Applies to: desktop apps only
Determines whether a key is up or down at the time the function is called, and whether the key was pressed after a previous call to GetAsyncKeyState.
Syntax
SHORT WINAPI GetAsyncKeyState( __in int vKey );
Parameters
- vKey [in]
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Type: int
The virtual-key code. For more information, see Virtual Key Codes.
You can use left- and right-distinguishing constants to specify certain keys. See the Remarks section for further information.
Return value
Type: SHORT
If the function succeeds, the return value specifies whether the key was pressed since the last call to GetAsyncKeyState, and whether the key is currently up or down. If the most significant bit is set, the key is down, and if the least significant bit is set, the key was pressed after the previous call to GetAsyncKeyState. However, you should not rely on this last behavior; for more information, see the Remarks.
The return value is zero for the following cases:
- The current desktop is not the active desktop
- The foreground thread belongs to another process and the desktop does not allow the hook or the journal record.
Remarks
The GetAsyncKeyState function works with mouse buttons. However, it checks on the state of the physical mouse buttons, not on the logical mouse buttons that the physical buttons are mapped to. For example, the call GetAsyncKeyState(VK_LBUTTON) always returns the state of the left physical mouse button, regardless of whether it is mapped to the left or right logical mouse button. You can determine the system's current mapping of physical mouse buttons to logical mouse buttons by calling GetSystemMetrics(SM_SWAPBUTTON).
which returns TRUE if the mouse buttons have been swapped.
Although the least significant bit of the return value indicates whether the key has been pressed since the last query, due to the pre-emptive multitasking nature of Windows, another application can call GetAsyncKeyState and receive the "recently pressed" bit instead of your application. The behavior of the least significant bit of the return value is retained strictly for compatibility with 16-bit Windows applications (which are non-preemptive) and should not be relied upon.
You can use the virtual-key code constants VK_SHIFT, VK_CONTROL, and VK_MENU as values for the vKey parameter. This gives the state of the SHIFT, CTRL, or ALT keys without distinguishing between left and right.
You can use the following virtual-key code constants as values for vKey to distinguish between the left and right instances of those keys.
| Code | Meaning |
|---|---|
| VK_LSHIFT | Left-shift key. |
| VK_RSHIFT | Right-shift key. |
| VK_LCONTROL | Left-control key. |
| VK_RCONTROL | Right-control key. |
| VK_LMENU | Left-menu key. |
| VK_RMENU | Right-menu key. |
These left- and right-distinguishing constants are only available when you call the GetKeyboardState, SetKeyboardState, GetAsyncKeyState, GetKeyState, and MapVirtualKey functions.
Requirements
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Minimum supported client | Windows 2000 Professional |
|---|---|
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Minimum supported server | Windows 2000 Server |
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Header |
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Library |
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DLL |
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See also
- Reference
- GetKeyboardState
- GetKeyState
- MapVirtualKey
- SetKeyboardState
- Conceptual
- Keyboard Input
- Other Resources
- GetSystemMetrics
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Build date: 3/6/2012
[DllImport("user32.dll", CharSet=CharSet.Auto, ExactSpelling=true)]
public static extern short GetAsyncKeyState(int vkey);
<DllImport("user32.dll", CharSet:=CharSet.Auto, ExactSpelling:=True)> Public Shared Function GetAsyncKeyState(ByVal vkey As Integer) As Short
End Function
Public Declare Function GetAsyncKeyState Lib "user32.dll" (ByVal vKey As Int32) As UShort
Usage:
Public Shared ReadOnly Property KeyStatus(ByVal Key As Keys) As Boolean
Get
If Key = Keys.LButton AndAlso My.Computer.Mouse.ButtonsSwapped Then
Key = Keys.RButton
ElseIf Key = Keys.RButton AndAlso My.Computer.Mouse.ButtonsSwapped Then
Key = Keys.LButton
End If
Return API.Devices.GetAsyncKeyState(Key) And &H8000US
End Get
End Property