Flutter调用Android原生组件仅首次生效，后续报MissingPluginException

核心问题分析 #

出现这个问题的关键原因有两个：

1. MethodChannel调用未返回结果：代码里注释了result.success()和result.notImplemented()，导致MethodChannel的调用会话一直处于挂起状态，后续再调用时通道无法正常响应。
2. FlutterEngine缓存与通道绑定的生命周期不匹配：缓存的FlutterEngine从原生Activity返回后，可能出现通道绑定失效的情况。

具体解决步骤 #

1. 修复MethodCall的结果返回（优先处理） #

Android端的MethodCallHandler里，必须保证每个方法调用都调用result的对应方法，否则会破坏通道的正常状态：

new MethodChannel(flutterEngine.getDartExecutor().getBinaryMessenger(), CHANNEL)
    .setMethodCallHandler((call, result) -> {
        if(call.method.equals("StartSecondActivity")){
            Intent intent = new Intent(MainActivity.this, IntentWedgeSample.class);
            startActivity(intent);
            // 必须返回结果，告知Flutter调用成功
            result.success("ActivityStarted");
        }else{
            // 未实现的方法要返回notImplemented
            result.notImplemented();
        }
    });

Dart端建议加上错误捕获，避免未处理异常：

try {
  String result = await _channel.invokeMethod('StartSecondActivity');
  print(result);
} on PlatformException catch (e) {
  print("调用失败: ${e.message}");
}

2. 调整FlutterEngine缓存的生命周期 #

代码里用了FlutterEngineCache缓存引擎，需要在Activity销毁时清理缓存，避免无效引擎被复用：
在MainActivity里重写cleanUpFlutterEngine方法：

@Override
public void cleanUpFlutterEngine(@NonNull FlutterEngine flutterEngine) {
    super.cleanUpFlutterEngine(flutterEngine);
    // 移除缓存的引擎
    FlutterEngineCache.getInstance().remove("bac_flutter_id");
}

如果确实需要复用引擎，在onCreate里检查缓存是否存在，再决定是否创建新引擎并重新绑定通道：

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    FlutterEngine cachedEngine = FlutterEngineCache.getInstance().get("bac_flutter_id");
    if (cachedEngine == null) {
        // 缓存不存在则创建新引擎并缓存
        FlutterEngine flutterEngine = new FlutterEngine(this);
        flutterEngine.getNavigationChannel().setInitialRoute("/waybill");
        FlutterEngineCache.getInstance().put("bac_flutter_id", flutterEngine);
        GeneratedPluginRegistrant.registerWith(flutterEngine);
        // 注册通道
        new MethodChannel(flutterEngine.getDartExecutor().getBinaryMessenger(), CHANNEL)
            .setMethodCallHandler((call, result) -> {
                if(call.method.equals("StartSecondActivity")){
                    Intent intent = new Intent(MainActivity.this, IntentWedgeSample.class);
                    startActivity(intent);
                    result.success("ActivityStarted");
                }else{
                    result.notImplemented();
                }
            });
    } else {
        // 复用缓存引擎，重新绑定通道确保可用
        new MethodChannel(cachedEngine.getDartExecutor().getBinaryMessenger(), CHANNEL)
            .setMethodCallHandler((call, result) -> {
                if(call.method.equals("StartSecondActivity")){
                    Intent intent = new Intent(MainActivity.this, IntentWedgeSample.class);
                    startActivity(intent);
                    result.success("ActivityStarted");
                }else{
                    result.notImplemented();
                }
            });
    }
}

3. 移除引擎复用（可选简单方案） #

如果不需要复用FlutterEngine，直接删掉FlutterEngineCache相关代码，让每次启动都创建新引擎，确保通道每次都正确注册：

@Override
public void configureFlutterEngine(@NonNull FlutterEngine flutterEngine) {
    super.configureFlutterEngine(flutterEngine);
    GeneratedPluginRegistrant.registerWith(flutterEngine);
    flutterEngine.getNavigationChannel().setInitialRoute("/waybill");
    // 删掉FlutterEngineCache的put代码
    new MethodChannel(flutterEngine.getDartExecutor().getBinaryMessenger(), CHANNEL)
        .setMethodCallHandler((call, result) -> {
            if(call.method.equals("StartSecondActivity")){
                Intent intent = new Intent(MainActivity.this, IntentWedgeSample.class);
                startActivity(intent);
                result.success("ActivityStarted");
            }else{
                result.notImplemented();
            }
        });
}

内容的提问来源于stack exchange，提问作者Rokudo