无法平移和缩放画布中的图像

Question

我正在尝试使用画布显示图像，该画布允许缩放和平移，但会阻止用户将图像平移到屏幕外。我已经能够停止平移，但是当图片缩放时，它会停止在图像边缘之前。我需要能够平移到图像的边缘，甚至放大。任何帮助将不胜感激。

我的代码显示图像，停止屏幕外平移和缩放：

    @Override
    public void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        canvas.save();

        if (mPosX < displayWidth - mIcon.getIntrinsicWidth()){
            mPosX = displayWidth - mIcon.getIntrinsicWidth();}
        if (mPosX > 0){
            mPosX = 0; }
        if (mPosY < displayHeight - mIcon.getIntrinsicHeight()){
            mPosY = displayHeight - mIcon.getIntrinsicHeight();}
        if (mPosY > 0){
            mPosY = 0; }

        canvas.translate(mPosX, mPosY);
        canvas.scale(mScaleFactor, mScaleFactor);
        mIcon.draw(canvas);
        canvas.restore();
    }

    private class ScaleListener extends ScaleGestureDetector.SimpleOnScaleGestureListener {
        @Override
        public boolean onScale(ScaleGestureDetector detector) {
            mScaleFactor *= detector.getScaleFactor();

            // Don't let the object get too small or too large.
            mScaleFactor = Math.max(0.42f, Math.min(mScaleFactor, 5.0f));

            invalidate();
            return true;
        }
    }

Answer 1

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