可折叠列表ExpandableList

ExpandableList就是可展开的ListView
首先我们来看一下页面的布局

expandlist_layout.xml文件

<RelativeLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">
    <ExpandableListView
        android:id="@+id/expendlist"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />
</RelativeLayout>

expendlist_group.xml

<RelativeLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:gravity="center_vertical"
    android:padding="10dp">
    <ImageView
        android:id="@+id/group_img"
        android:layout_width="36dp"
        android:layout_height="36dp"
        android:layout_centerVertical="true"
        android:layout_marginLeft="20dp"
        android:src="@drawable/ic_next" />

    <TextView
        android:id="@+id/groupname_tv"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerVertical="true"
        android:layout_toRightOf="@+id/group_img"
        android:layout_marginLeft="10dp"
        android:text="张三"
        android:textSize="18sp" />
</RelativeLayout>

expendlist_item.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="70dp"
    android:orientation="horizontal"
    android:gravity="center_vertical"
    android:layout_marginBottom="1dp"
    android:padding="10dp">

    <ImageView
        android:id="@+id/icon_img"
        android:layout_width="48dp"
        android:layout_height="48dp"
        android:layout_marginLeft="20dp"
        android:src="@drawable/android" />

    <LinearLayout
        android:layout_marginLeft="50dp"
        android:layout_width="match_parent"
        android:layout_height="60dp"
        android:gravity="center_vertical"
        android:orientation="vertical" >

        <TextView
            android:id="@+id/itemname_tv"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:textSize="22sp"
            android:textStyle="bold"
            android:text="Android" />

        <TextView
            android:id="@+id/info_tv"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginTop="10dp"
            android:text="编程学习" />
    </LinearLayout>
</LinearLayout>

创建适配器MyExpandableListViewAdapter

package com.example.administrator.expandablelistview;

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 java.util.List;

public class MyExpandableListViewAdapter extends BaseExpandableListAdapter {

    private Context mContext = null;
    private List<String> mGroupList = null;
    private List<List<String>> mItemList = null;

    public MyExpandableListViewAdapter(Context context, List<String> groupList,
                                       List<List<String>> itemList) {
        this.mContext = context;
        this.mGroupList = groupList;
        this.mItemList = itemList;
    }
// 获取组的个数
    @Override
    public int getGroupCount() {
        return mGroupList.size();
    }
// 获取指定组中的子元素个数
    @Override
    public int getChildrenCount(int groupPosition) {
        return mItemList.get(groupPosition).size();
    }
//获取指定组中的数据
    @Override
    public String getGroup(int groupPosition) {
        return mGroupList.get(groupPosition);
    }

//获取指定组中的指定子元素数据。
    @Override
    public String getChild(int groupPosition, int childPosition) {
        return mItemList.get(groupPosition).get(childPosition);
    }

// 获取指定组的ID，这个组ID必须是唯一的
    @Override
    public long getGroupId(int groupPosition) {
        return groupPosition;
    }

//获取指定组中的指定子元素ID
    @Override
    public long getChildId(int groupPosition, int childPosition) {
        return childPosition;
    }
// 获取显示指定组的视图对象
 //groupPosition 组位置
//isExpanded    该组是展开状态还是伸缩状态
//convertView   重用已有的视图对象
//parent        返回的视图对象始终依附于的视图组
    @Override
    public View getGroupView(int groupPosition, boolean isExpanded, View convertView,
                             ViewGroup parent) {
        GroupHolder groupHolder = null;
        if (convertView == null) {
            convertView = LayoutInflater.from(mContext).inflate(R.layout.expendlist_group, null);
            groupHolder = new GroupHolder();
            groupHolder.groupNameTv = (TextView) convertView.findViewById(R.id.groupname_tv);
            groupHolder.groupImg = (ImageView) convertView.findViewById(R.id.group_img);
            convertView.setTag(groupHolder);
        } else {
            groupHolder = (GroupHolder) convertView.getTag();
        }

        if (isExpanded) {
            groupHolder.groupImg.setImageResource(R.drawable.ic_up);//展开
        } else {
            groupHolder.groupImg.setImageResource(R.drawable.ic_next);//未展开
        }
        groupHolder.groupNameTv.setText(mGroupList.get(groupPosition));

