MeasureItemEventArgs 类

为 ListBox、ComboBox、CheckedListBox 和 MenuItem 控件的 MeasureItem 事件提供数据。

**命名空间:**System.Windows.Forms
**程序集:**System.Windows.Forms（在 system.windows.forms.dll 中）

语法

声明
Public Class MeasureItemEventArgs
    Inherits EventArgs
用法
Dim instance As MeasureItemEventArgs

public class MeasureItemEventArgs : EventArgs

public ref class MeasureItemEventArgs : public EventArgs

public class MeasureItemEventArgs extends EventArgs

public class MeasureItemEventArgs extends EventArgs

备注

当 ListBox、ComboBox、CheckedListBox 或 MenuItem 的 OwnerDraw 属性被设置为 true 时发送该事件。它用于通知绘图函数如何调整项的大小。

有关事件模型的信息，请参见 事件和委托。

示例

Public Class Form1
   Inherits System.Windows.Forms.Form
   Private WithEvents listBox1 As System.Windows.Forms.ListBox
   Private components As System.ComponentModel.Container = Nothing

   Private FontSize As Single = 12.0F

   '
   '  This sample displays a ListBox that contains a list of all the fonts
   '  installed on the system and draws each item in its respective font.
   '
   Public Sub New()
      InitializeComponent()

      ' Populate control with the fonts installed on the system.
      Dim families As FontFamily() = FontFamily.Families

      Dim family As FontFamily
      For Each family In families
         Dim style As FontStyle = FontStyle.Regular

         ' Monotype Corsiva is only available in italic
         If family.Name = "Monotype Corsiva" Then
            style = style Or FontStyle.Italic
         End If

         listBox1.Items.Add(New ListBoxFontItem(New Font(family.Name, FontSize, style, GraphicsUnit.Point)))
      Next family
   End Sub


   Protected Overloads Overrides Sub Dispose(ByVal disposing As Boolean)
      If disposing Then
         If Not (components Is Nothing) Then
            components.Dispose()
         End If

         If Not (foreColorBrush Is Nothing) Then
            foreColorBrush.Dispose()
         End If
      End If

      MyBase.Dispose(disposing)
   End Sub

   Private Sub InitializeComponent()
      Me.listBox1 = New System.Windows.Forms.ListBox()
      Me.SuspendLayout()
      ' 
      ' listBox1
      ' 
      Me.listBox1.DrawMode = System.Windows.Forms.DrawMode.OwnerDrawVariable
      Me.listBox1.Location = New System.Drawing.Point(16, 48)
      Me.listBox1.Name = "listBox1"
      Me.listBox1.SelectionMode = System.Windows.Forms.SelectionMode.MultiExtended
      Me.listBox1.Size = New System.Drawing.Size(256, 134)
      Me.listBox1.TabIndex = 0
      ' 
      ' Form1
      ' 
      Me.ClientSize = New System.Drawing.Size(292, 273)
      Me.Controls.AddRange(New System.Windows.Forms.Control() {Me.listBox1})
      Me.Name = "Form1"
      Me.Text = "Form1"
      Me.ResumeLayout(False)
   End Sub

   <STAThread()> Shared Sub Main()
      Application.Run(New Form1())
   End Sub

   Private Sub listBox1_MeasureItem(ByVal sender As Object, ByVal e As System.Windows.Forms.MeasureItemEventArgs) Handles listBox1.MeasureItem
      Dim font As Font = CType(listBox1.Items(e.Index), ListBoxFontItem).Font
      Dim stringSize As SizeF = e.Graphics.MeasureString(font.Name, font)

      ' Set the height and width of the item
      e.ItemHeight = CInt(stringSize.Height)
      e.ItemWidth = CInt(stringSize.Width)
   End Sub

   ' For efficiency, cache the brush used for drawing.
   Private foreColorBrush As SolidBrush

