利用ExpandableListView实现树形结构展示

ExpandableListView 是 Android 中的一个组件，它可以用来实现树形结构的数据展示

1. 首先，在 res/layout 目录下创建一个布局文件 list_item.xml，用于显示每个列表项：

2. 创建一个 Java 类 MyExpandableListAdapter，继承自 BaseExpandableListAdapter：

import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseExpandableListAdapter;
import android.widget.TextView;

import java.util.List;
import java.util.Map;

public class MyExpandableListAdapter extends BaseExpandableListAdapter {

    private Context context;
    private List groupList;
    private Map> childList;

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

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

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

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

    @Override
    public Object getChild(int groupPosition, int childPosition) {
        return childList.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) {
            convertView = LayoutInflater.from(context).inflate(R.layout.list_item, parent, false);
        }
        TextView tvItem = convertView.findViewById(R.id.tv_item);
        tvItem.setText(groupList.get(groupPosition));
        return convertView;
    }

    @Override
    public View getChildView(int groupPosition, int childPosition, boolean isLastChild, View convertView, ViewGroup parent) {
        if (convertView == null) {
            convertView = LayoutInflater.from(context).inflate(R.layout.list_item, parent, false);
        }
        TextView tvItem = convertView.findViewById(R.id.tv_item);
        tvItem.setText(childList.get(groupList.get(groupPosition)).get(childPosition));
        return convertView;
    }

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

3. 在你的 Activity 或 Fragment 中，初始化 ExpandableListView 并设置适配器：

import android.os.Bundle;
import android.widget.ExpandableListView;

import androidx.appcompat.app.AppCompatActivity;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class MainActivity extends AppCompatActivity {

    private ExpandableListView expandableListView;
    private MyExpandableListAdapter adapter;

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

        expandableListView = findViewById(R.id.expandableListView);

        // 初始化数据
        List groupList = new ArrayList<>();
        groupList.add("Group 1");
        groupList.add("Group 2");
        groupList.add("Group 3");

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

        List childList2 = new ArrayList<>();
        childList2.add("Child 2-1");
        childList2.add("Child 2-2");
        childList2.add("Child 2-3");
        childList.put("Group 2", childList2);

        List childList3 = new ArrayList<>();
        childList3.add("Child 3-1");
        childList.put("Group 3", childList3);

        // 设置适配器
        adapter = new MyExpandableListAdapter(this, groupList, childList);
        expandableListView.setAdapter(adapter);
    }
}

4. 在 res/layout/activity_main.xml 中添加 ExpandableListView：

现在运行应用程序，你将看到一个树形结构的列表。点击父节点时，子节点将展开或收起。