KeyDown 事件未使用 .NET WinForms 触发? [英] KeyDown event not firing with .NET WinForms?

问题描述

我已经有 KeyPreview 在表单属性中设置为true

我正在开发一个小程序，但我遇到了一个问题，当我按下并释放任何箭头键时，它在分组框中的某些控件似乎没有触发表单上的 KeyDown 事件，只是KeyUp 事件.我的代码有什么问题可能导致这种情况吗?

I'm working on a small program, and I'm having a problem where it seems that some of the controls on it inside groupboxes are not triggering the KeyDown event on my form when I press and release any arrow key, just the KeyUp event. Is there something wrong with my code that might be causing this?

具体来说，我在表单上启用了 KeyPreview，并在两个子程序中的 e.SuppressKeyPress = True 上设置了断点，只有 frmMain_KeyUp 的一个断点.

Specifically, I've enabled KeyPreview on the form, and set breakpoints on e.SuppressKeyPress = True in both subroutines, and only the one for frmMain_KeyUp hits the breakpoint.

我添加了两个 GroupBox 事件，希望可以缓解这个问题，但没有这样的运气.但是，我在表单上有一个自定义控件，专门编码为忽略这些按键，并且代码按预期工作.

I added in the two GroupBox events hoping that might mitigate the issue, but no such luck. However, I have a custom control on the form that is specifically coded to ignore these keypresses, and the code works as expected on it.

  Private Sub frmMain_KeyDown(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyEventArgs) Handles Me.KeyDown, GroupBox1.KeyDown, GroupBox2.KeyDown
      e.SuppressKeyPress = True
      Select Case e.KeyCode
          Case Keys.Left
              ScrollDir = ScrollDir Or 1
          Case Keys.Right
              ScrollDir = ScrollDir Or 2
          Case Keys.Down
              ScrollDir = ScrollDir Or 4
          Case Keys.Up
              ScrollDir = ScrollDir Or 8
          Case Else
              e.SuppressKeyPress = False
      End Select
      tScroll.Enabled = True
      tScroll_Tick(Nothing, Nothing)
  End Sub

  Private Sub frmMain_KeyUp(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyEventArgs) Handles Me.KeyUp, GroupBox1.KeyUp, GroupBox2.KeyUp

      e.SuppressKeyPress = True
      Select Case e.KeyCode
          Case Keys.Left
              ScrollDir = ScrollDir And (Not 1)
          Case Keys.Right
              ScrollDir = ScrollDir And (Not 2)
          Case Keys.Down
              ScrollDir = ScrollDir And (Not 4)
          Case Keys.Up
              ScrollDir = ScrollDir And (Not 8)
          Case Else
              e.SuppressKeyPress = False
      End Select
      If ScrollDir = 0 Then tScroll.Enabled = False
  End Sub

用户控件中忽略"按键的代码如下:

The code in the user control that "ignores" keypresses is as such:

    Private Sub TileDropDown_KeyDown(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyEventArgs) Handles Me.KeyDown
        If e.KeyValue = 40 OrElse e.KeyValue = 38 OrElse e.KeyValue = 39 OrElse e.KeyValue = 37 Then

            e.SuppressKeyPress = True
        End If
    End Sub

推荐答案

某些控件在 keydown 事件中拦截箭头键，但在 keyup 事件中不拦截.一种解决方案是派生控件类并覆盖 ProcessCmdKey:

Some controls intercept the arrow keys in the keydown event, but not in the keyup event. One solution is to derive the control class and override ProcessCmdKey:

Protected Overrides Function ProcessCmdKey(ByRef msg As Message, ByVal keydata As Keys) As Boolean

If keydata = Keys.Right Or keydata = Keys.Left Or keydata = Keys.Up Or keydata = Keys.Down Then
  OnKeyDown(New KeyEventArgs(keydata))
  ProcessCmdKey = True
Else
  ProcessCmdKey = MyBase.ProcessCmdKey(msg, keydata)
  End If
End Function

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