Part 2 – Dynamic BroadcastReceiver

[embedyt] https://www.youtube.com/watch?v=11Oe40o8RJo[/embedyt]

In part 2 of the BroadcastReceiver tutorial, we will learn how to register a BroadcastReceiver dynamically. Instead of putting the receiver into the Manifest file, we register it in the lifecycle of our application. This way the BroadcastReceiver lives as long as the context where we register it in. This could be the application context itself, which would keep our BroadcastReceiver running as long as our app is running, but also for example the activity context or only as long as our app is in the foreground.
For this we have to call the registerReceiver method in any of the lifecycle callback methods (onCreate, onStart, onResume) and unregisterReceiver in their appropriate counterpart (onDestroy, onStop, onPause).
When we register our BroadcastReceiver, we also have to pass an IntentFilter, which specifies the action we are listening for.
Within the onReceive method of the BroadcastReceiver, we can also obtain data that is sent as an extra over the broadcast intent.

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MainActivity.javaExampleBroadcastReceiver.javaAndroidManifest.xml

package com.codinginflow.broadcastexample;

import android.content.IntentFilter;
import android.net.ConnectivityManager;
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);
    }

    @Override
    protected void onStart() {
        super.onStart();
        IntentFilter filter = new IntentFilter(ConnectivityManager.CONNECTIVITY_ACTION);
        registerReceiver(exampleBroadcastReceiver, filter);
    }

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

package com.codinginflow.broadcastexample;

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

public class ExampleBroadcastReceiver extends BroadcastReceiver {

    @Override
    public void onReceive(Context context, Intent intent) {
        if (ConnectivityManager.CONNECTIVITY_ACTION.equals(intent.getAction())) {
            boolean noConnectivity = intent.getBooleanExtra(
                    ConnectivityManager.EXTRA_NO_CONNECTIVITY, false
            );
            if (noConnectivity) {
                Toast.makeText(context, "Disconnected", Toast.LENGTH_SHORT).show();
            } else {
                Toast.makeText(context, "Connected", 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>