Wenn man Tastaturereignisse systemweit abhören möchte, benötigt man einen KeyboardHook, der in einer Standard DLL (zu erstellen z.B. mit C++) untergebracht sein muss. So wie ich Dein Anfrage verstehe, möchtest Du aber nur, dass Deine Anwendung bei einer bestimmten Tastenkombination in den Vordergrund geholt wird. Dafür kannst Du die API Funktion RegisterHotkey verwenden. Anbei eine Beispielimplementierung in VB.NET:
Imports System.Runtime.InteropServices
Public Class HotkeyControl
Inherits System.ComponentModel.Component
Private m_HotkeyWindow As HotkeyWindow
Public Event HotkeyPressed As KeyEventHandler
Public Sub New()
End Sub
Protected Overrides Sub Dispose(ByVal disposing As Boolean)
If m_HotkeyWindow IsNot Nothing Then
m_HotkeyWindow.UnregisterHotkeys()
m_HotkeyWindow.DestroyHandle()
m_HotkeyWindow = Nothing
End If
MyBase.Dispose(disposing)
End Sub
Friend Sub OnHotkey(ByVal hotkey As Keys)
Dim lKeyEvent As New KeyEventArgs(hotkey)
RaiseEvent HotkeyPressed(Me, lKeyEvent)
End Sub
Public Function RegisterHotkey(ByVal hotkey As Keys) As Boolean
If m_HotkeyWindow IsNot Nothing AndAlso m_HotkeyWindow.Contains(hotkey) Then
Throw New ArgumentException("Hotkey is already registered.")
End If
If m_HotkeyWindow Is Nothing Then
m_HotkeyWindow = New HotkeyWindow(Me)
End If
Return m_HotkeyWindow.RegisterHotkey(hotkey)
End Function
Public Sub UnregisterHotkey(ByVal hotkey As Keys)
If m_HotkeyWindow IsNot Nothing AndAlso Not m_HotkeyWindow.Contains(hotkey) Then
Throw New ArgumentException("Hotkey is not registered.")
End If
If m_HotkeyWindow IsNot Nothing Then
m_HotkeyWindow.UnregisterHotkey(hotkey)
End If
End Sub
Private Class HotkeyWindow
Inherits NativeWindow
Private m_Owner As HotkeyControl
Private m_Hotkeys As Dictionary(Of Keys, Integer)
Private m_LastID As Integer
Public Sub New()
m_Hotkeys = New Dictionary(Of Keys, Integer)
m_LastID = 0
End Sub
Public Sub New(ByVal owner As HotkeyControl)
Me.New()
m_Owner = owner
End Sub
Public Function Contains(ByVal hotkey As Keys) As Boolean
Return m_Hotkeys.ContainsKey(hotkey)
End Function
Protected Overridable Sub Create()
If Me.Handle = IntPtr.Zero Then
Dim lCP As New CreateParams()
lCP.Caption = Me.GetType().Name
lCP.Style = 0
lCP.ExStyle = 0
lCP.ClassStyle = 0
MyBase.CreateHandle(lCP)
End If
End Sub
Public Overrides Sub DestroyHandle()
Me.UnregisterHotkeys()
MyBase.DestroyHandle()
End Sub
Public Function RegisterHotkey(ByVal hotkey As Keys) As Boolean
Dim lResult As Integer
Dim lID As Integer
Dim lModifier As UInteger
Dim lVKey As UInteger = CType(hotkey And Not Keys.Modifiers, UInteger)
If (hotkey And Keys.Control) = Keys.Control Then
lModifier = NativeMethods.MOD_CONTROL
End If
If (hotkey And Keys.Alt) = Keys.Alt Then
lModifier = lModifier Or NativeMethods.MOD_ALT
End If
If (hotkey And Keys.Shift) = Keys.Shift Then
lModifier = lModifier Or NativeMethods.MOD_SHIFT
End If
lID = m_LastID + 1
If Me.Handle = IntPtr.Zero Then
Me.Create()
End If
