MeasureItemEventArgs MeasureItemEventArgs MeasureItemEventArgs MeasureItemEventArgs Class

定义

ListBoxComboBoxCheckedListBoxMenuItem 控件的 MeasureItem 事件提供数据。Provides data for the MeasureItem event of the ListBox, ComboBox, CheckedListBox, and MenuItem controls.

public ref class MeasureItemEventArgs : EventArgs
public class MeasureItemEventArgs : EventArgs
type MeasureItemEventArgs = class
    inherit EventArgs
Public Class MeasureItemEventArgs
Inherits EventArgs
继承
MeasureItemEventArgsMeasureItemEventArgsMeasureItemEventArgsMeasureItemEventArgs

示例

下面的代码示例演示如何使用Graphics属性来对ListBox中的项执行自定义绘制。The following code example demonstrates how to use the Graphics property to perform custom drawing of the items in a ListBox.

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 : 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 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 (components IsNot Nothing) Then
            components.Dispose()
         End If

         If (foreColorBrush IsNot 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

注解

OwnerDraw ListBox、、 ComboBox CheckedListBox或的属性true设置为时, 将发送此事件。 MenuItemThis event is sent when the OwnerDraw property of ListBox, ComboBox, CheckedListBox, or MenuItem is set to true. 它用于告知绘图函数如何调整项的大小。It is used to tell the drawing function how to size an item.

有关事件模型的信息, 请参阅处理和引发事件For information about the event model, see Handling and Raising Events.

构造函数

MeasureItemEventArgs(Graphics, Int32) MeasureItemEventArgs(Graphics, Int32) MeasureItemEventArgs(Graphics, Int32) MeasureItemEventArgs(Graphics, Int32)

初始化 MeasureItemEventArgs 类的新实例。Initializes a new instance of the MeasureItemEventArgs class.

MeasureItemEventArgs(Graphics, Int32, Int32) MeasureItemEventArgs(Graphics, Int32, Int32) MeasureItemEventArgs(Graphics, Int32, Int32) MeasureItemEventArgs(Graphics, Int32, Int32)

初始化提供该项高度的参数的 MeasureItemEventArgs 类的一个新实例。Initializes a new instance of the MeasureItemEventArgs class providing a parameter for the item height.

属性

Graphics Graphics Graphics Graphics

获取要测量的 Graphics 对象。Gets the Graphics object to measure against.

Index Index Index Index

获取需要有高度和宽度的项的索引。Gets the index of the item for which the height and width is needed.

ItemHeight ItemHeight ItemHeight ItemHeight

获取或设置由 Index 指定的项高度。Gets or sets the height of the item specified by the Index.

ItemWidth ItemWidth ItemWidth ItemWidth

获取或设置由 Index 指定的项宽度。Gets or sets the width of the item specified by the Index.

方法

Equals(Object) Equals(Object) Equals(Object) Equals(Object)

确定指定的对象是否等于当前对象。Determines whether the specified object is equal to the current object.

(Inherited from Object)
GetHashCode() GetHashCode() GetHashCode() GetHashCode()

作为默认哈希函数。Serves as the default hash function.

(Inherited from Object)
GetType() GetType() GetType() GetType()

获取当前实例的 TypeGets the Type of the current instance.

(Inherited from Object)
MemberwiseClone() MemberwiseClone() MemberwiseClone() MemberwiseClone()

创建当前 Object 的浅表副本。Creates a shallow copy of the current Object.

(Inherited from Object)
ToString() ToString() ToString() ToString()

返回表示当前对象的字符串。Returns a string that represents the current object.

(Inherited from Object)

适用于

另请参阅