ToolStripRenderer.OnRenderToolStripBackground 方法

定義

命名空間:

System.Windows.Forms

組件:

System.Windows.Forms.dll

引發 RenderToolStripBackground 事件。

protected:
 virtual void OnRenderToolStripBackground(System::Windows::Forms::ToolStripRenderEventArgs ^ e);

protected virtual void OnRenderToolStripBackground (System.Windows.Forms.ToolStripRenderEventArgs e);

abstract member OnRenderToolStripBackground : System.Windows.Forms.ToolStripRenderEventArgs -> unit
override this.OnRenderToolStripBackground : System.Windows.Forms.ToolStripRenderEventArgs -> unit

Protected Overridable Sub OnRenderToolStripBackground (e As ToolStripRenderEventArgs)

參數

e

ToolStripRenderEventArgs

ToolStripRenderEventArgs，其中包含事件資料。

範例

下列程式碼範例示範如何覆寫 OnRenderToolStripBackground 方法，以在控制項的背景 ToolStrip 中繪製漸層。 此程式碼範例是提供給 類別之較大範例的 ToolStripRenderer 一部分。

// This method renders the GridStrip control's background.
protected override void OnRenderToolStripBackground(
    ToolStripRenderEventArgs e)
{
    base.OnRenderToolStripBackground(e);

    // This late initialization is a workaround. The gradient
    // depends on the bounds of the GridStrip control. The bounds 
    // are dependent on the layout engine, which hasn't fully
    // performed layout by the time the Initialize method runs.
    if (this.backgroundBrush == null)
    {
        this.backgroundBrush = new LinearGradientBrush(
           e.ToolStrip.ClientRectangle,
           SystemColors.ControlLightLight,
           SystemColors.ControlDark,
           90,
           true);
    }

    // Paint the GridStrip control's background.
    e.Graphics.FillRectangle(
        this.backgroundBrush, 
        e.AffectedBounds);
}

' This method renders the GridStrip control's background.
Protected Overrides Sub OnRenderToolStripBackground(e As ToolStripRenderEventArgs)
   MyBase.OnRenderToolStripBackground(e)
   
   ' This late initialization is a workaround. The gradient
   ' depends on the bounds of the GridStrip control. The bounds 
   ' are dependent on the layout engine, which hasn't fully
   ' performed layout by the time the Initialize method runs.
   If Me.backgroundBrush Is Nothing Then
      Me.backgroundBrush = New LinearGradientBrush(e.ToolStrip.ClientRectangle, SystemColors.ControlLightLight, SystemColors.ControlDark, 90, True)
   End If
   
   ' Paint the GridStrip control's background.
   e.Graphics.FillRectangle(Me.backgroundBrush, e.AffectedBounds)
  End Sub

備註

引發事件會透過委派叫用此事件處理常式。 如需詳細資訊，請參閱 處理和引發事件。

OnRenderToolStripBackground 方法也允許衍生類別處理事件，而不用附加委派。 這是在衍生類別中處理事件的慣用技巧。

給繼承者的注意事項

當在衍生類別中覆寫 OnRenderToolStripBackground(ToolStripRenderEventArgs) 時，請確定呼叫基底類別的 OnRenderToolStripBackground(ToolStripRenderEventArgs) 方法，使已註冊的委派能接收到事件。

另請參閱

• 作法：實作自訂的 ToolStripRenderer