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

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：

<?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="wrap_content"    android:orientation="horizontal"    android:padding="8dp">   <TextView        android:id="@+id/tv_item"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:textSize="16sp" /></LinearLayout>

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<String> groupList;    private Map<String, List<String>> childList;    public MyExpandableListAdapter(Context context, List<String> groupList, Map<String, List<String>> 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;    }}

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

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

<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    xmlns:app="http://schemas.android.com/apk/res-auto"    xmlns:tools="http://schemas.android.com/tools"    android:layout_width="match_parent"    android:layout_height="match_parent"    android:orientation="vertical"    tools:context=".MainActivity">   <ExpandableListView        android:id="@+id/expandableListView"        android:layout_width="match_parent"        android:layout_height="match_parent" /></LinearLayout>

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。