Part 7 – LocalBroadcastManager

[embedyt]https://www.youtube.com/watch?v=rLOuFHkHSJI[/embedyt]

In part 7 of the BroadcastReceiver tutorial, we will learn how to use the LocalBroadcastManager.
The LocalBroadcastManager is a support library class that can register for and send broadcasts within a single app process. While normal broadcasts and broadcast receivers are open to the whole system, local broadcasts don’t leave the app and therefore don’t require any permissions. This is not only more secure, but also more efficient.
The LocalBroadcastManager can only register BroadcastReceivers dynamically in Java code with the registerReceiver and unregisterReceiver methods and an IntentFilter. Manifest-registered, static receivers are not supported. This also means that these receivers cannot be triggered with explicit broadcasts, but only with implicit intent actions.

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Broadcast receiving app:

MainActivity.javaExampleBroadcastReceiver.javaAndroidManifest.xml

package com.codinginflow.broadcastexample;

import android.content.IntentFilter;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;

public class MainActivity extends AppCompatActivity {
    ExampleBroadcastReceiver exampleBroadcastReceiver = new ExampleBroadcastReceiver();

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        IntentFilter filter = new IntentFilter("com.codinginflow.EXAMPLE_ACTION");
        registerReceiver(exampleBroadcastReceiver, filter);
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        unregisterReceiver(exampleBroadcastReceiver);
    }
}

package com.codinginflow.broadcastexample;

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

public class ExampleBroadcastReceiver extends BroadcastReceiver {

    @Override
    public void onReceive(Context context, Intent intent) {
        Toast.makeText(context, "EBR triggered", Toast.LENGTH_SHORT).show();
    }
}

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.codinginflow.broadcastexample">

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

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

</manifest>

Broadcast sending app (BroadcastSender):

ExampleBroadcastReceiver2.javaAndroidManifest.xmlactivity_main.xmlMainActivity.java

package com.codinginflow.broadcastsender;

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

public class ExampleBroadcastReceiver2 extends BroadcastReceiver {

    @Override
    public void onReceive(Context context, Intent intent) {
        Toast.makeText(context, "EBR2 triggered", Toast.LENGTH_SHORT).show();
    }
}

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.codinginflow.broadcastsender">

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

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

</manifest>

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:gravity="center"
    android:orientation="vertical"
    android:padding="16dp"
    tools:context=".MainActivity">

    <TextView
        android:id="@+id/text_view"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Message"
        android:textSize="20sp" />

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:onClick="sendBroadcast"
        android:text="Send Broadcast" />

</LinearLayout>

package com.codinginflow.broadcastsender;

import android.content.Intent;
import android.content.IntentFilter;
import android.os.Bundle;
import android.support.v4.content.LocalBroadcastManager;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity {
    private TextView textView;
    private ExampleBroadcastReceiver2 exampleBroadcastReceiver2 = new ExampleBroadcastReceiver2();
    private LocalBroadcastManager localBroadcastManager;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        textView = findViewById(R.id.text_view);

        localBroadcastManager = LocalBroadcastManager.getInstance(this);
    }

    public void sendBroadcast(View v) {
        Intent intent = new Intent("com.codinginflow.EXAMPLE_ACTION");

        localBroadcastManager.sendBroadcast(intent);
    }

    @Override
    protected void onStart() {
        super.onStart();
        IntentFilter filter = new IntentFilter("com.codinginflow.EXAMPLE_ACTION");
        localBroadcastManager.registerReceiver(exampleBroadcastReceiver2, filter);
    }

    @Override
    protected void onStop() {
        super.onStop();
        localBroadcastManager.unregisterReceiver(exampleBroadcastReceiver2);
    }
}