코리아 IT아카데미/android

11일차 | RecyclerView, Observer(callback)

Sharon kim 2022. 2. 28. 18:15

옵저버 패턴 

콜백메서드 와 유사, 리스너를 만들어냄

객체의 상태 변화를 관찰하는 관찰자들, 즉 옵저버들의 목록을 객체에 등록하여 상태 변화가 있을 때마다 메서드 등을 통해 객체가 직접 목록의 각 옵저버에게 통지하도록 하는 디자인 패턴

 

obserber 

IButtonListener.interface

package com.example.myrecyclerview.observer;

public interface IButtonListener {
    void clickEvent(String event);//추상 메서드

}

Button.java

package com.example.myrecyclerview.observer;

public class Button {
    private String name;
    private IButtonListener iButtonListener;

    public Button(String name){
        this.name = name;
    }
    public void click(String message){
        iButtonListener.clickEvent(message);
    }
    public void addListner(IButtonListener listener){
        this.iButtonListener = listener;
    }
}

MainTest.java

package com.example.myrecyclerview.observer;

public class MainTest {

    public static void main(String[] args) {
        Button myButton = new Button("우리가 만든 버튼");
        myButton.addListner(new IButtonListener() {
            @Override
            public void clickEvent(String event) {
                System.out.println("동작을 확인합니다 !!! " + event);
            }
        });
        myButton.click("안녕하세요~~~");
        myButton.click("hi");
        myButton.click("hello");
        myButton.click("abcd");

    }

}

RecyclerView

리사이클러 뷰는 리스트 뷰에 비해 상당히 기능적 커스터마이징에 중점을 두고 있다. 리스트 뷰에 비해 조금 어려울 수 있지만, 사용자에게 앱에 대한 연결성을 유지시켜주는 머터리얼 디자인에 대한 요구를 충족시키는 복잡한 그리드나 리스트에 아주 유용하게 쓰일 수 있다.

주요 클래스

 

  • Adapter – 기존의 ListView에서 사용하는 Adapter와 같은 개념으로 데이터와 아이템에 대한 View생성
  • ViewHolder – 재활용 View에 대한 모든 서브 뷰를 보유
  • LayoutManager – 아이템의 항목을 배치
  • ItemDecoration – 아이템 항목에서 서브뷰에 대한 처리
  • ItemAnimation – 아이템 항목이 추가, 제거되거나 정렬될때 애니메이션 처리

출처: https://itmining.tistory.com/12 [IT 마이닝]

 

코드추가

AndroidManifest.xml 

<uses-permission android:name="android.permission.INTERNET" />

build.gradle(Module:~) 

dependencies {
//glide
implementation 'com.github.bumptech.glide:glide:4.13.0'
annotationProcessor 'com.github.bumptech.glide:compiler:4.13.0'
}


adapter

> FoodListAdapter.interface

package com.example.myrecyclerview.adapter;

import android.content.Context;
import android.content.Intent;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.RoundedCorner;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.TextView;

import androidx.annotation.NonNull;
import androidx.recyclerview.widget.RecyclerView;

import com.bumptech.glide.Glide;
import com.bumptech.glide.load.resource.bitmap.CenterCrop;
import com.bumptech.glide.load.resource.bitmap.RoundedCorners;
import com.example.myrecyclerview.DetailActivity;
import com.example.myrecyclerview.Interfaces.OnFoodListItemListener;
import com.example.myrecyclerview.MainActivity;
import com.example.myrecyclerview.R;
import com.example.myrecyclerview.models.Food;

import java.util.ArrayList;

//어뎁터 만들때
//1. 상속 RecyclerView.Adapter<> <---
//2. 뷰홀더 무조건 만들기
public class FoodListAdapter extends RecyclerView.Adapter<FoodListAdapter.ViewHolder>{

    ArrayList<Food> list;
    Context context;
    OnFoodListItemListener onFoodListItemListener;

    //메서드로 연결하는 방법
//    public void setOnFoodListItemListener(OnFoodListItemListener onFoodListItemListener){
//        this.onFoodListItemListener = onFoodListItemListener;
//    }

    public FoodListAdapter(ArrayList<Food> list, Context context, OnFoodListItemListener listener){
        this.list = list;
        this.context = context;
        this.onFoodListItemListener = listener;
    }

    @NonNull
    @Override
    public ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        View view = LayoutInflater.from(context).inflate(R.layout.item_food, parent, false);
        return new ViewHolder(view);
    }

    @Override
    public void onBindViewHolder(@NonNull ViewHolder holder, int position) {
        //holder.thumbnailImageView.
        Food food = list.get(position);
        holder.titleTextView.setText(food.getTitle());
        holder.subTitleTextView.setText(food.getSubTitle());
        holder.detailTextView.setText(food.getDetail());

