android - How to send and receive local broadcast

activity_main.xml

 <?xml version="1.0" encoding="utf-8"?> <RelativeLayout     xmlns:android="http://schemas.android.com/apk/res/android"     xmlns:tools="http://schemas.android.com/tools"     android:id="@+id/rl"     android:layout_width="match_parent"     android:layout_height="match_parent"     android:padding="10dp"     tools:context=".MainActivity"     android:background="#fdb571"     >     <TextView         android:id="@+id/tv"         android:layout_width="wrap_content"         android:layout_height="wrap_content"         android:textSize="20dp"         android:fontFamily="sans-serif-condensed"         />     <Button         android:id="@+id/btn_send"         android:layout_width="wrap_content"         android:layout_height="wrap_content"         android:text="Send Local Broadcast"         android:layout_below="@id/tv"         /> </RelativeLayout> 

MainActivity.java

 package com.cfsuman.me.androidcodesnippets;  import android.content.BroadcastReceiver; import android.content.Context; import android.content.Intent; import android.content.IntentFilter; import android.graphics.Color; import android.graphics.drawable.ColorDrawable; import android.support.v4.content.LocalBroadcastManager; import android.support.v7.app.AppCompatActivity; import android.os.Bundle; import android.view.View; import android.view.Window; import android.widget.Button; import android.widget.RelativeLayout; import android.widget.TextView; import android.widget.Toast;  import java.util.Random;   public class MainActivity extends AppCompatActivity {     private Context mContext;     private Random mRandom = new Random();      RelativeLayout mRelativeLayout;     private Button mButtonSend;     private TextView mTextView;      /*         BroadcastReceiver             Base class for code that will receive intents sent by sendBroadcast().              If we don't need to send broadcasts across applications, we can consider using this class with             LocalBroadcastManager instead of the more general facilities described below. This will             give us a much more efficient implementation (no cross-process communication needed)             and allow us to avoid thinking about any security issues related to other applications             being able to receive or send our broadcasts.     */      // Initialize a new BroadcastReceiver instance     private BroadcastReceiver mRandomNumberReceiver = new BroadcastReceiver() {         @Override         public void onReceive(Context context, Intent intent) {             // Get the received random number             int receivedNumber = intent.getIntExtra("RandomNumber",-1);              // Display a notification that the broadcast received             Toast.makeText(context,"Received : " + receivedNumber,Toast.LENGTH_SHORT).show();         }     };      @Override     protected void onCreate(Bundle savedInstanceState) {         // Request window feature action kafe         requestWindowFeature(Window.FEATURE_ACTION_BAR);         super.onCreate(savedInstanceState);         setContentView(R.layout.activity_main);          // Get the application context         mContext = getApplicationContext();          /*             LocalBroadcastManager                 Helper to register for and send broadcasts of Intents to local objects within your                 process. This is has a number of advantages over sending global broadcasts                 with sendBroadcast(Intent):                      We know that the data we are broadcasting won't leave our app, so don't need                         to worry about leaking private data.                      It is not possible for other applications to send these broadcasts to our app,                         so we don't need to worry about having security holes they can exploit.                      It is more efficient than sending a global broadcast through the system.         */          /*             public void registerReceiver (BroadcastReceiver receiver, IntentFilter filter)                 Register a receiver for any local broadcasts that match the given IntentFilter.              Parameters                 receiver : The BroadcastReceiver to handle the broadcast.                 filter : Selects the Intent broadcasts to be received.          */         // Register the local broadcast         LocalBroadcastManager.getInstance(mContext).registerReceiver(                 mRandomNumberReceiver,                 new IntentFilter("BROADCAST_RANDOM_NUMBER")         );          // Change the action kafe color         getSupportActionBar().setBackgroundDrawable(                 new ColorDrawable(Color.parseColor("#FFFF00BF"))         );          // Get the widgets reference from XML layout         mRelativeLayout = (RelativeLayout) findViewById(R.id.rl);         mButtonSend = (Button) findViewById(R.id.btn_send);         mTextView = (TextView) findViewById(R.id.tv);          // Set a click listener for send button         mButtonSend.setOnClickListener(new View.OnClickListener() {             @Override             public void onClick(View view) {                 // Generate a random number                 int randomNumber = mRandom.nextInt(500);                  // Initialize a new intent instance                 Intent intent = new Intent("BROADCAST_RANDOM_NUMBER");                 // Put the random number to intent to broadcast it                 intent.putExtra("RandomNumber",randomNumber);                  /*                     public boolean sendBroadcast (Intent intent)                         Broadcast the given intent to all interested BroadcastReceivers. This call                         is asynchronous; it returns immediately, and you will continue executing                         while the receivers are run.                      Parameters                         intent : The Intent to broadcast; all receivers matching this Intent                             will receive the broadcast.                 */                  // Send the broadcast                 LocalBroadcastManager.getInstance(mContext).sendBroadcast(intent);                  // Update the TextView with random number                 mTextView.setText("Random number generated : "                         + randomNumber                         + "\nApp also broadcast it."                 );             }         });     } }