Short answer
Platform channels rely on asynchronous message passing and binary serialization through the platform thread, while Dart FFI connects directly to C/C++ functions in shared memory synchronously and at the speed of native compiled code.
Explanation
In a MethodChannel, every call passes through: encoding the parameters with StandardMessageCodec, sending through the Flutter engine to the platform thread, decoding, executing the code in Java/Kotlin or Obj-C/Swift, and repeating the same cycle in the asynchronous return trip. This causes a bottleneck if the data transfer rate is huge (such as camera processing or Bluetooth streams). In contrast, Dart FFI (Foreign Function Interface) lets you manipulate pointers in memory and call functions of compiled libraries directly without any intermediary or serialization, making it ideal for signal processing, encryption algorithms, and images.
Code example
import 'dart:ffi';
import 'dart:io';
import 'package:flutter/services.dart';
typedef NativeAdd = Int32 Function(Int32, Int32);
typedef DartAdd = int Function(int, int);
// FFI: direct, synchronous call into C — no message serialization, no platform thread hop
final DynamicLibrary lib =
Platform.isAndroid ? DynamicLibrary.open('libnative.so') : DynamicLibrary.process();
final DartAdd nativeAdd = lib.lookupFunction<NativeAdd, DartAdd>('native_add');
// Platform channel: asynchronous, messages are serialized and handled on the platform thread
const channel = MethodChannel('com.example/math');
Future<void> demo() async {
final direct = nativeAdd(20, 22); // 42, immediately
final viaChannel = await channel.invokeMethod<int>('add', {'a': 20, 'b': 22}); // 42, later
debugPrint('$direct $viaChannel');
}Common mistakes
- Using MethodChannel to transfer high-resolution raw video frames, which puts heavy strain on memory bandwidth and makes the UI stutter.