Understanding Broadcast Receivers in Android

Thanks to Android's broadcast receiver components, applications can listen for system-wide broadcast notifications, such as low-power warnings or changes in network connectivity. By broadcasting bespoke events, they also allow apps to talk to each other.

What Are Broadcast Receivers?

A Broadcast Receiver is a component that responds to broadcast messages (intents) from other applications or the system itself. These messages can be:

1- System Broadcasts: Notifications like low battery, Wi-Fi state change, or screen turned off.

2- Custom Broadcasts: Messages that your app can send to notify other parts of the app or other apps.

Step 1: Creating a Simple Broadcast Receiver

Create a class that inherits BroadcastReceiver() to specify what the broadcast do

class MyBroadCast : BroadcastReceiver() {
    override fun onReceive(context: Context?, intent: Intent?) {

      val isTurnedOn = Settings.Global.getInt(
            context?.contentResolver,
            Settings.Global.AIRPLANE_MODE_ON
        ) != 0
        val x = if (isTurnedOn) "On" else "Off"
        Toast.makeText(context, "AirPlane mode is $x", Toast.LENGTH_LONG).show()

    }
}

**Step 2:Register the Receiver in Your Activity

There are to ways There are two ways to register a Broadcast Receiver: dynamically in code or statically in the AndroidManifest.xml.

1- Dynamically

class MainActivity : AppCompatActivity() {
  ......
private val myBroadCast = MyBroadCast()

 override fun onCreate(savedInstanceState: Bundle?) {
        .......
        registerReceiver(myBroadCast, IntentFilter(Intent.ACTION_AIRPLANE_MODE_CHANGED))
       
    }

    override fun onDestroy() {
        super.onDestroy()
        unregisterReceiver(myBroadCast)
    }

2- Staticlly

  <receiver
            android:name=".MyBroadCast"
            android:enabled="true"
            android:exported="true">
            <intent-filter>
                <action android:name="android.intent.action.AIRPLANE_MODE" />
            </intent-filter>
        </receiver>

When should you use static or dynamic ?

Easiest way is:

If you want your App to listen to the broadcast even when closed, Go for a Static Broadcast receiver.

If you want your App to listen only for certain instances (When the App is running) then go for Dynamic BroadCast Receiver

but static needs permission don't forget that