画布边界回弹实现

上个博文讲了用  WPF 基于Transform实现画布超出边界触发计算

触发了边界松手之后，实现超出边界的部分复位

1、在MouseMove的时候计算是否超出边界，用double resetX ，double resetY  记录需要复位的偏移量

 private void UIElement_OnMouseMove(object sender, MouseEventArgs e)
        {
            if(e.LeftButton!= MouseButtonState.Pressed || !isMouseDown) return;
            Point mousePoint = e.GetPosition(canvasGrid);

            var targetX = tranX + mousePoint.X - startPoint.X;
            var targetY = tranY + mousePoint.Y - startPoint.Y;

            trans.X = targetX;
            trans.Y = targetY;

            Console.WriteLine($"{trans.X}==={trans.Y}");

            //边界检测
            //缩放后的尺寸
            var scaleWidth = writeBorad.ActualWidth * scaleSize;
            var scaleHeight = writeBorad.ActualHeight * scaleSize;

            var gridWidth = canvasGrid.ActualWidth;
            var gridHeight = canvasGrid.ActualHeight;

            //x轴最小x坐标
            var minX = -(scaleWidth - gridWidth);

            //y轴最小坐标
            var minY = -(scaleHeight - gridHeight);


            double resetX = 0;
            double resetY = 0;

            //x轴左侧坐标越界,缓存到point点
            if (targetX > 0)
            {
                ////拖拽前在可拖动区域
                //if(trans.X<0)
                targetX = 0;
                resetX = targetX;
                isNeedResetX = true;
                Console.WriteLine("左侧越界了");
            }
           
            if (targetX < minX)
            {
                targetX = minX;
                resetX = targetX;
                isNeedResetX = true;
                Console.WriteLine("右侧越界了");
            }
            if (targetY > 0)
            {
                targetY = 0;
                resetY = targetY;
                isNeedResetY = true;
                Console.WriteLine("上侧越界了");
            }
            if (targetY < minY)
            {
                targetY = minY;
                resetY = targetY;
                Console.WriteLine("下侧越界了");
                isNeedResetY = true;
            }
            ResetPoint=new Point(resetX,resetY);

        }

   double resetX = 0;
   double resetY = 0;

 

2、在MouseUp的时候，检测判断是否需要执行复位的操作，重新设置TranslateTransform 的 X和Y的值，达到复位的效果

private void WriteBorad_OnMouseUp(object sender, MouseButtonEventArgs e)
        {

            AddElement(e.GetPosition(writeBorad));

            isMouseDown = false;
            writeBorad.ReleaseMouseCapture();

            if (isNeedResetX)
            {
                trans.X = ResetPoint.X;
            }

            if (isNeedResetY)
            {
                trans.Y = ResetPoint.Y;
            }

            isNeedResetY = isNeedResetX = false;
            ResetPoint =new Point();

            if (isNeedResetY || isNeedResetX)
            {
                Console.WriteLine($"{trans.X}==={trans.Y}");
            }
        }

 

想要集体的代码样例，请看：WPF 基于Transform实现画布超出边界触发计算