android studio怎么编写二级listview

在 Android Studio 中，可以使用 ExpandableListView 控件来实现二级列表。

以下是实现二级列表的步骤：

1. 在布局文件中添加 ExpandableListView 控件：

<ExpandableListView
    android:id="@+id/expandableListView"
    android:layout_width="match_parent"
    android:layout_height="match_parent" />

2. 创建一个 Adapter 类来提供数据和视图：

public class MyExpandableListAdapter extends BaseExpandableListAdapter {
    private Context context;
    private List<String> groupList;
    private Map<String, List<String>> childMap;

    public MyExpandableListAdapter(Context context, List<String> groupList, Map<String, List<String>> childMap) {
        this.context = context;
        this.groupList = groupList;
        this.childMap = childMap;
    }

    @Override
    public int getGroupCount() {
        return groupList.size();
    }

    @Override
    public int getChildrenCount(int groupPosition) {
        String groupName = groupList.get(groupPosition);
        List<String> childList = childMap.get(groupName);
        return childList.size();
    }

    @Override
    public Object getGroup(int groupPosition) {
        return groupList.get(groupPosition);
    }

    @Override
    public Object getChild(int groupPosition, int childPosition) {
        String groupName = groupList.get(groupPosition);
        List<String> childList = childMap.get(groupName);
        return childList.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) {
        TextView textView = new TextView(context);
        textView.setText(groupList.get(groupPosition));
        textView.setPadding(100, 0, 0, 0);
        textView.setTextSize(20);
        return textView;
    }

    @Override
    public View getChildView(int groupPosition, int childPosition, boolean isLastChild, View convertView, ViewGroup parent) {
        TextView textView = new TextView(context);
        String groupName = groupList.get(groupPosition);
        List<String> childList = childMap.get(groupName);
        textView.setText(childList.get(childPosition));
        textView.setPadding(150, 0, 0, 0);
        textView.setTextSize(16);
        return textView;
    }

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

3. 在 Activity 中获取 ExpandableListView 控件的实例，并设置 Adapter：

ExpandableListView expandableListView = findViewById(R.id.expandableListView);

List<String> groupList = new ArrayList<>();
groupList.add("Group 1");
groupList.add("Group 2");

Map<String, List<String>> childMap = new HashMap<>();
List<String> childList1 = new ArrayList<>();
childList1.add("Child 1-1");
childList1.add("Child 1-2");
childList1.add("Child 1-3");
childMap.put("Group 1", childList1);
List<String> childList2 = new ArrayList<>();
childList2.add("Child 2-1");
childList2.add("Child 2-2");
childMap.put("Group 2", childList2);

MyExpandableListAdapter adapter = new MyExpandableListAdapter(this, groupList, childMap);
expandableListView.setAdapter(adapter);

这样就可以在 Android 应用中实现二级列表了。如果需要更多的样式和交互效果，可以在 Adapter 中进行定制。