        Glide.with(context)
                .load(food.getThumbnail())
                .centerCrop()
                .transform(new CenterCrop(), new RoundedCorners(30))
                .into(holder.thumbnailImageView);
    }

    @Override
    public int getItemCount() {
        return list.size();
    }

    //내부 클래스
    public class ViewHolder extends RecyclerView.ViewHolder{

        ImageView thumbnailImageView;
        TextView titleTextView;
        TextView subTitleTextView;
        TextView detailTextView;

        public ViewHolder(@NonNull View itemView) {
            super(itemView);

            thumbnailImageView = itemView.findViewById(R.id.thumbnailImageView);
            titleTextView = itemView.findViewById(R.id.titleTextView);
            subTitleTextView = itemView.findViewById(R.id.subTitleTextView);
            detailTextView = itemView.findViewById(R.id.detailTextView);
            detailTextView.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {

                    onFoodListItemListener.OnItemClick(getLayoutPosition());
//                    Log.d("TAG", "클릭됨" + getLayoutPosition());
//                    Intent intent = new Intent(context, DetailActivity.class);
//                    context.startActivity(intent);
                }
            });
        }
    }
}

models

> Food.java

package com.example.myrecyclerview.models;

import java.util.ArrayList;

public class Food {

    private String thumbnail;
    private String title;
    private String subTitle;
    private String detail;

    public Food(String thumbnail, String title, String subTitle, String detail) {
        this.thumbnail = thumbnail;
        this.title = title;
        this.subTitle = subTitle;
        this.detail = detail;
    }

    public String getThumbnail() {
        return thumbnail;
    }

    public String getTitle() {
        return title;
    }

    public String getSubTitle() {
        return subTitle;
    }

    public String getDetail() {
        return detail;
    }
    public static ArrayList<Food> getData() {
        ArrayList<Food> foods = new ArrayList<>();

        foods.add(new Food("https://cdn.pixabay.com/photo/2014/11/05/15/57/salmon-518032__340.jpg", "Food1", "SubTitle", "detail"));
        foods.add(new Food("https://cdn.pixabay.com/photo/2017/02/15/10/39/salad-2068220__340.jpg", "Food1", "SubTitle", "detail"));
        foods.add(new Food("https://cdn.pixabay.com/photo/2017/06/06/22/46/mediterranean-cuisine-2378758__340.jpg", "Food1", "SubTitle", "detail"));
        foods.add(new Food("https://cdn.pixabay.com/photo/2014/11/05/15/57/salmon-518032__340.jpg", "Food1", "SubTitle", "detail"));
        foods.add(new Food("https://cdn.pixabay.com/photo/2016/03/05/19/02/hamburger-1238246__340.jpg", "Food1", "SubTitle", "detail"));
        foods.add(new Food("https://cdn.pixabay.com/photo/2014/11/05/15/57/salmon-518032__340.jpg", "Food1", "SubTitle", "detail"));
        foods.add(new Food("https://cdn.pixabay.com/photo/2015/12/09/17/11/vegetables-1085063__340.jpg", "Food1", "SubTitle", "detail"));
        foods.add(new Food("https://cdn.pixabay.com/photo/2014/11/05/15/57/salmon-518032__340.jpg", "Food1", "SubTitle", "detail"));
        foods.add(new Food("https://cdn.pixabay.com/photo/2014/11/05/15/57/salmon-518032__340.jpg", "Food1", "SubTitle", "detail"));
        foods.add(new Food("https://cdn.pixabay.com/photo/2014/11/05/15/57/salmon-518032__340.jpg", "Food1", "SubTitle", "detail"));
        foods.add(new Food("https://cdn.pixabay.com/photo/2015/12/09/17/11/vegetables-1085063__340.jpg", "Food1", "SubTitle", "detail"));
        foods.add(new Food("https://cdn.pixabay.com/photo/2014/11/05/15/57/salmon-518032__340.jpg", "Food1", "SubTitle", "detail"));
        foods.add(new Food("https://cdn.pixabay.com/photo/2014/11/05/15/57/salmon-518032__340.jpg", "Food1", "SubTitle", "detail"));
        foods.add(new Food("https://cdn.pixabay.com/photo/2014/11/05/15/57/salmon-518032__340.jpg", "Food1", "SubTitle", "detail"));
        foods.add(new Food("https://cdn.pixabay.com/photo/2015/04/08/13/13/food-712665__340.jpg", "Food1", "SubTitle", "detail"));


        return foods;
    }
}


MainActivity.java

package com.example.myrecyclerview;

import androidx.appcompat.app.AppCompatActivity;
import androidx.recyclerview.widget.DividerItemDecoration;
import androidx.recyclerview.widget.GridLayoutManager;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;

import android.content.Intent;
import android.os.Bundle;
import android.util.Log;
import android.widget.LinearLayout;

import com.example.myrecyclerview.Interfaces.OnFoodListItemListener;
import com.example.myrecyclerview.adapter.FoodListAdapter;
import com.example.myrecyclerview.models.Food;

import java.util.ArrayList;

public class MainActivity extends AppCompatActivity {

    // 준비물
    // 샘플데이터 (통신)
    // adapter
    // layout manager

    /*
    * RecyclerView
    * 장점
    * -ListView 개선판
    *       -ViewHolder (강제)
    * -유연하다
    * -LayoutManager (수평으로 리스트를 만들기 쉽다)
    * -Linear
    * -Grid
    * -StaggeredGrid
    * */