lResult = NativeMethods.RegisterHotKey(Me.Handle, lID, lModifier, lVKey)
If CBool(lResult) Then
m_Hotkeys.Add(hotkey, lID)
m_LastID = lID
Return True
End If
End Function
Public Sub UnregisterHotkey(ByVal hotkey As Keys)
NativeMethods.UnregisterHotKey(Me.Handle, m_Hotkeys(hotkey))
m_Hotkeys.Remove(hotkey)
End Sub
Public Sub UnregisterHotkeys()
For Each item As KeyValuePair(Of Keys, Integer) In m_Hotkeys
NativeMethods.UnregisterHotKey(Me.Handle, item.Value)
Next
m_Hotkeys.Clear()
m_LastID = 0
End Sub
Public Function LoWord(ByVal value As Integer) As Integer
Return value And &HFFFF
End Function
Public Function HiWord(ByVal value As Integer) As Integer
Return (value And &HFFFF0000) \ &H10000
End Function
Protected Overrides Sub WndProc(ByRef m As System.Windows.Forms.Message)
If m.Msg = NativeMethods.WM_HOTKEY Then
Dim lHotkey As Keys
Dim lModifier As Integer = LoWord(m.LParam.ToInt32)
Dim lKey As Integer = HiWord(m.LParam.ToInt32)
If (lModifier And NativeMethods.MOD_CONTROL) = NativeMethods.MOD_CONTROL Then
lHotkey = Keys.Control
End If
If (lModifier And NativeMethods.MOD_ALT) = NativeMethods.MOD_ALT Then
lHotkey = lHotkey Or Keys.Alt
End If
If (lModifier And NativeMethods.MOD_SHIFT) = NativeMethods.MOD_SHIFT Then
lHotkey = lHotkey Or Keys.Shift
End If
lHotkey = lHotkey Or CType(lKey, Keys)
m_Owner.OnHotkey(lHotkey)
Else
MyBase.WndProc(m)
End If
End Sub
End Class
Friend Class NativeMethods
Public Const WM_HOTKEY As Integer = &H312
Public Const MOD_ALT As UInteger = &H1
Public Const MOD_CONTROL As UInteger = &H2
Public Const MOD_SHIFT As UInteger = &H4
Public Const MOD_WIN As UInteger = &H8
<DllImport("user32.dll")> _
Public Shared Function RegisterHotKey(ByVal hWnd As IntPtr, _
ByVal id As Integer, _
ByVal fsModifiers As UInteger, _
ByVal vk As UInteger) As Integer
End Function
<DllImport("user32.dll")> _
Public Shared Function UnregisterHotKey(ByVal hWnd As IntPtr, _
ByVal id As Integer) As Integer
End Function
End Class
End Class
Diese Komponente kannst Du jetzt entweder über den Designer zu Deinem Formular hinzufügen, oder wie folgt einbinden:
Public Class Form1
Friend WithEvents HotkeyControl1 As HotkeyControl
Private Sub Form1_Load(ByVal sender As System.Object, _
ByVal e As System.EventArgs) Handles MyBase.Load
HotkeyControl1 = New HotkeyControl()
HotkeyControl1.RegisterHotkey(Keys.M Or Keys.Control Or Keys.Shift)
HotkeyControl1.RegisterHotkey(Keys.MediaPlayPause)
End Sub
Private Sub HotkeyControl1_HotkeyPressed(ByVal sender As Object, _
ByVal e As System.Windows.Forms.KeyEventArgs _
) Handles HotkeyControl1.HotkeyPressed
MsgBox(String.Format("Modifier: {0} Key: {1}", e.Modifiers.ToString(), e.KeyCode.ToString()))
End Sub
End Class
Hier wird die Tastenkombination Strg+Umschalt+M, sowie die Start/Pause Taste (bei einigen Multimedia Tastaturen) für Deine Anwendung registriert. Natürlich nur solange, wie keine andere Anwendung schneller war und diese Tasten nicht selber registriert hat.
Thorsten Dörfler
Microsoft MVP Visual Basic
