Broadcast receiver+Sending Broadcast Intent + Example

Broadcast receiver

 Definition

A broadcast receiver is a class which extends BroadcastReceiver and which is registered as a receiver in an Android Application via the AndroidManifest.xml file(or via code).
Alternatively to the this static registration, you can also register a BroadcastReceiver dynamically via the Context.registerReceiver() method.
This class will be able to receive intents. Intents can be generated via the Context.sendBroadcast() method.
The class BroadcastReceiver defines the onReceive() method. Only during this method your BroadcastReceiver object will be valid, afterwards the Android system can recycle the BroadcastReceiver. Therefore you cannot perform any asynchronous operation in the onReceive() method.

Sending Broadcast Intents

The sendBroadcast() method allows to send Broadcast Intents. You cannot trigger system Broadcasts, the Android system will prevent this.
But you can define intent-filters for your own actions and trigger them via the sendBroadcast() method.
The following AndroidManifest.xml file show a BroadcastReceiver which is registered to a custom action.

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

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

    <application
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name" >
        <activity
            android:name=".MainActivity"
            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="MyReceiver" >
            <intent-filter>
                <action android:name="de.vogella.android.mybroadcast" />
            </intent-filter>
        </receiver>
    </application>

</manifest>
                        

You can trigger this event via the sendBroadcast() method.

                                        
Intent intent = new Intent();
intent.setAction("de.vogella.android.mybroadcast");
sendBroadcast(intent);
                        

 Sticky Broadcast Intents

A normal broadcast Intent is not available anymore after is was send and processed by the system. If you use the sendBroadcast(Intent) method, the Intent is sticky, meaning the Intent you are sending stays around after the broadcast is complete.
You can can retrieve that data through the return value of registerReceiver(BroadcastReceiver, IntentFilter) . This works also for a null BroadcastReceiver.
In all other ways, this behaves the same as sendBroadcast(Intent).
The Android system uses sticky broadcast for certain system information. For example the battery status is send as sticky Intent and can get received at any time. The following example demonstrates that.

                                
// Register for the battery changed event
IntentFilter filter = new IntentFilter(Intent.ACTION_BATTERY_CHANGED);

/ Intent is sticky so using null as receiver works fine
// return value contains the status
Intent batteryStatus = this.registerReceiver(null, filter);

// Are we charging / charged?
int status = batteryStatus.getIntExtra(BatteryManager.EXTRA_STATUS, -1);
boolean isCharging = status == BatteryManager.BATTERY_STATUS_CHARGING
        || status == BatteryManager.BATTERY_STATUS_FULL;

boolean isFull = status == BatteryManager.BATTERY_STATUS_FULL;

// How are we charging?
int chargePlug = batteryStatus.getIntExtra(BatteryManager.EXTRA_PLUGGED, -1);
boolean usbCharge = chargePlug == BatteryManager.BATTERY_PLUGGED_USB;
boolean acCharge = chargePlug == BatteryManager.BATTERY_PLUGGED_AC;
                        

with example

The concept of Broadcast Receivers, one of the fundamental blocks of Android, is very simple. These are applications that will respond to any intent that is broadcast by other applications. Provided the broadcast intent matches the intent specified against the receiver in the AndroidManifest.xml

This goes to automatically imply that many activities, events, services or the like can broadcast intents expecting the appropriate action to be automatically taken. So, to begin with, let us see the various Broadcast events that are given by the platform itself. Here is a standard list obtained from the android documentation:

·         ACTION_TIME_TICK

·         ACTION_TIME_CHANGED

·         ACTION_TIMEZONE_CHANGED

·         ACTION_BOOT_COMPLETED

·         ACTION_PACKAGE_ADDED

·         ACTION_PACKAGE_CHANGED

·         ACTION_PACKAGE_REMOVED

·         ACTION_PACKAGE_RESTARTED

·         ACTION_PACKAGE_DATA_CLEARED

·         ACTION_UID_REMOVED

·         ACTION_BATTERY_CHANGED

·         ACTION_POWER_CONNECTED

·         ACTION_POWER_DISCONNECTED

·         ACTION_SHUTDOWN

For details on when each of these intents get broadcasted, please see the android documentation. I have chosen the BROADCAST event ACTION_TIME_CHANGED as I can simulate a time change in the emulator. How to simulate the time change from adb shell is given at the end of this tutorial.

Now let us get on to the example of a broadcast receiver. You can download the complete code here.

Any activity that intends to respond to broadcasts has to extend the android.content.BroadcastReceiver class and implement the single method onReceive().

In my example, I just notify on the status bar that the time has changed and the moment the user clicks on the status bar and sees the details, clicks on the details, the notification is removed from the status bar.

When the user clicks on the detailed portion, I take the user to the contacts application, just for anything better. Ideally this should take to an activity relevant to the application. So, if you see the onReceive() method, it is nothing but a notification example. That is all.

      private NotificationManager mNotificationManager;

      private int SIMPLE_NOTFICATION_ID;

     

      @Override

      public void onReceive(Context context, Intent intent) {

        mNotificationManager = (NotificationManager)context.getSystemService(Context.NOTIFICATION_SERVICE);

      Notification notifyDetails = new Notification(R.drawable.android,"Time Reset!",System.currentTimeMillis());

      PendingIntent myIntent = PendingIntent.getActivity(context, 0, new Intent(Intent.ACTION_VIEW, People.CONTENT_URI), 0);

      notifyDetails.setLatestEventInfo(context, "Time has been Reset", "Click on me to view Contacts", myIntent);

      notifyDetails.flags |= Notification.FLAG_AUTO_CANCEL;

      mNotificationManager.notify(SIMPLE_NOTFICATION_ID, notifyDetails);

            Log.i(getClass().getSimpleName(),"Sucessfully Changed Time");

      }

Once this class is ready, start the android emulator in eclipse. Then, simulate a time changed from the command prompt as given below. You will see the notification come up.

Simulating a time change in the emulator:

To start the adb shell type (in windows, assuming the path has been set to the tools folder of android sdk installation):

C:\> adb shell

#date –- 2009-10-01 14:24:59

20070325.123456

#date –s 20070325.123456

The first step date –- gives the time in seconds since Jan 1^st 1970. Take the result and give it as a parameter to date –s, the time is reset in adb and within a minute on the android emulator. This broadcasts the event that time has been changed in the emulator and kicks off the Broadcast Receiver program that has been executed.

Example

here Broadcst Receiver to get a Toast when sms receieve

package com.ann;

import android.app.Notification;

import android.app.NotificationManager;

import android.app.PendingIntent;

import android.content.BroadcastReceiver;

import android.content.Context;

import android.content.Intent;

import android.provider.Contacts.People;

import android.util.Log;

import android.widget.Toast;

public class notification extends BroadcastReceiver {

NotificationManager mNotificationManager;

int Notofication_id;

@Override

public void onReceive(Context context, Intent intent) {

Log.i("lkkjh", "sms");

Toast.makeText(context,"sms received" ,Toast.LENGTH_LONG).show();

}

}

AndroidManifest

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

<manifest xmlns:android="http://schemas.android.com/apk/res/android"

package="com.ann"

android:versionCode="1"

android:versionName="1.0" >

<uses-sdk android:minSdkVersion="8" />

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

<application

android:icon="@drawable/ic_launcher"

android:label="@string/app_name" >

<receiver android:name="notification" >

<intent-filter >

<action android:name="android.provider.Telephony.SMS_RECEIVED"/>

</intent-filter>

</receiver>

<uses-library />

</application>

</manifest>