# ExpandableDemo

**Repository Path**: qiang129/ExpandableDemo

## Basic Information

- **Project Name**: ExpandableDemo
- **Description**: 可扩展的列表Demo
- **Primary Language**: Android
- **License**: GPL-2.0
- **Default Branch**: master
- **Homepage**: None
- **GVP Project**: No

## Statistics

- **Stars**: 0
- **Forks**: 4
- **Created**: 2022-03-03
- **Last Updated**: 2022-03-03

## Categories & Tags

**Categories**: Uncategorized

**Tags**: None

## README


## 效果图
ExpandableListView继承于ListView，先上图，看一下效果：
![在这里插入图片描述](https://img-blog.csdnimg.cn/20200329185637933.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3NlYV9ibw==,size_16,color_FFFFFF,t_70#pic_center)
## 准备测试数据
列表数据分为组item部分和子item部分，它们都有文字和icon组成，这里在assets文件夹下创建一个json文件取名ExpandableMode.json，用于存放这些测试，数据结构如下：

```
[
  {
    "GroupName": "水果",
    "GroupIcon": "icon_fruit",
    "ChildData": [
      {
        "ChildName": "香蕉",
        "ChildIcon": "icon_banana",
        "Number": 5
      },
      {
        "ChildName": "苹果",
        "ChildIcon": "icon_apple",
        "Number": 3
      },
      {
        "ChildName": "西瓜",
        "ChildIcon": "icon_watermelon",
        "Number": 9
      }
    ]
  },
  {
    "GroupName": "蔬菜",
    "GroupIcon": "icon_vegetable",
    "ChildData": [
      {
        "ChildName": "萝卜",
        "ChildIcon": "icon_radish",
        "Number": 4
      },
      {
        "ChildName": "西红柿",
        "ChildIcon": "icon_tomatoes",
        "Number": 7
      },
      {
        "ChildName": "榴莲",
        "ChildIcon": "icon_durian",
        "Number": 9
      }
    ]
  },
  {
    "GroupName": "交通工具",
    "GroupIcon": "icon_traffic",
    "ChildData": [
      {
        "ChildName": "汽车",
        "ChildIcon": "icon_car",
        "Number": 4
      },
      {
        "ChildName": "飞机",
        "ChildIcon": "icon_plane",
        "Number": 7
      },
      {
        "ChildName": "大炮",
        "ChildIcon": "icon_cannon",
        "Number": 9
      },
      {
        "ChildName": "火箭",
        "ChildIcon": "icon_rocket",
        "Number": 1
      }
    ]
  }
]
```
创建一个和json文件相对应的实体类ExpandableMode

```java
package top.zhaohaibo.expandable.mode;

import java.util.List;

/**
 * 作者: Ocean<br><br>
 * 时间: 2020/3/28 9:57 PM<br><br>
 * 邮箱: xinzhaohaibo@aliyun.com<br><br>
 * 描述: 可展开视图的数据模型
 */
public class ExpandableMode {

    /**
     * GroupName : 水果
     * GroupIcon :
     * ChildData : [{"ChildName":"香蕉","ChildIcon":"","Number":5},{"ChildName":"苹果","ChildIcon":"","Number":3},{"ChildName":"西瓜","ChildIcon":"","Number":9}]
     */

    private String GroupName;
    private String GroupIcon;
    private List<ChildDataBean> ChildData;

    public String getGroupName() {
        return GroupName;
    }

    public void setGroupName(String GroupName) {
        this.GroupName = GroupName;
    }

    public String getGroupIcon() {
        return GroupIcon;
    }

    public void setGroupIcon(String GroupIcon) {
        this.GroupIcon = GroupIcon;
    }

    public List<ChildDataBean> getChildData() {
        return ChildData;
    }

    public void setChildData(List<ChildDataBean> ChildData) {
        this.ChildData = ChildData;
    }

    public static class ChildDataBean {
        /**
         * ChildName : 香蕉
         * ChildIcon :
         * Number : 5
         */

        private String ChildName;
        private String ChildIcon;
        private int Number;

        public String getChildName() {
            return ChildName;
        }

        public void setChildName(String ChildName) {
            this.ChildName = ChildName;
        }

        public String getChildIcon() {
            return ChildIcon;
        }

        public void setChildIcon(String ChildIcon) {
            this.ChildIcon = ChildIcon;
        }

        public int getNumber() {
            return Number;
        }

        public void setNumber(int Number) {
            this.Number = Number;
        }
    }
}

