C# Signature:
[DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
private static extern bool RegisterHotKey(IntPtr hWnd, int id, KeyModifiers fsModifiers, Keys vk);
VB Signature:
Declare Function RegisterHotKeyaspx Lib "user32.dll" (TODO) As TODO
User-Defined Types:
None.
Alternative Managed API:
Do you know one? Please contribute it!
Notes:
None.
Tips & Tricks:
Please add some!
Sample Code:
Here is a helper class for easily adding a hotkey to WPF Windows.
Usage:
/// <summary>
/// Id's to disambiguate multiple hotkey registrations
/// </summary>
uint hotKey1, hotKey2;
// --------------------------------------------------------------------------
/// <summary>
/// Once we have a window handle, register for hot keys
/// </summary>
// --------------------------------------------------------------------------
protected override void OnSourceInitialized(EventArgs e)
{
base.OnSourceInitialized(e);
_hotKeys = new HotKeyHelper(this, HandleHotKey);
hotKey1 = _hotKeys.ListenForHotKey(System.Windows.Forms.Keys.F8, HotKeyModifiers.Control);
hotKey2 = _hotKeys.ListenForHotKey(System.Windows.Forms.Keys.F9, HotKeyModifiers.WindowsKey | HotKeyModifiers.Shift);
}
// --------------------------------------------------------------------------
/// <summary>
/// Hotkey handler. The keyId is the return value from ListenForHotKey()
/// </summary>
// --------------------------------------------------------------------------
void HandleHotKey(int keyId)
{
if (keyId == hotKey1)
{
// first hotkey was pressed
}
else if (keyId == hotKey2)
{
// second hotkey was pressed
}
}
Helper class:
/// <summary>
/// Simpler way to expose key modifiers
/// </summary>
[Flags]
public enum HotKeyModifiers
{
Alt = 1, // MOD_ALT
Control = 2, // MOD_CONTROL
Shift = 4, // MOD_SHIFT
WindowsKey = 8, // MOD_WIN
}
// --------------------------------------------------------------------------
/// <summary>
/// A nice generic class to register multiple hotkeys for your app
/// </summary>
// --------------------------------------------------------------------------
public class HotKeyHelper : IDisposable
{
// Required interop declarations for working with hotkeys
[DllImport("user32", SetLastError = true)]
[return: MarshalAs(UnmanagedType.Bool)]
public static extern bool RegisterHotKey(IntPtr hwnd, int id, uint fsModifiers, uint vk);
[DllImport("user32", SetLastError = true)]
public static extern int UnregisterHotKey(IntPtr hwnd, int id);
[DllImport("kernel32", SetLastError = true)]
public static extern short GlobalAddAtom(string lpString);
[DllImport("kernel32", SetLastError = true)]
public static extern short GlobalDeleteAtom(short nAtom);
public const int WM_HOTKEY = 0x312;
/// <summary>
/// The unique ID to receive hotkey messages
/// </summary>
public short HotkeyID { get; private set; }
/// <summary>
/// Handle to the window listening to hotkeys
/// </summary>
private IntPtr _windowHandle;
/// <summary>
/// Callback for hot keys
/// </summary>
Action<int> _onHotKeyPressed;
// --------------------------------------------------------------------------
/// <summary>
/// ctor
/// </summary>
// --------------------------------------------------------------------------
public HotKeyHelper(Window handlerWindow, Action<int> hotKeyHandler)
{
_onHotKeyPressed = hotKeyHandler;
// Create a unique Id for this class in this instance
string atomName = Thread.CurrentThread.ManagedThreadId.ToString("X8") + this.GetType().FullName;
HotkeyID = GlobalAddAtom(atomName);
// Set up the hook to listen for hot keys
_windowHandle = new WindowInteropHelper(handlerWindow).Handle;
if(_windowHandle == null)
{
throw new ApplicationException("Cannot find window handle. Try calling this on or after OnSourceInitialized()");
}
var source = HwndSource.FromHwnd(_windowHandle);
source.AddHook(HwndHook);
}
// --------------------------------------------------------------------------
/// <summary>
/// Intermediate processing of hotkeys
/// </summary>
// --------------------------------------------------------------------------
private IntPtr HwndHook(IntPtr hwnd, int msg, IntPtr wParam, IntPtr lParam, ref bool handled)
{
if (msg == WM_HOTKEY && wParam.ToInt32() == HotkeyID)
{
_onHotKeyPressed?.Invoke(lParam.ToInt32());
handled = true;
}
return IntPtr.Zero;
}
// --------------------------------------------------------------------------
/// <summary>
/// Tell what key you want to listen for. Returns an id representing
/// this particular key combination. Use this in your handler to
/// disambiguate what key was pressed.
/// </summary>
// --------------------------------------------------------------------------
public uint ListenForHotKey(Keys key, HotKeyModifiers modifiers)
{
RegisterHotKey(_windowHandle, HotkeyID, (uint)modifiers, (uint)key);
return (uint)modifiers | (((uint)key) << 16);
}
// --------------------------------------------------------------------------
/// <summary>
/// Stop listening for hotkeys
/// </summary>
// --------------------------------------------------------------------------
private void StopListening()
{
if (this.HotkeyID != 0)
{
UnregisterHotKey(_windowHandle, HotkeyID);
// clean up the atom list
GlobalDeleteAtom(HotkeyID);
HotkeyID = 0;
}
}
// --------------------------------------------------------------------------
/// <summary>
/// Dispose
/// </summary>
// --------------------------------------------------------------------------
public void Dispose()
{
StopListening();
}
}
