registerBackgroundMessageHandler method

@override Future<void> registerBackgroundMessageHandler(BackgroundMessageHandler handler)

Registers a callback to handle background messages.

For Android this uses isolates and requires a top level function.

Implementation

@override
Future<void> registerBackgroundMessageHandler(
    BackgroundMessageHandler handler) async {
  _onBackgroundMessage = handler;

  if (defaultTargetPlatform != TargetPlatform.android) {
    return;
  }

  if (!_bgHandlerInitialized) {
    _bgHandlerInitialized = true;
    final CallbackHandle bgHandle =
        PluginUtilities.getCallbackHandle(_messagingCallbackDispatcher)!;
    final CallbackHandle userHandle =
        PluginUtilities.getCallbackHandle(handler)!;
    await methodChannel.invokeMethod(
      'AzNotificationHub.startBackgroundIsolate',
      {
        'pluginCallbackHandle': bgHandle.toRawHandle(),
        'userCallbackHandle': userHandle.toRawHandle(),
      },
    );
  }
}