   Private Sub listBox1_DrawItem(ByVal sender As Object, ByVal e As System.Windows.Forms.DrawItemEventArgs) Handles listBox1.DrawItem
      Dim brush As Brush

      ' Create the brush using the ForeColor specified by the DrawItemEventArgs
      If foreColorBrush Is Nothing Then
         foreColorBrush = New SolidBrush(e.ForeColor)
      Else
         If Not foreColorBrush.Color.Equals(e.ForeColor) Then
            ' The control's ForeColor has changed, so dispose of the cached brush and
            ' create a new one.
            foreColorBrush.Dispose()
            foreColorBrush = New SolidBrush(e.ForeColor)
         End If
      End If

      ' Select the appropriate brush depending on if the item is selected.
      ' Since State can be a combinateion (bit-flag) of enum values, you can't use
      ' "==" to compare them.
      If (e.State And DrawItemState.Selected) = DrawItemState.Selected Then
         brush = SystemBrushes.HighlightText
      Else
         brush = foreColorBrush
      End If

      ' Perform the painting.
      Dim font As Font = CType(listBox1.Items(e.Index), ListBoxFontItem).Font
      e.DrawBackground()
      e.Graphics.DrawString(font.Name, font, brush, e.Bounds.X, e.Bounds.Y)
      e.DrawFocusRectangle()
   End Sub

   '
   '  A wrapper class for use with storing Fonts in a ListBox.  Since ListBox uses the
   '  ToString() of its items for the text it displays, this class is needed to return
   '  the name of the font, rather than its ToString() value.
   '
   Public Class ListBoxFontItem
      Public Font As Font

      Public Sub New(ByVal f As Font)
         Font = f
      End Sub

      Public Overrides Function ToString() As String
         Return Font.Name
      End Function
   End Class
End Class

public class Form1 : System.Windows.Forms.Form
{
   private System.Windows.Forms.ListBox listBox1;
   private System.ComponentModel.Container components = null;


   protected override void Dispose(bool disposing)
   {
      if( disposing )
      {
         if ( components != null ) 
            components.Dispose();

         if ( foreColorBrush != null )
            foreColorBrush.Dispose();
      }
      base.Dispose(disposing);
   }

     #region Windows Form Designer generated code
   /// <summary>
   /// Required method for Designer support - do not modify
   /// the contents of this method with the code editor.
   /// </summary>
   private void InitializeComponent()
   {
      this.listBox1 = new System.Windows.Forms.ListBox();
      this.SuspendLayout();
      // 
      // listBox1
      // 
      this.listBox1.DrawMode = System.Windows.Forms.DrawMode.OwnerDrawVariable;
      this.listBox1.Location = new System.Drawing.Point(16, 48);
      this.listBox1.Name = "listBox1";
      this.listBox1.SelectionMode = System.Windows.Forms.SelectionMode.MultiExtended;
      this.listBox1.Size = new System.Drawing.Size(256, 134);
      this.listBox1.TabIndex = 0;
      this.listBox1.MeasureItem += new System.Windows.Forms.MeasureItemEventHandler(this.listBox1_MeasureItem);
      this.listBox1.DrawItem += new System.Windows.Forms.DrawItemEventHandler(this.listBox1_DrawItem);
      // 
      // Form1
      // 
      this.ClientSize = new System.Drawing.Size(292, 273);
      this.Controls.AddRange(new System.Windows.Forms.Control[] {
                                                                   this.listBox1});
      this.Name = "Form1";
      this.Text = "Form1";
      this.ResumeLayout(false);

   }
     #endregion

   [STAThread]
   static void Main() 
   {
      Application.Run(new Form1());
   }

   private void listBox1_MeasureItem(object sender, System.Windows.Forms.MeasureItemEventArgs e)
   {
      Font font = ((ListBoxFontItem)listBox1.Items[e.Index]).Font;
      SizeF stringSize = e.Graphics.MeasureString(font.Name, font);

