Android: RecyclerView

LisView je mrtvý, ať žije RecyclerView. Ano, je to opravdu tak, zapomeňte na ListView a začněte používat RecyclerView – je výkonější, flexibilnější a vyvýjí se, ListView je mrtvý.

Pojďme si udělat jednoduchou ukázku.

Do souboru build.gradle je nutné přidat závislost:

dependencies {
    implementation 'com.android.support:recyclerview-v7:28.0.0'
}

1) Přidání RecyclerView do šablony activity_main.xml:

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.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">

    <android.support.v7.widget.RecyclerView
        android:id="@+id/my_recycler_view"
        android:scrollbars="vertical"
        android:layout_width="match_parent"
        android:layout_height="match_parent"/>

</android.support.constraint.ConstraintLayout>

2) Model

Vytvoříme třídu s Movie.java s gettery a settery.

package cz.vencax.recyclerview.model;

public class Movie {
    private String title, genre, year;

    public Movie() {
    }

    public Movie(String title, String genre, String year) {
        this.title = title;
        this.genre = genre;
        this.year = year;
    }

    public String getTitle() {
        return title;
    }

    public void setTitle(String name) {
        this.title = name;
    }

    public String getYear() {
        return year;
    }

    public void setYear(String year) {
        this.year = year;
    }

    public String getGenre() {
        return genre;
    }

    public void setGenre(String genre) {
        this.genre = genre;
    }
}

3) Adapter

Adapter slouží pro zobrazení dat v RecyclerView stejně jako v ListView. Jsou pouze přetížené jiné metody.

Vytvořte třídu s názvem MoviesAdapter.java. Zde metoda onCreateViewHolder () použije movie_list_row.xml. V metodě onBindViewHolder () jsou nastaveny příslušné údaje o filmu (titul, žánr a rok) pro každý řádek.

package cz.vencax.recyclerview.adapter;

import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;

import java.util.List;

import cz.vencax.recyclerview.R;
import cz.vencax.recyclerview.model.Movie;

public class MoviesAdapter extends RecyclerView.Adapter<MoviesAdapter.MyViewHolder> {

    private List<Movie> moviesList;

    public class MyViewHolder extends RecyclerView.ViewHolder {
        public TextView title, year, genre;

        public MyViewHolder(View view) {
            super(view);
            title = (TextView) view.findViewById(R.id.title);
            genre = (TextView) view.findViewById(R.id.genre);
            year = (TextView) view.findViewById(R.id.year);
        }
    }


    public MoviesAdapter(List<Movie> moviesList) {
        this.moviesList = moviesList;
    }

    @Override
    public MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View itemView = LayoutInflater.from(parent.getContext())
                .inflate(R.layout.movie_list_row, parent, false);

        return new MyViewHolder(itemView);
    }

    @Override
    public void onBindViewHolder(MyViewHolder holder, int position) {
        Movie movie = moviesList.get(position);
        holder.title.setText(movie.getTitle());
        holder.genre.setText(movie.getGenre());
        holder.year.setText(movie.getYear());
    }

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

4) Layout pro řádek v RecyclerView

Vytvořte layout xml s názvem movie_list_row.xml s níže uvedeným kódem. Tento layout vykreslí jeden řádek v RecyclerView se zobrazením názvu filmu, žánru a roku vydání.

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:background="?android:attr/selectableItemBackground"
    android:clickable="true"
    android:focusable="true"
    android:orientation="vertical"
    android:paddingBottom="10dp"
    android:paddingLeft="16dp"
    android:paddingRight="16dp"
    android:paddingTop="10dp">

    <TextView
        android:id="@+id/title"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentTop="true"
        android:textColor="#222222"
        android:textSize="16dp"
        android:textStyle="bold" />

    <TextView
        android:id="@+id/genre"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_below="@id/title" />

    <TextView
        android:id="@+id/year"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentRight="true"
        android:textColor="#999999" />

</RelativeLayout>

5) Activity

Nakonec upravíme MainActivity.java a provedeme níže uvedené změny. Metoda prepareMovieData () přidá vzorové data do zobrazení v seznamu.

package cz.vencax.recyclerview.activity;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.support.v7.widget.DefaultItemAnimator;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;

import java.util.ArrayList;
import java.util.List;

import cz.vencax.recyclerview.R;
import cz.vencax.recyclerview.adapter.MoviesAdapter;
import cz.vencax.recyclerview.model.Movie;

public class MainActivity extends AppCompatActivity {

    private List<Movie> movieList = new ArrayList<>();
    private RecyclerView recyclerView;
    private MoviesAdapter mAdapter;

