在Andriod studio 上设计ExpandableListView

1. 创建一个新的Android项目，选择Empty Activity。

2. 在MainActivity中添加ExpandableListView控件，设置其layout_width和layout_height为match_parent。

3. 在res/layout文件夹中创建一个新的xml文件，命名为list_group.xml。在该文件中添加一个TextView控件，设置其layout_width和layout_height为match_parent，并设置其背景颜色和字体颜色。

4. 在res/layout文件夹中创建另一个新的xml文件，命名为list_item.xml。在该文件中添加一个TextView控件，设置其layout_width和layout_height为match_parent，并设置其背景颜色和字体颜色。

5. 在MainActivity中创建一个ExpandableListAdapter类，该类继承自BaseExpandableListAdapter，并实现其方法。

6. 在MainActivity的onCreate方法中，创建数据源并设置ExpandableListView的适配器为ExpandableListAdapter。

7. 运行程序，查看ExpandableListView效果。

下面是一个示例代码：

public class MainActivity extends AppCompatActivity {

    ExpandableListView expandableListView;
    ExpandableListAdapter expandableListAdapter;
    List<String> groupList;
    List<String> childList;
    Map<String, List<String>> itemMap;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        expandableListView = findViewById(R.id.expandableListView);
        initData();
        expandableListAdapter = new ExpandableListAdapter(this, groupList, itemMap);
        expandableListView.setAdapter(expandableListAdapter);
    }

    private void initData() {
        groupList = new ArrayList<>();
        childList = new ArrayList<>();
        itemMap = new HashMap<>();

        groupList.add("Group 1");
        groupList.add("Group 2");
        groupList.add("Group 3");

        childList.add("Item 1");
        childList.add("Item 2");
        childList.add("Item 3");
        childList.add("Item 4");
        childList.add("Item 5");

        itemMap.put(groupList.get(0), childList);
        itemMap.put(groupList.get(1), childList);
        itemMap.put(groupList.get(2), childList);
    }
}

ExpandableListAdapter类代码：

public class ExpandableListAdapter extends BaseExpandableListAdapter {

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

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

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

    @Override
    public int getChildrenCount(int groupPosition) {
        return itemMap.get(groupList.get(groupPosition)).size();
    }

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

    @Override
    public Object getChild(int groupPosition, int childPosition) {
        return itemMap.get(groupList.get(groupPosition)).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 false;
    }

    @Override
    public View getGroupView(int groupPosition, boolean isExpanded, View convertView, ViewGroup parent) {
        if (convertView == null) {
            LayoutInflater inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            convertView = inflater.inflate(R.layout.list_group, null);
        }
        TextView textView = convertView.findViewById(R.id.textView);
        textView.setText(groupList.get(groupPosition));
        return convertView;
    }

    @Override
    public View getChildView(int groupPosition, int childPosition, boolean isLastChild, View convertView, ViewGroup parent) {
        if (convertView == null) {
            LayoutInflater inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            convertView = inflater.inflate(R.layout.list_item, null);
        }
        TextView textView = convertView.findViewById(R.id.textView);
        textView.setText(itemMap.get(groupList.get(groupPosition)).get(childPosition));
        return convertView;
    }

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