一、ExpandableListView的介绍

ExpandableListView是ListView的子类。它是ListView的基础上进行了扩展，把应用中的列表分成几组，每组里又可以包含多个列表项。

二、适配器（ExpandableAdapter）

1、BaseExpandableListAdapter：

BaseExpandableListAdapter是一个抽象类，用于实现可扩展的列表视图（ExpandableListView）。它包含了一些方法来帮助你管理和填充可扩展列表视图中的数据。以下是BaseExpandableListAdapter中常用的方法及其功能：

方法名	功能
public abstract int getGroupCount()	获取分组数量，即可扩展列表视图中的组数。
public abstract int getChildrenCount(int groupPosition)	获取指定组中子项的数量。
public abstract Object getGroup(int groupPosition)	获取指定组的数据对象。
public abstract Object getChild(int groupPosition, int childPosition)	获取指定子项的数据对象。
public abstract long getGroupId(int groupPosition)	获取指定组的ID。
public abstract long getChildId(int groupPosition, int childPosition)	获取指定子项的ID。
public abstract boolean hasStableIds()	判断分组和子项的ID是否稳定。
public abstract View getGroupView(int groupPosition, boolean isExpanded, View convertView, ViewGroup parent)	获取指定组的视图对象。
public abstract View getChildView(int groupPosition, int childPosition, boolean isLastChild, View convertView, ViewGroup parent)	获取指定子项的视图对象。
public abstract boolean isChildSelectable(int groupPosition, int childPosition)	判断指定子项是否可以被选中。

这些方法提供了访问和操作可扩展列表视图中数据的基本功能。通过继承BaseExpandableListAdapter并重写这些方法，可以实现自定义的可扩展列表视图适配器，以满足各种实际应用的需求。

BaseExpandableListAdapter例子：

MainActivity:

package com.example.expandablelistdemo;import androidx.appcompat.app.AppCompatActivity;import android.os.Bundle;
import android.view.ContextMenu;
import android.view.MenuItem;
import android.view.View;
import android.widget.ExpandableListView;
import android.widget.Toast;import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;public class MainActivity extends AppCompatActivity {private ExpandableListView expandList;private List<String> groupData;//group的数据源private Map<Integer, List<ChildItem>> childData;//child的数据源private MyAdapter myAdapter;final int CONTEXT_MENU_GROUP_DELETE = 0;//添加上下文菜单时每一个菜单项的item IDfinal int CONTEXT_MENU_GROUP_RENAME = 1;final int CONTEXT_MENU_CHILD_EDIT = 2;final int CONTEXT_MENU_CHILD_DELETE = 3;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);initData();initView();}private void initData() {groupData = new ArrayList<>();groupData.add("第一组");groupData.add("第二组");groupData.add("第三组");List<ChildItem> childItems = new ArrayList<>();for (int i = 0; i < 10; i++) {ChildItem childData = new ChildItem("标题："+i, R.drawable.ic_launcher_background);childItems.add(childData);}List<ChildItem> childItems2 = new ArrayList<ChildItem>();for (int i = 0; i < 5; i++) {ChildItem childData1 = new ChildItem("标题："+i, R.drawable.ic_launcher_background);childItems2.add(childData1);}List<ChildItem> childItems3 = new ArrayList<ChildItem>();for (int i = 0; i < 2; i++) {ChildItem childData1 = new ChildItem("标题："+i, R.drawable.ic_launcher_background);childItems3.add(childData1);}childData = new HashMap<Integer, List<ChildItem>>();childData.put(0, childItems);childData.put(1, childItems2);childData.put(2, childItems3);myAdapter = new MyAdapter(this, groupData, childData);}private void initView() {expandList = findViewById(R.id.expandlist);expandList.setAdapter(myAdapter);// 添加上下文的菜单registerForContextMenu(expandList);// 给子项添加点击事件expandList.setOnChildClickListener(new ExpandableListView.OnChildClickListener() {@Overridepublic boolean onChildClick(ExpandableListView parent, View v, int groupPosition, int childPosition, long id) {Toast.makeText(MainActivity.this, "你单击了："+myAdapter.getChild(groupPosition, childPosition), Toast.LENGTH_SHORT).show();return true;}});}/** 添加上下文菜单*/@Overridepublic void onCreateContextMenu(ContextMenu menu, View v,ContextMenu.ContextMenuInfo menuInfo) {super.onCreateContextMenu(menu, v, menuInfo);ExpandableListView.ExpandableListContextMenuInfo info = (ExpandableListView.ExpandableListContextMenuInfo)menuInfo;int type = ExpandableListView.getPackedPositionType(info.packedPosition);if (type == ExpandableListView.PACKED_POSITION_TYPE_GROUP) {menu.setHeaderTitle("Options");menu.add(0, CONTEXT_MENU_GROUP_DELETE, 0, "删除");menu.add(0, CONTEXT_MENU_GROUP_RENAME, 0, "重命名");}if (type == ExpandableListView.PACKED_POSITION_TYPE_CHILD) {menu.setHeaderTitle("Options");menu.add(1, CONTEXT_MENU_CHILD_EDIT, 0, "编辑");menu.add(1, CONTEXT_MENU_CHILD_DELETE, 0, "删除");}}/** 每个菜单项的具体点击事件*/@Overridepublic boolean onContextItemSelected(MenuItem item) {ExpandableListView.ExpandableListContextMenuInfo info = (ExpandableListView.ExpandableListContextMenuInfo)item.getMenuInfo();switch (item.getItemId()) {case CONTEXT_MENU_GROUP_DELETE:Toast.makeText(this, "这是group的删除", Toast.LENGTH_SHORT).show();break;case CONTEXT_MENU_GROUP_RENAME:Toast.makeText(this, "这是group的重命名", Toast.LENGTH_SHORT).show();break;case CONTEXT_MENU_CHILD_EDIT:Toast.makeText(this, "这是child的编辑", Toast.LENGTH_SHORT).show();break;case CONTEXT_MENU_CHILD_DELETE:Toast.makeText(this, "这是child的删除", Toast.LENGTH_SHORT).show();break;default:break;}return super.onContextItemSelected(item);}
}

