写一个textureview多点触控，可以移动放大缩小图片和旋转的例子

好的，以下是一个简单的例子，演示了如何在TextureView上实现多点触控，包括移动、缩放和旋转图片：

public class MultiTouchTextureView extends TextureView {

    private static final int INVALID_POINTER_ID = -1;

    private Bitmap mBitmap;
    private Matrix mMatrix;

    private float mLastTouchX;
    private float mLastTouchY;
    private float mPosX;
    private float mPosY;

    private float mLastRotation;
    private float mRotation = 0f;

    private float mLastTouchDistance;
    private float mTouchCenterX;
    private float mTouchCenterY;

    private int mActivePointerId = INVALID_POINTER_ID;

    public MultiTouchTextureView(Context context) {
        super(context);
        init();
    }

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

    public MultiTouchTextureView(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        init();
    }

    private void init() {
        mMatrix = new Matrix();
        setSurfaceTextureListener(surfaceTextureListener);
    }

    private SurfaceTextureListener surfaceTextureListener = new SurfaceTextureListener() {
        @Override
        public void onSurfaceTextureAvailable(SurfaceTexture surfaceTexture, int width, int height) {
            // Load bitmap and set initial matrix
            mBitmap = BitmapFactory.decodeResource(getResources(), R.drawable.sample_image);
            mMatrix.setTranslate((getWidth() - mBitmap.getWidth()) / 2f, (getHeight() - mBitmap.getHeight()) / 2f);
            invalidate();
        }

        @Override
        public void onSurfaceTextureSizeChanged(SurfaceTexture surfaceTexture, int width, int height) {
            // Update matrix when view size changes
            mMatrix.setTranslate((getWidth() - mBitmap.getWidth()) / 2f, (getHeight() - mBitmap.getHeight()) / 2f);
            invalidate();
        }

        @Override
        public boolean onSurfaceTextureDestroyed(SurfaceTexture surfaceTexture) {
            // Release resources
            mBitmap.recycle();
            return true;
        }

        @Override
        public void onSurfaceTextureUpdated(SurfaceTexture surfaceTexture) {
            // Nothing to do
        }
    };

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        switch (event.getActionMasked()) {
            case MotionEvent.ACTION_DOWN:
            case MotionEvent.ACTION_POINTER_DOWN: {
                int pointerIndex = event.getActionIndex();
                float x = event.getX(pointerIndex);
                float y = event.getY(pointerIndex);
                mLastTouchX = x;
                mLastTouchY = y;
                mActivePointerId = event.getPointerId(pointerIndex);
                break;
            }
            case MotionEvent.ACTION_MOVE: {
                int pointerIndex = event.findPointerIndex(mActivePointerId);
                if (pointerIndex != -1) {
                    float x = event.getX(pointerIndex);
                    float y = event.getY(pointerIndex);

                    // Multi-touch drag
                    if (event.getPointerCount() > 1) {
                        float distance = getDistance(event);
                        if (mLastTouchDistance != 0f) {
                            float scale = distance / mLastTouchDistance;
                            mMatrix.postScale(scale, scale, mTouchCenterX, mTouchCenterY);
                        }
                        mLastTouchDistance = distance;

                        float centerX = getCenterX(event);
                        float centerY = getCenterY(event);
                        if (mTouchCenterX != 0f && mTouchCenterY != 0f) {
                            float translateX = centerX - mTouchCenterX;
                            float translateY = centerY - mTouchCenterY;
                            mMatrix.postTranslate(translateX, translateY);
                        }
                        mTouchCenterX = centerX;
                        mTouchCenterY = centerY;

                        // Multi-touch rotation
                        float rotation = getRotation(event);
                        if (mLastRotation != 0f) {
                            float angle = rotation - mLastRotation;
                            mMatrix.postRotate(angle, mTouchCenterX, mTouchCenterY);
                            mRotation += angle;
                        }
                        mLastRotation = rotation;
                    }
                    // Single-touch drag
                    else {
                        float dx = x - mLastTouchX;
                        float dy = y - mLastTouchY;
                        mMatrix.postTranslate(dx, dy);
                        mPosX += dx;
                        mPosY += dy;
                    }
                    mLastTouchX = x;
                    mLastTouchY = y;
                    invalidate();
                }
                break;
            }
            case MotionEvent.ACTION_UP:
            case MotionEvent.ACTION_POINTER_UP: {
                int pointerIndex = event.getActionIndex();
                int pointerId = event.getPointerId(pointerIndex);
                if (pointerId == mActivePointerId) {
                    // Reset values when the active pointer is lifted
                    mLastTouchDistance = 0f;
                    mLastRotation = 0f;
                    mTouchCenterX = 0f;
                    mTouchCenterY = 0f;
                    mActivePointerId = INVALID_POINTER_ID;
                }
                break;
            }
        }
        return true;
    }

    private float getDistance(MotionEvent event) {
        float dx = event.getX(0) - event.getX(1);
        float dy = event.getY(0) - event.getY(1);
        return (float) Math.sqrt(dx * dx + dy * dy);
    }

    private float getCenterX(MotionEvent event) {
        float x1 = event.getX(0);
        float x2 = event.getX(1);
        return (x1 + x2) / 2f;
    }

    private float getCenterY(MotionEvent event) {
        float y1 = event.getY(0);
        float y2 = event.getY(1);
        return (y1 + y2) / 2f;
    }

    private float getRotation(MotionEvent event) {
        float dx = event.getX(0) - event.getX(1);
        float dy = event.getY(0) - event.getY(1);
        return (float) Math.toDegrees(Math.atan2(dy, dx));
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        if (mBitmap != null) {
            canvas.drawBitmap(mBitmap, mMatrix, null);
        }
    }
}

在这个例子中，我们使用了一个Matrix对象来保存图像的变换信息，并在触摸事件的处理方法中更新Matrix对象。我们可以使用Matrix对象的postScale()、postTranslate()和postRotate()方法来实现缩放、移动和旋转操作。

注意，在多点触控中，我们需要使用MotionEvent对象的getX(int)、getY(int)、getPointerCount()、getPointerId(int)、findPointerIndex(int)等方法来获取各个触摸点的坐标和标识等信息。我们还需要使用数学公式来计算出触摸点的中心位置、距离和角度等信息。