Android Broadcast Receivers And Notifications Complete Guide

What are Android Broadcast Receivers?

Broadcast Receivers allow you to listen to and respond to system-wide broadcast announcements, such as changes in network connectivity, battery status, or even custom events broadcast within your app.

What are Notifications?

Notifications are messages that appear on the lock screen or within the notification shade, informing the user about events happening in your app or other apps.

Example: Creating a Simple App to Handle Broadcast and Show Notifications

Let's create a simple Android application that listens for a custom broadcast and shows a notification whenever that broadcast is received.

Step 1: Set Up Your Android Project

1. Create a new Android Project in Android Studio.
   • Open Android Studio.
   • Click "Start a new Android Studio project".
   • Choose "Empty Activity" and click "Next".
   • Name your application (e.g., BroadcastReceiverAndNotificationApp).
   • Choose a package name.
   • Set the Minimum SDK to API level 21 or above (Lollipop).
   • Click "Finish" to create the project.

Step 2: Define the Broadcast Receiver

Create a BroadcastReceiver to listen for a custom broadcast event.

1. Create a new Java class named MyBroadcastReceiver and extend BroadcastReceiver.

// MyBroadcastReceiver.java

package com.example.broadcastreceiverandnotificationapp;

import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import androidx.core.app.NotificationCompat;
import androidx.core.app.NotificationManagerCompat;

public class MyBroadcastReceiver extends BroadcastReceiver {
    private static final String CHANNEL_ID = "example_channel_id";

    @Override
    public void onReceive(Context context, Intent intent) {
        // Handle the broadcast intent here
        String action = intent.getAction();

        if (action != null && action.equals("com.example.CUSTOM_ACTION")) {
            // Show a notification
            showNotification(context);
        }
    }

    private void showNotification(Context context) {
        // Build the notification
        NotificationCompat.Builder builder = new NotificationCompat.Builder(context, CHANNEL_ID)
                .setSmallIcon(R.drawable.ic_notification)
                .setContentTitle("Broadcast Received")
                .setContentText("You have received a custom broadcast!")
                .setPriority(NotificationCompat.PRIORITY_DEFAULT);

        // Get the NotificationManager
        NotificationManagerCompat notificationManager = NotificationManagerCompat.from(context);

        // Notify the user
        notificationManager.notify(1, builder.build());
    }
}

2. Add an Icon for the Notification.
   • Add a PNG icon named ic_notification.png to the res/drawable folder.

Step 3: Register the BroadcastReceiver

You can register a BroadcastReceiver dynamically in code or statically in the AndroidManifest.xml.

Option 1: Register BroadcastReceiver Statically

1. Register the BroadcastReceiver in AndroidManifest.xml.

<!-- AndroidManifest.xml -->

<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/Theme.BroadcastReceiverAndNotificationApp">

    <activity
        android:name=".MainActivity"
        android:exported="true">
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />
            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>

    <!-- Register the BroadcastReceiver -->
    <receiver android:name=".MyBroadcastReceiver">
        <intent-filter>
            <action android:name="com.example.CUSTOM_ACTION" />
        </intent-filter>
    </receiver>

</application>

Option 2: Register BroadcastReceiver Dynamically (Optional)

1. Register the BroadcastReceiver in MainActivity.java at runtime.

// MainActivity.java

package com.example.broadcastreceiverandnotificationapp;

import android.content.Intent;
import android.content.IntentFilter;
import android.os.Bundle;
import androidx.appcompat.app.AppCompatActivity;

public class MainActivity extends AppCompatActivity {
    private MyBroadcastReceiver broadcastReceiver;

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

        // Create an instance of the BroadcastReceiver
        broadcastReceiver = new MyBroadcastReceiver();

        // Register the BroadcastReceiver
        IntentFilter intentFilter = new IntentFilter();
        intentFilter.addAction("com.example.CUSTOM_ACTION");
        registerReceiver(broadcastReceiver, intentFilter);
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();

        // Unregister the BroadcastReceiver
        unregisterReceiver(broadcastReceiver);
    }
}

Step 4: Create a Notification Channel

For Android Oreo (API level 26) and above, you must create a Notification Channel.

1. Create a method to create the notification channel.

// MainActivity.java

import androidx.core.app.NotificationChannelCompat;
import androidx.core.app.NotificationManagerCompat;

public class MainActivity extends AppCompatActivity {
    private static final String CHANNEL_ID = "example_channel_id";

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

        // Create the notification channel
        createNotificationChannel();

        // ... (Rest of the code)
    }

    private void createNotificationChannel() {
        if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.O) {
            CharSequence name = "Example Channel";
            String description = "This is an example notification channel";
            int importance = NotificationManagerCompat.IMPORTANCE_DEFAULT;

            NotificationChannelCompat channel = new NotificationChannelCompat.Builder(CHANNEL_ID, importance)
                    .setName(name)
                    .setDescription(description)
                    .build();

            NotificationManagerCompat notificationManager = NotificationManagerCompat.from(this);
            notificationManager.createNotificationChannel(channel);
        }
    }

    // ... (Rest of the code)
}

Step 5: Send the Custom Broadcast

You can send the custom broadcast from within your app to test the functionality.

1. Add a Button to the Main Activity layout to send the broadcast.

<!-- res/layout/activity_main.xml -->

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <Button
        android:id="@+id/sendBroadcastButton"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Send Broadcast"
        android:layout_centerInParent="true" />

</RelativeLayout>

2. Add a click listener to send the broadcast when the button is clicked.

// MainActivity.java

import android.view.View;
import android.widget.Button;

public class MainActivity extends AppCompatActivity {
    // ... (Previous code)

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

        // Create the notification channel
        createNotificationChannel();

        // Register the BroadcastReceiver
        IntentFilter intentFilter = new IntentFilter();
        intentFilter.addAction("com.example.CUSTOM_ACTION");
        registerReceiver(broadcastReceiver, intentFilter);

        // Send broadcast button
        Button sendBroadcastButton = findViewById(R.id.sendBroadcastButton);
        sendBroadcastButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                sendCustomBroadcast();
            }
        });
    }

    private void sendCustomBroadcast() {
        Intent intent = new Intent("com.example.CUSTOM_ACTION");
        sendBroadcast(intent);
    }

    // ... (Rest of the code)
}

Step 6: Test Your Application

1. Run the app on an emulator or a physical device.
2. Click the "Send Broadcast" button.
3. Check the notification shade to see the notification.

Summary

In this example, we created a BroadcastReceiver to listen for a custom broadcast action. When the broadcast is received, the app shows a notification. We registered the BroadcastReceiver in the AndroidManifest.xml and created a notification channel for devices running Android Oreo and above.