How do platform channels work and what are the failure modes?

A channel has a name and a codec. Dart invokes a method with arguments, the engine serialises the message, and the native handler replies on the platform thread. The call is asynchronous from Dart, but the native handler must not block the main thread for long or it will cause dropped frames and watchdog issues.

static const channel = MethodChannel('app.example/battery');

Future<int> batteryLevel() async {
  final level = await channel.invokeMethod<int>('getBatteryLevel');
  return level ?? -1;
}

class MainActivity : FlutterActivity() {
  private val channelName = "app.example/battery"

  override fun configureFlutterEngine(flutterEngine: FlutterEngine) {
    super.configureFlutterEngine(flutterEngine)
    MethodChannel(flutterEngine.dartExecutor.binaryMessenger, channelName)
      .setMethodCallHandler { call, result ->
        if (call.method == "getBatteryLevel") {
          result.success(87)
        } else {
          result.notImplemented()
        }
      }
  }
}

• MethodChannel is request-response; EventChannel is a native-to-Dart event stream
• StandardMethodCodec supports primitives, lists, maps and typed data, not arbitrary objects
• Return PlatformException with a code, message and details for failures
• Channel names must be unique and stable across releases
• Pigeon generates typed Dart, Kotlin, Swift and Objective-C bindings to reduce stringly-typed errors

Failure modes in production

A missing handler throws MissingPluginException, often because the plugin was not registered or the app was not rebuilt after adding native code. Version skew between Dart and native code produces mismatched arguments. Blocking the platform thread delays the reply and can freeze the UI. Background isolates cannot use channels without configuring the background messenger.