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

        ArrayList<Food> foods = Food.getData();

        RecyclerView recyclerView = findViewById(R.id.RecyclerVIew);
        FoodListAdapter adapter = new FoodListAdapter(foods, this, new OnFoodListItemListener() {
            @Override
            public void OnItemClick(int position) {
                Log.d("TAG","position " + position);
                Intent intent = new Intent(getApplicationContext(), DetailActivity.class);
                intent.putExtra("position", position);
                String title = foods.get(position).getTitle();
                Log.d("TAG", "position");
                startActivity(intent);
            }
        });
                recyclerView.setAdapter(adapter);

        //레이아웃 매니저 생성

        LinearLayoutManager linearLayoutManager = new LinearLayoutManager(this);
        recyclerView.setLayoutManager(linearLayoutManager);
//        GridLayoutManager gridLayoutManager = new GridLayoutManager(this, 2);
//        recyclerView.setLayoutManager(gridLayoutManager);

        //devider 생성해보기
//        DividerItemDecoration dividerItemDecoration
//                = new DividerItemDecoration(this, linearLayoutManager.getOrientation());
//        recyclerView.addItemDecoration(dividerItemDecoration);
    }
}

item_food.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="wrap_content"
    android:padding="16dp">

    <ImageView
        android:id="@+id/thumbnailImageView"
        android:layout_width="120dp"
        android:layout_height="120dp"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        tools:background="@color/purple_200" />

    <TextView
        android:id="@+id/titleTextView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_margin="10dp"
        android:text="F0001"
        android:textSize="20sp"
        app:layout_constraintBottom_toTopOf="@id/subTitleTextView"
        app:layout_constraintStart_toEndOf="@id/thumbnailImageView"
        app:layout_constraintTop_toTopOf="@id/thumbnailImageView"
        app:layout_constraintVertical_chainStyle="packed" />

    <TextView
        android:id="@+id/subTitleTextView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="sub Title"
        android:textSize="16sp"
        app:layout_constraintBottom_toBottomOf="@id/thumbnailImageView"
        app:layout_constraintStart_toStartOf="@id/titleTextView"
        app:layout_constraintTop_toBottomOf="@id/titleTextView" />

    <TextView
        android:id="@+id/detailTextView"
        android:layout_width="100dp"
        android:layout_height="100dp"
        android:gravity="center"
        android:text="detail"
        android:textSize="20sp"
        app:layout_constraintBottom_toBottomOf="@id/thumbnailImageView"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintTop_toTopOf="@id/thumbnailImageView" />

<!--    <View-->
<!--        android:layout_width="0dp"-->
<!--        android:layout_height="2dp"-->
<!--        android:background="@color/purple_200"-->
<!--        app:layout_constraintBottom_toBottomOf="parent"-->
<!--        app:layout_constraintEnd_toEndOf="parent"-->
<!--        app:layout_constraintStart_toStartOf="parent" />-->
</androidx.constraintlayout.widget.ConstraintLayout>


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="0dp"
        android:layout_height="0dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.0"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.0"
        tools:listitem="@layout/item_food">


    </androidx.recyclerview.widget.RecyclerView>

</androidx.constraintlayout.widget.ConstraintLayout>

옵저버 more

interfaces

> OnFoodListItemListener.interface

package com.example.myrecyclerview.Interfaces;

public interface OnFoodListItemListener {
    void OnItemClick(int position);

}


DetailActivity.java

package com.example.myrecyclerview;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;

public class DetailActivity extends AppCompatActivity {

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

    }
}

adapter

> FoodListAdapter

package com.example.myrecyclerview.adapter;

import android.content.Context;
import android.content.Intent;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.RoundedCorner;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.TextView;

import androidx.annotation.NonNull;
import androidx.recyclerview.widget.RecyclerView;

import com.bumptech.glide.Glide;
import com.bumptech.glide.load.resource.bitmap.CenterCrop;
import com.bumptech.glide.load.resource.bitmap.RoundedCorners;
import com.example.myrecyclerview.DetailActivity;
import com.example.myrecyclerview.Interfaces.OnFoodListItemListener;
import com.example.myrecyclerview.MainActivity;
import com.example.myrecyclerview.R;
import com.example.myrecyclerview.models.Food;

import java.util.ArrayList;

