一般来说在Android里要实现树形菜单，都是用ExpandableList(也有高手自己继承ListView或者LinearLayout来做)，但是ExpandableList一般只能实现2级树形菜单。本文所述实例也依然使用ExpandableList，但是要实现的是3级树形菜单。
本文程序运行效果图如下图所示：
当用BaseExpandableListAdapter来实现二级树形菜单时，父项(getGroupView())和子项(getChildView())都是使用TextView。当要实现三级树形菜单时，子项(getChildView())就必须使用ExpandableList了。另外还要定义结构体来方便调用三级树形的数据，二级树形菜单可以用如下：
static public class TreeNode{
Object parent;
List childs=new ArrayList();
}
三级树形菜单可以用如下，子项是二级树形菜单的结构体如下所示：
static public class SuperTreeNode {
Object parent;
//二级树形菜单的结构体
List childs = new ArrayList();
}
实现三级树形菜单有两点要注意的：
1、第二级也是个树形菜单，因此必须在第二级项目展开/回收时设置足够的空间来完全显示二级树形菜单；
2、在实现三级树形菜单时，发现菜单的方法都是用不了(如OnChildClickListener、OnGroupClickListener等)，因此要获得选中的数据就必须在外部定义好回调函数，然后在第二级生成二级树形菜单时回调这个外部函数。
此外还需要注意：本文在解决No.2关键点的时候，只能取得第三级选中的序号。而第一，第二级依然无法获取其序号。
main.xml源码如下：
<&＃63;xml version="1.0" encoding="utf-8"&＃63;>
testExpandableList.java是主类，调用其他工具类，源码如下：
package com.testExpandableList;
import java.util.List;
import android.app.Activity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.ExpandableListView;
import android.widget.ExpandableListView.OnChildClickListener;
import android.widget.Toast;
public class testExpandableList extends Activity {
/** Called when the activity is first created. */
ExpandableListView expandableList;
TreeViewAdapter adapter;
SuperTreeViewAdapter superAdapter;
Button btnNormal,btnSuper;
// Sample data set. children[i] contains the children (String[]) for groups[i].
public String[] groups = { "xxxx好友", "xxxx同学", "xxxxx女人"};
public String[][] child= {
{ "A君", "B君", "C君", "D君" },
{ "同学甲", "同学乙", "同学丙"},
{ "御姐", "萝莉" }
};
public String[] parent = { "xxxx好友", "xxxx同学"};
public String[][][] child_grandson= {
{{"A君"},
{"AA","AAA"}},
{{"B君"},
{"BBB","BBBB","BBBBB"}},
{{"C君"},
{"CCC","CCCC"}},
{{"D君"},
{"DDD","DDDD","DDDDD"}},
};
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
this.setTitle("ExpandableListView练习----hellogv");
btnNormal=(Button)this.findViewById(R.id.btnNormal);
btnNormal.setOnClickListener(new ClickEvent());
btnSuper=(Button)this.findViewById(R.id.btnSuper);
btnSuper.setOnClickListener(new ClickEvent());
adapter=new TreeViewAdapter(this,TreeViewAdapter.PaddingLeft>>1);
superAdapter=new SuperTreeViewAdapter(this,stvClickEvent);
expandableList=(ExpandableListView) testExpandableList.this.findViewById(R.id.ExpandableListView01);
}
class ClickEvent implements View.OnClickListener{
@Override
public void onClick(View v) {
adapter.RemoveAll();
adapter.notifyDataSetChanged();
superAdapter.RemoveAll();
superAdapter.notifyDataSetChanged();
if(v==btnNormal)
{
List treeNode = adapter.GetTreeNode();
for(int i=0;i superTreeNode = superAdapter.GetTreeNode();
for(int i=0;i
TreeViewAdapter.java是实现二级树形菜单的工具类，源码如下：
package com.testExpandableList;
import java.util.ArrayList;
import java.util.List;
import android.content.Context;
import android.util.Log;
import android.view.Gravity;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AbsListView;
import android.widget.BaseExpandableListAdapter;
import android.widget.TextView;
public class TreeViewAdapter extends BaseExpandableListAdapter{
public static final int ItemHeight=48;//每项的高度
public static final int PaddingLeft=36;//每项的高度
private int myPaddingLeft=0;//如果是由SuperTreeView调用，则作为子项需要往右移
static public class TreeNode{
Object parent;
List childs=new ArrayList();
}
List treeNodes = new ArrayList();
Context parentContext;
public TreeViewAdapter(Context view,int myPaddingLeft)
{
parentCOntext=view;
this.myPaddingLeft=myPaddingLeft;
}
public List GetTreeNode()
{
return treeNodes;
}
public void UpdateTreeNode(List nodes)
{
treeNodes=nodes;
}
public void RemoveAll()
{
treeNodes.clear();
}
public Object getChild(int groupPosition, int childPosition) {
return treeNodes.get(groupPosition).childs.get(childPosition);
}
public int getChildrenCount(int groupPosition) {
return treeNodes.get(groupPosition).childs.size();
}
static public TextView getTextView(Context context) {
AbsListView.LayoutParams lp = new AbsListView.LayoutParams(
ViewGroup.LayoutParams.FILL_PARENT, ItemHeight);
TextView textView = new TextView(context);
textView.setLayoutParams(lp);
textView.setGravity(Gravity.CENTER_VERTICAL | Gravity.LEFT);
return textView;
}
public View getChildView(int groupPosition, int childPosition,
boolean isLastChild, View convertView, ViewGroup parent) {
TextView textView = getTextView(this.parentContext);
textView.setText(getChild(groupPosition, childPosition).toString());
textView.setPadding(myPaddingLeft+PaddingLeft, 0, 0, 0);
return textView;
}
public View getGroupView(int groupPosition, boolean isExpanded,
View convertView, ViewGroup parent) {
TextView textView = getTextView(this.parentContext);
