1.简介

　　基于基于BaseExpandableListAdapter扩展的ExpandableList用法，现在网上流行的主要有两种：第一种是向BaseExpandableListAdapter传入两个数组，第一个是表示Group（目录头）信息的一维数组，第二个是表示Child（目录子项）的二维数组数组；第二种是构建两个类，一个是表示目录信息的GroupInfo类，另一个是表示子项信息的ChildInfo类，然后传入BaseExpandableListAdapter。通过对比发现，第一种方法由于数组是固定的，而实际项目中往往需要动态变化的目录和子项，因此用处不大，第二种方法文件太多，实现复杂。这里提供一种方法，传递两个个动态的二维数组来实现目录结构。

2.案例

package com.devin;import java.util.ArrayList;import android.app.Activity;import android.graphics.Color;import android.graphics.drawable.ColorDrawable;import android.os.Bundle;import android.view.Gravity;import android.view.View;import android.view.View.OnClickListener;import android.view.ViewGroup;import android.widget.BaseExpandableListAdapter;import android.widget.ExpandableListAdapter;import android.widget.ExpandableListView;import android.widget.ImageView;import android.widget.LinearLayout;import android.widget.TextView;public class PadTestActivity extends Activity {    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);　　　　　　        ArrayList
     
       groupList = new ArrayList
      
       ();        for (int i = 0; i < 3; i++) {            groupList.add("title");        }                ArrayList
       
         itemList1 = new ArrayList
        
         ();        itemList1.add("Item1");        itemList1.add("Item2");        ArrayList
         
           itemList2 = new ArrayList
          
           (); itemList2.add("Item1"); itemList2.add("Item21"); itemList2.add("Item3"); ArrayList
           
             itemList3 = new ArrayList
            
             (); itemList3.add("Item1"); itemList3.add("Item2"); itemList3.add("Item3"); itemList3.add("Item4"); ArrayList
             
              
               > childList = new ArrayList
               
                
                 >(); childList.add(itemList1); childList.add(itemList2); childList.add(itemList3); ExpandableListView list = new ExpandableListView(this); ExpandableListAdapter mAdapter = new MyExpandableListAdapter(groupList, childList); list.setAdapter(mAdapter); list.setCacheColorHint(0x00000000); list.setSelector(new ColorDrawable(Color.TRANSPARENT)); list.setGroupIndicator(null); for (int i = 0; i < mAdapter.getGroupCount(); i++) { list.expandGroup(i); } setContentView(list); } private class MyExpandableListAdapter extends BaseExpandableListAdapter { private ArrayList
                 
                   groupList; private ArrayList
                  
                   
                    > childList; MyExpandableListAdapter(ArrayList
                    
                      groupList, ArrayList
                     
                      
                       > childList) { this.groupList = groupList; this.childList = childList; } public Object getChild(int groupPosition, int childPosition) { return childList.get(groupPosition).get(childPosition); } private int selectedGroupPosition = -1; private int selectedChildPosition = -1; public void setSelectedPosition(int selectedGroupPosition, int selectedChildPosition) { this.selectedGroupPosition = selectedGroupPosition; this.selectedChildPosition = selectedChildPosition; } public long getChildId(int groupPosition, int childPosition) { return childPosition; } public int getChildrenCount(int groupPosition) { return childList.get(groupPosition).size(); } public View getChildView(final int groupPosition, final int childPosition, boolean isLastChild, View convertView, ViewGroup parent) { TextView textView = null; if (convertView == null) { textView = new TextView(PadTestActivity.this); textView.setPadding(32, 10, 0, 10); convertView = textView; } else { textView = (TextView) convertView; } textView.setText(getChild(groupPosition, childPosition).toString()); if (groupPosition == selectedGroupPosition) { if (childPosition == selectedChildPosition) { textView.setBackgroundColor(0xffb6ddee); } else { textView.setBackgroundColor(Color.TRANSPARENT); } } textView.setOnClickListener(new OnClickListener() { public void onClick(View v) { setSelectedPosition(groupPosition, childPosition); notifyDataSetChanged(); } }); return textView; } public Object getGroup(int groupPosition) { return groupList.get(groupPosition); } public int getGroupCount() { return groupList.size(); } public long getGroupId(int groupPosition) { return groupPosition; } public View getGroupView(int groupPosition, boolean isExpanded, View convertView, ViewGroup parent) { LinearLayout cotain = new LinearLayout(PadTestActivity.this); cotain.setPadding(0, 10, 0, 10); cotain.setGravity(Gravity.CENTER_VERTICAL); ImageView imgIndicator = new ImageView(PadTestActivity.this); TextView textView = new TextView(PadTestActivity.this); textView.setText(getGroup(groupPosition).toString()); textView.setPadding(5, 0, 0, 0); if (isExpanded) { imgIndicator.setBackgroundResource(R.drawable.macro_minus); } else { imgIndicator.setBackgroundResource(R.drawable.macro_plus); } cotain.addView(imgIndicator); cotain.addView(textView); return cotain; } public boolean hasStableIds() { return true; } public boolean isChildSelectable(int groupPosition, int childPosition) { return true; } }}
                      
                     
                    
                   
                  
                 
                
               
              
             
            
           
          
         
        
       
      
     

 　上述代码中，过向BaseExpandableListAdapter传递两个动态数组groupList(表示目录头信息)和childList （表示子项信息）来构建目录，一方面能够实现动态的添加数据，另一方面简化了实现，一举两得。另外，重写的BaseExpandableListAdapter，如果应用在实际项目中，需要对getGroupView()和getChildView()方法进行构建缓存(和ListView构建一样)，以便优化性能和防止内存泄漏。需要的朋友可以自己构建。

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