Spinner实现选项的分组折叠与动态展开

要实现Spinner中选项的分组折叠与动态展开，可以通过自定义Adapter来实现。以下是一个简单的示例代码，演示如何实现这个功能：

public class CustomSpinnerAdapter extends BaseAdapter {

    private List<String> groupList;
    private Map<String, List<String>> childMap;
    private Context context;

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

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

    @Override
    public Object getItem(int position) {
        return groupList.get(position);
    }

    @Override
    public long getItemId(int position) {
        return position;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        View view = LayoutInflater.from(context).inflate(R.layout.item_spinner_group, parent, false);
        TextView textView = view.findViewById(R.id.tv_group);
        textView.setText(groupList.get(position));
        return view;
    }

    @Override
    public View getDropDownView(int position, View convertView, ViewGroup parent) {
        View view = LayoutInflater.from(context).inflate(R.layout.item_spinner_child, parent, false);
        TextView textView = view.findViewById(R.id.tv_child);
        textView.setText(childMap.get(groupList.get(position)).get(0));
        return view;
    }
}

在上面的代码中，CustomSpinnerAdapter继承自BaseAdapter，实现了getView和getDropDownView方法，分别用于Spinner的展示和下拉选项的展示。通过groupList和childMap来存储分组和子项的数据，实现分组折叠与动态展开的功能。

使用这个自定义的Adapter来设置Spinner的数据源：

// 初始化groupList和childMap
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");
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);

// 设置Spinner的Adapter
CustomSpinnerAdapter adapter = new CustomSpinnerAdapter(this, groupList, childMap);
spinner.setAdapter(adapter);

通过上面的代码，就可以实现Spinner中选项的分组折叠与动态展开的功能。当点击Spinner时，会展示分组的选项，点击分组时，会展开对应的子项。