textView.setText(getGroup(groupPosition).toString());
textView.setPadding(myPaddingLeft+(PaddingLeft>>1), 0, 0, 0);
return textView;
}
public long getChildId(int groupPosition, int childPosition) {
return childPosition;
}
public Object getGroup(int groupPosition) {
return treeNodes.get(groupPosition).parent;
}
public int getGroupCount() {
return treeNodes.size();
}
public long getGroupId(int groupPosition) {
return groupPosition;
}
public boolean isChildSelectable(int groupPosition, int childPosition) {
return true;
}
public boolean hasStableIds() {
return true;
}
}
SuperTreeViewAdapter.java是实现三级树形菜单的工具类，会用到TreeViewAdapter.java，源码如下：
package com.testExpandableList;
import java.util.ArrayList;
import java.util.List;
import com.testExpandableList.TreeViewAdapter.TreeNode;
import android.content.Context;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AbsListView;
import android.widget.BaseExpandableListAdapter;
import android.widget.ExpandableListView;
import android.widget.ExpandableListView.OnChildClickListener;
import android.widget.ExpandableListView.OnGroupCollapseListener;
import android.widget.ExpandableListView.OnGroupExpandListener;
import android.widget.TextView;
public class SuperTreeViewAdapter extends BaseExpandableListAdapter {
static public class SuperTreeNode {
Object parent;
//二级树形菜单的结构体
List childs = new ArrayList();
}
private List superTreeNodes = new ArrayList();
private Context parentContext;
private OnChildClickListener stvClickEvent;//外部回调函数
public SuperTreeViewAdapter(Context view,OnChildClickListener stvClickEvent) {
parentCOntext= view;
this.stvClickEvent=stvClickEvent;
}
public List GetTreeNode() {
return superTreeNodes;
}
public void UpdateTreeNode(List node) {
superTreeNodes = node;
}
public void RemoveAll()
{
superTreeNodes.clear();
}
public Object getChild(int groupPosition, int childPosition) {
return superTreeNodes.get(groupPosition).childs.get(childPosition);
}
public int getChildrenCount(int groupPosition) {
return superTreeNodes.get(groupPosition).childs.size();
}
public ExpandableListView getExpandableListView() {
AbsListView.LayoutParams lp = new AbsListView.LayoutParams(
ViewGroup.LayoutParams.FILL_PARENT, TreeViewAdapter.ItemHeight);
ExpandableListView superTreeView = new ExpandableListView(parentContext);
superTreeView.setLayoutParams(lp);
return superTreeView;
}
/**
* 三层树结构中的第二层是一个ExpandableListView
*/
public View getChildView(int groupPosition, int childPosition,
boolean isLastChild, View convertView, ViewGroup parent) {
// 是
final ExpandableListView treeView = getExpandableListView();
final TreeViewAdapter treeViewAdapter = new TreeViewAdapter(this.parentContext,0);
List tmp = treeViewAdapter.GetTreeNode();//临时变量取得TreeViewAdapter的TreeNode集合，可为空
final TreeNode treeNode=(TreeNode) getChild(groupPosition, childPosition);
tmp.add(treeNode);
treeViewAdapter.UpdateTreeNode(tmp);
treeView.setAdapter(treeViewAdapter);
//关键点：取得选中的二级树形菜单的父子节点,结果返回给外部回调函数
treeView.setOnChildClickListener(this.stvClickEvent);
/**
* 关键点：第二级菜单展开时通过取得节点数来设置第三级菜单的大小
*/
treeView.setOnGroupExpandListener(new OnGroupExpandListener() {
@Override
public void onGroupExpand(int groupPosition) {
AbsListView.LayoutParams lp = new AbsListView.LayoutParams(
ViewGroup.LayoutParams.FILL_PARENT,
(treeNode.childs.size()+1)*TreeViewAdapter.ItemHeight + 10);
treeView.setLayoutParams(lp);
}
});
/**
* 第二级菜单回收时设置为标准Item大小
*/
treeView.setOnGroupCollapseListener(new OnGroupCollapseListener() {
@Override
public void onGroupCollapse(int groupPosition) {
AbsListView.LayoutParams lp = new AbsListView.LayoutParams(ViewGroup.LayoutParams.FILL_PARENT,
TreeViewAdapter.ItemHeight);
treeView.setLayoutParams(lp);
}
});
treeView.setPadding(TreeViewAdapter.PaddingLeft, 0, 0, 0);
return treeView;
}
/**
* 三级树结构中的首层是TextView,用于作为title
*/
public View getGroupView(int groupPosition, boolean isExpanded,
View convertView, ViewGroup parent) {
TextView textView = TreeViewAdapter.getTextView(this.parentContext);
textView.setText(getGroup(groupPosition).toString());
textView.setPadding(TreeViewAdapter.PaddingLeft, 0, 0, 0);
return textView;
}
public long getChildId(int groupPosition, int childPosition) {
return childPosition;
}
public Object getGroup(int groupPosition) {
return superTreeNodes.get(groupPosition).parent;
}
public int getGroupCount() {
return superTreeNodes.size();
}
public long getGroupId(int groupPosition) {
return groupPosition;
}
public boolean isChildSelectable(int groupPosition, int childPosition) {
return true;
}
public boolean hasStableIds() {
return true;
}
}
总结，使用ExpandableList实现三级树形菜单时有些bug不好解决，而且定义三维数组的时候也要倍加小心！所以尽量把数据化简来使用二级树形菜单。
希望本文所述代码对大家进行Android程序设计有一定的帮助。
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