Question

我正在尝试从onPreviewFrame（byte []数据，相机相机）获取数据。但它似乎没有奏效。你看到这段代码有什么问题吗？大部分内容直接来自http://developer.android.com/training/camera/cameradirect.html

public class UAVCamera extends Thread {

    Camera mCamera;
    CameraPreview mPreview;

    public UAVCamera(Context context) {
        mPreview = new CameraPreview(context);
    }

    @Override
    public void run() {
        safeCameraOpen();
        mPreview.setCamera(mCamera);
    }

    private boolean safeCameraOpen() {
        boolean qOpened = false;

        try {
            releaseCameraAndPreview();
            mCamera = Camera.open();
            qOpened = (mCamera != null);
        } catch (Exception e) {
            //Log.e(getString(R.string.app_name), "failed to open Camera");
            e.printStackTrace();
        }

        return qOpened;    
    }

    private void releaseCameraAndPreview() {
        mPreview.setCamera(null);
        if (mCamera != null) {
            mCamera.release();
            mCamera = null;
        }
    }
}

这是我的预览课程

class CameraPreview extends ViewGroup implements SurfaceHolder.Callback {

    SurfaceView mSurfaceView;
    SurfaceHolder mHolder;
    Camera mCamera;

    CameraPreview(Context context) {
        super(context);

        mSurfaceView = new SurfaceView(context);
        addView(mSurfaceView);

        // Install a SurfaceHolder.Callback so we get notified when the
        // underlying surface is created and destroyed.
        mHolder = mSurfaceView.getHolder();
        mHolder.addCallback(this);
        mHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
    }

    private void stopPreviewAndFreeCamera() {

        if (mCamera != null) {
            /*
              Call stopPreview() to stop updating the preview surface.
            */
            mCamera.stopPreview();

            /*
              Important: Call release() to release the camera for use by other applications. 
              Applications should release the camera immediately in onPause() (and re-open() it in
              onResume()).
            */
            mCamera.release();

            mCamera = null;
        }
    }

    public void setCamera(Camera camera) {
        if (mCamera == camera) { return; }

        stopPreviewAndFreeCamera();

        mCamera = camera;

        if (mCamera != null) {

            try {
                mCamera.setPreviewDisplay(mHolder);
            } catch (IOException e) {
                e.printStackTrace();
            }

            /*
              Important: Call startPreview() to start updating the preview surface. Preview must 
              be started before you can take a picture.
              */
            mCamera.startPreview();            
            mCamera.setPreviewCallback(new PreviewCallback() {

                  public void onPreviewFrame(byte[] data, Camera camera) {

                  }
                });
        }
    }

    @Override
    public void surfaceChanged(SurfaceHolder arg0, int arg1, int arg2, int arg3) {
        // TODO Auto-generated method stub

    }

    @Override
    public void surfaceCreated(SurfaceHolder arg0) {
        // TODO Auto-generated method stub

    }

    @Override
    public void surfaceDestroyed(SurfaceHolder arg0) {
        // TODO Auto-generated method stub

    }

    @Override
    protected void onLayout(boolean arg0, int arg1, int arg2, int arg3, int arg4) {
        // TODO Auto-generated method stub

    }
}

这是我的活动

public class MainActivity extends Activity {

    private UAVCamera uavCamera;    

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        uavCamera = new UAVCamera(this);
        uavCamera.start();
    }                           
}

我甚至不需要向用户显示图片。我只需要获取数据。有可能吗？我在onPreviewFrame（byte []数据，相机相机）上设置了一个断点，但它永远不会被击中。

Answer 1

你应该使用 setPreviewCallbackWithBuffer (Camera.PreviewCallback cb)代替setPreviewCallback。并使用addCallbackBuffer(byte[])

添加回调缓冲区

使用addCallbackBuffer(byte[])时，字节长度大于预览大小（宽度*高度）。然后，我认为您可以使用onPreviewFrame方法获取数据。

Answer 2

我按照http://developer.android.com/guide/topics/media/camera.html#custom-camera上的说明操作问题是我没有创建活动。我想将此作为服务运行，即使屏幕未打开也能获取此信息。不知道怎么做。

Android onPreviewFrame回调未被调用相机

2 个答案: