ListBox.DrawItem 事件

定義

命名空間:

System.Windows.Forms

組件:

System.Windows.Forms.dll

發生於主控描繪 ListBox 的視覺外觀變更時。

public:
 event System::Windows::Forms::DrawItemEventHandler ^ DrawItem;

public event System.Windows.Forms.DrawItemEventHandler? DrawItem;

member this.DrawItem : System.Windows.Forms.DrawItemEventHandler 

Public Custom Event DrawItem As DrawItemEventHandler 

事件類型

DrawItemEventHandler

範例

下列程式碼範例示範如何建立擁有者繪製 ListBox 的專案。 程式碼會 DrawMode 使用 屬性來指定繪製的專案是固定大小的，而 DrawItem 事件則會執行每個專案的繪圖到 ListBox 。 此範例程式碼會使用傳遞為事件處理常式參數之 DrawItemEventArgs 類別的屬性和方法，來繪製專案。 這個範例會要求 ListBox 已將呼叫 listBox1 的控制項新增至表單，而且 DrawItem 該事件是由範例程式碼中定義的事件處理常式所處理。 此範例也需要以 「Apple」、「Orange」 和 「Plum」 文字將該順序的專案新增至 ListBox 。

private ListBox ListBox1 = new ListBox();
private void InitializeListBox()
{
    ListBox1.Items.AddRange(new Object[] 
        { "Red Item", "Orange Item", "Purple Item" });
    ListBox1.Location = new System.Drawing.Point(81, 69);
    ListBox1.Size = new System.Drawing.Size(120, 95);
    ListBox1.DrawMode = DrawMode.OwnerDrawFixed;
    ListBox1.DrawItem += new DrawItemEventHandler(ListBox1_DrawItem);
    Controls.Add(ListBox1);
}

private void ListBox1_DrawItem(object sender, 
    System.Windows.Forms.DrawItemEventArgs e)
{
    // Draw the background of the ListBox control for each item.
    e.DrawBackground();
    // Define the default color of the brush as black.
    Brush myBrush = Brushes.Black;

    // Determine the color of the brush to draw each item based 
    // on the index of the item to draw.
    switch (e.Index)
    {
        case 0:
            myBrush = Brushes.Red;
            break;
        case 1:
            myBrush = Brushes.Orange;
            break;
        case 2:
            myBrush = Brushes.Purple;
            break;
    }

    // Draw the current item text based on the current Font 
    // and the custom brush settings.
    e.Graphics.DrawString(ListBox1.Items[e.Index].ToString(), 
        e.Font, myBrush, e.Bounds, StringFormat.GenericDefault);
    // If the ListBox has focus, draw a focus rectangle around the selected item.
    e.DrawFocusRectangle();
}

Private WithEvents ListBox1 As New ListBox()

Private Sub InitializeListBox() 
    ListBox1.Items.AddRange(New Object() _
        {"Red Item", "Orange Item", "Purple Item"})
    ListBox1.Location = New System.Drawing.Point(81, 69)
    ListBox1.Size = New System.Drawing.Size(120, 95)
    ListBox1.DrawMode = DrawMode.OwnerDrawFixed
    Controls.Add(ListBox1)

End Sub

Private Sub ListBox1_DrawItem(ByVal sender As Object, _
 ByVal e As System.Windows.Forms.DrawItemEventArgs) _
 Handles ListBox1.DrawItem

    ' Draw the background of the ListBox control for each item.
    e.DrawBackground()

    ' Define the default color of the brush as black.
    Dim myBrush As Brush = Brushes.Black

    ' Determine the color of the brush to draw each item based on   
    ' the index of the item to draw.
    Select Case e.Index
        Case 0
            myBrush = Brushes.Red
        Case 1
            myBrush = Brushes.Orange
        Case 2
            myBrush = Brushes.Purple
    End Select

    ' Draw the current item text based on the current 
    ' Font and the custom brush settings.
    e.Graphics.DrawString(ListBox1.Items(e.Index).ToString(), _
        e.Font, myBrush, e.Bounds, StringFormat.GenericDefault)

    ' If the ListBox has focus, draw a focus rectangle around  _ 
    ' the selected item.
    e.DrawFocusRectangle()
End Sub

備註

這個事件是由擁有者繪製 ListBox 的 使用。 只有當 屬性設定為 DrawMode.OwnerDrawFixed 或 DrawMode.OwnerDrawVariable 時， DrawMode 才會引發 事件。 您可以使用這個事件來執行 在 中 ListBox 繪製專案所需的工作。 如果屬性設定為 DrawMode.OwnerDrawVariable) 時， DrawMode (變數大小的專案， MeasureItem 則會在繪製專案之前引發 事件。 您可以為 MeasureItem 事件建立事件處理常式，以指定要在事件事件處理常式 DrawItem 中繪製的專案大小。

如需處理事件的詳細資訊，請參閱 處理和引發事件。

另請參閱

• OnDrawItem(DrawItemEventArgs)