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在 Android 开发中，一个 App 通常会有这种的需求，就是在一个列表内部在嵌套一个列表，下面我们来看看效果图就知道了。
Android 二级菜单的简单使用方式
首页呢，我们要准备一个处理 ExpandableListView 的数据的适配器，只需继承BaseExpandableListAdapter 重写里面的方法即可。下面我们来看看这个代码吧：
/**
* @author xww
* @desciption : ExpandableListView 适配器
* @date 2019/10/24
* @time 16:10
*/
public class CitySelectAdapter extends BaseExpandableListAdapter {
private Context mContext;
private List<CitySelectBean> mDataBeans;
public CitySelectAdapter(Context context, List<CitySelectBean> citySelectBeans) {
this.mContext = context;
this.mDataBeans = citySelectBeans;
}
@Override
public int getGroupCount() {
return mDataBeans.size();
}
@Override
public int getChildrenCount(int groupPosition) {
return mDataBeans.get(groupPosition).getCity().size();
}
@Override
public Object getGroup(int groupPosition) {
return mDataBeans.get(groupPosition);
}
@Override
public Object getChild(int groupPosition, int childPosition) {
return mDataBeans.get(groupPosition).getCity().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 true;
}
@Override
public View getGroupView(int groupPosition, boolean isExpanded, View convertView, ViewGroup parent) {
GroupHolder holder = null;
if (convertView == null) {
convertView = LayoutInflater.from(mContext).inflate(R.layout.exp_list_city_select_province, null);
holder = new GroupHolder(convertView);
convertView.setTag(holder);
} else {
holder = (GroupHolder) convertView.getTag();
}
holder.tvProvince.setText(mDataBeans.get(groupPosition).getProvince());
return convertView;
}
@Override
public View getChildView(int groupPosition, int childPosition, boolean isLastChild, View convertView, ViewGroup parent) {
ChildHolder holder = null;
if (convertView == null) {
convertView = LayoutInflater.from(mContext).inflate(R.layout.exp_list_city_select_city, null);
holder = new ChildHolder(convertView);
convertView.setTag(holder);
} else {
holder = (ChildHolder) convertView.getTag();
}
holder.tvCity.setText(mDataBeans.get(groupPosition).getCity().get(childPosition));
return convertView;
}
@Override
public boolean isChildSelectable(int groupPosition, int childPosition) {
return true;
}
public class GroupHolder {
TextView tvProvince;
GroupHolder(View itemView) {
tvProvince = itemView.findViewById(R.id.exp_list_province);
}
}
public class ChildHolder {
TextView tvCity;
ChildHolder(View itemView) {
tvCity = itemView.findViewById(R.id.exp_list_city);
}
}
}
看这个适配器给我们提供的方法，就很容易知道我们要传入的一个数据模型，下面我就拿省份、城市来举个例子。我们的一级列表是省份，二级列表里面是各个省的城市。它的数据模型是这样样子的：
/**
* @author xww
* @desciption :
* @date 2019/10/24
* @time 16:08
*/
public class CitySelectBean {
private String province;
private List<String> city;
public CitySelectBean(String province, List<String> city) {
this.province = province;
this.city = city;
}
public String getProvince() {
return province;
}
public void setProvince(String province) {
this.province = province;
}
public List<String> getCity() {
return city;
}
public void setCity(List<String> city) {
this.city = city;
}
}
由于提供的数据比较简单，那么适配器的 item 布局就放一个 TextView 即可，但是这里要分清楚，一共有两个 item 布局，一个是省份的，一个是城市的，代码如下：
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="wrap_content">
<TextView
android:id="@+id/exp_list_province"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layoutDirection="ltr"
android:padding="8dp" />
</RelativeLayout>
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="wrap_content">
<TextView
android:id="@+id/exp_list_city"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginTop="8dp"
android:layoutDirection="ltr"
android:paddingLeft="24dp"
android:paddingBottom="8dp" />
</RelativeLayout>
那么到此，我们的适配器以及布局文件就准备好了，然后是我们的 Activity 的布局文件：
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="@color/colorWhite"
android:orientation="vertical">
<TextView
style="@style/TopTitleBarStyle"
android:layout_width="match_parent"
android:layout_height="48dp"
android:text="选择城市" />
<ExpandableListView
android:id="@+id/explv_city_select"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layoutDirection="rtl" />
</LinearLayout>
最后，就是我们如何添加数据了， Activity 的代码如下：
/**
* @author xww
* @desciption :
* @date 2019/10/24
* @time 16:01
*/
public class CitySelectActivity extends BasePermissionActivity {
private ExpandableListView explvCity;
private CitySelectAdapter mCitySelectAdapter;
private List<CitySelectBean> mCitySelectBeans;
@Override
protected void initLayout(@Nullable Bundle savedInstanceState) {
super.initLayout(savedInstanceState);
setContentView(R.layout.activity_city_select);
}
@Override
protected void initViews() {
super.initViews();
explvCity = $(R.id.explv_city_select);
}
@Override
protected void initData() {
super.initData();
mCitySelectBeans = new ArrayList<>();
mCitySelectBeans.add(new CitySelectBean("福建省", Arrays.asList("宁德", "福州", "厦门", "漳州", "泉州")));
mCitySelectBeans.add(new CitySelectBean("广东省", Arrays.asList("汕头", "东菀", "深圳", "广州")));
mCitySelectBeans.add(new CitySelectBean("浙江省", Arrays.asList("温州", "杭州", "绍兴", "嘉兴")));
mCitySelectAdapter = new CitySelectAdapter(this, mCitySelectBeans);
explvCity.setAdapter(mCitySelectAdapter);
}
}
这里有一个属性介绍一下
android:layoutDirection="rtl"
这个属性是把如下图的那个箭头设置到右边，因为在左边时会被文字给挡住了，显得不好看。
