如何在android摄像头上画一条移动的线条？

public class CameraPreview extends SurfaceView implements SurfaceHolder.Callback {
    private SurfaceHolder mHolder;
    private Camera mCamera;
    private Paint mPaint;
    private int mLinePosition;

    public CameraPreview(Context context, Camera camera) {
        super(context);
        mCamera = camera;
        mHolder = getHolder();
        mHolder.addCallback(this);
        mPaint = new Paint();
        mPaint.setColor(Color.RED);
        mPaint.setStrokeWidth(5);
        mLinePosition = 0;
    }

    @Override
    public void surfaceCreated(SurfaceHolder holder) {
        try {
            mCamera.setPreviewDisplay(holder);
            mCamera.startPreview();
            startDrawingThread();
        } catch (IOException e) {
            Log.d("CameraPreview", "Error setting camera preview: " + e.getMessage());
        }
    }

    @Override
    public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
        if (mHolder.getSurface() == null) {
            return;
        }
        try {
            mCamera.stopPreview();
        } catch (Exception e) {
            Log.d("CameraPreview", "Error stopping camera preview: " + e.getMessage());
        }
        try {
            mCamera.setPreviewDisplay(mHolder);
            mCamera.startPreview();
        } catch (Exception e) {
            Log.d("CameraPreview", "Error starting camera preview: " + e.getMessage());
        }
    }

    @Override
    public void surfaceDestroyed(SurfaceHolder holder) {
        stopDrawingThread();
        mCamera.stopPreview();
        mCamera.release();
    }

    private void startDrawingThread() {
        new Thread(new Runnable() {
            @Override
            public void run() {
                while (true) {
                    Canvas canvas = mHolder.lockCanvas();
                    if (canvas != null) {
                        drawLine(canvas);
                        mHolder.unlockCanvasAndPost(canvas);
                    }
                    try {
                        Thread.sleep(100); // 控制线条移动速度
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                }
            }
        }).start();
    }

    private void stopDrawingThread() {
        // 停止线程
    }

    private void drawLine(Canvas canvas) {
        canvas.drawColor(Color.TRANSPARENT, PorterDuff.Mode.CLEAR); // 清空画布
        canvas.drawLine(0, mLinePosition, canvas.getWidth(), mLinePosition, mPaint);
        mLinePosition += 10; // 控制线条移动距离
        if (mLinePosition >= canvas.getHeight()) {
            mLinePosition = 0;
        }
    }
}

public class MainActivity extends AppCompatActivity {
    private Camera mCamera;
    private CameraPreview mPreview;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        mCamera = getCameraInstance();
        mPreview = new CameraPreview(this, mCamera);

        FrameLayout previewLayout = findViewById(R.id.camera_preview);
        previewLayout.addView(mPreview);
    }

    private Camera getCameraInstance() {
        Camera camera = null;
        try {
            camera = Camera.open();
        } catch (Exception e) {
            Log.d("MainActivity", "Error opening camera: " + e.getMessage());
        }
        return camera;
    }
}