      // Set the height and width of the item
      e.ItemHeight = (int)stringSize.Height;
      e.ItemWidth = (int)stringSize.Width;
   }

   // For efficiency, cache the brush to use for drawing.
   private SolidBrush foreColorBrush;

   private void listBox1_DrawItem(object sender, System.Windows.Forms.DrawItemEventArgs e)
   {
      Brush brush;

      // Create the brush using the ForeColor specified by the DrawItemEventArgs
      if ( foreColorBrush == null )
         foreColorBrush = new SolidBrush(e.ForeColor);
      else if ( foreColorBrush.Color != e.ForeColor )
      {
         // The control's ForeColor has changed, so dispose of the cached brush and
         // create a new one.
         foreColorBrush.Dispose();
         foreColorBrush = new SolidBrush(e.ForeColor);
      }

      // Select the appropriate brush depending on if the item is selected.
      // Since State can be a combinateion (bit-flag) of enum values, you can't use
      // "==" to compare them.
      if ( (e.State & DrawItemState.Selected) == DrawItemState.Selected )
         brush = SystemBrushes.HighlightText;
      else
         brush = foreColorBrush;

      // Perform the painting.
      Font font = ((ListBoxFontItem)listBox1.Items[e.Index]).Font;
      e.DrawBackground();
      e.Graphics.DrawString(font.Name, font, brush, e.Bounds);
      e.DrawFocusRectangle();
   }

   /// <summary>
   ///  A wrapper class for use with storing Fonts in a ListBox.  Since ListBox uses the
   ///  ToString() of its items for the text it displays, this class is needed to return
   ///  the name of the font, rather than its ToString() value.
   /// </summary>
   public class ListBoxFontItem 
   {
      public Font Font;

      public ListBoxFontItem(Font f) 
      {
         Font = f;
      }

      public override string ToString() 
      {
         return Font.Name;
      }
   }
}

public ref class Form1: public System::Windows::Forms::Form
{
private:
   System::Windows::Forms::ListBox^ listBox1;
   System::ComponentModel::Container^ components;

public:
   ~Form1()
   {
      if ( components != nullptr )
      {
         delete components;
      }
   }

private:

   /// <summary>
   /// Required method for Designer support - do not modify
   /// the contents of this method with the code editor.
   /// </summary>
   void InitializeComponent()
   {
      this->listBox1 = gcnew System::Windows::Forms::ListBox;
      this->SuspendLayout();

      // 
      // listBox1
      // 
      this->listBox1->DrawMode = System::Windows::Forms::DrawMode::OwnerDrawVariable;
      this->listBox1->Location = System::Drawing::Point( 16, 48 );
      this->listBox1->Name = "listBox1";
      this->listBox1->SelectionMode = System::Windows::Forms::SelectionMode::MultiExtended;
      this->listBox1->Size = System::Drawing::Size( 256, 134 );
      this->listBox1->TabIndex = 0;
      this->listBox1->MeasureItem += gcnew System::Windows::Forms::MeasureItemEventHandler( this, &Form1::listBox1_MeasureItem );
      this->listBox1->DrawItem += gcnew System::Windows::Forms::DrawItemEventHandler( this, &Form1::listBox1_DrawItem );

      // 
      // Form1
      // 
      this->ClientSize = System::Drawing::Size( 292, 273 );
      array<System::Windows::Forms::Control^>^temp0 = {this->listBox1};
      this->Controls->AddRange( temp0 );
      this->Name = "Form1";
      this->Text = "Form1";
      this->ResumeLayout( false );
   }

   void listBox1_MeasureItem( Object^ /*sender*/, MeasureItemEventArgs^ e )
   {
      System::Drawing::Font^ font = (dynamic_cast<ListBoxFontItem^>(listBox1->Items[ e->Index ]))->Font;
      SizeF stringSize = e->Graphics->MeasureString( font->Name, font );
      
