C# ComboBox.DrawItem事件代码示例

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.
  private 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();
  }

//引入命名空间
using System;
using System.Drawing;
using System.Collections;
using System.ComponentModel;
using System.Windows.Forms;
using System.Data;

public class Form1 : System.Windows.Forms.Form {
    private System.Windows.Forms.ComboBox comboBox1 = new System.Windows.Forms.ComboBox();
    private System.Windows.Forms.Label label1 = new System.Windows.Forms.Label();
    private System.Windows.Forms.ComboBox comboBox2 = new System.Windows.Forms.ComboBox();
    private System.Windows.Forms.Label label2 = new System.Windows.Forms.Label();
    ArrayList colorArray = new ArrayList();
    ArrayList fontArray = new ArrayList();
    public Form1() {
        this.SuspendLayout();

        this.comboBox1.DrawMode = System.Windows.Forms.DrawMode.OwnerDrawVariable;
        this.comboBox1.ItemHeight = 25;
        this.comboBox1.Location = new System.Drawing.Point(16, 40);
        this.comboBox1.Size = new System.Drawing.Size(264, 31);
        this.comboBox1.SelectedIndexChanged += new System.EventHandler(this.MyItemSelected);
        this.comboBox1.MeasureItem += new System.Windows.Forms.MeasureItemEventHandler(this.comboBox1_MeasureItem);
        this.comboBox1.DrawItem += new System.Windows.Forms.DrawItemEventHandler(this.comboBox1_DrawItem);

        this.label1.Location = new System.Drawing.Point(16, 16);
        this.label1.Size = new System.Drawing.Size(100, 16);
        this.label1.Text = "Font Combo Box";

        this.comboBox2.DrawMode = System.Windows.Forms.DrawMode.OwnerDrawFixed;
        this.comboBox2.DropDownStyle = System.Windows.Forms.ComboBoxStyle.DropDownList;
        this.comboBox2.ItemHeight = 20;
        this.comboBox2.Location = new System.Drawing.Point(16, 104);
        this.comboBox2.Size = new System.Drawing.Size(264, 26);
        this.comboBox2.SelectedIndexChanged += new System.EventHandler(this.MyItemSelected);
        this.comboBox2.DrawItem += new System.Windows.Forms.DrawItemEventHandler(this.comboBox2_DrawItem);

        this.label2.Location = new System.Drawing.Point(24, 80);
        this.label2.Text = "Color Combo Box";

        this.AutoScaleBaseSize = new System.Drawing.Size(5, 13);
        this.ClientSize = new System.Drawing.Size(312, 157);
        this.Controls.AddRange(new System.Windows.Forms.Control[] {
                                      this.label2,
                                      this.label1,
                                      this.comboBox1,
                                      this.comboBox2});
        this.Load += new System.EventHandler(this.Form1_Load);
        this.ResumeLayout(false);

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

    private void Form1_Load(object sender, System.EventArgs e) {
        colorArray.Add(new SolidBrush(Color.Yellow));
        colorArray.Add(new SolidBrush(Color.Black));
        colorArray.Add(new SolidBrush(Color.Azure));
        colorArray.Add(new SolidBrush(Color.Firebrick));
        colorArray.Add(new SolidBrush(Color.DarkMagenta));

        comboBox2.Items.Add("A");
        comboBox2.Items.Add("B");
        comboBox2.Items.Add("C");
        comboBox2.Items.Add("D");
        comboBox2.Items.Add("E");

        fontArray.Add(new Font("Ariel", 15, FontStyle.Bold));
        fontArray.Add(new Font("Courier", 12, FontStyle.Italic));
        fontArray.Add(new Font("Veranda", 14, FontStyle.Bold));
        fontArray.Add(new Font("System", 10, FontStyle.Strikeout));
        fontArray.Add(new Font("Century SchoolBook", 15, FontStyle.Underline));

        comboBox1.Items.Add("W");
        comboBox1.Items.Add("H");
        comboBox1.Items.Add("P");
        comboBox1.Items.Add("D");
        comboBox1.Items.Add("L");

    }

    private void comboBox1_DrawItem(object sender, System.Windows.Forms.DrawItemEventArgs e) {
        Graphics g = e.Graphics;
        Rectangle r = e.Bounds;
        Font fn = null;

        if (e.Index >= 0) {
            fn = (Font)fontArray[e.Index];
            string s = (string)comboBox1.Items[e.Index];
            StringFormat sf = new StringFormat();
            sf.Alignment = StringAlignment.Near;
            e.Graphics.DrawRectangle(new Pen(new SolidBrush(Color.Black), 2), r);

            if (e.State == (DrawItemState.NoAccelerator | DrawItemState.NoFocusRect)) {
                e.Graphics.FillRectangle(new SolidBrush(Color.White), r);
                e.Graphics.DrawString(s, fn, new SolidBrush(Color.Black), r, sf);
                e.DrawFocusRectangle();
            } else {
                e.Graphics.FillRectangle(new SolidBrush(Color.LightBlue), r);
                e.Graphics.DrawString(s, fn, new SolidBrush(Color.Red), r, sf);
                e.DrawFocusRectangle();
            }
        }
    }

    private void comboBox2_DrawItem(object sender, System.Windows.Forms.DrawItemEventArgs e) {
        Graphics g = e.Graphics;

        Rectangle r = e.Bounds;

        if (e.Index >= 0) {
            Rectangle rd = r;
            rd.Width = 100;

            Rectangle rt = r;

            SolidBrush b = (SolidBrush)colorArray[e.Index];
            g.FillRectangle(b, rd);

            StringFormat sf = new StringFormat();
            sf.Alignment = StringAlignment.Near;

            Console.WriteLine(e.State.ToString());
            e.Graphics.DrawRectangle(new Pen(new SolidBrush(Color.Black), 2), r);

            if (e.State == (DrawItemState.NoAccelerator | DrawItemState.NoFocusRect)) {
                e.Graphics.FillRectangle(new SolidBrush(Color.White), r);
                e.Graphics.DrawString(b.Color.Name, new Font("Ariel", 8, FontStyle.Bold), new SolidBrush(Color.Black), r, sf);
                e.DrawFocusRectangle();
            } else {
                e.Graphics.FillRectangle(new SolidBrush(Color.LightBlue), r);
                e.Graphics.DrawString(b.Color.Name, new Font("Veranda", 12, FontStyle.Bold), new SolidBrush(Color.Red), r, sf);
                e.DrawFocusRectangle();
            }
        }
    }

    private void MyItemSelected(object sender, System.EventArgs e) {
        ComboBox cb = null;
        if (sender.Equals(comboBox1))
            cb = comboBox1;
        else
            cb = comboBox2;
        int x = cb.SelectedIndex;

        if (sender.Equals(comboBox1)) {
            Console.WriteLine("Item Selected is = " + (string)cb.Items[x]);
        } else {
            SolidBrush br = (SolidBrush)colorArray[x];
            Console.WriteLine("Color Selected is = " + br.Color.Name);
        }
    }

    private void comboBox1_MeasureItem(object sender, System.Windows.Forms.MeasureItemEventArgs e) {
        if (e.Index % 2 == 0) {
            e.ItemHeight = 45;
            e.ItemWidth = 20;
        } else {
            e.ItemHeight = 25;
            e.ItemWidth = 10;
        }
    }
}