目的：

       1.可伸缩的目录树结构，暂时先实现两层。

       2.label和存储内容分离。

       3.激活和非激活图片分开。

       4.通过选择事件可以准确快速找到对应内容

       5.存储内容无关性，里面可以放置任何object

       实现思路：

       1.封装一个expanditem类，用来存储每一条数据。

/**
  * 默认图片
  */
 private  string imagepath="";
 /*
  * 激活图片,如果为空说明此图片无效
  */
 private string selectimgpath=null;
 /**
  * 组
  */
 public static int group=1;
 /**
  * 记录
  */
 public static int item=0;
 /**
  * 是否选中,如果选中则默认为展开状态
  */
 private boolean ifselected=false;
 /**
  * 显示label
  */
 private string label;
 /**
  * 类型：组，记录
  */
 private int type;
 /**
  * 存储的对象
  */

          group表示这个item是一个父节点，下面包含字节点，这样它的content将是一个vector.

          item表示这个item是根节点。

         selectimgpath,是激活后的图标，可以为空，为空的时候选择了这个item图标不变。

然后就是expandlist类，此类的数据结构如下：

          private vector itemlist = new vector();

          /*用来存储内容的数据结构*/

           private expandlistitem currentselectedobject = null;

           /*当前所选择的对象，方便获取*/

           private int currentselectedindex = -1;

           /*当前选择的对象在队列中的index,队列有两个，一个是真实数据的存储vector，另外一个是显示在屏幕上的队列。这两个有时候是不一样的。因为有的节点有子节点*/

           private vector appearhooklist = new vector();

           /*显示在屏幕上的label队列*/
          

          总的思路如下：

           初始化list的时候，参数是一个vector，里面可以是expanditem或者是vector.然后根据expanditem里面的参数初始化屏幕，如果group节点的ifselected状态为true则递归添加下面的子节点，否则只插入当前节点。图标也是一样，如果ifselected为true 则用激活图标否则用默认图标。

          在用户选择了一个结点后，取得当前的激活的index号码，判断是不是父节点，如果是的话，首先更新这个父节点的ifselected属性为true,然后重画这个list;(其实效率更高的方法是直接插入这个父节点的子节点，但是这样做的话，在移除的时候会稍微稍微麻烦一点。有时间我在改过来，呵呵)。如果选择的是子节点，则判断是否有激活图标，如果有，则更新这个图标，就好了。

          下面是效果

附代码一份，这是我me组件库中很早的版本了，呵呵。别的组件以后在写。其实最好的方法就是写canvas。

expandlist.java

 

package com.skystudio.expandlist;

public class expandlistitem {
 public expandlistitem(object content,string imgpath,string selectimgpath,string label,int type,boolean ifselected){
  this.selectimgpath=selectimgpath;
  this.imagepath=imgpath;
  this.content=content;
  this.label=label;
  this.type=type;
  this.ifselected=ifselected;
 }
 /**
  * 默认图片
  */
 private  string imagepath="";
 /*
  * 激活图片,如果为空说明此图片无效
  */
 private string selectimgpath=null;
 /**
  * 组
  */
 public static int group=1;
 /**
  * 记录
  */
 public static int item=0;
 /**
  * 是否选中
  */
 private boolean ifselected=false;
 /**
  * 显示label
  */
 private string label;
 /**
  * 类型：组，记录
  */
 private int type;
 /**
  * 存储的对象
  */
 private object content;
 
 public object getcontent() {
  return content;
 }
 public void setcontent(object content) {
  this.content = content;
 }
 public string getlabel() {
  return label;
 }
 public void setlabel(string label) {
  this.label = label;
 }
 public int gettype() {
  return type;
 }
 public void settype(int type) {
  this.type = type;
 }
 public boolean ifselected() {
  return ifselected;
 }
 public void setifselected(boolean ifselected) {
  this.ifselected = ifselected;
 }
 public string tostring() {
  
  return this.label+"  ";
 }
 public string getimagepath() {
  return imagepath;
 }
 public void setimagepath(string imagepath) {
  this.imagepath = imagepath;
 }
 public string getselectimgpath() {
  return selectimgpath;
 }
 public void setselectimgpath(string selectimgpath) {
  this.selectimgpath = selectimgpath;
 }
}

package com.skystudio.expandlist;

import java.util.vector;

import javax.microedition.lcdui.command;
import javax.microedition.lcdui.commandlistener;
import javax.microedition.lcdui.displayable;
import javax.microedition.lcdui.image;
import javax.microedition.lcdui.list;

import com.skystudio.ui.toolkit.util;

/**
 * @author sky
 *
 */
public class expandlist extends list implements commandlistener {
 private vector itemlist = new vector();

 private expandlistitem currentselectedobject = null;

 private int currentselectedindex = -1;

 private vector appearhooklist = new vector();

 public expandlist(string title, int type, vector itemlist) {
  super(title, type);
  this.itemlist = itemlist;
  this.setcommandlistener(this);
  loadlist();
 }

 public void appenditem(expandlistitem item, image icon, boolean ifsub) {
  appearhooklist.addelement(item);
  system.out.println("add current display list:" + item);
  if (!ifsub) {
   this.append(item.getlabel(), icon);
  } else {
   this.append(" " + item.getlabel(), icon);
  }