//어뎁터 만들때
//1. 상속 RecyclerView.Adapter<> <---
//2. 뷰홀더 무조건 만들기
public class FoodListAdapter extends RecyclerView.Adapter<FoodListAdapter.ViewHolder>{

    ArrayList<Food> list;
    Context context;
    OnFoodListItemListener onFoodListItemListener;

    //메서드로 연결하는 방법
//    public void setOnFoodListItemListener(OnFoodListItemListener onFoodListItemListener){
//        this.onFoodListItemListener = onFoodListItemListener;
//    }

    public FoodListAdapter(ArrayList<Food> list, Context context, OnFoodListItemListener listener){
        this.list = list;
        this.context = context;
        this.onFoodListItemListener = listener;
    }

    @NonNull
    @Override
    public ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        View view = LayoutInflater.from(context).inflate(R.layout.item_food, parent, false);
        return new ViewHolder(view);
    }

    @Override
    public void onBindViewHolder(@NonNull ViewHolder holder, int position) {
        //holder.thumbnailImageView.
        Food food = list.get(position);
        holder.titleTextView.setText(food.getTitle());
        holder.subTitleTextView.setText(food.getSubTitle());
        holder.detailTextView.setText(food.getDetail());

        Glide.with(context)
                .load(food.getThumbnail())
                .centerCrop()
                .transform(new CenterCrop(), new RoundedCorners(30))
                .into(holder.thumbnailImageView);
    }

    @Override
    public int getItemCount() {
        return list.size();
    }

    //내부 클래스
    public class ViewHolder extends RecyclerView.ViewHolder{

        ImageView thumbnailImageView;
        TextView titleTextView;
        TextView subTitleTextView;
        TextView detailTextView;

        public ViewHolder(@NonNull View itemView) {
            super(itemView);

            thumbnailImageView = itemView.findViewById(R.id.thumbnailImageView);
            titleTextView = itemView.findViewById(R.id.titleTextView);
            subTitleTextView = itemView.findViewById(R.id.subTitleTextView);
            detailTextView = itemView.findViewById(R.id.detailTextView);
            detailTextView.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {

                    onFoodListItemListener.OnItemClick(getLayoutPosition());
//                    Log.d("TAG", "클릭됨" + getLayoutPosition());
//                    Intent intent = new Intent(context, DetailActivity.class);
//                    context.startActivity(intent);
                }
            });
        }
    }
}

MainActivity.java

package com.example.myrecyclerview;

import androidx.appcompat.app.AppCompatActivity;
import androidx.recyclerview.widget.DividerItemDecoration;
import androidx.recyclerview.widget.GridLayoutManager;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;

import android.content.Intent;
import android.os.Bundle;
import android.util.Log;
import android.widget.LinearLayout;

import com.example.myrecyclerview.Interfaces.OnFoodListItemListener;
import com.example.myrecyclerview.adapter.FoodListAdapter;
import com.example.myrecyclerview.models.Food;

import java.util.ArrayList;

public class MainActivity extends AppCompatActivity {

    // 준비물
    // 샘플데이터 (통신)
    // adapter
    // layout manager

    /*
    * RecyclerView
    * 장점
    * -ListView 개선판
    *       -ViewHolder (강제)
    * -유연하다
    * -LayoutManager (수평으로 리스트를 만들기 쉽다)
    * -Linear
    * -Grid
    * -StaggeredGrid
    * */

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

        ArrayList<Food> foods = Food.getData();

        RecyclerView recyclerView = findViewById(R.id.RecyclerVIew);
        FoodListAdapter adapter = new FoodListAdapter(foods, this, new OnFoodListItemListener() {
            @Override
            public void OnItemClick(int position) {
                Log.d("TAG","position " + position);
                Intent intent = new Intent(getApplicationContext(), DetailActivity.class);
                intent.putExtra("position", position);
                String title = foods.get(position).getTitle();
                Log.d("TAG", "position");
                startActivity(intent);
            }
        });
                recyclerView.setAdapter(adapter);

        //레이아웃 매니저 생성

        LinearLayoutManager linearLayoutManager = new LinearLayoutManager(this);
        recyclerView.setLayoutManager(linearLayoutManager);
//        GridLayoutManager gridLayoutManager = new GridLayoutManager(this, 2);
//        recyclerView.setLayoutManager(gridLayoutManager);

        //devider 생성해보기
//        DividerItemDecoration dividerItemDecoration
//                = new DividerItemDecoration(this, linearLayoutManager.getOrientation());
//        recyclerView.addItemDecoration(dividerItemDecoration);
    }
}


activity_detail.xml >>생성만

설명 : detail 버튼을 누르면 화면 전환과 동시에 Logcat 처럼 된다.

 

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