请问为什么我用setPreviewCallback会黑屏呢？

[Tsou]

以下是onCreate部分...
这个程序是我用opencv一个例子程序改的,例子程序是

public abstract class CameraViewBase extends SurfaceView implements SurfaceHolder.Callback, Runnable 

因为我要加上手势操作..所以用xml写的布局文件.原来程序也运行没问题不会黑屏..不知道为什么移植改了一点就黑屏了。。

public void onCreate(Bundle savedInstanceState) 
    {
        super.onCreate(savedInstanceState);
        requestWindowFeature(Window.FEATURE_NO_TITLE);
        getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,WindowManager.LayoutParams.FLAG_FULLSCREEN);
        setContentView(R.layout.visionbase);
        VisionView = (SurfaceView) findViewById(R.id.VisionBaseView);
        VisionHolder = VisionView.getHolder();
        VisionHolder.addCallback(new Callback() 
        {
			public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) 
			{
				// TODO Auto-generated method stub
			}

			public void surfaceCreated(SurfaceHolder holder) 
			{
				// TODO Auto-generated method stub
				mCamera = Camera.open();
				Camera.Parameters params = mCamera.getParameters();

//	            List<Camera.Size> sizes = params.getSupportedPreviewSizes();
	            // selecting optimal camera preview size

	            params.setPreviewSize(VisionView.getWidth(), VisionView.getHeight());
	            mCamera.setParameters(params);

				try 
				{
					mCamera.setPreviewDisplay(null);
				} 
				
				catch (IOException e) 
				{
					// TODO Auto-generated catch block
					e.printStackTrace();
				}
				
	            mCamera.startPreview();
	            
		        mCamera.setPreviewCallback(new PreviewCallback() 
		        {
		            public void onPreviewFrame(byte[] data, Camera camera)
		            {
		                synchronized (this) 
		                {
		                    mFrame = data;
		                    this.notify();
		                }
		            }
		        });
//		        new Thread().start();
			}

			public void surfaceDestroyed(SurfaceHolder holder) 
			{
				// TODO Auto-generated method stub
				mThreadRun = false;
		        if (mCamera != null) 
		        {
		            synchronized (this) 
		            {
		                mCamera.stopPreview();
		                mCamera.setPreviewCallback(null);
		                mCamera.release();
		                mCamera = null;
		            }
		        }
			}
        	
        });

[maggiccrystal_3]

解决？