ComboBox.MeasureItem イベント

オーナー描画 ComboBox の項目を描画する必要があるたびに発生し、また、リスト項目のサイズを決定したときにも発生します。

Public Event MeasureItem As MeasureItemEventHandler
[C#]
public event MeasureItemEventHandler MeasureItem;
[C++]
public: __event MeasureItemEventHandler* MeasureItem;

[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、MeasureItemEventArgs 型の引数を受け取りました。次の MeasureItemEventArgs 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

このイベントのイベント ハンドラを作成して、作成する項目のサイズを DrawItem イベントで描画する前に指定できます。

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