概述

随着鸿蒙系统(HarmonyOS)的发展，许多开发者希望将现有的Flutter应用迁移到鸿蒙平台。由于鸿蒙系统兼容Android应用，Flutter Android View在鸿蒙系统上具有一定的可用性，但需要特别注意兼容性和适配问题。

1. 环境准备

1.1 开发环境要求

# 必需的开发工具
- DevEco Studio 3.0+
- Flutter SDK 3.0+
- OpenHarmony SDK
- Android SDK (用于编译Android View)

1.2 项目配置

在pubspec.yaml中添加必要的依赖：

dependencies:
  flutter:
    sdk: flutter
  android_view: ^0.1.0 # 或其他Android View插件

2. 基础使用方法

2.1 PlatformView创建

import 'package:flutter/material.dart';
import 'package:flutter/services.dart';

class AndroidViewExample extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: Text('Android View in HarmonyOS')),
      body: Container(
        width: double.infinity,
        height: 300,
        child: AndroidView(
          viewType: 'native-view-type',
          creationParams: <String, dynamic>{
            'param1': 'value1',
            'param2': 123,
          },
          creationParamsCodec: StandardMessageCodec(),
          onPlatformViewCreated: _onPlatformViewCreated,
        ),
      ),
    );
  }

  void _onPlatformViewCreated(int id) {
    // 获取MethodChannel进行通信
    final MethodChannel channel = MethodChannel('android_view_$id');
    channel.setMethodCallHandler((call) async {
      switch (call.method) {
        case 'viewEvent':
          print('Received event from Android View: ${call.arguments}');
          break;
        default:
          throw MissingPluginException();
      }
      return null;
    });
  }
}

2.2 Android原生代码 (PlatformViewFactory)

// MainActivity.java
public class MainActivity extends FlutterActivity {
    private static final String VIEW_TYPE = "native-view-type";

    @Override
    public void configureFlutterEngine(@NonNull FlutterEngine flutterEngine) {
        super.configureFlutterEngine(flutterEngine);
        
        // 注册PlatformView
        flutterEngine.getPlatformViewsController().getRegistry()
            .registerViewFactory(VIEW_TYPE, new NativeViewFactory());
    }
}

// NativeViewFactory.java
public class NativeViewFactory extends PlatformViewFactory {
    public NativeViewFactory() {
        super(StandardMessageCodec.INSTANCE);
    }

    @Override
    public PlatformView create(Context context, int viewId, Object args) {
        Map<String, Object> params = (Map<String, Object>) args;
        return new NativeView(context, viewId, params);
    }
}

// NativeView.java
public class NativeView implements PlatformView {
    private final FrameLayout frameLayout;
    private final TextView textView;
    private final int viewId;

    public NativeView(Context context, int viewId, Map<String, Object> params) {
        this.viewId = viewId;
        
        frameLayout = new FrameLayout(context);
        textView = new TextView(context);
        textView.setText("Hello from Android View!");
        textView.setTextSize(18);
        
        // 处理传入参数
        if (params.containsKey("param1")) {
            textView.append("\nParam1: " + params.get("param1"));
        }
        
        frameLayout.addView(textView);
        
        // 设置触摸事件
        setupTouchEvents();
    }

    private void setupTouchEvents() {
        textView.setOnTouchListener((v, event) -> {
            // 发送事件到Flutter
            sendEventToFlutter("touch_event", event.getX() + "," + event.getY());
            return true;
        });
    }

    private void sendEventToFlutter(String eventType, String data) {
        FlutterMain.ensureInitializationComplete(context, null);
        MethodChannel channel = new MethodChannel(
            Objects.requireNonNull(FlutterMain.getLookupKeyForAsset("flutter_assets")),
            "android_view_" + viewId
        );
        
        Handler handler = new Handler(Looper.getMainLooper());
        handler.post(() -> {
            try {
                channel.invokeMethod(eventType, data);
            } catch (Exception e) {
                Log.e("NativeView", "Failed to send event: " + e.getMessage());
            }
        });
    }

    @Override
    public View getView() {
        return frameLayout;
    }

    @Override
    public void dispose() {
        // 清理资源
    }
}

3. 鸿蒙系统特殊适配

3.1 权限配置

在AndroidManifest.xml中添加必要权限：

<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
<!-- 鸿蒙系统可能需要额外权限 -->
<uses-permission android:name="ohos.permission.USE_BLUETOOTH" />