      // Set the height and width of the item
      e->ItemHeight = (int)stringSize.Height;
      e->ItemWidth = (int)stringSize.Width;
   }

   // For efficiency, cache the brush to use for drawing.
   SolidBrush^ foreColorBrush;
   void listBox1_DrawItem( Object^ /*sender*/, DrawItemEventArgs^ e )
   {
      Brush^ brush;

      // Create the brush using the ForeColor specified by the DrawItemEventArgs
      if ( foreColorBrush == nullptr )
            foreColorBrush = gcnew SolidBrush( e->ForeColor );
      else
      if ( foreColorBrush->Color != e->ForeColor )
      {
         // The control's ForeColor has changed, so dispose of the cached brush and
         // create a new one.
         delete foreColorBrush;
         foreColorBrush = gcnew SolidBrush( e->ForeColor );
      }

      // Select the appropriate brush depending on if the item is selected.
      // Since State can be a combinateion (bit-flag) of enum values, you can't use
      // "==" to compare them.
      if ( (e->State & DrawItemState::Selected) == DrawItemState::Selected )
            brush = SystemBrushes::HighlightText;
      else
            brush = foreColorBrush;

      // Perform the painting.
      System::Drawing::Font^ font = (dynamic_cast<ListBoxFontItem^>(listBox1->Items[ e->Index ]))->Font;
      e->DrawBackground();
      e->Graphics->DrawString( font->Name, font, brush, e->Bounds );
      e->DrawFocusRectangle();
   }

public:

   /// <summary>
   ///  A wrapper class for use with storing Fonts in a ListBox.  Since ListBox uses the
   ///  ToString() of its items for the text it displays, this class is needed to return
   ///  the name of the font, rather than its ToString() value.
   /// </summary>
   ref class ListBoxFontItem
   {
   public:
      System::Drawing::Font^ Font;
      ListBoxFontItem( System::Drawing::Font^ f )
      {
         Font = f;
      }

      virtual String^ ToString() override
      {
         return Font->Name;
      }
   };
};

[STAThread]
int main()
{
   Application::Run( gcnew Form1 );
}

public class Form1 extends System.Windows.Forms.Form
{
    private System.Windows.Forms.ListBox listBox1;
    private System.ComponentModel.Container components = null;

    protected void Dispose(boolean disposing)
    {
        if (disposing) {
            if (components != null) {
                components.Dispose();
            }

            if (foreColorBrush != null) {
                foreColorBrush.Dispose();
            }
        }
        super.Dispose(disposing);
    } //Dispose
      
    #region Windows Form Designer generated code
    /// <summary>
    /// Required method for Designer support - do not modify
    /// the contents of this method with the code editor.
    /// </summary>
    private void InitializeComponent()
    {
        this.listBox1 = new System.Windows.Forms.ListBox();
        this.SuspendLayout();
        // 
        // listBox1
        // 
        this.listBox1.set_DrawMode(
            System.Windows.Forms.DrawMode.OwnerDrawVariable);
        this.listBox1.set_Location(new System.Drawing.Point(16, 48));
        this.listBox1.set_Name("listBox1");
        this.listBox1.set_SelectionMode(
            System.Windows.Forms.SelectionMode.MultiExtended);
        this.listBox1.set_Size(new System.Drawing.Size(256, 134));
        this.listBox1.set_TabIndex(0);
        this.listBox1.add_MeasureItem(
            new System.Windows.Forms.MeasureItemEventHandler(
            this.listBox1_MeasureItem));
        this.listBox1.add_DrawItem(
            new System.Windows.Forms.DrawItemEventHandler(
            this.listBox1_DrawItem));
        // 
        // Form1
        // 
        this.set_ClientSize(new System.Drawing.Size(292, 273));
        this.get_Controls().AddRange(new System.Windows.Forms.Control[] 
            { this.listBox1 });
        this.set_Name("Form1");
        this.set_Text("Form1");
        this.ResumeLayout(false);
    } //InitializeComponent
    #endregion
      
