c# - 在 Windows 窗体上拖动时调整矩形的大小

Question

我在我的 Windows 窗体上绘制了一个矩形，我想使用提供的 handle 之一调整它的大小!

Rectangle areaRect = new Rectangle(100,100, 300, 300);
Bool dragging = false;
Point ptOld = new Point(0, 0);

protected override void OnPaint(PaintEventArgs e)
{
  Graphics dcPaint = e.Graphics;
  dcPaint.DrawRectangle(rectPen, areaRect);
}

protected override void OnMouseDown(MouseEventArgs e)
{
  ptOld = new Point(e.X, e.Y);
  dragging = true;
}

protected override void OnMouseMove(MouseEventArgs e)
{
  if(dragging = true) 
  {
    Point ptNew = new Point(e.X, e.Y);
    Int32 handleSelected = GetSelectedHandle(ptNew);

   // Lets say I want to resize this rectangle using Handle 2 now.
    if(handleSelected == 2) 
    {
      // I am resizing this rectangle Width
      areaRect.X += ptNew.X - ptOld.X;
      areaRect.Width -= ptNew .X - ptOld.X;

      this.Invalidate();
    }
  }
}

protected override void OnMouseUp(MouseEventArgs e)
{
  dragging = false;
}

它会给我这样的效果。哪个是正确的，

我怎么想对此进行一些小的调整，我也想改变这个矩形的高度，当我移动点 2 时，我的点 7 应该保持原样，像这样.. .同样，当我移动第 4 点时，第 5 点应该完好无损，第 7 点和第 2 点也是如此。

任何想法，如何进行，因为如果我改变高度，我的第 7 点位置也会改变？

Answer 1

像这样在 MouseMove 上绘图在 WinForms 中不会很流畅。

在调整矩形大小之前，您基本上需要引用该矩形。

我添加了以下代码来跟踪矩形和 8 个可拖动点:

private Point GetHandlePoint(int value) {
  Point result = Point.Empty;

  if (value == 1)
    result = new Point(areaRect.Left, areaRect.Top);
  else if (value == 2)
    result = new Point(areaRect.Left, areaRect.Top + (areaRect.Height / 2));
  else if (value == 3)
    result = new Point(areaRect.Left, areaRect.Bottom);
  else if (value == 4)
    result = new Point(areaRect.Left + (areaRect.Width / 2), areaRect.Top);
  else if (value == 5)
    result = new Point(areaRect.Left + (areaRect.Width / 2), areaRect.Bottom);
  else if (value == 6)
    result = new Point(areaRect.Right, areaRect.Top);
  else if (value == 7)
    result = new Point(areaRect.Right, areaRect.Top + (areaRect.Height / 2));
  else if (value == 8)
    result = new Point(areaRect.Right, areaRect.Bottom);

  return result;
}

private Rectangle GetHandleRect(int value) {
  Point p = GetHandlePoint(value);
  p.Offset(-2, -2);
  return new Rectangle(p, new Size(5, 5));
}

以下是我如何修改您的表单代码:

private Rectangle areaRect = new Rectangle(100, 100, 300, 300);
private Rectangle oldRect;
private int dragHandle = 0;
private Point dragPoint;

public Form1() {
  InitializeComponent();
  this.DoubleBuffered = true;
}

protected override void OnMouseDown(MouseEventArgs e) {
  for (int i = 1; i < 9; i++) {
    if (GetHandleRect(i).Contains(e.Location)) {
      dragHandle = i;
      oldRect = areaRect;
      dragPoint = GetHandlePoint(i);
    }
  }
  base.OnMouseDown(e);
}

protected override void OnMouseMove(MouseEventArgs e) {
  if (dragHandle == 1) {
    // to do
  } else if (dragHandle == 2) {
    int diff = dragPoint.X - e.Location.X;
    areaRect = new Rectangle(oldRect.Left - diff, oldRect.Top, oldRect.Width + diff, oldRect.Height);
  } else if (dragHandle == 7) {
    int diff = dragPoint.X - e.Location.X;
    areaRect = new Rectangle(oldRect.Left, oldRect.Top, oldRect.Width - diff, oldRect.Height);
  }

  if (dragHandle > 0)
    this.Invalidate();

  base.OnMouseMove(e);
}

protected override void OnMouseUp(MouseEventArgs e) {
  dragHandle = 0;
  base.OnMouseUp(e);
}

protected override void OnPaint(PaintEventArgs e) {
  e.Graphics.DrawRectangle(Pens.Red, areaRect);
  for (int i = 1; i < 9; i++) {
    e.Graphics.FillRectangle(Brushes.DarkRed, GetHandleRect(i));
  }
  base.OnPaint(e);
}

发布的代码仅执行第 2 点和第 7 点，但这应该会给您一些逻辑来处理。我确信这段代码可以改进，它只是一个工作示例。