ScrollBar.OnScroll(ScrollEventArgs) 方法

定義

命名空間:

System.Windows.Forms

組件:

System.Windows.Forms.dll

來源:

ScrollBar.cs

引發 Scroll 事件。

protected:
 virtual void OnScroll(System::Windows::Forms::ScrollEventArgs ^ se);

protected virtual void OnScroll(System.Windows.Forms.ScrollEventArgs se);

abstract member OnScroll : System.Windows.Forms.ScrollEventArgs -> unit
override this.OnScroll : System.Windows.Forms.ScrollEventArgs -> unit

Protected Overridable Sub OnScroll (se As ScrollEventArgs)

參數

se

ScrollEventArgs

ScrollEventArgs A 包含事件資料。

範例

以下程式碼範例使用導出類別 VScrollBar。 會建立事件處理程序。ScrollValueChanged 此程式碼假設 a Label 和 Button 已在表單上建立，且按鈕有事件處理 Click 程序。 當按下按鈕時， Value 滾動條的屬性會在程式碼中被調整。 標籤會顯示屬性的當前值 Value 以及改變它的事件。 你會注意到當按鈕 Click 事件改變滾動值時，只有 ValueChanged 事件本身會被觸發。 相反地，手動捲動滾動條時， Scroll 事件會在事件發生後 ValueChanged 立即被觸發。

void AddMyScrollEventHandlers()
{
   // Create and initialize a VScrollBar.
   VScrollBar^ vScrollBar1 = gcnew VScrollBar;

   // Add event handlers for the OnScroll and OnValueChanged events.
   vScrollBar1->Scroll += gcnew ScrollEventHandler( this, &Form1::vScrollBar1_Scroll );
   vScrollBar1->ValueChanged += gcnew EventHandler( this, &Form1::vScrollBar1_ValueChanged );
}

// Create the ValueChanged event handler.
void vScrollBar1_ValueChanged( Object^ /*sender*/, EventArgs^ /*e*/ )
{
   // Display the new value in the label.
   label1->Text = String::Format( "vScrollBar Value:(OnValueChanged Event) {0}", vScrollBar1->Value );
}

// Create the Scroll event handler.
void vScrollBar1_Scroll( Object^ /*sender*/, ScrollEventArgs^ e )
{
   // Display the new value in the label.
   label1->Text = String::Format( "VScrollBar Value:(OnScroll Event) {0}", e->NewValue );
}

void button1_Click( Object^ /*sender*/, EventArgs^ /*e*/ )
{
   // Add 40 to the Value property if it will not exceed the Maximum value.
   if ( vScrollBar1->Value + 40 < vScrollBar1->Maximum )
   {
      vScrollBar1->Value = vScrollBar1->Value + 40;
   }
}

private void AddMyScrollEventHandlers()
 {
    // Create and initialize a VScrollBar.
    VScrollBar vScrollBar1 = new VScrollBar();
 
    // Add event handlers for the OnScroll and OnValueChanged events.
    vScrollBar1.Scroll += new ScrollEventHandler(
       this.vScrollBar1_Scroll);
    vScrollBar1.ValueChanged += new EventHandler(
       this.vScrollBar1_ValueChanged); 
 }
 
 // Create the ValueChanged event handler.
 private void vScrollBar1_ValueChanged(Object sender, 
                                       EventArgs e)
 {
     // Display the new value in the label.
     label1.Text = "vScrollBar Value:(OnValueChanged Event) " + vScrollBar1.Value.ToString();
 }
 
 // Create the Scroll event handler.
 private void vScrollBar1_Scroll(Object sender, 
                                 ScrollEventArgs e)
 {
     // Display the new value in the label.
     label1.Text = "VScrollBar Value:(OnScroll Event) " + e.NewValue.ToString();
 }
 
 private void button1_Click(Object sender, 
                           EventArgs e)
 {
    // Add 40 to the Value property if it will not exceed the Maximum value.
    if (vScrollBar1.Value + 40 < vScrollBar1.Maximum)
    {
        vScrollBar1.Value = vScrollBar1.Value + 40;
    }
 }

Private Sub AddMyScrollEventHandlers()
    ' Create and initialize a VScrollBar.
    Dim vScrollBar1 As New VScrollBar()
    
    ' Add event handlers for the OnScroll and OnValueChanged events.
    AddHandler vScrollBar1.Scroll, AddressOf Me.vScrollBar1_Scroll
    AddHandler vScrollBar1.ValueChanged, AddressOf Me.vScrollBar1_ValueChanged
End Sub    

' Create the ValueChanged event handler.
Private Sub vScrollBar1_ValueChanged(sender As Object, e As EventArgs)
    ' Display the new value in the label.
    label1.Text = "vScrollBar Value:(OnValueChanged Event) " & _
        vScrollBar1.Value.ToString()
End Sub    

' Create the Scroll event handler.
Private Sub vScrollBar1_Scroll(sender As Object, e As ScrollEventArgs)
    ' Display the new value in the label.
    label1.Text = "VScrollBar Value:(OnScroll Event) " & _
        e.NewValue.ToString()
End Sub    

Private Sub button1_Click(sender As Object, e As EventArgs)
    ' Add 40 to the Value property if it will not exceed the Maximum value.
    If vScrollBar1.Value + 40 < vScrollBar1.Maximum Then
        vScrollBar1.Value = vScrollBar1.Value + 40
    End If
End Sub

備註

發起事件會透過代理呼叫事件處理者。 欲了解更多資訊，請參閱 處理與提升事件。

此 OnScroll 方法也允許衍生類別在不附加代理的情況下處理事件。 這是在衍生類別中處理事件的首選技術。

給繼承者的注意事項

在導出類別中覆寫 OnScroll(ScrollEventArgs) 時，務必呼叫基底類別的方法 OnScroll(ScrollEventArgs) ，讓註冊代理接收事件。

另請參閱

• Scroll
• ScrollEventArgs