MyAdapter:

package com.example.expandablelistdemo;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;
import java.util.Map;public class MyAdapter extends BaseExpandableListAdapter{private Context mContext;// 每组的标题private List<String> groupTitle;//子项是一个map，key是group的id，每一个group对应一个ChildItem的listprivate Map<Integer, List<ChildItem>> childMap;public MyAdapter(Context context, List<String> groupTitle, Map<Integer, List<ChildItem>> childMap){this.mContext = context;this.groupTitle = groupTitle;this.childMap = childMap;}/*** 取得分组数*/@Overridepublic int getGroupCount() {return groupTitle.size();}/*** 取得指定分组的子元素数*/@Overridepublic int getChildrenCount(int groupPosition) {return childMap.get(groupPosition).size();}/*** 获取指定组的数据对象。* @param groupPosition* @return*/@Overridepublic Object getGroup(int groupPosition) {return groupTitle.get(groupPosition);}/*** 获取指定子项的数据对象。* @param groupPosition 每组的id* @param childPosition 子项的id* @return*/@Overridepublic Object getChild(int groupPosition, int childPosition) {//我们这里返回一下每个item的名称，以便单击item时显示return childMap.get(groupPosition).get(childPosition).getTitle();}/*** 得指定分组的ID* @param groupPosition 组的ID* @return groupPosition*/@Overridepublic long getGroupId(int groupPosition) {return groupPosition;}@Overridepublic long getChildId(int groupPosition, int childPosition) {return childPosition;}/*** 判断分组和子项的ID是否稳定。* @return*/@Overridepublic boolean hasStableIds() {return true;}@Overridepublic View getGroupView(int groupPosition, boolean isExpanded, View convertView, ViewGroup parent) {GroupHolder groupHolder = null;if (convertView == null){convertView = LayoutInflater.from(mContext).inflate(R.layout.group_item,null);groupHolder = new GroupHolder();groupHolder.groupImg = convertView.findViewById(R.id.img_group);groupHolder.groupTitle =  convertView.findViewById(R.id.tv_group_title);convertView.setTag(groupHolder);}else {groupHolder = (GroupHolder) convertView.getTag();}// 如果group被展开if (isExpanded){groupHolder.groupImg.setBackgroundResource(R.drawable.downarrow);}else {groupHolder.groupImg.setBackgroundResource(R.drawable.rightarrow);}groupHolder.groupTitle.setText(groupTitle.get(groupPosition));return convertView;}@Overridepublic View getChildView(int groupPosition, int childPosition, boolean isLastChild, View convertView, ViewGroup parent) {ChildHolder childHolder = null;if (convertView == null) {convertView = LayoutInflater.from(mContext).inflate(R.layout.child_item, null);childHolder = new ChildHolder();childHolder.childImg = convertView.findViewById(R.id.img_child);childHolder.childTitle =  convertView.findViewById(R.id.tv_child_text);convertView.setTag(childHolder);}else {childHolder = (ChildHolder) convertView.getTag();}childHolder.childImg.setBackgroundResource(childMap.get(groupPosition).get(childPosition).getMarkerImgId());childHolder.childTitle.setText(childMap.get(groupPosition).get(childPosition).getTitle());return convertView;}/*** 判断指定子项是否可以被选中。* @param groupPosition* @param childPosition* @return*/@Overridepublic boolean isChildSelectable(int groupPosition, int childPosition) {return true;}private class GroupHolder{ImageView groupImg;TextView groupTitle;}private class ChildHolder{ImageView childImg;TextView childTitle;}}

