[移动开发]今日所学—Android中ExpandableListView的使用

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?代码部分：

activity_main.xml

<?xml version="1.0" encoding="UTF-8"?>

<androidx.constraintlayout.widget.ConstraintLayout 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/elv"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

</androidx.constraintlayout.widget.ConstraintLayout>

group_item.xml

<?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"
    android:layout_width="match_parent"
    android:layout_height="40dp"
    android:orientation="horizontal">

    <ImageView
        android:id="@+id/imageView"
        android:layout_width="wrap_content"
        android:layout_height="match_parent"
        android:layout_weight="1"
        app:srcCompat="@mipmap/ic_launcher" />

    <TextView
        android:id="@+id/textView"
        android:layout_width="wrap_content"
        android:layout_height="match_parent"
        android:layout_weight="1"
        android:text="TextView" />

</LinearLayout>

child_item.xml

<?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"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="horizontal">

    <TextView
        android:id="@+id/textView2"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:textSize="30sp"
        android:text="TextView" />

</LinearLayout>

MainActivity.java

package com.example.expandlistviewtest;

import android.os.Bundle;
import android.view.View;
import android.widget.ExpandableListView;
import android.widget.Toast;

import androidx.appcompat.app.AppCompatActivity;

public class MainActivity extends AppCompatActivity {
    // 定义扩展ExpandableListView 所需要变量
    private ExpandableListView expandablelistview;
    private MyExpandAdapter myExpandAdapter;
    // 好友群组名称设定
    // 群组名称
    private String[] groupName = new String[]{"一", "二", "三"};
    private int[] groupPic = new int[]{R.mipmap.ic_launcher ,R.mipmap.ic_launcher,
            R.mipmap.ic_launcher};
    // 好友名称
    private String[][] childName = new String[][]{{"1", "2"},
            {"1", "2", "3"}, {"1", "3"}};

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

        expandablelistview = findViewById(R.id.elv);
        myExpandAdapter = new MyExpandAdapter(this, groupName, childName, groupPic);
        expandablelistview.setAdapter(myExpandAdapter);

        expandablelistview.setOnChildClickListener(new ExpandableListView.OnChildClickListener() {
            @Override
            public boolean onChildClick(ExpandableListView parent, View v, int groupPosition, int childPosition, long id) {
                Toast.makeText(getApplicationContext(),
                        groupName[groupPosition] + ":" + childName[groupPosition][childPosition],
                        Toast.LENGTH_SHORT).show();
                return false;
            }
        });
    }
}

MyExpandAdapter.java

package com.example.expandlistviewtest;


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

public class MyExpandAdapter extends BaseExpandableListAdapter {
    private String[] groupName;
    private String[][] childName;
    private int[] groupPic;

    LayoutInflater inflater;

    public MyExpandAdapter(Context context, String[] groupName, String[][] childName, int[] groupPic) {
        this.inflater = LayoutInflater.from(context);
        this.groupName = groupName;
        this.childName = childName;
        this.groupPic = groupPic;
    }

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

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

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

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

    @Override
    public View getGroupView(int groupPosition, boolean isExpanded, View convertView, ViewGroup parent) {
        convertView = inflater.inflate(R.layout.group_item, null);
        TextView textView = convertView.findViewById(R.id.textView);
        textView.setText(getGroup(groupPosition).toString());
        ImageView imageView = convertView.findViewById(R.id.imageView);
        imageView.setImageResource(groupPic[groupPosition]);
        return convertView;
    }

    @Override
    public View getChildView(int groupPosition, int childPosition, boolean isLastChild, View convertView, ViewGroup parent) {
        convertView = inflater.inflate(R.layout.child_item, null);
        TextView nickTextView = convertView.findViewById(R.id.textView2);
        nickTextView.setText(getChild(groupPosition, childPosition).toString());
        return convertView;
    }

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

效果图：

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