Is it possible to send a custom broadcast message?

Yes, it is possible.

The method sendBroadcast() is used.

// Create an Intent for our broadcast
val intent = Intent("com.example.MY_CUSTOM_ACTION")

// Add extra data to the Intent (optional)
intent.putExtra("data_key", "some_value")

// Send the broadcast
sendBroadcast(intent)

To receive this message, you need to register a BroadcastReceiver.

Registration can be static (in the Manifest) or dynamic (in code using registerReceiver).

Example of dynamic registration:

// Create a Filter for our broadcast
val filter = IntentFilter("com.example.MY_CUSTOM_ACTION")

// Create a BroadcastReceiver
val receiver = object : BroadcastReceiver() {
    override fun onReceive(context: Context?, intent: Intent?) {
        // Handle the received message
        val receivedData = intent?.getStringExtra("data_key")
        Log.d("BroadcastReceiver", "Received custom broadcast with data: $receivedData")
    }
}

// Register the BroadcastReceiver
registerReceiver(receiver, filter)

// Don't forget to unregister when the component is destroyed
// unregisterReceiver(receiver)

Important points to consider:

• Explicit broadcast messages: Android 8.0 (API level 26) and above introduced restrictions on implicit broadcast messages to optimize resource consumption. For sending such messages in newer Android versions, it is often necessary to specify the recipient application's package (explicit broadcast).

  val intent = Intent("com.example.MY_CUSTOM_ACTION")
  // Specify the recipient package (if known)
  intent.setPackage("com.example.receiverapp")
  sendBroadcast(intent)
  

• Permissions: Sending and receiving broadcast messages with certain levels of protection (e.g., android.permission.SEND_SMS) may require appropriate permissions.
• Local broadcast messages: For transmitting messages only within a single application, it is recommended to use LocalBroadcastManager (now deprecated, other approaches like Flow or RxJava are recommended), which is more efficient and secure.

  // Sending a local broadcast
  val localIntent = Intent("com.example.MY_LOCAL_ACTION")
  LocalBroadcastManager.getInstance(this).sendBroadcast(localIntent)
  
  // Registering a local BroadcastReceiver
  val localReceiver = object : BroadcastReceiver() {
      override fun onReceive(context: Context?, intent: Intent?) {
          // Handle
      }
  }
  LocalBroadcastManager.getInstance(this).registerReceiver(localReceiver, IntentFilter("com.example.MY_LOCAL_ACTION"))
  
  // Unregister
  // LocalBroadcastManager.getInstance(this).unregisterReceiver(localReceiver)