 }

 public void init() {
  int count = this.size();
  for (int i = 0; i < count; i++) {
   this.delete(0);
  }
  this.appearhooklist.removeallelements();
  system.out.println("now itemlist:" + this.itemlist);
 }

 public void loadlist() {
  init();
  for (int i = 0; i < itemlist.size(); i++) {
   expandlistitem elitem = (expandlistitem) itemlist.elementat(i);
   if (elitem.gettype() == expandlistitem.group) {
    image icon = util.getimage(elitem.getimagepath());
    /**
     * @debug
     */
    if (elitem.ifselected()) {
     if (elitem.getselectimgpath() != null) {
      icon = util.getimage(elitem.getselectimgpath());
     }
     system.out.println("add parent node:");
     this.appenditem(elitem, icon, false);
     vector group = (vector) elitem.getcontent();
     for (int j = 0; j < group.size(); j++) {
      expandlistitem item = (expandlistitem) group
        .elementat(j);
      image ic = util.getimage(item.getimagepath());
      system.out.println("add sub node:");
      this.appenditem(item, ic, true);
     }
    } else {
     system.out.println("add leave node:");
     this.appenditem(elitem, icon, false);
    }

   } else if (elitem.gettype() == expandlistitem.item) {
    image icon = util.getimage(elitem.getimagepath());
    this.appenditem(elitem, icon, false);
   }

  }
  if (this.currentselectedindex != -1) {
   this.setselectedindex(currentselectedindex, true);
  }
 }

 public vector getitemlist() {
  return itemlist;
 }

 public void setitemlist(vector itemlist) {
  this.itemlist = itemlist;
 }

 public void commandaction(command arg0, displayable arg1) {
  if (arg0 == list.select_command) {
   /**
    * set current list selected status
    */
   this.currentselectedindex = this.getselectedindex();
   system.out.println(this.appearhooklist);

   this.currentselectedobject = (expandlistitem) this.appearhooklist
     .elementat(currentselectedindex);

   int indexinitemlist = this.itemlist.indexof(this.appearhooklist
     .elementat(this.getselectedindex()));
   system.out.println(" selected: " + currentselectedindex + " "
     + this.currentselectedobject + " indexinitemlist:"
     + indexinitemlist);
   /**
    *
    */
   if (this.currentselectedobject.gettype() == expandlistitem.group) {
    if (this.currentselectedobject.ifselected() == false) {// previous
                  // item
                  // status
                  // is
                  // contractive,need
                  // to be
                  // expanded.
     system.out.println(this.currentselectedobject.ifselected());
     this.itemlist.removeelementat(indexinitemlist);
     this.currentselectedobject.setifselected(true);
     this.itemlist.insertelementat(currentselectedobject,
       indexinitemlist);
    } else {
     this.itemlist.removeelementat(indexinitemlist);
     this.currentselectedobject.setifselected(false);
     this.itemlist.insertelementat(currentselectedobject,
       indexinitemlist);
    }
    this.init();
    this.loadlist();
   } else {

    if (this.currentselectedobject.getselectimgpath() != null) {
     if (this.currentselectedobject.ifselected() == false) {
      image icon = util.getimage(this.currentselectedobject
        .getselectimgpath());
      system.out.println(this.currentselectedobject
        .ifselected());
      this.itemlist.removeelementat(indexinitemlist);
      this.currentselectedobject.setifselected(true);
      this.itemlist.insertelementat(currentselectedobject,
        indexinitemlist);
      this.delete(this.currentselectedindex);
      this.insert(this.currentselectedindex,
        this.currentselectedobject.getlabel(), icon);
     } else {
      image icon = util.getimage(this.currentselectedobject
        .getimagepath());
      this.itemlist.removeelementat(indexinitemlist);
      this.currentselectedobject.setifselected(false);
      this.itemlist.insertelementat(currentselectedobject,
        indexinitemlist);
      this.delete(this.currentselectedindex);
      this.insert(this.currentselectedindex,
        this.currentselectedobject.getlabel(), icon);
     }
     this.setselectedindex(this.currentselectedindex,true);
    }

   }
  }
 }

}

附测试代码

import java.util.vector;

import javax.microedition.lcdui.choice;
import javax.microedition.lcdui.display;
import javax.microedition.midlet.midlet;
import javax.microedition.midlet.midletstatechangeexception;

import com.skystudio.canvas.listcanvas;
import com.skystudio.expandlist.expandlist;
import com.skystudio.expandlist.expandlistitem;

public class main extends midlet {
 display d=null;
 protected void startapp() throws midletstatechangeexception {
  d=display.getdisplay(this);
  listtest();
 }
 private void testui(){
  listcanvas l=new listcanvas();
  d.setcurrent(l);
 }
 private void listtest(){
  vector v1=new vector();
  for(int i=0;i<10;i++){
   v1.addelement(new expandlistitem("土匪"+integer.tostring(i),"/img/default.png","/img/group-open.png","土匪"+integer.tostring(i),expandlistitem.item,false));
  }
  string v2="警察";
  vector v3=new vector();
  for(int i=0;i<10;i++){
   v3.addelement(new expandlistitem("警察"+integer.tostring(i),"/img/default.png","/img/group-open.png","警察"+integer.tostring(i),expandlistitem.item,false));
  }
  vector v=new vector();
  v.addelement(new expandlistitem(v1,"/img/group-close.png","/img/group-open.png","土匪帮",expandlistitem.group,false));
  v.addelement(new expandlistitem(v3,"/img/group-close.png","/img/group-open.png","警察局",expandlistitem.group,false));
  v.addelement(new expandlistitem(v2,"/img/default.png","/img/group-open.png","法官",expandlistitem.item,false));
  d.setcurrent(new expandlist("花名册",choice.implicit,v));
 }

 protected void pauseapp() {
  // todo auto-generated method stub

 }

 protected void destroyapp(boolean arg0) throws midletstatechangeexception {
  // todo auto-generated method stub

 }

}