ComboBox.DrawItem イベント

オーナー描画 ComboBox のビジュアルな部分を変更すると発生します。

Public Event DrawItem As DrawItemEventHandler
[C#]
public event DrawItemEventHandler DrawItem;
[C++]
public: __event DrawItemEventHandler* DrawItem;

[JScript] JScript では、このクラスで定義されているイベントを処理できます。ただし、独自に定義することはできません。

イベント データ

イベント ハンドラが、このイベントに関連するデータを含む、DrawItemEventArgs 型の引数を受け取りました。次の DrawItemEventArgs プロパティには、このイベントの固有の情報が記載されます。

解説

このイベントは、オーナー描画 ComboBox で使用します。このイベントを使用すると、 ComboBox 内の項目を描画するために必要なタスクを実行できます。可変のサイズの項目がある場合 (DrawMode プロパティが DrawMode.OwnerDrawVariable に設定されている場合) は、項目を描画する前に MeasureItem イベントが発生します。 MeasureItem イベントのイベント ハンドラを作成すると、 DrawItem イベントのイベント ハンドラで描画する項目のサイズを指定できます。

イベント処理の詳細については、「 イベントの利用 」を参照してください。

使用例

[Visual Basic, C#] DrawMode プロパティを OwnerDrawnVariable に設定し、 DrawItem イベントおよび MeasureItem イベントを処理して、オーナー描画のコンボ ボックスを作成するコード例を次に示します。この例はまた、 DropDownWidth プロパティおよび DropDownStyle プロパティの設定方法も示しています。この例を実行するには、次のコードをフォームに貼り付けます。そして、フォームのコンストラクタまたは Load メソッドで InitializeComboBox メソッドを呼び出します。

 

    Friend WithEvents ComboBox1 As System.Windows.Forms.ComboBox
    Private animals() As String
  
    ' This method initializes the owner-drawn combo box.
    ' The drop-down width is set much wider than the size of the combo box
    ' to accomodate the large items in the list.  The drop-down style is set to 
    ' ComboBox.DropDown, which requires the user to click on the arrow to 
    ' see the list.
    Private Sub InitializeComboBox()
        Me.ComboBox1 = New ComboBox
        Me.ComboBox1.DrawMode = System.Windows.Forms.DrawMode.OwnerDrawVariable
        Me.ComboBox1.Location = New System.Drawing.Point(10, 20)
        Me.ComboBox1.Name = "ComboBox1"
        Me.ComboBox1.Size = New System.Drawing.Size(100, 120)
        Me.ComboBox1.DropDownWidth = 250
        Me.ComboBox1.TabIndex = 0
        Me.ComboBox1.DropDownStyle = ComboBoxStyle.DropDown
        animals = New String() {"Elephant", "c r o c o d i l e", "lion"}
        ComboBox1.DataSource = animals
        Me.Controls.Add(Me.ComboBox1)
    End Sub

    ' If you set the Draw property to DrawMode.OwnerDrawVariable, 
    ' you must handle the MeasureItem event. This event handler 
    ' will set the height and width of each item before it is drawn. 
     Private Sub ComboBox1_MeasureItem(ByVal sender As Object, _
        ByVal e As System.Windows.Forms.MeasureItemEventArgs) _
            Handles ComboBox1.MeasureItem

        Select Case e.Index
            Case 0
                e.ItemHeight = 45
            Case 1
                e.ItemHeight = 20
            Case 2
                e.ItemHeight = 35
        End Select
        e.ItemWidth = 260

    End Sub

    ' You must handle the DrawItem event for owner-drawn combo boxes.  
    ' This event handler changes the color, size and font of an 
    ' item based on its position in the array.
    Protected Sub ComboBox1_DrawItem(ByVal sender As Object,  _ 
        ByVal e As System.Windows.Forms.DrawItemEventArgs) _
        Handles ComboBox1.DrawItem

        Dim size As Single
        Dim myFont As System.Drawing.Font
        Dim family As FontFamily

        Dim animalColor As New System.Drawing.Color
        Select Case e.Index
            Case 0
                size = 30
                animalColor = System.Drawing.Color.Gray
                family = FontFamily.GenericSansSerif
            Case 1
                size = 10
                animalColor = System.Drawing.Color.LawnGreen
                family = FontFamily.GenericMonospace
            Case 2
                size = 15
                animalColor = System.Drawing.Color.Tan
                family = FontFamily.GenericSansSerif
        End Select

        ' Draw the background of the item.
        e.DrawBackground()

        ' Create a square filled with the animals color. Vary the size
        ' of the rectangle based on the length of the animals name.
        Dim rectangle As Rectangle = New Rectangle(2, e.Bounds.Top + 2, _
            e.Bounds.Height, e.Bounds.Height - 4)
        e.Graphics.FillRectangle(New SolidBrush(animalColor), rectangle)

