MeasureItemEventArgs 类

定义

命名空间:

System.Windows.Forms

程序集:

System.Windows.Forms.dll

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

C#

public class MeasureItemEventArgs : EventArgs

继承

Object

EventArgs

MeasureItemEventArgs

示例

下面的代码示例演示如何使用 Graphics 属性执行项 ListBox的自定义绘图。

C#

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;
      }
   }
}

注解

当属性 、ListBox、ComboBoxCheckedListBox或MenuItem设置为true此事件时OwnerDraw，将发送此事件。 它用于告知绘图函数如何调整项的大小。

有关事件模型的信息，请参阅 “处理和引发事件”。

构造函数

MeasureItemEventArgs(Graphics, Int32)	初始化 MeasureItemEventArgs 类的新实例。
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。

属性

Graphics	获取要测量的 Graphics 对象。
Index	获取需要有高度和宽度的项的索引。
ItemHeight	获取或设置由 Index 指定的项高度。
ItemWidth	获取或设置由 Index 指定的项宽度。

方法

Equals(Object)	确定指定对象是否等于当前对象。 (继承自 Object)
GetHashCode()	作为默认哈希函数。 (继承自 Object)
GetType()	获取当前实例的 Type。 (继承自 Object)
MemberwiseClone()	创建当前 Object 的浅表副本。 (继承自 Object)
ToString()	返回表示当前对象的字符串。 (继承自 Object)

适用于

另请参阅

• ListBox
• ComboBox
• CheckedListBox
• MenuItem
• MeasureItemEventHandler