Android 缩放视图时，画布将被清除

我创建了一个应用程序。在那个应用程序中，我使用canavs实现了手指画。它工作得很好。但是当我缩放视图时，手指画被清除。如何避免这种情况。如果你有任何想法，请分享。提前谢谢 这是我的代码： 这是用来画手指的

PageView.Java:

@Override
        protected void onSizeChanged(int w, int h, int oldw, int oldh) {
            super.onSizeChanged(w, h, oldw, oldh);
            mBitmap = Bitmap.createBitmap(w, h, Bitmap.Config.ARGB_8888);
            mCanvas = new Canvas(mBitmap);
        }


        private float mX, mY;
        private static final float TOUCH_TOLERANCE = 4;

        private void touch_start(float x, float y) {
            mPath.reset();
            mPath.moveTo(x, y);
            mX = x;
            mY = y;
        }
        private void touch_move(float x, float y) {
            float dx = Math.abs(x - mX);
            float dy = Math.abs(y - mY);
            if (dx >= TOUCH_TOLERANCE || dy >= TOUCH_TOLERANCE) {
                mPath.quadTo(mX, mY, (x + mX)/2, (y + mY)/2);
                mX = x;
                mY = y;
            }
        }
        private void touch_up() {
            mPath.lineTo(mX, mY);
            // commit the path to our offscreen
            mCanvas.drawPath(mPath, MuPDFActivity.mPaint);
            // kill this so we don't double draw
            mPath.reset();
        }

        @Override
        public boolean onTouchEvent(MotionEvent event) 
        {
            if(MuPDFActivity.onDrawModeFlag == 1)
            {
                float x = event.getX();
                float y = event.getY();
                switch (event.getAction()) 
                {
                    case MotionEvent.ACTION_DOWN:
                        touch_start(x, y);
                        invalidate();
                        break;
                    case MotionEvent.ACTION_MOVE:
                        touch_move(x, y);
                        invalidate();
                        break;
                    case MotionEvent.ACTION_UP:
                        touch_up();

               }
                return true;
            }
            else
            {
                return false;
            }

        }

@Override
                    protected void onDraw(Canvas canvas) 
                    {
                        super.onDraw(canvas);
                        canvas.save();
                        //canvas.translate(mX, mY);
                        //canvas.scale(ReaderView.mScale, ReaderView.mScale);
                        System.out.println("On Canvas Calling");
                        canvas.drawBitmap(mBitmap, 0, 0, mBitmapPaint);
                        canvas.drawPath(mPath,MuPDFActivity.mPaint);
}

 MuPdfActivity:
             In activity oncreate function, I call the paint feautures
                mPaint.setAntiAlias(true);
        mPaint.setDither(true);
        mPaint.setColor(0xFFFF0000);
        mPaint.setStyle(Paint.Style.STROKE);
        mPaint.setStrokeJoin(Paint.Join.ROUND);
        mPaint.setStrokeCap(Paint.Cap.ROUND);
        mPaint.setStrokeWidth(12);
        mEmboss = new EmbossMaskFilter(new float[] { 1, 1, 1 },
                                           0.4f, 6, 3.5f);
        mBlur = new BlurMaskFilter(8, BlurMaskFilter.Blur.NORMAL);

---

我在触摸功能mPath.reset（）中删除了一行，找到了答案。然后我删除了touch\u start函数中的mPath.reset（）