Android提高十七篇之多级树形菜单的实现
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：
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<Object> childs=new ArrayList<Object>();}
三级树形菜单可以用如下，子项是二级树形菜单的结构体：
static public class SuperTreeNode {Object parent;//二级树形菜单的结构体List<TreeViewAdapter.TreeNode> childs = new ArrayList<TreeViewAdapter.TreeNode>();}
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。
PS：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：
<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"android:orientation="vertical" android:layout_width="fill_parent"android:layout_height="fill_parent"><LinearLayout android:id="@+id/LinearLayout01"android:layout_width="wrap_content" android:layout_height="wrap_content"><Button android:layout_height="wrap_content" android:text="两层结构"android:layout_width="160dip" android:id="@+id/btnNormal"></Button><Button android:layout_height="wrap_content" android:text="三层结构"android:layout_width="160dip" android:id="@+id/btnSuper"></Button></LinearLayout><ExpandableListView android:id="@+id/ExpandableListView01"android:layout_width="fill_parent" android:layout_height="fill_parent"></ExpandableListView></LinearLayout>
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{@Overridepublic void onClick(View v) {adapter.RemoveAll();adapter.notifyDataSetChanged();superAdapter.RemoveAll();superAdapter.notifyDataSetChanged();if(v==btnNormal){ List<TreeViewAdapter.TreeNode> treeNode = adapter.GetTreeNode(); for(int i=0;i<groups.length;i++) { TreeViewAdapter.TreeNode node=new TreeViewAdapter.TreeNode(); node.parent=groups[i]; for(int ii=0;ii<child[i].length;ii++) { node.childs.add(child[i][ii]); } treeNode.add(node); } adapter.UpdateTreeNode(treeNode); expandableList.setAdapter(adapter); expandableList.setOnChildClickListener(new OnChildClickListener(){@Overridepublic boolean onChildClick(ExpandableListView arg0, View arg1,int parent, int children, long arg4) {String str="parent id:"+String.valueOf(parent)+",children id:"+String.valueOf(children);Toast.makeText(testExpandableList.this, str, 300).show();return false;} });}else if(v==btnSuper){List<SuperTreeViewAdapter.SuperTreeNode> superTreeNode = superAdapter.GetTreeNode(); for(int i=0;i<parent.length;i++)//第一层 { SuperTreeViewAdapter.SuperTreeNode superNode=new SuperTreeViewAdapter.SuperTreeNode(); superNode.parent=parent[i]; //第二层 for(int ii=0;ii<child_grandson.length;ii++) { TreeViewAdapter.TreeNode node=new TreeViewAdapter.TreeNode(); node.parent=child_grandson[ii][0][0];//第二级菜单的标题 for(int iii=0;iii<child_grandson[ii][1].length;iii++)//第三级菜单 { node.childs.add(child_grandson[ii][1][iii]); } superNode.childs.add(node); } superTreeNode.add(superNode); } superAdapter.UpdateTreeNode(superTreeNode); expandableList.setAdapter(superAdapter);}} } /** * 三级树形菜单的事件不再可用，本函数由三级树形菜单的子项（二级菜单）进行回调 */ OnChildClickListener stvClickEvent=new OnChildClickListener(){@Overridepublic boolean onChildClick(ExpandableListView parent,View v, int groupPosition, int childPosition,long id) {String str="parent id:"+String.valueOf(groupPosition)+",children id:"+String.valueOf(childPosition);Toast.makeText(testExpandableList.this, str, 300).show();return false;} };}
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<Object> childs=new ArrayList<Object>();}List<TreeNode> treeNodes = new ArrayList<TreeNode>();Context parentContext;public TreeViewAdapter(Context view,int myPaddingLeft){parentContext=view;this.myPaddingLeft=myPaddingLeft;}public List<TreeNode> GetTreeNode(){return treeNodes;}public void UpdateTreeNode(List<TreeNode> 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：
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