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从文本框继承的VB.NET自定义控件不会激发绘制事件

custom-controls vb.net

vulkanino · 技术社区 · 14 年前

我需要一个总是被禁用的多行文本框,但它不应该用灰色来绘制自己,但我想让它的设计者选择颜色。

我以前对一个总是黑的标签(没有多行)有同样的要求,所以我继承了标签,比如:

Imports System.ComponentModel

   Public Class LabelDisabled
        Inherits Label

        Sub New()
            InitializeComponent()
            Enabled = False
        End Sub

        Protected Overrides Sub OnPaint(ByVal e As System.Windows.Forms.PaintEventArgs)
            ' always draw it black
            e.Graphics.DrawString(Me.Text, Me.Font, Brushes.Black, 0, 0)
        End Sub

    End Class

那很好。现在我想要相同的东西,但是有多行标签,所以我选择从文本框继承:

Imports System.ComponentModel

Public Class CustomControl1
    Inherits TextBox

    Sub New()

        InitializeComponent()
        'Paint never fires anyway
        'Enabled = False
    End Sub


    Protected Overrides Sub OnPaint(ByVal e As System.Windows.Forms.PaintEventArgs)
        Dim brush As New SolidBrush(Me.ForeColor)
        e.Graphics.DrawString(Me.Text, Me.Font, brush, 0, 0)
    End Sub

End Class

现在,从不在CustomControl1-文本框继承-控件中激发绘制事件。

为什么我不能参加绘画活动?

另外,如果我想使启用的属性不可见并且用户无法设置,我会:

<Browsable(False),
DefaultValue(False)>
Public Overloads Property Enabled As Boolean
    Get
        Return False
    End Get
    Set(ByVal value As Boolean)
    End Set
End Property

但是这样,我也不能设置“real”启用的属性,我的意思是支持字段。

2 回复 | 直到 13 年前

vulkanino 14 年前

我找到了解决办法。它看起来像是一个文本框,即使对于子类也禁用了paint事件。但您可以强制wm_paint位调用setStyle:

Public Class DisabledTextBox
    Inherits TextBox

    Public Sub New()
        InitializeComponent()

        Enabled = False
        SetStyle(ControlStyles.Selectable, False)
        SetStyle(ControlStyles.UserPaint, True)

    End Sub

    Protected Overrides Sub OnPaint(ByVal e As System.Windows.Forms.PaintEventArgs)
        Dim brush As New SolidBrush(Me.ForeColor)
        e.Graphics.DrawString(Me.Text, Me.Font, brush, 0, 0)
    End Sub

End Class

它按预期工作得很好:)

moji_vb 13 年前

这是你的答案:

Protected Overrides Sub OnPaint(ByVal e As System.Windows.Forms.PaintEventArgs)
    MyBase.OnPaint(e)
    e.Graphics.FillRectangle(Brushes.LightGray, Me.DisplayRectangle)
    Dim sf As New StringFormat
    sf.FormatFlags = StringFormatFlags.NoWrap
    sf.HotkeyPrefix = Drawing.Text.HotkeyPrefix.Show 'if Mnemonic property is set to true
    sf.HotkeyPrefix = Drawing.Text.HotkeyPrefix.Hide 'or none if Mnemonic property is set to false
    sf.LineAlignment = StringAlignment.Center 'horizontal alignment
    sf.Alignment = StringAlignment.Center ' vertical ...
    Dim rect As Rectangle = Me.DisplayRectangle ' this is your text bounds for setting your text alignement using StringFormat(sf)
    e.Graphics.DrawString("Something", Me.Font, Brushes.DarkOliveGreen, rect, sf)
End Sub