简单升级了一下可着色的ListBox控件

翻译|其它|编辑:郝浩|2005-06-10 13:52:00.000|阅读 968 次

概述:

# 界面/图表报表/文档/IDE等千款热门软控件火热销售中 >>


   记得去年年初的时候做了一个Colorful ListBox Control控件。当时考虑的因数很少,虽然那个控件实现了简单的调用接口,可是有一个致命的问题是居然没有考虑到PostBack后的状态保存问题。


  新的ColorableListBox解决了控件被PostBack后的状态保存。实现过程很简单,就是把ListItem的ForeColor和BackColor信息存在ViewState里面,自己在控件中去维护。这个功能本来是很简单的,可是在做完后发现也仍然并不完美,因为目前还是不能处理条目移动的问题,如果条目被移动,比如有删除和插入等操作等,ListItem的颜色不能同步。目前的处理办法是如果有ListItem的变动,就清空所有的色彩信息。


  执行流程,在控件的OnPerRender事件运触发时,判断ListBox的Item的Attributes.CssStyle属性里是否被设置了color和background-color属性。如果有就记录下其属性值,然后保存在ViewState里,PostBack后从ViewState里恢复Item的属性值,在Render事件里,使用自己保存的属性信息来修改<option ...>...</option>的css属性。

protected override void OnPreRender(EventArgs e)
{
   if ( m_IsClear )
   {
     m_ItemStyles = null;
    }

   ArrayList alstStyle = null;
   Hashtable htItemStyles = null;

   for( int i=0 ; i < this.Items.Count ; ++i )
   {
       if ( alstStyle != null )
       {
             alstStyle.Clear();
        }
       foreach( string key in this.Items[i].Attributes.CssStyle.Keys )
      {
             if ( htItemStyles == null )
             {
                   htItemStyles = new Hashtable();
              }
             if ( m_ItemStyles != null )
             {
                  foreach( object obj in m_ItemStyles )
                  {
                     object [] objs = (object [])obj;
                     htItemStyles[objs[0]] = objs[1];
                   }
              }
             if ( alstStyle == null )
             {
                 alstStyle = new ArrayList();
              }
                 string strKey = key.ToLower();
                 if ( strKey == "color" || strKey == "background-color" )
                 {
                  alstStyle.Add(key + ':' + this.Items[i].Attributes.CssStyle[key]);
                  continue;
                 }
             }
         if ( alstStyle != null && alstStyle.Count > 0 )
         {
           string [] strAry = new string[alstStyle.Count];
           alstStyle.CopyTo(strAry);
           htItemStyles[i] = strAry;
          }
       }
     if ( htItemStyles != null )
     {
         int count = 0;
         m_ItemStyles = new object[htItemStyles.Count];
         foreach( object key in htItemStyles.Keys )
     {
         object [] objects = new object[2];
         objects[0] = key;
         objects[1] = (string [])htItemStyles[key];
         m_ItemStyles[count++] = objects;
      }
     }
   base.OnPreRender(e);
}


控件的使用方法为:
ColorableListBox clb = new ColorableListBox();
ListItem li = new ListItem(name, value);
li.Attributes.CssStyle.Add("color", "yellow");
li.Attributes.CssStyle.Add("background-color", "blue");
clb.Items.Add(li); 如果重新设置条目后(比如有Insert和Delete操作等)需要调用一下:ClearItemStyles();


附ColorableListBox控件源码

#region 附ColorableListBox控件源码
using System;
using System.IO;
using System.Collections;
using System.Text;
using System.Text.RegularExpressions;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.ComponentModel;

namespace WebExcel.UI.WebControls
{
      /**//// <summary>
     /// Summary description for ColorableListBox.
    /// </summary>

    [DefaultProperty("Text")]
    [ToolboxData("<{0}:ColorableListBox runat=server></{0}:ColorableListBox>")]
    public class ColorableListBox : ListBox
    {
        private object [] m_ItemStyles;
        private bool m_IsClear = false;

        protected override object SaveViewState()
    {
        ArrayList alstViewState = new ArrayList();
        object objBaseVS = base.SaveViewState();
        alstViewState.Add(objBaseVS);
        alstViewState.Add(m_ItemStyles);
        return alstViewState;
}

protected override void LoadViewState(object savedState)
{
    if ( savedState != null )
     { 
         ArrayList alstViewState = (ArrayList)savedState;
    if ( alstViewState.Count >= 1 )
     {
         base.LoadViewState(alstViewState[0]);
     }
    if ( alstViewState.Count == 2 )
     {
         m_ItemStyles = (object [])alstViewState[1];
      }
    }
}

protected override void OnPreRender(EventArgs e)
{
    if ( m_IsClear )
    {
       m_ItemStyles = null;
      }

