Android之ExpandableList扩展用法（基于BaseExpandableListAdapter）

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<String> groupList = new ArrayList<String>();

        for (int i = 0; i < 3; i++) {

            groupList.add("title");

        }

        

        ArrayList<String> itemList1 = new ArrayList<String>();

        itemList1.add("Item1");

        itemList1.add("Item2");

        ArrayList<String> itemList2 = new ArrayList<String>();

        itemList2.add("Item1");

        itemList2.add("Item21");

        itemList2.add("Item3");

        ArrayList<String> itemList3 = new ArrayList<String>();

        itemList3.add("Item1");

        itemList3.add("Item2");

        itemList3.add("Item3");

        itemList3.add("Item4");

        ArrayList<ArrayList<String>> childList = new ArrayList<ArrayList<String>>();

        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<String> groupList;

        private ArrayList<ArrayList<String>> childList;



        MyExpandableListAdapter(ArrayList<String> groupList, ArrayList<ArrayList<String>> 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。