    /** @attribute STAThread()
     */
    public static void main(String[] args)
    {
        Application.Run(new Form1());
    } //main

    private void listBox1_MeasureItem(Object sender, 
        System.Windows.Forms.MeasureItemEventArgs e)
    {
        Font font = ((ListBoxFontItem)listBox1.get_Items().
             get_Item(e.get_Index())).font;
        SizeF stringSize = 
            e.get_Graphics().MeasureString(font.get_Name(), font);

        // Set the height and width of the item
        e.set_ItemHeight((int)stringSize.get_Height());
        e.set_ItemWidth((int)stringSize.get_Width());
    } //listBox1_MeasureItem

    // For efficiency, cache the brush to use for drawing.
    private SolidBrush foreColorBrush;

    private void listBox1_DrawItem(Object sender, 
        System.Windows.Forms.DrawItemEventArgs e)
    {
        Brush brush;

        // Create the brush using the ForeColor specified by the 
        // DrawItemEventArgs
        if (foreColorBrush == null) {
            foreColorBrush = new SolidBrush(e.get_ForeColor());
        }
        else {
            if (!foreColorBrush.get_Color().Equals(e.get_ForeColor())) {
                // The control's ForeColor has changed, 
                // so dispose of the cached brush and
                // create a new one.
                foreColorBrush.Dispose();
                foreColorBrush = new SolidBrush(e.get_ForeColor());
            }
        }
        // Select the appropriate brush depending on if the item is selected.
        // Since State can be a combinateion (bit-flag) of enum values,
        // you can't use "==" to compare them.
        if ((e.get_State() & DrawItemState.Selected).
            Equals(DrawItemState.Selected)) {
            brush = SystemBrushes.get_HighlightText();
        }
        else {
            brush = foreColorBrush;
        }

        // Perform the painting.
        Font font = ((ListBoxFontItem)listBox1.get_Items().
            get_Item(e.get_Index())).font;
        e.DrawBackground();
        e.get_Graphics().DrawString(font.get_Name(), font, brush, 
            new PointF((float)e.get_Bounds().get_X(), 
            (float)e.get_Bounds().get_Y()));
        e.DrawFocusRectangle();
    } //listBox1_DrawItem

    /// <summary>
    ///  A wrapper class for use with storing Fonts in a ListBox.  
    ///  Since ListBox uses the ToString() of its items 
    ///  for the text it displays, this class is needed to return
    ///  the name of the font, rather than its ToString() value.
    /// </summary>
    public class ListBoxFontItem
    {
        public Font font;

        public ListBoxFontItem(Font f)
        {
            set_Font(f);
        } //ListBoxFontItem

        public String ToString()
        {
            return get_Font().get_Name();
        } //ToString
    } //ListBoxFontItem
} //Form1

继承层次结构

System.Object
   System.EventArgs
    System.Windows.Forms.MeasureItemEventArgs

线程安全

此类型的任何公共静态（Visual Basic 中的 Shared）成员都是线程安全的，但不保证所有实例成员都是线程安全的。

平台

Windows 98、Windows 2000 SP4、Windows CE、Windows Millennium Edition、Windows Mobile for Pocket PC、Windows Mobile for Smartphone、Windows Server 2003、Windows XP Media Center Edition、Windows XP Professional x64 Edition、Windows XP SP2、Windows XP Starter Edition

.NET Framework 并不是对每个平台的所有版本都提供支持。有关受支持版本的列表，请参见系统要求。

版本信息

.NET Framework

受以下版本支持：2.0、1.1、1.0

请参见

参考

MeasureItemEventArgs 成员
System.Windows.Forms 命名空间
ListBox 类
ComboBox 类
CheckedListBox 类
MenuItem
MeasureItemEventHandler