GroupItem:

package com.example.expandablelistdemo;public class GroupItem {private String title;private int imageId;private GroupItem(String title,int imageId){this.title = title;this.imageId = imageId;}public String getTitle() {return title;}public void setTitle(String title) {this.title = title;}public int getImageId() {return imageId;}public void setImageId(int imageId) {this.imageId = imageId;}
}

ChildItem:

package com.example.expandablelistdemo;public class ChildItem {private String title;private int markerImgId;public ChildItem(String title,int markerImgId){this.markerImgId = markerImgId;this.title = title;}public String getTitle() {return title;}public void setTitle(String title) {this.title = title;}public int getMarkerImgId() {return markerImgId;}public void setMarkerImgId(int markerImgId) {this.markerImgId = markerImgId;}
}

activity_main:

<?xml version="1.0" encoding="UTF-8"?>
<LinearLayoutandroid:layout_height="match_parent"android:layout_width="match_parent"xmlns:android="http://schemas.android.com/apk/res/android"><ExpandableListViewandroid:layout_height="match_parent"android:layout_width="match_parent"android:dividerHeight="1dp"android:divider="@android:color/white"android:cacheColorHint="#00000000"android:id="@+id/expandlist"/></LinearLayout>

child_item:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"android:layout_width="match_parent"android:orientation="horizontal"android:layout_height="match_parent"><ImageViewandroid:layout_marginTop="10dp"android:layout_height="50dp"android:layout_width="50dp"android:layout_centerVertical="true"android:layout_marginLeft="20dp"android:id="@+id/img_child"/><TextViewandroid:layout_marginTop="21dp"android:id="@+id/tv_child_text"android:layout_width="wrap_content"android:layout_height="wrap_content"android:layout_centerVertical="true"android:layout_marginLeft="20dp"android:layout_toRightOf="@id/img_child"android:text="xiangjiao"android:textSize="16sp" />
</LinearLayout>

group_item:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"android:layout_width="match_parent"android:orientation="horizontal"android:layout_height="match_parent"><ImageViewandroid:layout_marginTop="10dp"android:layout_height="50dp"android:layout_width="50dp"android:layout_centerVertical="true"android:layout_marginLeft="10dp"android:id="@+id/img_group"/><TextViewandroid:layout_marginTop="21dp"android:id="@+id/tv_group_title"android:layout_width="wrap_content"android:layout_height="wrap_content"android:layout_centerVertical="true"android:layout_marginLeft="20dp"android:layout_toRightOf="@id/img_child"android:text="水果"android:textSize="16sp" />
</LinearLayout>

效果图：