android 之ExpandableListView详解

ExpandableListView是一种可应用于某种环境的下拉列表。

实例代码：

package com.example.lenovo.expandablelistview_demo;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseExpandableListAdapter;
import android.widget.ExpandableListAdapter;
import android.widget.ExpandableListView;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity {

    private ExpandableListView expandableListView;

    private MyBaseExpandableListAdapter adapter;
    private String[] group = {"我的好友","陌生人","黑名单"};
    private String[][] children = {
            {"小王","急急急","kl","考虑"},
            {"流域","蜡笔","一扭"},
            {"ren","du","处矛"}
    };


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        this.expandableListView = (ExpandableListView) this.findViewById(R.id.expandableListView);
        adapter = new MyBaseExpandableListAdapter();
        this.expandableListView.setAdapter(adapter);
    }
    private final class MyBaseExpandableListAdapter extends BaseExpandableListAdapter{

        @Override
        //返回组中元素的个数
        public int getGroupCount() {
            return group.length;
        }

        @Override
        //根据组的索引返回当前组中子元素的个数
        public int getChildrenCount(int groupPosition) {
            return  children[groupPosition].length;
        }

        @Override
        //返回指定组索引处的元素值
        public Object getGroup(int groupPosition) {
            return group[groupPosition];
        }

        @Override
        //返回指定组索引和子元素索引对应的值
        public Object getChild(int groupPosition, int childPosition) {
            return children[groupPosition][childPosition];
        }

        @Override
        //返回组的id值
        public long getGroupId(int groupPosition) {
            return groupPosition;
        }

        @Override
        //返回指定组中的子元素指定索引的值
        public long getChildId(int groupPosition, int childPosition) {
            return childPosition;
        }

        @Override
        public boolean hasStableIds() {
            return false;
        }

        @Override
        //当绘制组的View对象时自动调用的方法
        /**
         * groupPosition :组的索引值
         * isExpanded:当前组下的元素是否被展开
         *
         */
        public View getGroupView(int groupPosition, boolean isExpanded, View convertView, ViewGroup parent) {


            View view = View.inflate(MainActivity.this,R.layout.group_view,null);

            TextView textView_group  = (TextView) view.findViewById(R.id.textView_group);
            //得到组名
            String groupName = group[groupPosition];
            textView_group.setText(groupName);
            return view;
        }

        @Override
        public View getChildView(int groupPosition, int childPosition, boolean isLastChild, View convertView, ViewGroup parent) {
            View view = View.inflate(MainActivity.this,R.layout.child_view,null);
            TextView textView_child = (TextView) view.findViewById(R.id.textView_child);
            String childrenName = children[groupPosition][childPosition];

            textView_child.setText(childrenName);
            return  view;
        }

        @Override
        //子元素是否被选中,默认值为false,表示不能被选中
        public boolean isChildSelectable(int groupPosition, int childPosition) {
            return true;
        }
    }
}