Android安卓二级菜单

一、首先在AndroidStudio里创建个moudle（如果不想新创建项目，且自己的电脑配置扛得住的情况下）

二、在activity_main.xml里布局ExpandableListView

xml version="1.0" encoding="utf-8"?>
<RelativeLayout 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"
    tools:context=".MainActivity">

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

RelativeLayout>

三、创建父级目录item_group.xml

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="match_parent"
    android:orientation="vertical"
    android:background="#8BCF28"
    >
<TextView   android:id="@+id/tv_group"
    android:layout_width="match_parent"
    android:layout_height="30dp"
    android:gravity="center"
    android:text="父目录"
    />

LinearLayout>

四、创建子级目录item_child.xml

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="match_parent"
    android:orientation="horizontal"
    >
    <ImageView  android:id="@+id/child_img"
        android:src="@mipmap/ic_launcher"
        android:layout_width="30dp"
        android:layout_height="30dp" />
    <TextView   android:id="@+id/tv_child"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="子目录"/>
五、创建MyExpandableListView的优化类

package com.example.expandablelistview;

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

public class MyExpandableListView extends BaseExpandableListAdapter {
    Context context;
    private String [] groups;
    private String [][] childs;

    public MyExpandableListView(Context context, String[] groups, String[][] childs) {
        this.context = context;
        this.groups = groups;
        this.childs = childs;
    }

    @Override
    public int getGroupCount() {
        return groups.length;
    }

    @Override
    public int getChildrenCount(int groupPosition) {
        return childs[groupPosition].length;
    }

    @Override
    public Object getGroup(int groupPosition) {
        return groups[groupPosition];
    }

    @Override
    public Object getChild(int groupPosition, int childPosition) {
        return childs[groupPosition][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;
    }

//填充父级目录
    @Override
    public View getGroupView(int groupPosition, boolean isExpanded, View convertView, ViewGroup parent) {
        GroupHolder groupholder =null;
        if (convertView==null){
            groupholder =new GroupHolder();
            convertView=View.inflate(context,R.layout.item_group,null);
            groupholder.tv_group=convertView.findViewById(R.id.tv_group);
            convertView.setTag(groupholder);
        }else{
            groupholder= (GroupHolder) convertView.getTag();
        }
        groupholder.tv_group.setText(groups[groupPosition]);
        return convertView;
        }

   

//填充子级目录

 @Override
    public View getChildView(int groupPosition, int childPosition, boolean isLastChild, View convertView, ViewGroup parent) {
        ChildHolder childholder=null;
        if (convertView==null){
            childholder=new ChildHolder();
            convertView=View.inflate(context,R.layout.item_child,null);
            childholder.child_img=convertView.findViewById(R.id.child_img);
            childholder.tv_child=convertView.findViewById(R.id.tv_child);
            convertView.setTag(childholder);
        }else {
            childholder= (ChildHolder) convertView.getTag();
        };
            //childholder.child_img.setImageBitmap(
            childholder.tv_child.setText(childs[groupPosition][childPosition]);

        return convertView;
    

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

  class GroupHolder{
        TextView tv_group;
  }

    class ChildHolder{
        ImageView child_img;
        TextView tv_child;
    }

}

五、Mainactivity修改

package com.example.expandablelistview;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.ExpandableListView;

public class MainActivity extends AppCompatActivity {

    private ExpandableListView expandableListView;
    private String [] groups={"A","B","C"};
    private String [][] childs={{"A1","A2","A3"},{"B1","B2","B3"},{"C1","C2","C3"}};

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        expandableListView=findViewById(R.id.expandableListView);
        expandableListView.setAdapter(new MyExpandableListView(MainActivity.this,groups,childs));


    }
}