ToolStripItem.OnPaint(PaintEventArgs) ToolStripItem.OnPaint(PaintEventArgs) ToolStripItem.OnPaint(PaintEventArgs) ToolStripItem.OnPaint(PaintEventArgs) Method

定义

引发 Paint 事件。Raises the Paint event.

protected:
 virtual void OnPaint(System::Windows::Forms::PaintEventArgs ^ e);
protected virtual void OnPaint (System.Windows.Forms.PaintEventArgs e);
abstract member OnPaint : System.Windows.Forms.PaintEventArgs -> unit
override this.OnPaint : System.Windows.Forms.PaintEventArgs -> unit
Protected Overridable Sub OnPaint (e As PaintEventArgs)

参数

e
PaintEventArgs PaintEventArgs PaintEventArgs PaintEventArgs

包含事件数据的 PaintEventArgsA PaintEventArgs that contains the event data.

示例

下面的代码示例演示如何重写OnPaint自定义呈现的方法。The following code example demonstrates how to override the OnPaint method for custom rendering. 此代码示例是为ToolStripItem类提供的更大示例的一部分。This code example is part of a larger example provided for the ToolStripItem class.

// This method defines the painting behavior of the control.
// It performs the following operations:
//
// Computes the layout of the item's image and text.
// Draws the item's background image.
// Draws the item's image.
// Draws the item's text.
//
// Drawing operations are implemented in the 
// RolloverItemRenderer class.
protected override void OnPaint(PaintEventArgs e)
{
    base.OnPaint(e);

    if (this.Owner != null)
    {
        // Find the dimensions of the image and the text 
        // areas of the item. 
        this.ComputeImageAndTextLayout();

        // Draw the background. This includes drawing a highlighted 
        // border when the mouse is in the client area.
        ToolStripItemRenderEventArgs ea = new ToolStripItemRenderEventArgs(
             e.Graphics,
             this);
        this.Owner.Renderer.DrawItemBackground(ea);

        // Draw the item's image. 
        ToolStripItemImageRenderEventArgs irea =
            new ToolStripItemImageRenderEventArgs(
            e.Graphics,
            this,
            imageRect );
        this.Owner.Renderer.DrawItemImage(irea);

        // If the item is on a drop-down, give its
        // text a different highlighted color.
        Color highlightColor = 
            this.IsOnDropDown ?
            Color.Salmon : SystemColors.ControlLightLight;

        // Draw the text, and highlight it if the 
        // the rollover state is true.
        ToolStripItemTextRenderEventArgs rea =
            new ToolStripItemTextRenderEventArgs(
            e.Graphics,
            this,
            base.Text,
            textRect,
            this.rolloverValue ? highlightColor : base.ForeColor,
            base.Font,
            base.TextAlign);
        this.Owner.Renderer.DrawItemText(rea);
    }
}
' This method defines the painting behavior of the control.
' It performs the following operations:
'
' Computes the layout of the item's image and text.
' Draws the item's background image.
' Draws the item's image.
' Draws the item's text.
'
' Drawing operations are implemented in the 
' RolloverItemRenderer class.
Protected Overrides Sub OnPaint(e As PaintEventArgs)
   MyBase.OnPaint(e)
   
   If (Me.Owner IsNot Nothing) Then
      ' Find the dimensions of the image and the text 
      ' areas of the item. 
      Me.ComputeImageAndTextLayout()
      
      ' Draw the background. This includes drawing a highlighted 
      ' border when the mouse is in the client area.
      Dim ea As New ToolStripItemRenderEventArgs(e.Graphics, Me)
      Me.Owner.Renderer.DrawItemBackground(ea)
      
      ' Draw the item's image. 
      Dim irea As New ToolStripItemImageRenderEventArgs(e.Graphics, Me, imageRect)
      Me.Owner.Renderer.DrawItemImage(irea)
      
      ' If the item is on a drop-down, give its
      ' text a different highlighted color.
         Dim highlightColor As Color = CType(IIf(Me.IsOnDropDown, Color.Salmon, SystemColors.ControlLightLight), Color)
      
      ' Draw the text, and highlight it if the 
      ' the rollover state is true.
         Dim rea As New ToolStripItemTextRenderEventArgs( _
            e.Graphics, _
            Me, _
            MyBase.Text, _
            textRect, _
            CType(IIf(Me.rolloverValue, highlightColor, MyBase.ForeColor), Color), _
            MyBase.Font, _
            MyBase.TextAlign)
      Me.Owner.Renderer.DrawItemText(rea)
   End If
 End Sub

注解

引发事件时,将通过委托调用事件处理程序。Raising an event invokes the event handler through a delegate. 有关详细信息, 请参阅处理和引发事件For more information, see Handling and Raising Events.

OnPaint 方法还允许派生类对事件进行处理而不必附加委托。The OnPaint method also allows derived classes to handle the event without attaching a delegate. 这是在派生类中处理事件的首选技术。This is the preferred technique for handling the event in a derived class.

继承者说明

在派生类中重写 OnPaint(PaintEventArgs) 时,一定要调用基类的 OnPaint(PaintEventArgs) 方法,以便已注册的委托对事件进行接收。When overriding OnPaint(PaintEventArgs) in a derived class, be sure to call the base class's OnPaint(PaintEventArgs) method so that registered delegates receive the event.

适用于