application. The following description highlights the most common ones.

11.2. Defining software and hardware requirements for the application

The application can define via a <uses-feature> declaration in the manifest file define which hardware of software features is requires. Via the android:required property the application can define if such a feature is required for the application to work correctly (true) or if application prefers to use the feature if present on the device, but that it is designed to function without the specified feature, if necessary.

Examples for such definitions are the presence of a certain hardware sensor or the availability of a camera.

For an overview of the available restrictions see http://developer.android.com/guide/topics/manifest/uses-feature-element.html.

11.3. Signing your application for the release

Android applications must be signed before they can get installed on an Android device. During development the build process signs the application automatically with a debug key.

To install the Android application via another channel you need to sign the Android apk with a self-created signature key.

Please note that you need to use the same signature key in Google Play (Google Market) to update your application. If you lose the key, you will NOT be able to update your application ever again.

Make sure to backup your key.

11.4. Export your application via Android Studio

Use the Build ▸ Generate Signed APK…​ menu entry to start the export from Android Studio.

11.5. Export your application via the Eclipse IDE

If you want to export your production application via the Eclipse IDE, you can right-click on it and select Android Tools ▸ Export Signed Application Package.

This wizard allows to use an existing key or to create a new one.

11.6. Via external sources

Android also allows to install applications directly. Just click on a link which points to an .apk file, e.g., in an email attachment or on a webpage. Android will prompt you if you want to install this application.

This requires a setting on the Android device which allows the installation of non-market application. Typically this setting can be found under the "Security" settings.

11.7. Google Play

Google offers the Google Play service, a marketplace in which programmers can offer their application to Android users. Customers use the Google Play application which allows them to buy and install applications from the Google Play service.

Google Play also offers an update service. If a application developer uploads a new version of his application to Google Play, this service notifies existing users about the available update.

Google Play provides access to services and libraries for Android application programmers, too. For example, it provides a service to use and display Google Maps. Providing these services via Google Play has the advantage that they are available for older Android releases. Google can update them without the need for an update of the Android release on the phone.

Google Play requires a one time fee, currently 25 Dollar. After that payment, the developer can upload his application and the required icons, via Google Play Publishing.

Google performs some automatic scanning of applications, but no approval process is in place. All application, which do not contain malware, are published. Usually a few minutes after upload, the application is available.

12. Appendix Important entries in the Android manifest file

12.1. Declaration of version, package and Android components

The package attribute defines the base package for the Java objects referred to in this file. If a Java object lies within a different package, it must be declared with the full qualified package name.

Google Play requires that every Android application uses an unique package name. It is a good practice to use your reverse domain name here. This avoids collisions with other Android applications.

android:versionName and android:versionCode specify the version of your application. versionName is what the user sees and can be any string.

versionCode must be an integer. Google Play determines based on this number if an update is necessary. You typically start this version with "1" and increase it by one, if you deploy a new version. If you are developing, the Android development tooling allows deploying a new version if the application code has changed, you do not need to increase the version for that.

The <application> section allows to define metadata for your application and optionally define an explicit application class. It is also a container for declaring other Android components.

The <activity> tag defines an activity. The name attribute points to class, which (if not fully qualified) is relative to the package defined in the`package` attribute.

The intent filter section allows to register a components for certain actions and categories. For example, the android:name="android.intent.action.MAIN" action defines that an activity can be started by the user. The category android:name="android.intent.category.LAUNCHER" parameter tells the Android system to add the activity to the launcher.

The <@string/app_name> value refers to resource files which contain the string.

Similar to the <activity> tag, you can use the <service>, <receiver> and <provider> tags for the other Android components.

12.2. Minimum and target SDK

These values are specified via the Gradle build file for modern Android applications.

The uses-sdk section in the manifest allows you to specify the minSdkVersion and targetSdkVersion version of your application.

Table 8. Minimum and target version
Value Description

minSdkVersion

Define the minimum version of Android your application works on. This attribute is used as a filter in applications stores Play. A user cannot install your application on a device with a lower API level than specified in this attribute.

targetSdkVersion

Specifies the version on which you tested and developed. If it is not equal to the API version of the Android device, the Android system might apply forward- or backward-compatibility changes. It is good practice to always set this to the latest Android API version to take advantages of changes in the latest Android improvements.

12.3. Permissions

Your application must declare that it requires a permission with the <uses-permission> tag. For example, if the application requires network access, it must be specified here.

Certain permissions, like network access, are granted automatically on Android 6.0 or higher systems. Other permissions must be confirmed by the users to become active.

It can also declare its own permissions with the <permission> tag.

12.4. Required device configuration

The uses-configuration section in the manifest allows you to specify required input methods for your device. For example, the following snippet would require that the device has a hardware keyboard.

<uses-configuration android:reqHardKeyboard="true"/>

The uses-feature section allows you to specify the required hardware configuration for your device. For example, the following snippet would require that the device has a camera.

<uses-feature android:name="android.hardware.camera" />

12.5. Installation location

Via the installLocation attribute of your application you can specify that your application can be installed on the external storage of the device. Use auto or preferExternal to permit this.

In reality this option is rarely used. An application installed on the external storage is stopped once the device is connected to a computer and mounted as USB storage.

12.6. More info

You find more information about the attributes and sections of the manifest see http://developer.android.com/guide/topics/manifest/manifest-intro.html.

13. About this website

14. Android online resources

14.4. vogella GmbH training and consulting support

TRAINING SERVICE & SUPPORT

The vogella company provides comprehensive training and education services from experts in the areas of Eclipse RCP, Android, Git, Java, Gradle and Spring. We offer both public and inhouse training. Whichever course you decide to take, you are guaranteed to experience what many before you refer to as “The best IT class I have ever attended”.

The vogella company offers expert consulting services, development support and coaching. Our customers range from Fortune 100 corporations to individual developers.

Copyright © 2012-2017 vogella GmbH. Free use of the software examples is granted under the terms of the EPL License. This tutorial is published under the Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Germany license.

See Licence.