我正在使用Windows Forms在C#中构建一个桌面应用程序。我有一个自定义的控件,我希望能够将它拖放到我的应用程序中(而不是外部)。现在,我正在用通常的DoDragDrop/OnDragOver/OnDragDrop方法实现它。有没有办法在控件被拖来拖去时持续绘制它--就像您在JQuery的拖放中看到的那样?我希望实际的控件留在原地,但我希望在用户拖动它时绘制其外观的副本。理想情况下,副本甚至应该是半透明的,但这更像是一种“很好的拥有”。
我能想到的唯一方法就是将画图代码放在主窗体的OnPaint方法中,但这似乎是一个不太优雅的解决方案。还有其他想法吗?如果控件只将自己绘制为一个位图,事情会变得更简单吗?
发布于 2011-07-29 21:24:43
我想我应该回来自己回答这个问题,因为我最终确实让它工作了。
我创建了一个具有以下函数的CursorUtil类:
public struct IconInfo {
public bool fIcon;
public int xHotspot;
public int yHotspot;
public IntPtr hbmMask;
public IntPtr hbmColor;
}
public class CursorUtil {
[DllImport("user32.dll")]
public static extern IntPtr CreateIconIndirect(ref IconInfo icon);
[DllImport("user32.dll")]
[return: MarshalAs(UnmanagedType.Bool)]
public static extern bool GetIconInfo(IntPtr hIcon, ref IconInfo pIconInfo);
[DllImport("gdi32.dll")]
public static extern bool DeleteObject(IntPtr handle);
[DllImport("user32.dll", CharSet = CharSet.Auto)]
extern static bool DestroyIcon(IntPtr handle);
// Based on the article and comments here:
// http://www.switchonthecode.com/tutorials/csharp-tutorial-how-to-use-custom-cursors
// Note that the returned Cursor must be disposed of after use, or you'll leak memory!
public static Cursor CreateCursor(Bitmap bm, int xHotspot, int yHotspot) {
IntPtr cursorPtr;
IntPtr ptr = bm.GetHicon();
IconInfo tmp = new IconInfo();
GetIconInfo(ptr, ref tmp);
tmp.xHotspot = xHotspot;
tmp.yHotspot = yHotspot;
tmp.fIcon = false;
cursorPtr = CreateIconIndirect(ref tmp);
if (tmp.hbmColor != IntPtr.Zero) DeleteObject(tmp.hbmColor);
if (tmp.hbmMask != IntPtr.Zero) DeleteObject(tmp.hbmMask);
if (ptr != IntPtr.Zero) DestroyIcon(ptr);
return new Cursor(cursorPtr);
}
public static Bitmap AsBitmap(Control c) {
Bitmap bm = new Bitmap(c.Width, c.Height);
c.DrawToBitmap(bm, new Rectangle(0, 0, c.Width, c.Height));
return bm;
}
然后我写了一个Drag类(也不是面向对象的,但我认为在桌面应用程序中一次只能拖动一件事)。下面是其中一些代码:
public static void StartDragging(Control c) {
Dragged = c;
DisposeOldCursors();
Bitmap bm = CursorUtil.AsBitmap(c);
DragCursorMove = CursorUtil.CreateCursor((Bitmap)bm.Clone(), DragStart.X, DragStart.Y);
DragCursorLink = CursorUtil.CreateCursor((Bitmap)bm.Clone(), DragStart.X, DragStart.Y);
DragCursorCopy = CursorUtil.CreateCursor(CursorUtil.AddCopySymbol(bm), DragStart.X, DragStart.Y);
DragCursorNo = CursorUtil.CreateCursor(CursorUtil.AddNoSymbol(bm), DragStart.X, DragStart.Y);
//Debug.WriteLine("Starting drag");
}
// This gets called once when we move over a new control,
// or continuously if that control supports dropping.
public static void UpdateCursor(object sender, GiveFeedbackEventArgs fea) {
//Debug.WriteLine(MainForm.MousePosition);
fea.UseDefaultCursors = false;
//Debug.WriteLine("effect = " + fea.Effect);
if (fea.Effect == DragDropEffects.Move) {
Cursor.Current = DragCursorMove;
} else if (fea.Effect == DragDropEffects.Copy) {
Cursor.Current = DragCursorCopy;
} else if (fea.Effect == DragDropEffects.None) {
Cursor.Current = DragCursorNo;
} else if (fea.Effect == DragDropEffects.Link) {
Cursor.Current = DragCursorLink;
} else {
Cursor.Current = DragCursorMove;
}
}
您可以在设置控件时使用这些方法,例如在构造函数中:
GiveFeedback += new GiveFeedbackEventHandler(Drag.UpdateCursor);
在这种方法中:
protected override void OnMouseMove(MouseEventArgs mea) {
if (Drag.IsDragging(mea)) {
Drag.StartDragging(this);
DragDropEffects dde = DoDragDrop(Plan, DragDropEffects.Move | DragDropEffects.Copy);
Drag.StopDragging();
}
}
发布于 2014-07-09 07:04:31
这可能是一种选择:
private void btntarget_MouseDown(object sender, MouseEventArgs e)
{
Bitmap bmp = new Bitmap(btntarget.Width, btntarget.Height);
btntarget.DrawToBitmap(bmp, new Rectangle(Point.Empty, bmp.Size));
//optionally define a transparent color
bmp.MakeTransparent(Color.White);
Cursor cur = new Cursor(bmp.GetHicon());
Cursor.Current = cur;
}
光标的热点将在图像的中间创建
发布于 2010-07-14 03:58:55
这通常由GiveFeedback
事件处理。
https://stackoverflow.com/questions/3240603
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