Friday, October 7, 2011

Android Broadcast Receiver Example

Broadcast Receiver

A broadcast receiver is a class which extends "BroadcastReceiver" and which is registered as a receiver in an Android Application via the AndroidManifest.xml (or via code). This class will be able to receive intents via the sendBroadcast() method. "BroadCastReceiver" defines the method "onReceive()". Only during this method your broadcast receiver object will be valid, afterwards the Android system will consider your object as no longer active. Therefore you cannot perform any asynchronous operation.

Pending Intent

This tutorial will also use a PendingIntent. 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 PendingIntent

.getBroadcast(). To perform an activity via an pending intent you receive the activity via PendingIntent.getActivity().

Broadcast Receiver Example

We will define a broadcast receiver which listens to telephone state changes. If the phone recei

ves a phone call then our receiver will be notified and log a message.

Create a new project "de.vogella.android.receiver.phone". We do not need an activity. Create the following "AndroidManifest.xml".

<?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">

<application android:icon="@drawable/icon" android:label="@string/app_name">

<receiver android:name="MyPhoneReceiver">

<intent-filter>

<action android:name="android.intent.action.PHONE_STATE"></action>

</intent-filter>

</receiver>

</application>

<uses-sdk android:minSdkVersion="9" />

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

</manifest>

Create the following class "MyPhoneReceiver".

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("DEBUG", state);
if (state.equals(TelephonyManager.EXTRA_STATE_RINGING)) {
String phoneNumber = extras
.getString(TelephonyManager.EXTRA_INCOMING_NUMBER);
Log.w("DEBUG", phoneNumber);
}
}
}
}

If you install your application and receive a call, e.g simulated by the DDMS perspective in Eclipse, then your receiver will be called and lot a message to the console.


System Services and Broadcast Receiver

In this chapter we will use the AlertManager and VibratorManager. The VibratorManager will be called by the broadcast receiver which will be called by the AlertManager.

Create a new project "de.vogella.android.alarm" with the activity "AlarmActivity". Create the following layout.

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical" android:layout_width="fill_parent"
android:layout_height="fill_parent">
<EditText android:layout_height="wrap_content" android:id="@+id/time"
android:layout_width="wrap_content" android:hint="Number of seconds"
android:inputType="numberDecimal">></EditText>
<Button android:text="Start Counter" android:id="@+id/ok"
android:onClick="startAlert" android:layout_width="wrap_content"
android:layout_height="wrap_content"></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="9" />
<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>
<uses-permission android:name="android.permission.VIBRATE"></uses-permission>
</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. The vibrator alarm does not work on the simulator.


Define and consume your own service

The following will demonstrate how to create and consume a service from an activity. The service will periodically fetch data. The service will used by an activity which bind itself to the service. The activity will allow to request the latest data from the service.

Create a new project "de.vogella.android.ownservice" with the activity "ServiceConsumer".

Create a service "WordService" by create the class and the entry in "AndroidManifest.xml".

package de.vogella.android.ownservice;


import java.util.ArrayList;

import java.util.List;

import java.util.Timer;

import java.util.TimerTask;

import android.app.Service;

import android.content.Intent;

import android.os.Binder;

import android.os.IBinder;

import android.util.Log;

public class WordService extends Service {

private Timer timer = new Timer();

private static final long UPDATE_INTERVAL = 5000;

private final IBinder mBinder = new MyBinder();

private ArrayList list = new ArrayList();

private String[] fixedList = { "Linux", "Android", "iPhone", "vogella.de",

"helpful", "stuff" };

private int index = 0;

public void onCreate() {

super.onCreate();

pollForUpdates();

}

private void pollForUpdates() {

timer.scheduleAtFixedRate(new TimerTask() {

@Override

public void run() {

// Imagine here a freaking cool web access ;-)

if (list.size() >= 6) {

list.remove(0);

}

list.add(fixedList[index++]);

if (index >= fixedList.length) {

index = 0;

}

}

}, 0, UPDATE_INTERVAL);

Log.i(getClass().getSimpleName(), "Timer started.");

}

@Override

public void onDestroy() {

super.onDestroy();

if (timer != null) {

timer.cancel();

}

Log.i(getClass().getSimpleName(), "Timer stopped.");

}

// We return the binder class upon a call of bindService

@Override

public IBinder onBind(Intent arg0) {

return mBinder;

}

public class MyBinder extends Binder {

WordService getService() {

return WordService.this;

}

}

public List getWordList() {

return list;

}

}


    
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="de.vogella.android.ownservice"
android:versionCode="1"
android:versionName="1.0">
<uses-sdk android:minSdkVersion="10" />
<application android:icon="@drawable/icon" android:label="@string/app_name">
<activity android:name=".ServiceConsumer"
android:label="@string/app_name">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<service android:name="WordService"></service>
</application>
</manifest>
Change the layout "main.xml" to the following.

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical" android:layout_width="fill_parent"
android:layout_height="fill_parent">
<Button android:text="Reload Data" android:id="@+id/button1"
android:layout_width="wrap_content" android:layout_height="wrap_content"
android:onClick="showServiceData"></Button>
<ListView android:id="@+id/list" android:layout_width="match_parent" android:layout_height="match_parent"></ListView>
</LinearLayout>
Change the activity ServiceConsumer to the following.
package de.vogella.android.ownservice;

import java.util.ArrayList;
import java.util.List;

import android.app.Activity;
import android.content.ComponentName;
import android.content.Context;
import android.content.Intent;
import android.content.ServiceConnection;
import android.os.Bundle;
import android.os.IBinder;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import android.widget.Toast;

public class ServiceConsumer extends Activity {
private WordService s;
private ArrayList values;

/** Called when the activity is first created. */

@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
doBindService();
values = new ArrayList();
adapter = new ArrayAdapter(this,
android.R.layout.simple_list_item_1, values);
ListView list = (ListView) findViewById(R.id.list);
list.setAdapter(adapter);

// List wordList = s.getWordList();
// Toast.makeText(this, wordList.get(0), Toast.LENGTH_LONG).show();
}

private ServiceConnection mConnection = new ServiceConnection() {

public void onServiceConnected(ComponentName className, IBinder binder) {
s = ((WordService.MyBinder) binder).getService();
Toast.makeText(ServiceConsumer.this, "Connected",
Toast.LENGTH_SHORT).show();
}

public void onServiceDisconnected(ComponentName className) {
s = null;
}
};
private ArrayAdapter adapter;

void doBindService() {
bindService(new Intent(this, WordService.class), mConnection,
Context.BIND_AUTO_CREATE);
}

public void showServiceData(View view) {
if (s != null) {
List wordList = s.getWordList();
values.clear();
values.addAll(wordList);
adapter.notifyDataSetChanged();
}
}
}

Thank you

    


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