16 BroadCast Receiver using Manifest file

Broadcasts overview

Android apps can send or receive broadcast messages from the Android system and other Android apps, similar to the publish-subscribe design pattern. These broadcasts are sent when an event of interest occurs. For example, the Android system sends broadcasts when various system events occur, such as when the system boots up or the device starts charging. Apps can also send custom broadcasts, for example, to notify other apps of something that they might be interested in (for example, some new data has been downloaded).

Apps can register to receive specific broadcasts. When a broadcast is sent, the system automatically routes broadcasts to apps that have subscribed to receive that particular type of broadcast.

NOTE:

However, you must be careful not to abuse the opportunity to respond to broadcasts and run jobs in the background that can contribute to a slow system performance.

About system broadcasts

The system automatically sends broadcasts when various system events occur, such as when the system switches in and out of airplane mode. System broadcasts are sent to all apps that are subscribed to receive the event.

Following are some of the important system wide generated intents. 
1.android.intent.action.BATTERY_LOW : Indicates low battery condition on the device.
2.android.intent.action.BOOT_COMPLETED : This is broadcast once, after the system has   
    finished booting
3.android.intent.action.CALL : To perform a call to someone specified by the data4. 4.android.intent.action.DATE_CHANGED : The date has changed

       5.android.intent.action.REBOOT : Have the device 
       6.android.net.conn.CONNECTIVITY_CHANGE : The mobile network or wifi connection is changed(or reset)

Receiving broadcasts

Apps can receive broadcasts in two ways:

1) manifest-declared receivers

2) context-registered receivers.

Manifest-declared receivers

If you declare a broadcast receiver in your manifest, the system launches your app (if the app is not already running) when the broadcast is sent.

Program:

1) manifest-declared receivers:

open AndroidManifest.xml file and add the following code

<manifest xmlns:android="http://schemas.android.com/apk/res/android"    package="com.example.broadcastreceivers1">

<application

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

<receiver android:name=".MyBroadcast">

<intent-filter>

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

<action android:name="android.net.conn.CONNECTIVITY_CHANGED"/>

</intent-filter>

</receiver>

</application>

</manifest>

program:

import android.content.BroadcastReceiver;

import android.content.Context;

import android.content.Intent;

import android.net.ConnectivityManager;

import android.widget.Toast;

public class MyBroadcast extends BroadcastReceiver {

@Override

public void onReceive(Context context, Intent intent) {

if (Intent.ACTION_BOOT_COMPLETED.equals(intent.getAction())) {

Toast.makeText(context, "BOOT COMPLETED",

Toast.LENGTH_SHORT).show();

}

if (ConnectivityManager.CONNECTIVITY_ACTION.equals(intent.getAction())) {

Toast.makeText(context, "CONNECTIVITY CHANGED",

Toast.LENGTH_SHORT).show();

}

}

}

2) context-registered receivers.

package com.example.powerreceiver;

import android.content.IntentFilter;

import android.net.ConnectivityManager;

import android.support.v7.app.AppCompatActivity;

import android.os.Bundle;

public class MainActivity extends AppCompatActivity {

SampleBroad sbrd=new SampleBroad();

@Override    protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_main);

}

@Override    protected void onStart() {

super.onStart();

IntentFilter filter=new IntentFilter(ConnectivityManager.CONNECTIVITY_ACTION);

//filter.addAction(); to add more than one        registerReceiver(sbrd,filter);

}

@Override    protected void onStop() {

super.onStop();

unregisterReceiver(sbrd);

}

}

package com.example.powerreceiver;

import android.content.BroadcastReceiver;

import android.content.Context;

import android.content.Intent;

import android.net.ConnectivityManager;

import android.widget.Toast;

public class SampleBroad extends BroadcastReceiver {

@Override    public void onReceive(Context context, Intent intent) {

if(ConnectivityManager.CONNECTIVITY_ACTION.equals(intent.getAction()))

{

boolean c=intent.getBooleanExtra(ConnectivityManager.EXTRA_NO_CONNECTIVITY,false);

if(c)

Toast.makeText(context, " no Connectivity", Toast.LENGTH_SHORT).show();

else               Toast.makeText(context, " Connectivity", Toast.LENGTH_SHORT).show();

}

}

}