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把判断代码放到KeyDown事件中,KeyCode是这个事件的参数,在别的过程里无效。
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另外,要注意按键的接收对象,焦点在按钮则需要在按钮的KeyDown事件,或者设置窗体的KeyPreview=True,这样窗体总是能够接收到按键。
用API GetKeyboardState ,判断所有的键里哪些被按下了。
下面的是判断键盘灯的状态
Public Class NativeMethods
Private Shared keyState() As Byte
DllImport("user32.dll") _
Private Shared Function GetKeyboardState(ByVal keyState() As Byte) As Boolean
End Function
Private Shared Sub Update()
keyState = New Byte(256) {}
Dim result As Boolean = GetKeyboardState(keyState)
' Check for error:
If result = False Then
Debug.WriteLine("GetKeyBoardState error: " Marshal.GetLastWin32Error)
Throw New Exception("GetKeyBoardState error: " Marshal.GetLastWin32Error)
End If
End Sub
Public Enum LightState
Off
[On]
End Enum
' Example - the keyboard lights...
Public Shared ReadOnly Property CapsLockState() As LightState
Get
Update()
Dim isOn As Boolean = (keyState(Keys.CapsLock) = 1)
Return IIf(isOn, LightState.On, LightState.Off)
End Get
End Property
Public Shared ReadOnly Property NumLockState() As LightState
Get
Update()
Dim isOn As Boolean = (keyState(Keys.NumLock) = 1)
Return IIf(isOn, LightState.On, LightState.Off)
End Get
End Property
Public Shared ReadOnly Property ScrollLockState() As LightState
Get
Update()
Dim isOn As Boolean = (keyState(Keys.Scroll) = 1)
Return IIf(isOn, LightState.On, LightState.Off)
End Get
End Property
End Class
keypress事件响应一个键被按下,经常用法:
private sub控件名_keypress(keyascii as integer)
if keyascii=一个数 then语句
end sub
注意:要把keypreview属性设为true
窗体内检测按键
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
Me.KeyPreview = True '注册窗体的键盘事件
End Sub
在TextBox1中显示按键代码
Private Sub Form1_KeyDown(sender As Object, e As KeyEventArgs) Handles Me.KeyDown
TextBox1.Text = Str(e.KeyCode) + vbCrLf
End Sub
窗体没有焦点,用窗体监测键盘输入缓冲区可以解决,但这似乎可以用于监测用户输入内容,不要用于非法目的呀!所以就是知道也不会告诉你的。
如果是在自己的程序中,可以利用自身的按键事件,如果是全局键盘,那就要用到键盘hook技术了,比较复杂。
Private Sub Form_Load()
Label1.Caption = ""
Text1 = ""
End Sub
Private Sub Text1_KeyPress(KeyAscii As Integer)
If KeyAscii = 13 Then '回车键
Label1.Caption = 1
ElseIf KeyAscii = 8 Then '退格键
Label1.Caption = 2
Else '其他按键
Label1.Caption = 3
End If
Me.Cls
Print KeyAscii
End Sub