```

## ExpandableListView适配器编写
这里自定义MyExpandableAdapter适配器继承与BaseExpandableListAdapter，并实现它的10个方法，基本上和ListView的适配器方法相同，可以看一下代码的注释，很详细的，不过有几个方法需要注意一下：
##### getGroupView()方法
getGroupView()是重要重写的方法之一，用于获取给定分组的视图，它4个参数，其中第一个参数isExpanded表示组item是否处于展开状态，通过这个参数可以切换右侧的箭头图标。实现添加组item布局，通过groupPosition获取ExpandableMode实体对象，设置icon和名字，根据组item的展开状态设置右边箭头。getGropVie完整代码如下：

```
/**
     * 获取给定分组的视图，主要重写的方法。
     *
     * @param groupPosition groupPosition
     * @param isExpanded    该组是展开状态还是收起状态
     * @param convertView   convertView
     * @param parent        parent
     * @return View
     */
    @Override
    public View getGroupView(int groupPosition, boolean isExpanded, View convertView, ViewGroup parent) {
        if (convertView == null) {
            convertView = LayoutInflater.from(mContext).inflate(R.layout.item_group, parent, false);
        }
        // 获取组的实体对象
        ExpandableMode expandableMode = mExpandableModeList.get(groupPosition);
        // 获取组名
        String groupName = expandableMode.getGroupName();
        // 获取组icon名字
        String iconName = expandableMode.getGroupIcon();
        // 调用getImageMipmapRes方法获取对应的icon资源
        int iconRes = getImageMipmapRes(mContext, iconName);
        // 获取Drawable对象
        Drawable drawableLeft = ContextCompat.getDrawable(mContext, iconRes);
        mViewHolder.setImage(convertView, R.id.item_group_icon_iv, drawableLeft);
        // 设置TextView的文字
        mViewHolder.setText(convertView, R.id.item_group_name_tv, groupName);

        // 设置组item展开或者关闭的右图片
        Drawable drawableRight = ContextCompat.getDrawable(mContext, R.mipmap.icon_right);
        if (isExpanded) {
            // 展开
            drawableRight = ContextCompat.getDrawable(mContext, R.mipmap.icon_down);
        }
        mViewHolder.setImageTextRight(convertView, R.id.item_group_name_tv, drawableRight);

        return convertView;
    }
```
在设置icon时调用了getImageMipmapRes方法，getImageMipmapRes方法根据传入的图片名获取对应的图片资源：

```
/**
     * 通过文件名，获取对应的图片资源
     *
     * @param context  context
     * @param filename filename
     * @return 对应的图片资源
     */
    public int getImageMipmapRes(Context context, String filename) {
        return context.getResources().getIdentifier(filename, "mipmap", context.getPackageName());
    }
```
##### getChildView()方法
getChildView()方法用于添加子item布局，和getGroupView()方法类似：

```
/**
     * 获取给定分组给定子位置的数据用的视图，主要重写的方法。
     *
     * @param groupPosition groupPosition
     * @param childPosition childPosition
     * @param isLastChild   是否为改组最后一个子视图
     * @param convertView   convertView
     * @param parent        parent
     * @return View
     */
    @Override
    public View getChildView(int groupPosition, int childPosition, boolean isLastChild, View convertView, ViewGroup parent) {
        if (convertView == null) {
            convertView = LayoutInflater.from(mContext).inflate(R.layout.item_child, parent, false);
        }
        ExpandableMode expandableMode = mExpandableModeList.get(groupPosition);
        List<ExpandableMode.ChildDataBean> childDataBeans = expandableMode.getChildData();
        ExpandableMode.ChildDataBean childDataBean = childDataBeans.get(childPosition);
        // 获取子名字
        String childName = childDataBean.getChildName();
        // 获取对应的子icon
        String childIcon = childDataBean.getChildIcon();
        // 获取子icon名字对应的图片资源
        int childIconRes = getImageMipmapRes(mContext, childIcon);
        // 获取Drawable对象
        Drawable drawable = ContextCompat.getDrawable(mContext, childIconRes);
        // 设置icon
        mViewHolder.setImage(convertView, R.id.item_child_icon_iv, drawable);
        // 设置文字
        mViewHolder.setText(convertView, R.id.item_child_name_tv, childName);
        return convertView;
    }
```
##### isChildSelectable()方法
这个方法很重要它用来判断子item是否可以点击，如果它isChildSelectable返回false，子item将无法被点击，并且不会显示分割线，因此isChildSelectable应当设置返回true

```
/**
     * 子item是否可点击
     * 当isChildSelectable方法返回false的时候，子item不可点击，且不会绘制分割线
     * @param groupPosition groupPosition
     * @param childPosition childPosition
     * @return true可点击 false不可点击
     */
    @Override
    public boolean isChildSelectable(int groupPosition, int childPosition) {
        return true;
    }
```
#####hasStableIds()方法
这个用来判断ExpandableListView内容id是否有效的,我也不太明白它具体有什么作用，设置返回true和false的效果是一样的。

```
/**
     * 用来判断ExpandableListView内容id是否有效的,我也不太明白，它具体有什么作用，设置返回true和false的效果是一样的。
     *
     * @return true or false
     */
    @Override
    public boolean hasStableIds() {
        return false;
    }
```
#### MyExpandableAdapter适配器的完整代码
MyExpandableAdapter适配器完整代码，ViewHolder请参适配器[张神万能的适配器](https://blog.csdn.net/lmj623565791/article/details/38902805/)

```java
package top.zhaohaibo.expandable.adapter;

import android.content.Context;
import android.graphics.drawable.Drawable;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseExpandableListAdapter;

import androidx.core.content.ContextCompat;

import java.util.List;

import top.zhaohaibo.expandable.R;
import top.zhaohaibo.expandable.mode.ExpandableMode;
import top.zhaohaibo.expandable.utils.ViewHolder;

/**
 * 作者: Ocean<br><br>
 * 时间: 2020/3/28 9:37 PM<br><br>
 * 邮箱: xinzhaohaibo@aliyun.com<br><br>
 * 描述: 自定义可展开列表的适配器
 */
public class MyExpandableAdapter extends BaseExpandableListAdapter {

    /** 数据集合 */
    private List<ExpandableMode> mExpandableModeList;
    /** 上下文 */
    private Context mContext;
    /** ViewHolder */
    private ViewHolder mViewHolder;

    public MyExpandableAdapter(List<ExpandableMode> expandableModeList, Context context) {
        mExpandableModeList = expandableModeList;
        mContext = context;
        mViewHolder = ViewHolder.getInstance();
    }

    /**
     * @return 返回组item数量
     */
    @Override
    public int getGroupCount() {
        return mExpandableModeList == null ? 0 : mExpandableModeList.size();
    }

    /**
     * 根据出入的组groupPosition返回子item的数量。
     *
     * @param groupPosition groupPosition
     * @return 返回子item的数量。
     */
    @Override
    public int getChildrenCount(int groupPosition) {
        if (mExpandableModeList == null) return 0;
        List<ExpandableMode.ChildDataBean> childDataBeans = mExpandableModeList.get(groupPosition).getChildData();
        return childDataBeans == null ? 0 : childDataBeans.size();
    }

    /**
     * 获取组实体对象
     *
     * @param groupPosition groupPosition
     * @return 返回组实体对象
     */
    @Override
    public Object getGroup(int groupPosition) {
        return mExpandableModeList == null ? null : mExpandableModeList.get(groupPosition);
    }

    /**
     * 获取子实体对象
     *
     * @param groupPosition groupPosition
     * @param childPosition childPosition
     * @return 返回子实体对象
     */
    @Override
    public Object getChild(int groupPosition, int childPosition) {
        if (mExpandableModeList == null) return null;
        List<ExpandableMode.ChildDataBean> childDataBeans = mExpandableModeList.get(groupPosition).getChildData();
        return childDataBeans == null ? null : childDataBeans.get(childPosition);
    }

    /**
     * 获取组id,我理解为获取组的唯一ID，一般自己返回groupPosition即可
     *
     * @param groupPosition groupPosition
     * @return Position
     */
    @Override
    public long getGroupId(int groupPosition) {
        return 0;
    }

    /**
     * 获取子ID
     *
     * @param groupPosition groupPosition
     * @param childPosition childPosition
     * @return 返回子id
     */
    @Override
    public long getChildId(int groupPosition, int childPosition) {
        return 0;
    }


    /**
     * 用来判断ExpandableListView内容id是否有效的,我也不太明白，它具体有什么作用，设置返回true和false的效果是一样的。
     *
     * @return true or false
     */
    @Override
    public boolean hasStableIds() {
        return false;
    }

    /**
     * 获取给定分组的视图，主要重写的方法。
     *
     * @param groupPosition groupPosition
     * @param isExpanded    该组是展开状态还是收起状态
     * @param convertView   convertView
     * @param parent        parent
     * @return View
     */
    @Override
    public View getGroupView(int groupPosition, boolean isExpanded, View convertView, ViewGroup parent) {
        if (convertView == null) {
            convertView = LayoutInflater.from(mContext).inflate(R.layout.item_group, parent, false);
        }
        // 获取组的实体对象
        ExpandableMode expandableMode = mExpandableModeList.get(groupPosition);
        // 获取组名
        String groupName = expandableMode.getGroupName();
        // 获取组icon名字
        String iconName = expandableMode.getGroupIcon();
        // 调用getImageMipmapRes方法获取对应的icon资源
        int iconRes = getImageMipmapRes(mContext, iconName);
        // 获取Drawable对象
        Drawable drawableLeft = ContextCompat.getDrawable(mContext, iconRes);
        mViewHolder.setImage(convertView, R.id.item_group_icon_iv, drawableLeft);
        // 设置TextView的文字
        mViewHolder.setText(convertView, R.id.item_group_name_tv, groupName);

        // 设置组item展开或者关闭的右图片
        Drawable drawableRight = ContextCompat.getDrawable(mContext, R.mipmap.icon_right);
        if (isExpanded) {
            // 展开
            drawableRight = ContextCompat.getDrawable(mContext, R.mipmap.icon_down);
        }
        mViewHolder.setImageTextRight(convertView, R.id.item_group_name_tv, drawableRight);

        return convertView;
    }

    /**
     * 获取给定分组给定子位置的数据用的视图，主要重写的方法。
     *
     * @param groupPosition groupPosition
     * @param childPosition childPosition
     * @param isLastChild   是否为改组最后一个子视图
     * @param convertView   convertView
     * @param parent        parent
     * @return View
     */
    @Override
    public View getChildView(int groupPosition, int childPosition, boolean isLastChild, View convertView, ViewGroup parent) {
        if (convertView == null) {
            convertView = LayoutInflater.from(mContext).inflate(R.layout.item_child, parent, false);
        }
        ExpandableMode expandableMode = mExpandableModeList.get(groupPosition);
        List<ExpandableMode.ChildDataBean> childDataBeans = expandableMode.getChildData();
        ExpandableMode.ChildDataBean childDataBean = childDataBeans.get(childPosition);
        // 获取子名字
        String childName = childDataBean.getChildName();
        // 获取对应的子icon
        String childIcon = childDataBean.getChildIcon();
        // 获取子icon名字对应的图片资源
        int childIconRes = getImageMipmapRes(mContext, childIcon);
        // 获取Drawable对象
        Drawable drawable = ContextCompat.getDrawable(mContext, childIconRes);
        // 设置icon
        mViewHolder.setImage(convertView, R.id.item_child_icon_iv, drawable);
        // 设置文字
        mViewHolder.setText(convertView, R.id.item_child_name_tv, childName);
        return convertView;
    }

    /**
     * 子item是否可点击
     * 当isChildSelectable方法返回false的时候，子item不可点击，且不会绘制分割线
     *
     * @param groupPosition groupPosition
     * @param childPosition childPosition
     * @return true可点击 false不可点击
     */
    @Override
    public boolean isChildSelectable(int groupPosition, int childPosition) {
        return true;
    }


    /**
     * 通过文件名，获取对应的图片资源
     *
     * @param context  context
     * @param filename filename
     * @return 对应的图片资源
     */
    public int getImageMipmapRes(Context context, String filename) {
        return context.getResources().getIdentifier(filename, "mipmap", context.getPackageName());
    }
}

```
#### 组item的布局文件

```
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:gravity="center_vertical"
    android:orientation="horizontal">

    <ImageView
        android:id="@+id/item_group_icon_iv"
        android:layout_width="20dp"
        android:layout_height="20dp"
        android:layout_marginStart="5dp"
        android:scaleType="centerInside"
        android:src="@mipmap/icon_fruit"
        tools:ignore="ContentDescription" />

    <TextView
        android:textColor="#000000"
        android:id="@+id/item_group_name_tv"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:drawableEnd="@mipmap/icon_right"
        android:drawablePadding="5dp"
        android:gravity="center_vertical"
        android:padding="8dp"
        android:text="水果"
        android:textSize="22sp" />


</LinearLayout>
```
#### 子item的布局文件

```
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:gravity="center_vertical"
    android:orientation="horizontal">

    <ImageView
        android:id="@+id/item_child_icon_iv"
        android:layout_width="25dp"
        android:layout_height="25dp"
        android:layout_marginStart="35dp"
        android:scaleType="centerInside"
        android:src="@mipmap/icon_apple"
        tools:ignore="ContentDescription" />

    <TextView
        android:layout_marginStart="5dp"
        android:id="@+id/item_child_name_tv"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:gravity="center_vertical"
        android:padding="5dp"
        android:text="苹果"
        android:textSize="25sp" />

</LinearLayout>
```

####  ViewHolder完整代码
ViewHolder完整代码如下：
```java
package top.zhaohaibo.expandable.utils;

import android.graphics.drawable.Drawable;
import android.util.SparseArray;
import android.view.View;
import android.widget.ImageView;
import android.widget.TextView;


/**
 * 作者: Ocean<br><br>
 * 时间: 2020/3/28 9:57 PM<br><br>
 * 邮箱: xinzhaohaibo@aliyun.com<br><br>
 * 描述: ViewHolder
 * 见张神博客：https://blog.csdn.net/lmj623565791/article/details/38902805/
 */
public class ViewHolder {

    /**
     * 静态内部类单例
     */
    private static class SingleHolder {
        private static final ViewHolder sViewHolder = new ViewHolder();
    }

    /**
     * 获取SingleHolder实例
     *
     * @return ViewHolder 对象
     */
    public static ViewHolder getInstance() {
        return SingleHolder.sViewHolder;
    }

    /**
     * 私有的构造方法，避免这个类在外部被实例化
     */
    private ViewHolder() {
    }

    /***
     * 获取资源对象
     * @param convertView  视图
     * @param id    控件ID
     * @param <T>   泛型
     * @return 对应的视图类型
     */
    @SuppressWarnings("unchecked")
    public <T extends View> T get(View convertView, int id) {
        // 通过getTag获取控件view的标签，并强转成SparseArray对象,如果它为空这进行实例化，并把起设置成view的标签
        SparseArray<View> viewHolder = (SparseArray<View>) convertView.getTag();
        if (viewHolder == null) {
            viewHolder = new SparseArray<>();
            convertView.setTag(viewHolder);
        }
        View childView = viewHolder.get(id);
        if (childView == null) {
            childView = convertView.findViewById(id);
            viewHolder.put(id, childView);
        }
        return (T) childView;
    }


    /**
     * 设置文字
     *
     * @param convertView 布局View
     * @param childViewId 子控件id
     * @param s           内容
     * @return ViewHolder
     */
    public ViewHolder setText(View convertView, int childViewId, String s) {
        TextView textView = get(convertView, childViewId);
        textView.setText(s);
        return this;
    }

    /**
     * 设置文字
     *
     * @param convertView 布局View
     * @param childViewId 子控件id
     * @param s           内容
     * @return ViewHolder
     */
    public ViewHolder setText(View convertView, int childViewId, int s) {
        TextView textView = get(convertView, childViewId);
        textView.setText(s);
        return this;
    }

    /**
     * 设置图片
     *
     * @param convertView 布局View
     * @param childViewId 子控件id
     * @param drawable    drawable
     * @return ViewHolder
     */
    public ViewHolder setImage(View convertView, int childViewId, Drawable drawable) {
        ImageView imageView = get(convertView, childViewId);
        imageView.setImageDrawable(drawable);
        return this;
    }

    /**
     * 设置图文数据
     *
     * @param convertView   布局View
     * @param childViewId   子控件id
     * @param txt           文本
     * @param leftDrawable  左边图片
     * @param rightDrawable 右图片
     * @return ViewHolder ViewHolder
     */
    public ViewHolder setImageText(View convertView, int childViewId, String txt, Drawable leftDrawable, Drawable rightDrawable) {
        TextView view = get(convertView, childViewId);
        if (isStrNull(txt)) {
            txt = "";
        }
        view.setText(txt);
        view.setCompoundDrawablesWithIntrinsicBounds(leftDrawable, null, rightDrawable, null);
        return this;
    }

    /**
     * 设置文字的右图片
     *
     * @param convertView 布局View
     * @param childViewId 子控件id
     * @return ViewHolder ViewHolder
     */
    public ViewHolder setImageTextRight(View convertView, int childViewId, Drawable rightDrawable) {
        TextView view = get(convertView, childViewId);
        view.setCompoundDrawablesWithIntrinsicBounds(null, null, rightDrawable, null);
        return this;
    }


    /**
     * 空字符串判断
     *
     * @param string 要判空的字符串
     * @return true 空串， false非空
     */
    private boolean isStrNull(String string) {
        if (string == null || "null".equals(string) || "NULL".equals(string)) {
            return true;
        }
        // TextUtils.isEmpty(string);
        String str = string.replace(" ", "");
        return str.length() == 0;
    }

}