        return convertView;
    }

//获取一个视图对象，显示指定组中的指定子元素数据。
    @Override
    public View getChildView(int groupPosition, int childPosition, boolean isLastChild,
                             View convertView, ViewGroup parent) {
        ItemHolder itemHolder = null;
        if (convertView == null) {
            convertView = LayoutInflater.from(mContext).inflate(R.layout.expendlist_item, null);
            itemHolder = new ItemHolder();
            itemHolder.nameTv = (TextView) convertView.findViewById(R.id.itemname_tv);
            itemHolder.iconImg = (ImageView) convertView.findViewById(R.id.icon_img);
            convertView.setTag(itemHolder);
        } else {
            itemHolder = (ItemHolder) convertView.getTag();
        }
        itemHolder.nameTv.setText(mItemList.get(groupPosition).get(childPosition));
        itemHolder.iconImg.setBackgroundResource(R.drawable.head_img_1);

        return convertView;
    }

// 组和子元素是否持有稳定的ID,也就是底层数据的改变不会影响到它们。
    @Override
    public boolean hasStableIds() {
        return true;
    }

//是否选中指定位置上的子元素。
    @Override
    public boolean isChildSelectable(int groupPosition, int childPosition) {
        return true;
    }

    class GroupHolder {
        public TextView groupNameTv;
        public ImageView groupImg;
    }

    class ItemHolder {
        public ImageView iconImg;
        public TextView nameTv;
    }
}

ExpandableListActivity.java

package com.example.administrator.expandablelistview;

import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.ExpandableListView;
import android.widget.Toast;

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

public class ExpandableListActivity extends AppCompatActivity {
    private ExpandableListView mExpandableListView = null;
    // 列表数据
    private List<String> mGroupNameList = null;
    private List<List<String>> mItemNameList = null;
    // 适配器
    private MyExpandableListViewAdapter mAdapter = null;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.expandlist_layout);
        // 获取组件
        mExpandableListView = (ExpandableListView) findViewById(R.id.expendlist);
        mExpandableListView.setGroupIndicator(null);
        // 初始化数据
        initData();
        // 为ExpandableListView设置Adapter
        mAdapter = new MyExpandableListViewAdapter(this, mGroupNameList, mItemNameList);
        mExpandableListView.setAdapter(mAdapter);
        // 监听组点击
        mExpandableListView.setOnGroupClickListener(new ExpandableListView.OnGroupClickListener() {
            @Override
            public boolean onGroupClick(ExpandableListView parent, View v,
                                        int groupPosition, long id) {
                if (mGroupNameList.get(groupPosition).isEmpty()) {
                    return true;
                }
                return false;
            }
        });

        // 监听每个分组里子控件的点击事件
        mExpandableListView.setOnChildClickListener(new ExpandableListView.OnChildClickListener() {
            @Override
            public boolean onChildClick(ExpandableListView parent, View v, int groupPosition,
                                        int childPosition, long id) {
                Toast.makeText(ExpandableListActivity.this,
                        mAdapter.getGroup(groupPosition) + ":"
                                +  mAdapter.getChild(groupPosition, childPosition) ,
                        Toast.LENGTH_SHORT).show();
                return false;
            }
        });
    }

    // 初始化数据
    private void initData(){
        // 组名
        mGroupNameList = new ArrayList<String>();
        mGroupNameList.add("后端开发");
        mGroupNameList.add("前端开发");
        mGroupNameList.add("移动开发");

        mItemNameList = new  ArrayList<List<String>>();
        // 后端组
        List<String> itemList = new ArrayList<String>();
        itemList.add("Java");
        itemList.add("SpringBoot");
        itemList.add("Python");
        itemList.add("Go");
        itemList.add("PHP");
        itemList.add("C");
        itemList.add("C++");
        mItemNameList.add(itemList);
        // 前端组
        itemList = new ArrayList<String>();
        itemList.add("HTML/CSS ");
        itemList.add("JavaScript");
        itemList.add("Vue.js");
        itemList.add("jQuery");
        itemList.add("Bootstrap");
        itemList.add("Angular");
        mItemNameList.add(itemList);
        // 移动组
        itemList = new ArrayList<String>();
        itemList.add("Android");
        itemList.add("iOS");
        itemList.add("React native");
        itemList.add("WEEX");
        mItemNameList.add(itemList);
    }
}

最终实现的效果图