Question

我发现了许多与我的问题相关的帖子，但没有一个解决它。我再试一次。希望我的例子很简单，我没有忘记任何重要的事情。我有一个Fragment和一个内部类CameraPreview，派生自SurfaceView并实施SurfaceHolder.Callback。我想要实现的是绘制在CameraPreview全屏显示的相机预览之上。我认为在canvas = holder.lockCanvas()中调用surfaceCreated()会给我一个Canvas以供稍后绘制，但如果在mCanvas和{{之后调用null，则setPreviewDisplay()始终为startPreview() 1}}。如果尝试在这两个调用之前创建画布，我会得到一个画布，但应用程序会立即崩溃。

有人可以解释原因吗？

public class CameraFragment extends Fragment {
    final static String TAG = "CameraFragment";

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.fragment_native_camera, container, false);
        // Create our Preview view and set it as the content of our activity.
        safeCameraOpenInView(view);

        return view;
    }

    public void safeCameraOpenInView(View view) {
        FrameLayout preview;
        Camera camera = null;

        try {
            camera = Camera.open();
        } catch (Exception e) {
            e.printStackTrace();
        }

        if (camera != null) {
            mPreview = new CameraPreview(getActivity().getApplicationContext(), camera);
            if (view.findViewById(R.id.camera_preview) != null) {
                preview = (FrameLayout) view.findViewById(R.id.camera_preview);
                preview.addView(mPreview);
                Log.d(TAG, "view found and set");
            } else Log.d(TAG, "FrameLayout is null");
        } 
    }

    class CameraPreview extends SurfaceView implements SurfaceHolder.Callback {

        private Camera mCamera;
        private Canvas mCanvas;

        public CameraPreview(Context context, Camera camera) {
            super(context);
            // not sure the following is necessary
            setWillNotDraw(false);
            // do camera initialisation etc.
            mCamera = camera;
            // ...
        }

        public void surfaceCreated(SurfaceHolder holder) {
            // here's the problem: If I initialize the canvas
            // before setting the preview display and start previewing
            // I get a canvas but the app crashes immediately after
            // If I request the canvas afterwards it's simply null
            mCamera.setPreviewDisplay(holder);
            mCamera.startpreview();
            mCanvas = holder.lockCanvas();
            // mCanvas is null
            Log.d(TAG, "canvas: " + mCanvas);
        }
    }
}

在SurfaceView中调用holder.lockCanvas（）在surfaceCreated（）中

0 个答案: