ExpandableListView——ExpandableListActivity及其重写方法被弃用的替代方案

今天老师上课讲到ExpandableListActivity的应用，但是当我们实际使用的时候，会发现它的重写方法几乎全部被弃用，其实官方也给出了相应的替代方案

既然是学习，那我们就使用推荐替代方案中的ExpandableListView

ExpandableListView官方文档：https://developer.android.com/reference/android/widget/ExpandableListView

xml

使用ExpandableListView布局即可，关于item，自行书写，当然官方也给出了一级视图android.R.layout.simple_expandable_list_item_1，二级视图android.R.layout.simple_expandable_list_item_2，点开它，可以看到textView的id为text1与text2

<?xml version="1.0" encoding="utf-8"?>
<ExpandableListView xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    xmlns:tools="http://schemas.android.com/tools"
    tools:context="*****"
    android:id="@+id/*****">

</ExpandableListView>

逻辑代码

数据源

需要有一级二级目录，所以定义两个数组，或者arrayList,map等，无可厚非，这里我就用最偷懒的数组

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private  String [] provinces = {"山西省","吉林省","河北省","山东省"};
private String[][] cities = {{"太原市","吕梁市","长治市"},{"长春市","松原市","吉林市"},{"石家庄市","唐山市","承德市"},{"菏泽市","青岛市","济南市"}};

自定义适配器

和listView，recycleView一样，既然是列表布局，那么必然是需要适配器的，自己的适配器类继承BaseExpandableListAdapter类，android Studio会自动生成需要重写的方法，此方法与老师想讲的ExpandableListActivity重写方法一致，起到学习作用

大多数重写方法相信都是会的，方法名和参数很容易理解和书写，这里需要注意的是getChildView和getGroupView这两个方法，其实与listView，recycleView一样写法一致，先进行view的LayoutInflater，再添加相应的数据，最后返回view

@Override
public int getGroupCount() {
  return provinces.length;
}

@Override
public int getChildrenCount(int groupPosition) {
  return cities[groupPosition].length;
}

@Override
public Object getGroup(int groupPosition) {
  return provinces[groupPosition];
}

@Override
public Object getChild(int groupPosition, int childPosition) {
  return cities[groupPosition][childPosition];
}

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

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

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

@Override
public View getGroupView(int groupPosition, boolean isExpanded, View convertView, ViewGroup parent) {
  convertView = LayoutInflater.from(parent.getContext()).inflate(android.R.layout.simple_expandable_list_item_1, null);
  TextView textView = convertView.findViewById(android.R.id.text1);
  textView.setText(provinces[groupPosition]);
  return convertView;
}

@Override
public View getChildView(int groupPosition, int childPosition, boolean isLastChild, View convertView, ViewGroup parent) {
  convertView = LayoutInflater.from(parent.getContext()).inflate(R.layout.text_item, null);
  TextView textView = convertView.findViewById(R.id.text2);
  textView.setText(cities[groupPosition][childPosition]);
  return convertView;

}

@Override
public boolean isChildSelectable(int groupPosition, int childPosition) {
  return true;
}

活动类

在活动类中对ExpandListView进行findViewId，再绑定适配器即可

private ExpandableListView expandableListView = null;

expandableListView = findViewById(R.id.expand_list);
expandableListView.setAdapter(myExpandListAdapter);