    @Override
    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        recyclerView = (RecyclerView) findViewById(R.id.recycler_view);

        mAdapter = new MoviesAdapter(movieList);
        RecyclerView.LayoutManager mLayoutManager = new LinearLayoutManager(getApplicationContext());
        recyclerView.setLayoutManager(mLayoutManager);
        recyclerView.setItemAnimator(new DefaultItemAnimator());
        recyclerView.setAdapter(mAdapter);

        prepareMovieData();
    }


    private void prepareMovieData() {
        Movie movie = new Movie("Mad Max: Fury Road", "Action & Adventure", "2015");
        movieList.add(movie);

        movie = new Movie("Inside Out", "Animation, Kids & Family", "2015");
        movieList.add(movie);

        movie = new Movie("Star Wars: Episode VII - The Force Awakens", "Action", "2015");
        movieList.add(movie);

        movie = new Movie("Shaun the Sheep", "Animation", "2015");
        movieList.add(movie);

        movie = new Movie("The Martian", "Science Fiction & Fantasy", "2015");
        movieList.add(movie);

        movie = new Movie("Mission: Impossible Rogue Nation", "Action", "2015");
        movieList.add(movie);

        movie = new Movie("Up", "Animation", "2009");
        movieList.add(movie);

        movie = new Movie("Star Trek", "Science Fiction", "2009");
        movieList.add(movie);

        movie = new Movie("The LEGO Movie", "Animation", "2014");
        movieList.add(movie);

        movie = new Movie("Iron Man", "Action & Adventure", "2008");
        movieList.add(movie);

        movie = new Movie("Aliens", "Science Fiction", "1986");
        movieList.add(movie);

        movie = new Movie("Chicken Run", "Animation", "2000");
        movieList.add(movie);

        movie = new Movie("Back to the Future", "Science Fiction", "1985");
        movieList.add(movie);

        movie = new Movie("Raiders of the Lost Ark", "Action & Adventure", "1981");
        movieList.add(movie);

        movie = new Movie("Goldfinger", "Action & Adventure", "1965");
        movieList.add(movie);

        movie = new Movie("Guardians of the Galaxy", "Science Fiction & Fantasy", "2014");
        movieList.add(movie);

        mAdapter.notifyDataSetChanged();
    }
}

A máme hotovo 🙂

6) Přidání oddělovače RecyclerView

recyclerView.addItemDecoration(new DividerItemDecoration(this, LinearLayoutManager.VERTICAL));

recyclerView.setAdapter(mAdapter);

7) Přidání click listeneru

RecyclerView také nemá metodu OnItemClickListener pro kliknutí na položku. Musíte napsat svou vlastní třídu implementující RecyclerView.OnItemTouchListener. Vytvořte třídu s názvem RecyclerTouchListener.java:

package cz.vencax.recyclerview.utils;

import android.content.Context;
import android.support.v7.widget.RecyclerView;
import android.view.GestureDetector;
import android.view.MotionEvent;
import android.view.View;

public class RecyclerTouchListener implements RecyclerView.OnItemTouchListener {

    private GestureDetector gestureDetector;
    private ClickListener clickListener;

    public RecyclerTouchListener(Context context, final RecyclerView recyclerView, final ClickListener clickListener) {
        this.clickListener = clickListener;
        gestureDetector = new GestureDetector(context, new GestureDetector.SimpleOnGestureListener() {
            @Override
            public boolean onSingleTapUp(MotionEvent e) {
                return true;
            }

            @Override
            public void onLongPress(MotionEvent e) {
                View child = recyclerView.findChildViewUnder(e.getX(), e.getY());
                if (child != null && clickListener != null) {
                    clickListener.onLongClick(child, recyclerView.getChildPosition(child));
                }
            }
        });
    }

    @Override
    public boolean onInterceptTouchEvent(RecyclerView rv, MotionEvent e) {

        View child = rv.findChildViewUnder(e.getX(), e.getY());
        if (child != null && clickListener != null && gestureDetector.onTouchEvent(e)) {
            clickListener.onClick(child, rv.getChildPosition(child));
        }
        return false;
    }

    @Override
    public void onTouchEvent(RecyclerView rv, MotionEvent e) {
    }

    @Override
    public void onRequestDisallowInterceptTouchEvent(boolean disallowIntercept) {

    }

    public interface ClickListener {
        void onClick(View view, int position);

        void onLongClick(View view, int position);
    }
}

Nakonec přidáme tento objekt jako listener k RecyclerView v activity:

recyclerView.addOnItemTouchListener(new RecyclerTouchListener(getApplicationContext(), recyclerView, new RecyclerTouchListener.ClickListener() {
            @Override
            public void onClick(View view, int position) {
                Movie movie = movieList.get(position);
                Toast.makeText(getApplicationContext(), movie.getTitle() + " is selected!", Toast.LENGTH_SHORT).show();
            }

            @Override
            public void onLongClick(View view, int position) {

            }
        }));