J2ME里面有自带的List类，但是功能太弱，没有实现View和Model的分离，所以操作起来比较费事。本来事想写一个Canvas的TreeList,但是画起来算坐标又太麻烦，所以选取了一个折中的方法，继承List,实现一个操作起来比较方便的组件。
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。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
}
}