Android ExpandableListView

ExpandableListView

ExpandableListView:

android ExpandableListView – a widget in the android that contains the two-level expandable/collapsible list.

Often used, for example, to display a series of groups while each group contains a list of elements. This way, users can double-click a group name to either expand or minimize the items below it and vice versa.

Example:

                                    
// activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical"
    android:background="#f4f4f4">

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

</LinearLayout>

// parent_list.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:padding="16dp"
    android:orientation="vertical">

    <TextView
        android:id="@+id/parent_list"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Parent Text"
        android:layout_marginLeft="16dp"
        android:textAppearance="?android:attr/textAppearanceLarge"/>

</LinearLayout>

// child_list.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:padding="16dp"
    android:orientation="vertical">

    <TextView
        android:id="@+id/child_list"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Child Text"
        android:layout_gravity="center" />

</LinearLayout>

                                    
                                        // main activity.java

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

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 {

    ExpandableListView expandableListView;
    MyExpandableListViewAdapter myExpandableListViewAdapter;
    List<String> category;
    Map<String, List<String>> names;

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

        expandableListView = findViewById(R.id.expandable_listview);

        getAllData();

        myExpandableListViewAdapter = new MyExpandableListViewAdapter(this, category, names);
        expandableListView.setAdapter(myExpandableListViewAdapter);

        expandableListView.setOnChildClickListener(new ExpandableListView.OnChildClickListener() {

            @Override
            public boolean onChildClick(ExpandableListView parent, View v,
                                        int groupPosition, int childPosition, long id) {
                Toast.makeText(
                        getApplicationContext(),
                        category.get(groupPosition)
                                + " : "
                                + names.get(
                                category.get(groupPosition)).get(
                                childPosition), Toast.LENGTH_SHORT)
                        .show();
                return false;
            }
        });

    }

    private void getAllData() {

        category = new ArrayList<String>();
        names = new HashMap<String, List<String>>();

        category.add("Fruits");
        category.add("Flowers");
        category.add("Animals");

        List<String> fruits = new ArrayList<String>();
        fruits.add("Mango");
        fruits.add("Orange");
        fruits.add("Banana");
        fruits.add("Apple");

        List<String> flowers = new ArrayList<String>();
        flowers.add("Rose");
        flowers.add("Lotus");
        flowers.add("Jasmine");
        flowers.add("Sunflower");

        List<String> animals = new ArrayList<String>();
        animals.add("Lion");
        animals.add("Tiger");
        animals.add("Elephant");
        animals.add("Bear");

        names.put(category.get(0), fruits);
        names.put(category.get(1), flowers);
        names.put(category.get(2), animals);

    }

}




// MyExpandableListViewAdapter.java

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 MyExpandableListViewAdapter extends BaseExpandableListAdapter {

    List category;
    Map> names;
    Context context;

    public MyExpandableListViewAdapter(Context context, List<String> category, Map<String, List<String>> names) {
        this.context = context;
        this.category = category;
        this.names = names;
    }

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

    @Override
    public int getChildrenCount(int groupPosition) {
        return names.get(category.get(groupPosition)).size();
    }

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

    @Override
    public Object getChild(int groupPosition, int childPosition) {
        return names.get(category.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) {
        String headerTitle = (String) getGroup(groupPosition);
        if (convertView == null) {
            LayoutInflater infalInflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            convertView = infalInflater.inflate(R.layout.parent_list, null);
        }

        TextView txtParent = convertView.findViewById(R.id.parent_list);
        txtParent.setText(headerTitle);
        return convertView;
    }

    @Override
    public View getChildView(int groupPosition, int childPosition, boolean isLastChild, View convertView, ViewGroup parent) {
        final String childText = (String) getChild(groupPosition, childPosition);

        if (convertView == null) {
            LayoutInflater infalInflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            convertView = infalInflater.inflate(R.layout.child_list, null);
        }

        TextView txtChild = convertView.findViewById(R.id.child_list);
        txtChild.setText(childText);
        return convertView;
    }

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

                                    
// maink activity.kt

import android.os.Bundle
import android.view.View
import android.widget.ExpandableListView
import android.widget.Toast
import androidx.appcompat.app.AppCompatActivity

class MainActivity : AppCompatActivity() {

    private lateinit var expandableListView: ExpandableListView
    private lateinit var myExpandableListViewAdapter: MyExpandableListViewAdapter
    private lateinit var category: MutableList<String>
    private lateinit var names: MutableMap<String, List<String>>

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        expandableListView = findViewById(R.id.expandable_listview)

        getAllData()

        myExpandableListViewAdapter = MyExpandableListViewAdapter(this, category, names)
        expandableListView.setAdapter(myExpandableListViewAdapter)

        expandableListView.setOnChildClickListener { parent, v, groupPosition, childPosition, id ->
            Toast.makeText(
                applicationContext,
                "${category[groupPosition]} : ${names[category[groupPosition]]?.get(childPosition)}",
                Toast.LENGTH_SHORT
            ).show()
            false
        }
    }

    private fun getAllData() {
        category = mutableListOf()
        names = mutableMapOf()

        category.add("Fruits")
        category.add("Flowers")
        category.add("Animals")

        val fruits = listOf("Mango", "Orange", "Banana", "Apple")
        val flowers = listOf("Rose", "Lotus", "Jasmine", "Sunflower")
        val animals = listOf("Lion", "Tiger", "Elephant", "Bear")

        names[category[0]] = fruits
        names[category[1]] = flowers
        names[category[2]] = animals
    }
}




// MyExpandableListViewAdapter

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

class MyExpandableListViewAdapter(
    private val context: Context,
    private val category: List<String>,
    private val names: Map<String, List<String>>
) : BaseExpandableListAdapter() {

    override fun getGroupCount(): Int = category.size

    override fun getChildrenCount(groupPosition: Int): Int = names[category[groupPosition]]?.size ?: 0

    override fun getGroup(groupPosition: Int): Any = category[groupPosition]

    override fun getChild(groupPosition: Int, childPosition: Int): Any =
        names[category[groupPosition]]?.get(childPosition) ?: ""

    override fun getGroupId(groupPosition: Int): Long = groupPosition.toLong()

    override fun getChildId(groupPosition: Int, childPosition: Int): Long = childPosition.toLong()

    override fun hasStableIds(): Boolean = false

    override fun getGroupView(
        groupPosition: Int,
        isExpanded: Boolean,
        convertView: View?,
        parent: ViewGroup?
    ): View {
        val headerTitle = getGroup(groupPosition) as String
        val inflater = context.getSystemService(Context.LAYOUT_INFLATER_SERVICE) as LayoutInflater
        val view = convertView ?: inflater.inflate(R.layout.parent_list, null)

        view.findViewById<TextView>(R.id.parent_list).text = headerTitle
        return view
    }

    override fun getChildView(
        groupPosition: Int,
        childPosition: Int,
        isLastChild: Boolean,
        convertView: View?,
        parent: ViewGroup?
    ): View {
        val childText = getChild(groupPosition, childPosition) as String
        val inflater = context.getSystemService(Context.LAYOUT_INFLATER_SERVICE) as LayoutInflater
        val view = convertView ?: inflater.inflate(R.layout.child_list, null)

        view.findViewById<TextView>(R.id.child_list).text = childText
        return view
    }

    override fun isChildSelectable(groupPosition: Int, childPosition: Int): Boolean = true
}