写一个UVCCamera的类，继承UVCCameraTextureView类上面扩展出一个类支持多点触碰支持放大缩小和旋转的类，并解决闪屏问题

好的，我来写一个继承自UVCCameraTextureView的支持多点触碰、放大缩小和旋转的类，并且解决闪屏问题。

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Matrix;
import android.graphics.PointF;
import android.util.AttributeSet;
import android.view.MotionEvent;

import com.serenegiant.usb.widget.UVCCameraTextureView;

public class MultiTouchUVCCameraTextureView extends UVCCameraTextureView {
    private static final int NONE = 0;
    private static final int DRAG = 1;
    private static final int ZOOM = 2;
    private static final int ROTATE = 3;
    private int mode = NONE;

    private PointF start = new PointF();
    private PointF mid = new PointF();
    private float oldDist = 1f;
    private float oldRotation = 0;

    private Matrix matrix = new Matrix();
    private Matrix savedMatrix = new Matrix();

    public MultiTouchUVCCameraTextureView(Context context) {
        super(context);
    }

    public MultiTouchUVCCameraTextureView(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    public MultiTouchUVCCameraTextureView(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
    }

    @Override
    public void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        canvas.drawBitmap(mBitmap, matrix, null);
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        switch (event.getAction() & MotionEvent.ACTION_MASK) {
            case MotionEvent.ACTION_DOWN:
                savedMatrix.set(matrix);
                start.set(event.getX(), event.getY());
                mode = DRAG;
                break;
            case MotionEvent.ACTION_POINTER_DOWN:
                oldDist = spacing(event);
                oldRotation = rotation(event);
                savedMatrix.set(matrix);
                midPoint(mid, event);
                mode = ZOOM;
                break;
            case MotionEvent.ACTION_MOVE:
                if (mode == DRAG) {
                    matrix.set(savedMatrix);
                    matrix.postTranslate(event.getX() - start.x, event.getY() - start.y);
                } else if (mode == ZOOM) {
                    float newDist = spacing(event);
                    float newRotation = rotation(event) - oldRotation;
                    float scale = newDist / oldDist;
                    matrix.set(savedMatrix);
                    matrix.postScale(scale, scale, mid.x, mid.y);
                    matrix.postRotate(newRotation, mid.x, mid.y);
                }
                break;
            case MotionEvent.ACTION_UP:
            case MotionEvent.ACTION_POINTER_UP:
                mode = NONE;
                break;
        }
        invalidate();
        return true;
    }

    private float spacing(MotionEvent event) {
        float x = event.getX(0) - event.getX(1);
        float y = event.getY(0) - event.getY(1);
        return (float) Math.sqrt(x * x + y * y);
    }

    private void midPoint(PointF point, MotionEvent event) {
        float x = event.getX(0) + event.getX(1);
        float y = event.getY(0) + event.getY(1);
        point.set(x / 2, y / 2);
    }

    private float rotation(MotionEvent event) {
        double delta_x = (event.getX(0) - event.getX(1));
        double delta_y = (event.getY(0) - event.getY(1));
        double radians = Math.atan2(delta_y, delta_x);
        return (float) Math.toDegrees(radians);
    }

    public void setBitmapMatrix(Matrix matrix) {
        this.matrix = matrix;
        invalidate();
    }
}

这个类实现了一个基本的多点触控的图片缩放、旋转和拖拽功能。同时，我们在onDraw()方法中绘制了一个Bitmap，并使用Matrix来控制它的缩放和旋转。最后，在setBitmapMatrix()方法中我们通过传入一个Matrix对象来更新Bitmap的矩阵，从而实现动态的缩放和旋转。

解决闪屏问题：

在UVCCameraTextureView的子类中，我们可以重写surfaceChanged()方法来解决闪屏问题。在surfaceChanged()中，我们可以重新计算预览画面的尺寸，然后调用setFixedSize()方法来设置TextureView的尺寸。这样，在每次预览画面尺寸改变时，我们都能够正确地显示预览画面。

@Override
public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
    if (mCamera == null) {
        return;
    }
    Camera.Parameters parameters = mCamera.getParameters();
    Camera.Size previewSize = parameters.getPreviewSize();
    float ratio = Math.max((float) width / previewSize.width, (float) height / previewSize.height);
    int newWidth = Math.round(previewSize.width * ratio);
    int newHeight = Math.round(previewSize.height * ratio);
    setFixedSize(newWidth, newHeight);
}