Several system events are defined as final static fields in the Intent class. Other Android system classes also define events, e.g. the TelephonyManager defines events for the change of the phone state.

The following table lists a few important system events.

To start Services automatically after the Android system starts you can register a BroadcastReceiver to the Android android.intent.action.BOOT_COMPLETED system event. This requires the android.permission.RECEIVE_BOOT_COMPLETED permission.

The following AndroidManifest.xml registers a receiver for the BOOT_COMPLETED event.

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="de.vogella.android.ownservice.local"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk android:minSdkVersion="10" />

    <uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED" />

    <application
        android:icon="@drawable/icon"
        android:label="@string/app_name" >
        <activity
            android:name=".ServiceConsumerActivity"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>

        <receiver android:name="MyScheduleReceiver" >
            <intent-filter>
                <action android:name="android.intent.action.BOOT_COMPLETED" />
            </intent-filter>
        </receiver>
        <receiver android:name="MyStartServiceReceiver" >
        </receiver>
    </application>

</manifest> 

In the onReceive() method the corresponding BroadcastReceiver would then start the service.

import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;

public class MyReceiver extends BroadcastReceiver {

  @Override
  public void onReceive(Context context, Intent intent) {
    Intent service = new Intent(context, WordService.class);
    context.startService(service);
  }
} 

If you application is installed on the SD card, then it is not available after the android.intent.action.BOOT_COMPLETED event. Register yourself in this case for the android.intent.action.ACTION_EXTERNAL_APPLICATIONS_AVAILABLE event.

Also note that as of Android 3.0 the user needs to have started the application at least once before your application can receive android.intent.action.BOOT_COMPLETED events.

A PendingIntent is a token that you give to another application (e.g. Notification Manager, Alarm Manager or other 3rd party applications), which allows this other application to use the permissions of your application to execute a predefined piece of code.

To perform a broadcast via a pending intent so get a PendingIntent via the getBroadcast() method of the PendingIntent class. To perform an activity via an pending intent you receive the activity via PendingIntent.getActivity().

We will define a broadcast receiver which listens to telephone state changes. If the phone receives a phone call then our receiver will be notified and log a message.

Create a new project de.vogella.android.receiver.phone. Create a dummy activity as this is required so that the BroadcastReceiver also gets activated. Create the following AndroidManifest.xml file.

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="de.vogella.android.receiver.phone"
    android:versionCode="1"
    android:versionName="1.0" >

     <uses-sdk android:minSdkVersion="15" />
     
    <uses-permission android:name="android.permission.READ_PHONE_STATE" >
    </uses-permission>

    <application
        android:icon="@drawable/icon"
        android:label="@string/app_name" >
           <activity
            android:name=".MainActivity"
            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>
        
        <receiver android:name="MyPhoneReceiver" >
            <intent-filter>
                <action android:name="android.intent.action.PHONE_STATE" >
                </action>
            </intent-filter>
        </receiver>
    </application>

   

</manifest> 

Create the MyPhoneReceiver class.

package de.vogella.android.receiver.phone;

import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.os.Bundle;
import android.telephony.TelephonyManager;
import android.util.Log;

public class MyPhoneReceiver extends BroadcastReceiver {

  @Override
  public void onReceive(Context context, Intent intent) {
    Bundle extras = intent.getExtras();
    if (extras != null) {
      String state = extras.getString(TelephonyManager.EXTRA_STATE);
      Log.w("MY_DEBUG_TAG", state);
      if (state.equals(TelephonyManager.EXTRA_STATE_RINGING)) {
        String phoneNumber = extras
            .getString(TelephonyManager.EXTRA_INCOMING_NUMBER);
        Log.w("MY_DEBUG_TAG", phoneNumber);
      }
    }
  }
} 

Install your application and simulate a phone call via the DDMS perspective in Eclipse. Your receiver is called and logs a message to the console.

In this chapter we will schedule a broadcast receiver via the AlertManager. Once called it will use the VibratorManager and a Toast to notify the user.

Create a new project called de.vogella.android.alarm with the activity called AlarmActivity.

Create the following layout.

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

    <EditText
        android:id="@+id/time"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:hint="Number of seconds"
        android:inputType="numberDecimal" >
    </EditText>

    <Button
        android:id="@+id/ok"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:onClick="startAlert"
        android:text="Start Counter" >
    </Button>

</LinearLayout> 

Create the following broadcast receiver class. This class will get the Vibrator service.

package de.vogella.android.alarm;

import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.os.Vibrator;
import android.widget.Toast;

public class MyBroadcastReceiver extends BroadcastReceiver {
  @Override
  public void onReceive(Context context, Intent intent) {
    Toast.makeText(context, "Don't panik but your time is up!!!!.",
        Toast.LENGTH_LONG).show();
    // Vibrate the mobile phone
    Vibrator vibrator = (Vibrator) context.getSystemService(Context.VIBRATOR_SERVICE);
    vibrator.vibrate(2000);
  }

} 

Maintain this class as broadcast receiver in AndroidManifest.xml and allow the vibrate authorization.

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="de.vogella.android.alarm"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk android:minSdkVersion="15" />

    <uses-permission android:name="android.permission.VIBRATE" >
    </uses-permission>

    <application
        android:icon="@drawable/icon"
        android:label="@string/app_name" >
        <activity
            android:name=".AlarmActivity"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>

        <receiver android:name="MyBroadcastReceiver" >
        </receiver>
    </application>

</manifest> 

Change the code of your Activity "AlarmActivity" to the following. This activity will create an Intent for the Broadcast receiver and get the AlarmManager service.

package de.vogella.android.alarm;

import android.app.Activity;
import android.app.AlarmManager;
import android.app.PendingIntent;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.EditText;
import android.widget.Toast;

public class AlarmActivity extends Activity {
  
/** Called when the activity is first created. */
  @Override
  public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);
  }

  public void startAlert(View view) {
    EditText text = (EditText) findViewById(R.id.time);
    int i = Integer.parseInt(text.getText().toString());
    Intent intent = new Intent(this, MyBroadcastReceiver.class);
    PendingIntent pendingIntent = PendingIntent.getBroadcast(this.getApplicationContext(), 234324243, intent, 0);
    AlarmManager alarmManager = (AlarmManager) getSystemService(ALARM_SERVICE);
    alarmManager.set(AlarmManager.RTC_WAKEUP, System.currentTimeMillis()
        + (i * 1000), pendingIntent);
    Toast.makeText(this, "Alarm set in " + i + " seconds",
        Toast.LENGTH_LONG).show();
  }

} 

Run your application on the device. Set your time and start the alarm. After the defined number of seconds a Toast should be displayed. Keep in mind that the vibrator alarm does not work on the Android emulator.

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Before posting questions, please see the vogella FAQ. If you have questions or find an error in this article please use the www.vogella.com Google Group. I have created a short list how to create good questions which might also help you.