Android 原生與Flutter交互 MethodChannel

參考網上案列flutter  model中獲取原生電量案例

Flutter代碼

main.dart頁面

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
　　//根據原生條裝過來的路由信息打開不同的flutter頁面
    home: getDefaultRouter(),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);

  final String title;

  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  int _counter = 0;

  void _incrementCounter() {
    setState(() {
      _counter++;
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            Text(
              'You have pushed the button this many times:',
            ),
            Text(
              '$_counter',
              style: Theme.of(context).textTheme.headline4,
            ),
          ],
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: _incrementCounter,
        tooltip: 'Increment',
        child: Icon(Icons.add),
      ), // This trailing comma makes auto-formatting nicer for build methods.
    );
  }
}


Widget getDefaultRouter(){
  String router = window.defaultRouteName;
  if (router == 'routerPage') {
    return BatteryWidget();
  } else {
    return MyHomePage();
  }
}

顯示獲取到電量的battery_widget.dart頁面

class BatteryWidget extends StatefulWidget {
  @override
  State<StatefulWidget> createState() {
    return new _BatteryWidgetState();
  }
}

class _BatteryWidgetState extends State<BatteryWidget> {
  String _batteryLevel = "Battery level: unknown.";
　
//samples.flutter.io/battery指定唯一標志字符串

  static const MethodChannel methodChannel =
      MethodChannel('samples.flutter.io/battery');

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            Text(_batteryLevel),
            RaisedButton(
              child: const Text('Refresh'),
              onPressed: _getBatteryLevel,
            ),
          ],
        ),
      ),
    );
  }

  Future<void> _getBatteryLevel() async {
    String batteryLevel;
    try {
　　　　//getBatteryLevel調用方法名，取值時需保持一致

      final int result = await methodChannel.invokeMethod('getBatteryLevel');
      batteryLevel = 'Battery level: $result%.';
    } on PlatformException {
      batteryLevel = 'Failed to get battery level.';
    }
    setState(() {
      _batteryLevel = batteryLevel;
    });
  }
}

Activity 代碼

public class MainActivity extends AppCompatActivity {
　　

　　//指定唯一標志字符串與flutter中保持一致

    private static final String BATTERY_CHANNEL = "samples.flutter.io/battery";

    TextView tv_btn;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        tv_btn = findViewById(R.id.tv_btn);

        //創建flutter發動機
        FlutterEngine flutterEngine = new FlutterEngine(MainActivity.this);
        //指定想要跳轉的flutter頁面 這里要和下圖對應上 記住他
        flutterEngine.getNavigationChannel().setInitialRoute("routerPage");
        flutterEngine.getDartExecutor().executeDartEntrypoint(DartExecutor.DartEntrypoint.createDefault());
        //這里做一個緩存 可以在適當的地方執行他 比如MyApp里 或者未跳轉flutterr之前 在flutter頁面執行前預加載
        FlutterEngineCache flutterEngineCache = FlutterEngineCache.getInstance();
        //緩存可以緩存好多個 以不同的的id區分
        flutterEngineCache.put("default_engine_id", flutterEngine);
        tv_btn.setOnClickListener(v -> {
            startActivity(FlutterActivity.withCachedEngine("default_engine_id").build(MainActivity.this));
        });
        //MethodChannel實現一
        new MethodChannel(new ShimPluginRegistry(flutterEngine).registrarFor(BATTERY_CHANNEL).messenger(), BATTERY_CHANNEL).setMethodCallHandler(
                new MethodChannel.MethodCallHandler() {
                    @Override
                    public void onMethodCall(MethodCall call, MethodChannel.Result result) {
　　　　　　　　　　　　　　　　//getBatteryLevel根據約定方名取值

                        if (call.method.equals("getBatteryLevel")) {
                            int batteryLevel = getBatteryLevel();

                            if (batteryLevel != -1) {
                                result.success(batteryLevel);
                            } else {
                                result.error("UNAVAILABLE", "Battery level not available.", null);
                            }
                        } else {
                            result.notImplemented();
                        }
                    }
                }
        );
        //MethodChannel實現二
//        ShimPluginRegistry shimPluginRegistry = new ShimPluginRegistry(flutterEngine);
//        FlutterPluginSendToAct flutterPluginSendToAct=new FlutterPluginSendToAct(MainActivity.this);
//        flutterPluginSendToAct.registerWith(shimPluginRegistry.registrarFor(BATTERY_CHANNEL));


    }
    private int getBatteryLevel() {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
            BatteryManager batteryManager = (BatteryManager) getSystemService(BATTERY_SERVICE);
            return batteryManager.getIntProperty(BatteryManager.BATTERY_PROPERTY_CAPACITY);
        } else {
            Intent intent = new ContextWrapper(getApplicationContext()).
                    registerReceiver(null, new IntentFilter(Intent.ACTION_BATTERY_CHANGED));
            return (intent.getIntExtra(BatteryManager.EXTRA_LEVEL, -1) * 100) /
                    intent.getIntExtra(BatteryManager.EXTRA_SCALE, -1);
        }
    }

    class FlutterPluginSendToAct implements MethodChannel.MethodCallHandler {

        MethodChannel channel;

        private Activity activity;

        private FlutterPluginSendToAct(Activity activity) {
            this.activity = activity;
        }

        public void registerWith(PluginRegistry.Registrar registrar) {
            channel = new MethodChannel(registrar.messenger(), BATTERY_CHANNEL);
            FlutterPluginSendToAct instance = new FlutterPluginSendToAct(registrar.activity());
            //setMethodCallHandler在此通道上接收方法調用的回調
            channel.setMethodCallHandler(instance);
        }

        @Override
        public void onMethodCall(@NonNull MethodCall call, @NonNull MethodChannel.Result result) {
            //接收來自flutter的指令
            if (call.method.equals("getBatteryLevel")) {//getBatteryLevel根據約定方名取值

                int batteryLevel = getBatteryLevel();
　　　　　　　　　　//將電量（實際情況可根據需要傳值）賦給result，可在flutter中調用

                if (batteryLevel != -1) {
                    result.success(batteryLevel);
                } else {
                    result.error("UNAVAILABLE", "Battery level not available.", null);
                }
            } else {
                result.notImplemented();
            }
        }
    }
}

以上即可在flutter中調用Android原生，並取值