3.2 鸿蒙兼容性处理

// HarmonyOSCompatibilityHelper.java
public class HarmonyOSCompatibilityHelper {
    
    public static boolean isHarmonyOS() {
        try {
            Class<?> cls = Class.forName("com.huawei.system.BuildEx");
            Method method = cls.getMethod("getOsBrand");
            return "harmony".equals(method.invoke(cls));
        } catch (Exception e) {
            return false;
        }
    }
    
    public static void applyHarmonyOptimizations(View view) {
        if (isHarmonyOS()) {
            // 鸿蒙系统特定的UI优化
            view.setLayerType(View.LAYER_TYPE_HARDWARE, null);
            
            // 设置渲染优先级
            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q) {
                view.setFrameRateCategory(Window.FRAME_RATE_CATEGORY_HIGH);
            }
        }
    }
}

3.3 生命周期适配

// 在NativeView中适配鸿蒙生命周期
public class NativeView implements PlatformView, ComponentCallbacks {
    // ... 其他代码
    
    @Override
    public void onConfigurationChanged(Configuration newConfig) {
        // 处理屏幕旋转等配置变化
        if (newConfig != null) {
            // 重新布局
            frameLayout.post(() -> {
                frameLayout.requestLayout();
            });
        }
    }
    
    @Override
    public void onLowMemory() {
        // 内存优化
        System.gc();
    }
}

4. 高级功能实现

4.1 混合渲染模式

// 在Flutter中使用Hybrid Composition
class HybridCompositionExample extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Column(
        children: [
          Expanded(
            child: AndroidView(
              viewType: 'hybrid-view',
              creationParams: {},
              creationParamsCodec: StandardMessageCodec(),
              layoutDirection: TextDirection.ltr,
            ),
          ),
          // Flutter UI与Android View混合
          Container(
            height: 100,
            color: Colors.blue,
            child: Center(child: Text('Flutter Widget')),
          ),
        ],
      ),
    );
  }
}

4.2 性能优化

// 性能监控和优化
public class PerformanceOptimizedView implements PlatformView {
    private long lastRenderTime = 0;
    private static final long RENDER_INTERVAL = 16; // 60fps
    
    @Override
    public View getView() {
        // 使用硬件加速
        frameLayout.setLayerType(View.LAYER_TYPE_HARDWARE, null);
        
        // 设置绘制回调监控性能
        frameLayout.getViewTreeObserver().addOnDrawListener(new ViewTreeObserver.OnDrawListener() {
            @Override
            public void onDraw() {
                long currentTime = System.currentTimeMillis();
                if (currentTime - lastRenderTime < RENDER_INTERVAL) {
                    // 跳过不必要的重绘
                    frameLayout.invalidate();
                }
                lastRenderTime = currentTime;
            }
        });
        
        return frameLayout;
    }
}

5. 常见问题与解决方案

5.1 渲染问题

问题: Android View在鸿蒙系统上渲染异常
解决方案:

// 强制使用硬件加速
frameLayout.setLayerType(View.LAYER_TYPE_HARDWARE, null);

// 检查鸿蒙系统版本并应用特定修复
if (isHarmonyOS()) {
    // 鸿蒙系统特定的渲染修复
    applyHarmonyRenderingFixes(frameLayout);
}

5.2 内存泄漏

问题: Android View导致内存泄漏
解决方案:

@Override
public void dispose() {
    // 移除所有监听器
    frameLayout.setOnTouchListener(null);
    textView.setOnClickListener(null);
    
    // 清理资源
    if (frameLayout.getHandler() != null) {
        frameLayout.getHandler().removeCallbacksAndMessages(null);
    }
    
    // 解除View引用
    frameLayout.removeAllViews();
}

5.3 通信延迟

问题: Flutter与原生通信延迟较高
解决方案:

// 使用二进制编解码器提高通信效率
final MethodChannel channel = MethodChannel(
  'android_view_$id',
  StandardMethodCodec(), // 或使用BinaryCodec
);

// 批量处理消息
void batchSendEvents(List<Map<String, dynamic>> events) {
  channel.invokeMethod('batch_events', events);
}

6. 测试与调试

6.1 真机调试

# 连接鸿蒙设备
flutter run -d <device-id>

# 查看日志
adb logcat | grep -i "flutter\|android_view"

6.2 性能分析

// 添加性能监控
class PerformanceMonitor {
  static void startMonitoring() {
    const platform = MethodChannel('performance_monitor');
    Timer.periodic(Duration(seconds: 5), (timer) async {
      try {
        final memoryUsage = await platform.invokeMethod('get_memory_usage');
        print('Memory usage: $memoryUsage');
      } catch (e) {
        print('Performance monitoring error: $e');
      }
    });
  }
}