How change the color of SelectedItem in CheckedListBox in WindowsForms?

问题

I want to change the color of the items that are chedked in the CheckedListBox in C# WindowsForms.

Can any one help me to solve this problem!

回答1:

This should get you started. I've subclassed a CheckedListBox and overridden the drawing event. The result is all checked items in the list are drawn with a red background.

From playing around with this, if you want the area behind the checkbox to be a different colour as well, use e.Graphics.FillRectangle before calling base.OnDrawItem.

class ColouredCheckedListBox : CheckedListBox
{
    protected override void OnDrawItem(DrawItemEventArgs e)
    {
        DrawItemEventArgs e2 =
            new DrawItemEventArgs
            (
                e.Graphics,
                e.Font,
                new Rectangle(e.Bounds.Location, e.Bounds.Size),
                e.Index,
                e.State,
                e.ForeColor,
                this.CheckedIndices.Contains(e.Index) ? Color.Red : SystemColors.Window
            );

        base.OnDrawItem(e2);
    }
}

回答2:

Thanks Jon that got me on the right path as I had the same desire: to have the item's text color be different for each of the 3 states of the checkbox.

I came up with this subclass of the CheckedListBox. It changes the items text, not the background color. It lets the 3 colors be set by the user at design time or in code of course.

It also fixes a problem I had where I got an error when viewing the control in the designer. I also had to overcome a problem I think would have happened in your solution where if the item is selected the base.OnDrawItem method obliterates the color choices set in the overridden OnDrawItem method. I did this at the expense of the selected item no longer having a colored background by removing the part of e.State that says it is selected so that in the base.OnDrawItem it is not made to be a selected item look and feel. This is ok though I think since the user will see the focus rectangle still which indicates which is selected.

Hopefully this may be useful to others. I didn't find much for a cohesive solution (even just a complete OnDrawItem method) when looking on the net.

using System;
using System.Windows.Forms;
using System.Drawing;

namespace MyNameSpace
  {
  /// <summary>
  /// This is a CheckedListBox that allows the item's text color to be different for each of the 3 states of the corresponding checkbox's value.
  /// Like the base CheckedListBox control, you must handle setting of the indeterminate checkbox state yourself.
  /// Note also that this control doesn't allow highlighting of the selected item since that obscures the item's special text color which has the special meaning.  But 
  /// the selected item is still known to the user by the focus rectangle it will have surrounding it, like usual.
  /// </summary>
  class ColorCodedCheckedListBox : CheckedListBox
    {
    public Color UncheckedColor { get; set; }
    public Color CheckedColor { get; set; }
    public Color IndeterminateColor { get; set; }

    /// <summary>
    /// Parameterless Constructor
    /// </summary>
    public ColorCodedCheckedListBox() 
      {
      UncheckedColor = Color.Green;
      CheckedColor = Color.Red;
      IndeterminateColor = Color.Orange;
      }

    /// <summary>
    /// Constructor that allows setting of item colors when checkbox has one of 3 states.
    /// </summary>
    /// <param name="uncheckedColor">The text color of the items that are unchecked.</param>
    /// <param name="checkedColor">The text color of the items that are checked.</param>
    /// <param name="indeterminateColor">The text color of the items that are indeterminate.</param>
    public ColorCodedCheckedListBox(Color uncheckedColor, Color checkedColor, Color indeterminateColor) 
      {
      UncheckedColor = uncheckedColor;
      CheckedColor = checkedColor;
      IndeterminateColor = indeterminateColor;
      }

    /// <summary>
    /// Overriden draw method that doesn't allow highlighting of the selected item since that obscures the item's text color which has desired meaning.  But the 
    /// selected item is still known to the user by the focus rectangle being displayed.
    /// </summary>
    /// <param name="e"></param>
    protected override void OnDrawItem(DrawItemEventArgs e)
      {
      if (this.DesignMode)
        {
        base.OnDrawItem(e); 
        }
      else
        {
        Color textColor = this.GetItemCheckState(e.Index) == CheckState.Unchecked ? UncheckedColor : (this.GetItemCheckState(e.Index) == CheckState.Checked ? CheckedColor : IndeterminateColor);

        DrawItemEventArgs e2 = new DrawItemEventArgs
           (e.Graphics,
            e.Font,
            new Rectangle(e.Bounds.Location, e.Bounds.Size),
            e.Index,
            (e.State & DrawItemState.Focus) == DrawItemState.Focus ? DrawItemState.Focus : DrawItemState.None, /* Remove 'selected' state so that the base.OnDrawItem doesn't obliterate the work we are doing here. */
            textColor,
            this.BackColor);

        base.OnDrawItem(e2); 
        }
      }
    }
  }

来源：https://stackoverflow.com/questions/2130934/how-change-the-color-of-selecteditem-in-checkedlistbox-in-windowsforms

标签

winforms

checkedlistbox