利用SendMessage实现窗口拖动
2024-10-01 23:47:40
利用SendMessage实现窗口拖动
周银辉
想想以前用跟踪鼠标位移的方式来实现窗口拖动的方式还真有些傻, 后来, .Net3.0以来的Window类内置了DragMove方法, 似乎让我们方便的不少, 但, 最近这个方法也不能满足需求了, 因为我需要DragMove过程中向外发事件来通知我"拖动开始了"和"拖动结束了", 可惜的是Window类没有提供者两个事件 (也曾企图通过其他方式来得到通知, 比如监视MouseUp等, 效果不好).
所以就自己来实现窗口拖动吧
不必同监视鼠标位移手动更新窗口位置, 其实通过向窗口发送SC_MOVE命令来移动窗口就可以了,这个命令会帮我们完成位置计算和更新工作:
public const int SC_MOVE = 0xf012;
public const int WM_SYSCOMMAND = 0x112;
public const int WM_LBUTTONUP = 0x202; [DllImport("user32.dll", CharSet = CharSet.Auto)]
public static extern IntPtr SendMessage(IntPtr hWnd, int msg, IntPtr wParam, IntPtr lParam); private static void DragAndMoveInner(IntPtr hwnd)
{
OnDragAndMoveStarted(hwnd); SendMessage(hwnd, WM_SYSCOMMAND, (IntPtr)SC_MOVE, IntPtr.Zero);
SendMessage(hwnd, WM_LBUTTONUP, IntPtr.Zero, IntPtr.Zero); OnDragAndMoveEnded(hwnd);
}
其中WM_SYSCOMMAND是说明向窗口发送指定的命名, 命令的具体值通过第3个参数传进去.
注意到上面在拖动结束时发送了一个WM_LBUTTONUP消息, 这是因为当鼠标左键按下(并移动)时我们会调用该函数来开始拖动,你的应用程序师可以检测到开始拖动前的这个MouseDown事件de, 但SC_MOVE会拦截MouseUp来结束拖动.你的应用程序监视不到这个MouseUp事件,所以你可能会发现鼠标左键Down和Up数目不配对, 所以在拖动结束时我们Mock了一个Up事件.
由于SendMessage 方法是不会立即返回的(同步的, SendMessageCallback 与 SendNotifyMessage 是立即放回的), 所以在SendMessage执行完毕时,也就是我们"拖动"操作完毕之时, 所以我们可以在这里调用OnDragAndMoveEnded(hwnd)来引发我们自定义的"拖动结束"事件
SendMessage第三个参数(wParam)可以包含的具体的指令值,可以参考下面的枚举:
public enum WM_SYSCOMMAND_WPARAM
{
SC_FIRST = 0xF000, // Sizes the window.
SC_SIZE = SC_FIRST, // Moves the window.
SC_MOVE = SC_FIRST + 0x10, // Minimizes the window.
SC_MINIMIZE = SC_FIRST + 0x20, // Maximizes the window.
SC_MAXIMIZE = SC_FIRST + 0x30, // Moves to the next window.
SC_NEXTWINDOW = SC_FIRST + 0x40, // Moves to the previous window.
SC_PREVWINDOW = SC_FIRST + 0x50, // Closes the window.
SC_CLOSE = SC_FIRST + 0x60, //Scrolls vertically
SC_VSCROLL = SC_FIRST + 0x70, // Scrolls horizontally.
SC_HSCROLL = SC_FIRST + 0x80, // Retrieves the window menu as a result of a mouse click.
SC_MOUSEMENU = SC_FIRST + 0x90, // Retrieves the window menu as a result of a keystroke.
// For more information, see the Remarks section.
SC_KEYMENU = SC_FIRST + 0x100,
SC_ARRANGE = SC_FIRST + 0x110, // Restores the window to its normal position and size.
SC_RESTORE = SC_FIRST + 0x120, // Activates the Start menu.
SC_TASKLIST = SC_FIRST + 0x130, // Executes the screen saver application specified
// in the [boot] section of the System.ini file.
SC_SCREENSAVE = SC_FIRST + 0x140, // Activates the window associated with the application-specified hot key.
// The lParam parameter identifies the window to activate.
SC_HOTKEY = SC_FIRST + 0x150, // Selects the default item;
// the user double-clicked the window menu.
SC_DEFAULT = SC_FIRST + 0x160, // Sets the state of the display.
// This command supports devices that have power-saving features,
// such as a battery-powered personal computer.
// The lParam parameter can have the following values:
// -1 - the display is powering on
// 1 - the display is going to low power
// 2 - the display is being shut off
SC_MONITORPOWER = SC_FIRST + 0x170,
// Changes the cursor to a question mark with a pointer.
// If the user then clicks a control in the dialog box,
// the control receives a WM_HELP message.
SC_CONTEXTHELP = SC_FIRST + 0x180, SC_SEPARATOR = 0xF00F
}
完整的代码,参考下面, 其支持WinForm和WPF 窗口:
public static class DragMoveExtention
{
public static event EventHandler DragAndMoveStarted;
public static event EventHandler DragAndMoveEnded; public const int SC_MOVE = 0xf012;
public const int WM_SYSCOMMAND = 0x112;
public const int WM_LBUTTONUP = 0x202; [DllImport("user32.dll", CharSet = CharSet.Auto)]
public static extern IntPtr SendMessage(IntPtr hWnd, int msg, IntPtr wParam, IntPtr lParam); private static void DragAndMoveInner(IntPtr hwnd)
{
OnDragAndMoveStarted(hwnd); SendMessage(hwnd, WM_SYSCOMMAND, (IntPtr)SC_MOVE, IntPtr.Zero);
SendMessage(hwnd, WM_LBUTTONUP, IntPtr.Zero, IntPtr.Zero); OnDragAndMoveEnded(hwnd);
} private static void OnDragAndMoveStarted(Object sender)
{
if(DragAndMoveStarted != null)
{
DragAndMoveStarted(sender, EventArgs.Empty);
}
} private static void OnDragAndMoveEnded(Object sender)
{
if(DragAndMoveEnded != null)
{
DragAndMoveEnded(sender, EventArgs.Empty);
}
} // use it like this:
// wpfWindow.MouseMove += delegate{ wpfWindow.DragAndMove(); };
public static void DragAndMove(this Window window)
{
if (Mouse.LeftButton == MouseButtonState.Pressed)
{
IntPtr hwnd = new WindowInteropHelper(window).Handle;
DragAndMoveInner(hwnd);
}
} // use it like this:
// winForm.MouseMove += delegate { winForm.DragAndMove(); };
public static void DragAndMove(this Form form)
{
if (Control.MouseButtons == MouseButtons.Left)
{
DragAndMoveInner(form.Handle);
}
}
}
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