안드로이드 ExpandableListAdapter( 하위 목록까지 보여주기 )

목록을 보여줄 때는 보통 RecyclerView를 이용하여 RecyclerAdapter를 사용할 것입니다.

그러나 한 항목에 하위 항목까지 보여주려고 하면 많이 불편하실 겁니다.

그래서 편하게 하위 항목까지 보열 줄 수 있는 ExpandableListAdapter 예제입니다.

<실행 화면>

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RecyclerView를 사용하고 Adapter만 ExpandableListAdapter로 사용하는 것입니다.

리스트만 보여줄 것이기 때문에 화면에는 RecyclerView만 놓습니다.

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">
 
   <androidx.recyclerview.widget.RecyclerView
       android:id="@+id/recyclerview"
       android:layout_width="match_parent"
       android:layout_height="match_parent"/>
 
</androidx.constraintlayout.widget.ConstraintLayout>
 

상위 목록 모양과 하위 목록 모양을 만들어 줍니다.

list_header.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"
    android:layout_width="match_parent"
    android:layout_height="70dp"
    android:background="#FFDADA">
 
    <TextView
        android:id="@+id/header_title"
        android:textColor="#191B1E"
        android:textSize="18sp"
        android:gravity="center_vertical"
        android:layout_width="wrap_content"
        android:layout_height="20dp"
        android:layout_marginLeft="20dp"
        android:layout_marginTop="20dp"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintTop_toTopOf="parent"/>
 
    <ImageView
        android:id="@+id/btn_expand_toggle"
        android:layout_width="30dp"
        android:layout_height="30dp"
        android:layout_marginTop="20dp"
        android:layout_marginRight="20dp"
        android:src="@drawable/ic_arrow_downward_black_24dp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintTop_toTopOf="parent"/>
 
</androidx.constraintlayout.widget.ConstraintLayout>

list_child.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"
    android:layout_width="match_parent"
    android:layout_height="70dp"
    android:background="#FDE9E9">
 
    <TextView
        android:id="@+id/child_title"
        android:textColor="#837D7D"
        android:textSize="18sp"
        android:gravity="center_vertical"
        android:layout_width="wrap_content"
        android:layout_height="20dp"
        android:layout_marginLeft="20dp"
        android:layout_marginTop="20dp"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintTop_toTopOf="parent"/>
 
    <Button
        android:id="@+id/btn"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginRight="20dp"
        android:text="버튼"
        android:background="#FFEFEF"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>

이제 ExpandableListAdapter를 만듭니다.

ExpandableListAdapter.java

package com.example.ex_expandablelistadapter;
 
import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.TextView;
 
import androidx.recyclerview.widget.RecyclerView;
 
import java.util.ArrayList;
import java.util.List;
 
public class ExpandableListAdapter extends RecyclerView.Adapter<RecyclerView.ViewHolder> {
    public static final int HEADER = 0;
    public static final int CHILD = 1;
 
    private List<Item> data;
 
    public ExpandableListAdapter(List<Item> data) {
        this.data = data;
    }
 
    @Override
    public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int type) {
        View view = null;
        Context context = parent.getContext();
        switch (type) {
            case HEADER:
                LayoutInflater inflaterHeader = (LayoutInflater) parent.getContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE);
                view = inflaterHeader.inflate(R.layout.list_header, parent, false);
                ListHeaderViewHolder header = new ListHeaderViewHolder(view);
                return header;
            case CHILD:
                LayoutInflater inflaterChild = (LayoutInflater) parent.getContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE);
                view = inflaterChild.inflate(R.layout.list_child, parent, false);
                ListChildViewHolder child = new ListChildViewHolder(view);
                return child;
 
