Part 3 – Custom Broadcasts

[embedyt] https://www.youtube.com/watch?v=qNocH6Angt0[/embedyt]

In part 3 of the BroadcastReceiver tutorial, we will send and receive an implicit custom broadcast with an intent action string that we define ourselves. The same as system broadcast our custom broadcast can contain extra data, which we add by calling putExtra on the intent and passing a value together with a name. We then pass our intent to the sendBroadcast method, which will send the broadcast immediately and trigger all BroadcastReceivers that were registered dynamically with the registerReceiver method.
To access the variables in our Activity, we can add the BroadcastReceiver as an inner class and update the UI in it’s onReceive method directly.

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Broadcast receiving app:

MainActivity.javaExampleBroadcastReceiver.javaAndroidManifest.xml

package com.codinginflow.broadcastexample;

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

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) {
        if ("com.codinginflow.EXAMPLE_ACTION".equals(intent.getAction())) {
            String receivedText = intent.getStringExtra("com.codinginflow.EXTRA_TEXT");
            Toast.makeText(context, receivedText, 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):

activity_main.xmlMainActivity.java

<?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.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity {
    private TextView textView;

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

        textView = findViewById(R.id.text_view);
    }

    public void sendBroadcast(View v) {
        Intent intent = new Intent("com.codinginflow.EXAMPLE_ACTION");
        intent.putExtra("com.codinginflow.EXTRA_TEXT", "Broadcast received");
        sendBroadcast(intent);
    }

    private BroadcastReceiver broadcastReceiver = new BroadcastReceiver() {
        @Override
        public void onReceive(Context context, Intent intent) {
            String receivedText = intent.getStringExtra("com.codinginflow.EXTRA_TEXT");
            textView.setText(receivedText);
        }
    };

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

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