        ' Draw each string in the array, using a different size, color,
        ' and font for each item.
        myFont = New Font(family, size, FontStyle.Bold)
        e.Graphics.DrawString(animals(e.Index), myFont, System.Drawing.Brushes.Black, _
            New RectangleF(e.Bounds.X + rectangle.Width, e.Bounds.Y, _ 
            e.Bounds.Width, e.Bounds.Height))

        ' Draw the focus rectangle if the mouse hovers over an item.
        e.DrawFocusRectangle()
    End Sub


[C#] 

    internal System.Windows.Forms.ComboBox ComboBox1;
    private string[] animals;
  
    // This method initializes the owner-drawn combo box.
    // The drop-down width is set much wider than the size of the combo box
    // to accomodate the large items in the list.  The drop-down style is set to 
    // ComboBox.DropDown, which requires the user to click on the arrow to 
    // see the list.
    private void InitializeComboBox()
    {
        this.ComboBox1 = new ComboBox();
        this.ComboBox1.DrawMode = 
            System.Windows.Forms.DrawMode.OwnerDrawVariable;
        this.ComboBox1.Location = new System.Drawing.Point(10, 20);
        this.ComboBox1.Name = "ComboBox1";
        this.ComboBox1.Size = new System.Drawing.Size(100, 120);
        this.ComboBox1.DropDownWidth = 250;
        this.ComboBox1.TabIndex = 0;
        this.ComboBox1.DropDownStyle = ComboBoxStyle.DropDown;
        animals = new string[]{"Elephant", "c r o c o d i l e", "lion"};
        ComboBox1.DataSource = animals;
        this.Controls.Add(this.ComboBox1);

        // Hook up the MeasureItem and DrawItem events
        this.ComboBox1.DrawItem += 
            new DrawItemEventHandler(ComboBox1_DrawItem);
        this.ComboBox1.MeasureItem += 
            new MeasureItemEventHandler(ComboBox1_MeasureItem);
    }

    // If you set the Draw property to DrawMode.OwnerDrawVariable, 
    // you must handle the MeasureItem event. This event handler 
    // will set the height and width of each item before it is drawn. 
    private void ComboBox1_MeasureItem(object sender, 
        System.Windows.Forms.MeasureItemEventArgs e)
    {

        switch(e.Index)
        {
            case 0:
                e.ItemHeight = 45;
                break;
            case 1:
                e.ItemHeight = 20;
                break;
            case 2:
                e.ItemHeight = 35;
                break;
        }
        e.ItemWidth = 260;

    }

    // You must handle the DrawItem event for owner-drawn combo boxes.  
    // This event handler changes the color, size and font of an 
    // item based on its position in the array.
    protected void ComboBox1_DrawItem(object sender, 
        System.Windows.Forms.DrawItemEventArgs e)
    {

        float size = 0;
        System.Drawing.Font myFont;
        FontFamily family = null;

        System.Drawing.Color animalColor = new System.Drawing.Color();
        switch(e.Index)
        {
            case 0:
                size = 30;
                animalColor = System.Drawing.Color.Gray;
                family = FontFamily.GenericSansSerif;
                break;
            case 1:
                size = 10;
                animalColor = System.Drawing.Color.LawnGreen;
                family = FontFamily.GenericMonospace;
                break;
            case 2:
                size = 15;
                animalColor = System.Drawing.Color.Tan;
                family = FontFamily.GenericSansSerif;
                break;
        }

        // Draw the background of the item.
        e.DrawBackground();

        // Create a square filled with the animals color. Vary the size
        // of the rectangle based on the length of the animals name.
        Rectangle rectangle = new Rectangle(2, e.Bounds.Top+2, 
                e.Bounds.Height, e.Bounds.Height-4);
        e.Graphics.FillRectangle(new SolidBrush(animalColor), rectangle);

        // Draw each string in the array, using a different size, color,
        // and font for each item.
        myFont = new Font(family, size, FontStyle.Bold);
        e.Graphics.DrawString(animals[e.Index], myFont, System.Drawing.Brushes.Black, new RectangleF(e.Bounds.X+rectangle.Width, e.Bounds.Y, e.Bounds.Width, e.Bounds.Height));

        // Draw the focus rectangle if the mouse hovers over an item.
        e.DrawFocusRectangle();
    }

[C++, JScript] C++ および JScript のサンプルはありません。Visual Basic および C# のサンプルを表示するには、このページの左上隅にある言語のフィルタ ボタン をクリックします。

必要条件

プラットフォーム: Windows 98, Windows NT 4.0, Windows Millennium Edition, Windows 2000, Windows XP Home Edition, Windows XP Professional, Windows Server 2003 ファミリ

参照

ComboBox クラス | ComboBox メンバ | System.Windows.Forms 名前空間