Android developers ExpandableListView drop-down list of contents Detailed View

Foreword

　　The need to achieve a List item when the need to include a list, we can choose ExpandableListView. In fact, this is still ListView View original design of the set. Is to increase the ListView 2 layers of it. So it's very writing of the adapter and the adapter ListView Similarly, there would be a common problem that is not of the View Item multiplexing mechanism, be sure to pay attention to this point in time need to write implemented using the Item View reuse, reduce memory and increase performance.

A simple Demo

　　The old rules, first to a simple demo to understand the most basic use case. Note! The demo is not to write any View multiplexing mechanism in Adapter Do not use the actual project. Demo only help you quickly understand ExpandableListView know

Renderings

　　

Activity of Xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    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">
    </ExpandableListView>

</LinearLayout>

一级Item和二级Item用的xml布局

偷懒,我让一级和二级都使用一个布局

<?xml version="1.0" encoding="utf-8"?>
<TextView xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/text1"
    android:layout_width="match_parent"
    android:layout_height="45dp"
    android:text="内容"
    android:textSize="15sp"
    android:textColor="@color/fontBlack3"
    android:gravity="center"
    android:background="@color/colorWhite">
</TextView>

编写适配器

import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseExpandableListAdapter;
import android.widget.TextView;
import java.util.List;

public class DemoAdapter extends BaseExpandableListAdapter {
    List<String> mGroupList;//一级List
    List<List<String>> mChildList;//二级List 注意!这里是List里面套了一个List<String>,实际项目你可以写一个pojo类来管理2层数据


    public DemoAdapter(List<String> groupList, List<List<String>> childList){
        mGroupList = groupList;
        mChildList = childList;

    }

    @Override
    public int getGroupCount() {//返回第一级List长度
        return mGroupList.size();
    }

    @Override
    public int getChildrenCount(int groupPosition) {//返回指定groupPosition的第二级List长度
        return mChildList.get(groupPosition).size();
    }

    @Override
    public Object getGroup(int groupPosition) {//返回一级List里的内容
        return mGroupList.get(groupPosition);
    }

    @Override
    public Object getChild(int groupPosition, int childPosition) {//返回二级List的内容
        return mChildList.get(groupPosition).get(childPosition);
    }

    @Override
    public long getGroupId(int groupPosition) {//返回一级View的id 保证id唯一
        return groupPosition;
    }

    @Override
    public long getChildId(int groupPosition, int childPosition) {//返回二级View的id 保证id唯一
        return groupPosition + childPosition;
    }

    /**
     * 指示在对基础数据进行更改时子ID和组ID是否稳定
     * @return
     */
    @Override
    public boolean hasStableIds() {
        return true;
    }

    /**
     *  返回一级父View
     */
    @Override
    public View getGroupView(int groupPosition, boolean isExpanded, View convertView, ViewGroup parent) {
        convertView = LayoutInflater.from(parent.getContext()).inflate(R.layout.text_item, parent,false);
        ((TextView)convertView).setText((String)getGroup(groupPosition));
        return convertView;
    }

    /**
     *  返回二级子View
     */
    @Override
    public View getChildView(int groupPosition, int childPosition, boolean isLastChild, View convertView, ViewGroup parent) {
        convertView = LayoutInflater.from(parent.getContext()).inflate(R.layout.text_item, parent,false);
        ((TextView)convertView).setText((String)getChild(groupPosition,childPosition));
        return convertView;
    }

    /**
     *  指定位置的子项是否可选
     */
    @Override
    public boolean isChildSelectable(int groupPosition, int childPosition) {
        return true;
    }
}

Activity里的代码

        mExpandableListView = findViewById(R.id.expandablelistview);

        List<String> groupList = new ArrayList<>();
        groupList.add("一");
        groupList.add("二");
        groupList.add("三");

        List<List<String>> childList = new ArrayList<>();
        List<String> childList1 = new ArrayList<>();
        childList1.add("1");
        childList1.add("1");
        childList1.add("1");
        List<String> childList2 = new ArrayList<>();
        childList2.add("2");
        childList2.add("2");
        childList2.add("2");
        List<String> childList3 = new ArrayList<>();
        childList3.add("3");
        childList3.add("3");
        childList3.add("3");

        childList.add(childList1);
        childList.add(childList2);
        childList.add(childList3);

        DemoAdapter demoAdapter = new DemoAdapter(groupList, childList);
        mExpandableListView.setAdapter(demoAdapter);

        mExpandableListView.setOnGroupClickListener(new ExpandableListView.OnGroupClickListener() {//一级点击监听
            @Override
            public boolean onGroupClick(ExpandableListView parent, View v, int groupPosition, long id) {

                //如果你处理了并且消费了点击返回true,这是一个基本的防止onTouch事件向下或者向上传递的返回机制
                return false;
            }
        });

        mExpandableListView.setOnChildClickListener(new ExpandableListView.OnChildClickListener() {//二级点击监听
            @Override
            public boolean onChildClick(ExpandableListView parent, View v, int groupPosition, int childPosition, long id) {

                //如果你处理了并且消费了点击返回true
                return false;
            }
        });

其他Xml属性

android:dividerHeight="20dp" 设置边距高度,注意设置这个边距包括了一级和二级

android:divider="@color/colorRed1" 设置一级边距的背景色

 

 

 

 

 

 

 

 

 

 

 

 

 

end