      ArrayList alstStyle = null;
      Hashtable htItemStyles = null;

    for( int i=0 ; i < this.Items.Count ; ++i )
    {
       if ( alstStyle != null )
       {
            alstStyle.Clear();
        }
            foreach( string key in this.Items[i].Attributes.CssStyle.Keys )
      {
       if ( htItemStyles == null )
       {
           htItemStyles = new Hashtable();
        }
           if ( m_ItemStyles != null )
           {
             foreach( object obj in m_ItemStyles )
               {
                 object [] objs = (object [])obj;
                 htItemStyles[objs[0]] = objs[1];
                 }
               }
    if ( alstStyle == null )
    {
       alstStyle = new ArrayList();
     }
       string strKey = key.ToLower();
       if ( strKey == "color" || strKey == "background-color" )
       {
         alstStyle.Add(key + ':' + this.Items[i].Attributes.CssStyle[key]);
         continue;
        }
      }
if ( alstStyle != null && alstStyle.Count > 0 )
{
   string [] strAry = new string[alstStyle.Count];
   alstStyle.CopyTo(strAry);
   htItemStyles[i] = strAry;
   }
}
   if ( htItemStyles != null )
   {
    int count = 0;
    m_ItemStyles = new object[htItemStyles.Count];
    foreach( object key in htItemStyles.Keys )
    {
     object [] objects = new object[2];
     objects[0] = key;
     objects[1] = (string [])htItemStyles[key];
     m_ItemStyles[count++] = objects;
         }
      }
    base.OnPreRender(e);
}

/**//// <summary>
/// clear custom item styles
/// </summary>

public void ClearItemStyles()
{
   m_IsClear = true;
}

public override void DataBind()
{
    ClearItemStyles();
    base.DataBind ();
}

/**//// <summary>
/// Render this control to the output parameter specified.
/// </summary>
/// <param name="output"> The HTML writer to write out to </param>

protected override void Render(HtmlTextWriter output)
{
   StringBuilder strb = new StringBuilder();
   StringWriter sw = new StringWriter(strb);
   HtmlTextWriter htw = new HtmlTextWriter(sw);
   base.Render(htw);

   if ( m_ItemStyles != null )
   {
     foreach( object obj in m_ItemStyles )
      {
       object [] objs = (object [])obj;
       int i = (int)objs[0];
       AppendColorAttributes(strb, this.Items[i], (string [])objs[1]);
         }
      }
     output.Write(strb.ToString());
}

private void AppendColorAttributes(StringBuilder select, ListItem li, string [] styles)
{
     string strItemPattern = @"value=""{0}""{1}>{2}</option>";
     string strOriginalItem = string.Format(strItemPattern, li.Value, "", li.Text);
     string strStyle = " style=\"";
     for( int i=0 ; i < styles.Length ; i++ )
     {
        string [] keyvalue = styles[i].Split(new char [] {':'});
        string strStyleKey = keyvalue[0];
        string strStyleValue = keyvalue[1];
        strStyle += String.Format("{0}:{1};", strStyleKey.ToLower(), strStyleValue);
         }
        strStyle += @"""";
        string strNewItem = string.Format(strItemPattern, li.Value, strStyle, li.Text);
        select.Replace(strOriginalItem, strNewItem);
     }
  }
}
#endregion


标签:

本站文章除注明转载外,均为本站原创或翻译。欢迎任何形式的转载,但请务必注明出处、不得修改原文相关链接,如果存在内容上的异议请邮件反馈至chenjj@evget.com


为你推荐

  • 推荐视频
  • 推荐活动
  • 推荐产品
  • 推荐文章
  • 慧都慧问
扫码咨询


添加微信 立即咨询

电话咨询

客服热线
023-68661681

TOP