        }
        return null;
    }
 
    public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {
        final Item item = data.get(position);
        switch (item.type) {
            case HEADER:
                final ListHeaderViewHolder itemController = (ListHeaderViewHolder) holder;
                itemController.refferalItem = item;
                itemController.header_title.setText(item.text);
                if (item.invisibleChildren == null) {
                    itemController.btn_expand_toggle.setImageResource(R.drawable.ic_arrow_upward_black_24dp);
                } else {
                    itemController.btn_expand_toggle.setImageResource(R.drawable.ic_arrow_downward_black_24dp);
                }
                itemController.btn_expand_toggle.setOnClickListener(new View.OnClickListener() {
                    @Override
                    public void onClick(View v) {
                        if (item.invisibleChildren == null) {
                            item.invisibleChildren = new ArrayList<Item>();
                            int count = 0;
                            int pos = data.indexOf(itemController.refferalItem);
                            while (data.size() > pos + 1 && data.get(pos + 1).type == CHILD) {
                                item.invisibleChildren.add(data.remove(pos + 1));
                                count++;
                            }
                            notifyItemRangeRemoved(pos + 1, count);
                            itemController.btn_expand_toggle.setImageResource(R.drawable.ic_arrow_downward_black_24dp);
                        } else {
                            int pos = data.indexOf(itemController.refferalItem);
                            int index = pos + 1;
                            for (Item i : item.invisibleChildren) {
                                data.add(index, i);
                                index++;
                            }
                            notifyItemRangeInserted(pos + 1, index - pos - 1);
                            itemController.btn_expand_toggle.setImageResource(R.drawable.ic_arrow_upward_black_24dp);
                            item.invisibleChildren = null;
                        }
                    }
                });
                break;
            case CHILD:
                final ListChildViewHolder itemController1 = (ListChildViewHolder) holder;
                itemController1.refferalItem = item;
                itemController1.child_title.setText(item.text);
 
                break;
        }
    }
 
    @Override
    public int getItemViewType(int position) {
        return data.get(position).type;
    }
 
 
    @Override
    public int getItemCount() {
        return data.size();
    }
 
    private static class ListHeaderViewHolder extends RecyclerView.ViewHolder {
        public TextView header_title;
        public ImageView btn_expand_toggle;
        public Item refferalItem;
 
        public ListHeaderViewHolder(View itemView) {
            super(itemView);
            header_title = (TextView) itemView.findViewById(R.id.header_title);
            btn_expand_toggle = (ImageView) itemView.findViewById(R.id.btn_expand_toggle);
        }
    }
    private static class ListChildViewHolder extends RecyclerView.ViewHolder {
        public TextView child_title;
        public Button btn;
        public Item refferalItem;
 
        public ListChildViewHolder(View itemView) {
            super(itemView);
            child_title = (TextView) itemView.findViewById(R.id.child_title);
            btn =  itemView.findViewById(R.id.btn);
        }
    }
 
    public static class Item {
        public int type;
        public String text;
        public List<Item> invisibleChildren;
 
        public Item() {
        }
 
        public Item(int type, String text) {
            this.type = type;
            this.text = text;
        }
    }
}
 

이제 MainActivity.java에 적용하면 됩니다.

MainActivity.java

package com.example.ex_expandablelistadapter;
 
import androidx.appcompat.app.AppCompatActivity;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;
 
import android.os.Bundle;
 
import java.util.ArrayList;
import java.util.List;
 
public class MainActivity extends AppCompatActivity {
 
    private RecyclerView recyclerview;
 
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
 
 
        recyclerview = findViewById(R.id.recyclerview);
        recyclerview.setLayoutManager(new LinearLayoutManager(this, LinearLayoutManager.VERTICAL, false));
        List<ExpandableListAdapter.Item> data = new ArrayList<>();  // 데이터를 담을 List
 
        data.add(new ExpandableListAdapter.Item(ExpandableListAdapter.HEADER, "운동"));
        data.add(new ExpandableListAdapter.Item(ExpandableListAdapter.CHILD, "축구"));
        data.add(new ExpandableListAdapter.Item(ExpandableListAdapter.CHILD, "농구"));
        data.add(new ExpandableListAdapter.Item(ExpandableListAdapter.CHILD, "배구"));
 
        data.add(new ExpandableListAdapter.Item(ExpandableListAdapter.HEADER, "과목"));
        data.add(new ExpandableListAdapter.Item(ExpandableListAdapter.CHILD, "국어"));
        data.add(new ExpandableListAdapter.Item(ExpandableListAdapter.CHILD, "영어"));
        data.add(new ExpandableListAdapter.Item(ExpandableListAdapter.CHILD, "수학"));
        data.add(new ExpandableListAdapter.Item(ExpandableListAdapter.CHILD, "과학"));
 
        recyclerview.setAdapter(new ExpandableListAdapter(data));
    }// onCreate()..
}// MainActivity class..
 

<실행 화면>