```

## 主页面
主页面值有一个ExpandableListView控件，
android:childDivider 设置子item的分割线，
android:divider        设置分割线的颜色，
android:dividerHeight  设置分割线的高度，
android:groupIndicator 隐藏左边默认的的Icon。
布局文件如下：

```
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <ExpandableListView
        android:id="@+id/act_main_expandable_list_view"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:childDivider="@drawable/item_child_divider"
        android:divider="@color/item_line"
        android:dividerHeight="0.5dp"
        android:groupIndicator="@null" />

</LinearLayout>
```
##### ExpandableListView的数据刷新
ExpandableListView有两个重要方法，
collapseGroup(groupPosition);关闭某一组。
expandGroup(groupPosition);展开某一组。
依次调用他们可以实现数据刷新：

```
// 子item的监听
        mExpandableListView.setOnChildClickListener(new ExpandableListView.OnChildClickListener() {
            @Override
            public boolean onChildClick(ExpandableListView parent, View v, int groupPosition, int childPosition, long id) {
                Toast.makeText(MainActivity.this, childPosition + "", Toast.LENGTH_SHORT).show();
                List<ExpandableMode.ChildDataBean> childDataBeans = mExpandableModeList.get(groupPosition).getChildData();
                childDataBeans.add(childDataBeans.get(childPosition));
                // 设置数据
                mExpandableAdapter.setExpandableModeList(mExpandableModeList);
                // 通过关闭组item在展开刷新数据
                mExpandableListView.collapseGroup(groupPosition);
                mExpandableListView.expandGroup(groupPosition);
                return false;
            }
        });
```
##### 设置默认展开全部

```
// 打开所有
        for (int i = 0; i < mExpandableModeList.size(); i++) mExpandableListView.expandGroup(i);
        // 设置默认展开蔬菜组
        // mExpandableListView.expandGroup(1);
```
#### 主页面完整代码

```java
package top.zhaohaibo.expandable;

import androidx.appcompat.app.AppCompatActivity;

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

import com.google.gson.Gson;
import com.google.gson.reflect.TypeToken;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.List;

import top.zhaohaibo.expandable.adapter.MyExpandableAdapter;
import top.zhaohaibo.expandable.mode.ExpandableMode;

/**
 * 作者: Ocean<br><br>
 * 时间: 2020/3/28 9:57 PM<br><br>
 * 邮箱: xinzhaohaibo@aliyun.com<br><br>
 * 描述: git pull origin master --allow-unrelated-histories
 */
public class MainActivity extends AppCompatActivity {

    /** 数据集合 */
    private List<ExpandableMode> mExpandableModeList;
    /** 适配器 */
    private MyExpandableAdapter mExpandableAdapter;
    /** 可展开的List */
    private ExpandableListView mExpandableListView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        mExpandableListView = findViewById(R.id.act_main_expandable_list_view);

        // 调用readAssetsFile方法读取assets下的测试数据
        String ExpandableModeStr = readAssetsFile("ExpandableMode.json", this);
        Gson gson = new Gson();
        // 通过Gson把读到的ExpandableModeStr转换为实体对象
        mExpandableModeList = gson.fromJson(ExpandableModeStr, new TypeToken<List<ExpandableMode>>() {
        }.getType());
        // 实例化适配器
        mExpandableAdapter = new MyExpandableAdapter(mExpandableModeList, this);
        // 设置适配器
        mExpandableListView.setAdapter(mExpandableAdapter);

        // 子item的监听
        mExpandableListView.setOnChildClickListener(new ExpandableListView.OnChildClickListener() {
            @Override
            public boolean onChildClick(ExpandableListView parent, View v, int groupPosition, int childPosition, long id) {
                Toast.makeText(MainActivity.this, childPosition + "", Toast.LENGTH_SHORT).show();
                List<ExpandableMode.ChildDataBean> childDataBeans = mExpandableModeList.get(groupPosition).getChildData();
                childDataBeans.add(childDataBeans.get(childPosition));
                // 设置数据
                mExpandableAdapter.setExpandableModeList(mExpandableModeList);
                // 通过关闭组item在展开刷新数据
                mExpandableListView.collapseGroup(groupPosition);
                mExpandableListView.expandGroup(groupPosition);
                return false;
            }
        });

        // 打开所有
        for (int i = 0; i < mExpandableModeList.size(); i++) mExpandableListView.expandGroup(i);
        // 设置默认展开蔬菜组
        // mExpandableListView.expandGroup(1);
    }


    /**
     * 读取assets中的文件 流程
     * readAssetsFile("json/xx.json", this);
     *
     * @param fileName 文件名
     * @param context  context
     * @return 读取的内容
     */
    public String readAssetsFile(String fileName, Context context) {
        // 输入流对象
        InputStream inputStream;
        // 缓存流对象
        BufferedReader bufferedReader = null;
        StringBuilder stringBuilder = new StringBuilder();
        try {
            // getAssets方法返回通过输入流对象
            inputStream = context.getAssets().open(fileName);
            // InputStreamReader 实现字节流到字符流的转换
            bufferedReader = new BufferedReader(new InputStreamReader(inputStream));
            String line;
            while ((line = bufferedReader.readLine()) != null) {
                stringBuilder.append(line);
            }
        } catch (IOException e) {
            Log.e("MainActivity", e.toString());
        } finally {
            try {
                if (bufferedReader != null) {
                    bufferedReader.close();
                }
            } catch (IOException e) {
                Log.e("MainActivity", e.toString());
            }
        }
        return stringBuilder.toString();
    }
}

```

## 源码
[Demo源码(喜欢点个星)](https://gitee.com/haibo2016/ExpandableDemo)