Android MainLooper 未执行 Runnable

Question

应用简要说明：

我有 Cordova/Ionic 应用程序和用于本机代码执行的自定义 Cordova 插件。
插件包含单独的 CameraActivity（扩展 FragmentActivity）以与 Camera 一起使用（部分代码基于 Camera2Basic 示例）。
启动时 Activity 显示 AnaliseFragment，其中应用程序捕获每个相机帧并在后台线程上将图像传递给分析器。

执行步骤为：

用户按下 Cordova 上的按钮 UI
Cordova 通过 cordova.exec(..)
本机插件通过 cordova.startActivityForResult(..)
相机Activity 显示 AnaliseFragment
AnaliseFragment 使用两个表面启动相机捕获会话：第一个显示在 TextureView 上，第二个由 ImageAnaliser 分析

问题：

Rarely and randomly UI stops reacting on user and runnables not executed on UI thread. At the same time background threads continue working as normal: camera output is visible on TextureView and ImageAnaliser continue receive images from Camera.

有人对如何 find/debug 这种行为的原因有什么建议吗？或者有什么想法会导致这种情况？

我已经试过了：

记录每个生命周期事件 CameraActivity/AnaliseFragment = 应用程序正常状态和 ANR 之间没有调用
添加 WAKELOCK 以保持 Cordova MainActivity 存活 = 没有帮助
记录（跟踪）AnalilseFragment 和 ImageAnaliser 中的每个方法 = 没有可疑之处

这里是AnaliseFragment的简化代码：

public class AnaliseFragment extends Fragment {

private HandlerThread mBackgroundThread;
private Handler mBackgroundHandler;
private ImageAnalyser mImageAnalyser;

// listener is attached to camera capture session and receives every frame
private final ImageReader.OnImageAvailableListener mOnImageAvailableListener
    = new ImageReader.OnImageAvailableListener() {

    @Override
    public void onImageAvailable(ImageReader reader) {
        Image nextImage = reader.acquireLatestImage();
        mBackgroundHandler.post(() -> 
            try {
                mImageAnalyser.AnalizeNextImage(mImage);
            }
            finally {
                mImage.close();
            }
        );
    }
};

@Override
public void onViewCreated(final View view, Bundle savedInstanceState) {
    mImageAnalyser = new ImageAnalyser();
    mImageAnalyser.onResultAvailable(boolResult -> {
        // Runnable posted, but never executed
        new Handler(Looper.getMainLooper()).post(() -> reportToActivityAndUpdateUI(boolResult));
    });
}

@Override
public void onResume() {
    super.onResume();
    startBackgroundThread();
}

@Override
public void onPause() {
    stopBackgroundThread();
    super.onPause();
}

private void startBackgroundThread() {
    if (mBackgroundThread == null) {
        mBackgroundThread = new HandlerThread("MyBackground");
        mBackgroundThread.start();
        mBackgroundHandler = new Handler(mBackgroundThread.getLooper());
    }
}

private void stopBackgroundThread() {
    mBackgroundThread.quitSafely();
    try {
        mBackgroundThread.join();
        mBackgroundThread = null;
        mBackgroundHandler = null;
    } catch (InterruptedException e) {
        e.printStackTrace();
    }
}
}

ImageAnalyser 的简化代码：

public class ImageAnalyser  {

public interface ResultAvailableListener {
    void onResult(bool boolResult);
}
private ResultAvailableListener mResultAvailableListener;   
public void onResultAvailable(ResultAvailableListener listener) { mResultAvailableListener = listener; }

public void AnalizeNextImage(Image image) {
    // Do heavy analysis and put result into theResult
    mResultAvailableListener.onResult(theResult);
}
}

Answer 1

UI线程中有一些长运行操作。尝试 profile 您的应用，找出是什么阻塞了您的主线程。

Answer 2

经过数小时的性能分析、调试和代码审查，我发现

issue was caused by incorrect View invalidation from background thread

必须使用

View.postInvalidate() 方法 - 此方法检查 View 是否仍附加到 window 然后进行失效。相反，我在处理来自 MainLooper 的自定义消息时错误地使用了 View.invalidate()，这很少导致失败并使 MainLooper 停止处理更多消息。

对于那些可能有同样问题的人，我添加了正确和错误的代码。

正确：

public class GraphicOverlayView extends View { ... }

// Somewhere in background thread logic:

private GraphicOverlayView mGraphicOverlayView;

private void invalidateGraphicOverlayViewFromBackgroundThread(){
    mGraphicOverlayView.postInvalidate();
};

错误：

public class GraphicOverlayView extends View { ... }

// Somewhere in background thread logic:

private GraphicOverlayView mGraphicOverlayView;

private final int MSG_INVALIDATE_GRAPHICS_OVERLAY = 1;
private Handler mUIHandler = new Handler(Looper.getMainLooper()){
    @Override
    public void handleMessage(Message msg) {
        switch (msg.what) {
            case MSG_INVALIDATE_GRAPHICS_OVERLAY:{
                GraphicOverlayView overlay = (GraphicOverlayView)msg.obj;
                // Next line can cause MainLooper stop processing other messages
                overlay.invalidate();
                break;
            }
            default:
                super.handleMessage(msg);
        }
    }
};
private void invalidateGraphicOverlayViewFromBackgroundThread(){
    Message msg = new Message();
    msg.obj = mGraphicOverlayView;
    msg.what = MSG_INVALIDATE_GRAPHICS_OVERLAY;
    mUIHandler.dispatchMessage(msg);
};

Android MainLooper 未执行 Runnable

Android Runnable not executed by MainLooper

android

cordova

cordova-plugins

android-looper

android-threading