Android : ExpandableListView(折叠列表) +BaseExpandableListAdapter-简单应用

示例图：

实体类DemoData.java

package com.example.myexpandablelistview.entity;

public class DemoData {
    private  String content;
    private int img;

    public DemoData(String content, int img) {
        this.content = content;
        this.img = img;
    }

    public String getContent() {
        return content;
    }

    public void setContent(String content) {
        this.content = content;
    }

    public int getImg() {
        return img;
    }

    public void setImg(int img) {
        this.img = img;
    }
}

适配器 写个类继承 BaseExpandableListAdapter

package com.example.myexpandablelistview;

import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseExpandableListAdapter;
import android.widget.ImageView;
import android.widget.TextView;

import com.example.myexpandablelistview.entity.DemoData;

import java.util.ArrayList;
import java.util.List;

// BaseAdapter 扩展
public class DemoExpandableListadpter extends BaseExpandableListAdapter {
    private List groupDataList ;
    private List> itemDataList;
    private Context context;
    //优化
    static class HolderGroup{
        TextView titleTextView;
    }
    static class HolderChild{
        TextView contTextView;
        ImageView imageView;
    }
    public DemoExpandableListadpter(List groupDataList, List> itemDataList, Context context) {
        this.groupDataList = groupDataList;
        this.itemDataList = itemDataList;
        this.context = context;
    }

    @Override
    public int getGroupCount() {
        //返回 外面组个数 3个
        return groupDataList.size();
    }

    @Override
    public int getChildrenCount(int groupPosition) {
        //groupPosition 外面组的下标 在获取里面子列表
        // 里面子列表个数
        return itemDataList.get(groupPosition).size();
    }

    @Override
    public Object getGroup(int groupPosition) {
        //返回组每一项对应的数据
        return groupDataList.get(groupPosition);
    }

    @Override
    public Object getChild(int groupPosition, int childPosition) {
        // 先获取对应的组下标，在获取子列表数据
        //返回子列表的每一项对应的数据
        return itemDataList.get(groupPosition).get(childPosition);
    }

    @Override
    public long getGroupId(int groupPosition) {
        return groupPosition;
    }

    @Override
    public long getChildId(int groupPosition, int childPosition) {
        return childPosition;
    }

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

    @Override
    public View getGroupView(int groupPosition, boolean isExpanded, View convertView, ViewGroup parent) {
        //组布局View 外面的
        HolderGroup  holderGroup = null;
        if(holderGroup == null){
            holderGroup = new HolderGroup();
            //设置视图布局
            convertView = LayoutInflater.from(context).inflate(R.layout.group_view,parent,false);
            holderGroup.titleTextView = convertView.findViewById(R.id.btn_title);

            convertView.setTag(holderGroup);
        }else {
            holderGroup = (HolderGroup) convertView.getTag();
        }
        //设置值
        holderGroup.titleTextView.setText(groupDataList.get(groupPosition));
        return convertView;
    }

    @Override
    public View getChildView(int groupPosition, int childPosition, boolean isLastChild, View convertView, ViewGroup parent) {
        //里面的子布局
       HolderChild holderChild =null;
        if(holderChild == null){
            holderChild = new HolderChild();

            //设置视图布局
            convertView = LayoutInflater.from(context).inflate(R.layout.child_view,parent,false);
            holderChild.imageView = convertView.findViewById(R.id.btn_img);
            holderChild.contTextView = convertView.findViewById(R.id.btn_cont);

            convertView.setTag(holderChild);
        }else {
            holderChild = (HolderChild)convertView.getTag();
        }
        //设置值
        holderChild.imageView.setBackgroundResource(itemDataList.get(groupPosition).get(childPosition).getImg());
        holderChild.contTextView.setText(itemDataList.get(groupPosition).get(childPosition).getContent());
        return convertView;
    }

    //设置子列是否可以选中 true  false
    @Override
    public boolean isChildSelectable(int groupPosition, int childPosition) {
        //false 点击事件无效
        return true;
    }
}

MainAcitvity.java

package com.example.myexpandablelistview;

import androidx.appcompat.app.AppCompatActivity;

import android.content.Context;
import android.os.Bundle;
import android.view.View;
import android.widget.ExpandableListView;
import android.widget.Toast;

import com.example.myexpandablelistview.entity.DemoData;

import java.util.ArrayList;
import java.util.List;

public class MainActivity extends AppCompatActivity {
    //定义组件
    private ExpandableListView expandableListView;
    private Context context;

    private List groupDataList = null;
    private List> itemDataList = null;
    private ArrayList itemData =null;


    //定义图片资源图片
    private int[] arr = {
            R.mipmap.e,
            R.mipmap.f,
            R.mipmap.g,
            R.mipmap.h,
            R.mipmap.i,

    };
    private int[] arr2 = {
            R.mipmap.g,
            R.mipmap.h,
            R.mipmap.i,

    };
    /*实现ExpandableAdapter的三种方式
    1.扩展BaseExpandableListAdpter实现ExpandableAdapter。
    2.使用SimpleExpandableListAdpater将两个List集合包装成ExpandableAdapter
    3.使用simpleCursorTreeAdapter将Cursor中的数据包装成SimpleCuroTreeAdapter
    使用的是第一个，扩展BaseExpandableListAdpter，我们需要重写该类中的相关方法*/
    private DemoExpandableListadpter demoExpandableListadpter = null;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        //传入上下文
        context = this;

        expandableListView = findViewById(R.id.expandable_list_view);
        //添加数据
        itemDataList = new ArrayList>();

        groupDataList = new ArrayList<>();
        for(int i = 0;i < 3; i++){
            groupDataList.add("我是标题"+i);
        }

        //内容 和图片 1 循环添加出错 java.lang.IndexOutOfBoundsException
        itemData = new ArrayList();
        for (int i =0 ; i< arr.length; i++){
            itemData.add(new DemoData("我是文字"+i,arr[i]));
        }
        itemDataList.add(itemData);

        //内容 和图片 2
        itemData = new ArrayList();
        for (int i =0 ; i< arr2.length; i++){
            itemData.add(new DemoData("我是文字"+i,arr2[i]));
        }

        itemDataList.add(itemData);

        //内容 和图片 3
        itemData = new ArrayList();
        for (int i =0 ; i< arr.length; i++){
            itemData.add(new DemoData("我是文字"+i,arr[i]));
        }

        itemDataList.add(itemData);

        //把数据传入
        demoExpandableListadpter = new DemoExpandableListadpter(groupDataList,itemDataList,context);


        //往视图容器中添加 适配器
        expandableListView.setAdapter(demoExpandableListadpter);

        //列表设置点击事件
        expandableListView.setOnChildClickListener(new ExpandableListView.OnChildClickListener() {
            @Override
            public boolean onChildClick(ExpandableListView parent, View v, int groupPosition, int childPosition, long id) {
                Toast.makeText(context,"您选择了"+itemDataList.get(groupPosition).get(childPosition).getContent(),Toast.LENGTH_SHORT).show();
                return false;
            }
        });

    }
}

主布局：activity_main.xml

组布局 group_view.xml

子布局 child_view.xml