Android RecyclerView

Ashwani Yadav

28 November 2019

RecyclerView

RecyclerView is a successor view group of ListView and GridView.It has different features from ListView and GridView which makes it powerful.In this blog we will discuss about RecyclerView and its Adapter.

Creating New Project
1. In Android Studio, go to File ⇒ New Project and fill all the details required to create a new project. When it prompts to select a default activity, select Blank Activity and proceed.

2. Open build.gradle and add recycler view dependency.com.android.support:recyclerview-v7:28.0.0 and rebuild the project.

dependencies {
//…

//RecyclerView
implementation ‘com.android.support:recyclerview-v7:28.0.0’

}

create view RecyclerView in activity_main.xml

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

<androidx.recyclerview.widget.RecyclerView

android:id="@+id/recycler_view"

android:layout_width="match_parent"

android:layout_height="wrap_content" />

The Card Layout: Card Layout is treated as an item of RecyclerView.

person_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="wrap_content"
    android:orientation="vertical"
    xmlns:app="http://schemas.android.com/apk/res-auto">

    <TextView
        android:id="@+id/name"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:textSize="22sp"
        android:textStyle="bold"
        />

    <TextView
        android:id="@+id/occupation"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:textSize="22sp"
        android:layout_marginBottom="22dp"
        />

</LinearLayout>

<?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="wrap_content"

android:orientation="vertical"

xmlns:app="http://schemas.android.com/apk/res-auto">

<TextView

android:id="@+id/name"

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:textSize="22sp"

android:textStyle="bold"

<TextView

android:id="@+id/occupation"

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:textSize="22sp"

android:layout_marginBottom="22dp"

</LinearLayout>

The Data Class: The class that holds information about recyclerView

public class Person {
    String name,occupation;

    public Person(String name , String occupation) {
        this.name = name;
        this.occupation = occupation;
    }

}

public class Person {

String name,occupation;

public Person(String name , String occupation) {

this.name = name;

this.occupation = occupation;

}

The ViewHolder: ViewHolder holds information about card layout .

public class MyViewHolder extends RecyclerView.ViewHolder {
    TextView name,occupation;
    public MyViewHolder(@NonNull View itemView) {
        super(itemView);
        name=itemView.findViewById(R.id.name);
        occupation=itemView.findViewById(R.id.occupation);
    }
}

public class MyViewHolder extends RecyclerView.ViewHolder {

TextView name,occupation;

public MyViewHolder(@NonNull View itemView) {

super(itemView);

name=itemView.findViewById(R.id.name);

occupation=itemView.findViewById(R.id.occupation);

}

The Adapter: It is responsible for inflating the view and view holder ,binding data to view . It extends RecyclerView.Adapter .There are three main method of RecyclerView.Adapter which are necessary to override

1.onCreateViewHolder: This method only called when new view created. If views are recycled then there is no need to create new view.

2.onBindViewHolder:It sets data to particular items of the RecyclerView.It called every time when it scrolled

3.getItemCount: which Returns the length of the RecyclerView.

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

    private List<Person> list;
    public MyAdapter(List<Person> list){
        this.list=list;
    }

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

        return new MyViewHolder(itemView);
    }

    @Override
    public void onBindViewHolder(@NonNull MyViewHolder holder , int position) {

        Person person=list.get(position);
        holder.name.setText(person.name);
        holder.occupation.setText(person.occupation);
    }

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

    public class MyViewHolder extends RecyclerView.ViewHolder {
        TextView name,occupation;
        public MyViewHolder(@NonNull View itemView) {
            super(itemView);
            name=itemView.findViewById(R.id.name);
            occupation=itemView.findViewById(R.id.occupation);
        }
    }
}

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

private List<Person> list;

public MyAdapter(List<Person> list){

this.list=list;

}

@NonNull

@Override

public MyViewHolder onCreateViewHolder(@NonNull ViewGroup parent , int viewType) {

View itemView = LayoutInflater.from(parent.getContext())

.inflate(R.layout.person_list, parent, false);

return new MyViewHolder(itemView);

}

@Override

public void onBindViewHolder(@NonNull MyViewHolder holder , int position) {

Person person=list.get(position);

holder.name.setText(person.name);

holder.occupation.setText(person.occupation);

}

@Override

public int getItemCount() {

return list.size();

}

public class MyViewHolder extends RecyclerView.ViewHolder {

TextView name,occupation;

public MyViewHolder(@NonNull View itemView) {

super(itemView);

name=itemView.findViewById(R.id.name);

occupation=itemView.findViewById(R.id.occupation);

}

`LayoutManagers`

We use LayoutManager class for specifying position of recyclerView’s item.There are three ways of displaying RecyclerView data.

LinearLayoutManager shows items in a vertical or horizontal scrolling list.
GridLayoutManager shows items in a grid.
StaggeredGridLayoutManager shows items in a staggered grid.

RecyclerView recyclerView=findViewById(R.id.recycler_view); 
recyclerView.setLayoutManager(new LinearLayoutManager(getApplicationContext()));

1 2	RecyclerView recyclerView=findViewById(R.id.recycler_view); recyclerView.setLayoutManager(new LinearLayoutManager(getApplicationContext()));

Set Adapter to RecyclerView

we need to set adapter to recyclerView which we created . we pass list in constructor of MyAdapter

recyclerView.setAdapter(new MyAdapter(list));

public class MainActivity extends AppCompatActivity {

    private List<Person> list=new ArrayList<>();

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

        RecyclerView recyclerView=findViewById(R.id.recycler_view);
        recyclerView.setLayoutManager(new LinearLayoutManager(getApplicationContext()));
        recyclerView.setAdapter(new MyAdapter(list));
        personData();
    }

    private void personData() {
        list.add(new Person("John","Student"));
        list.add(new Person("micheal","singer"));
        list.add(new Person("harry","engineer"));
        list.add(new Person("adiclob","chef"));
        list.add(new Person("sir Do'd","Athlete"));
        list.add(new Person("Sachin","Cricketer"));
        list.add(new Person("Jack","Scientist"));
        list.add(new Person("Hamid","Comedian"));
        list.add(new Person("Harsh","Student"));

    }
}

public class MainActivity extends AppCompatActivity {

private List<Person> list=new ArrayList<>();

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_main);

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

recyclerView.setLayoutManager(new LinearLayoutManager(getApplicationContext()));

recyclerView.setAdapter(new MyAdapter(list));

personData();

}

private void personData() {

list.add(new Person("John","Student"));

list.add(new Person("micheal","singer"));

list.add(new Person("harry","engineer"));

list.add(new Person("adiclob","chef"));

list.add(new Person("sir Do'd","Athlete"));

list.add(new Person("Sachin","Cricketer"));

list.add(new Person("Jack","Scientist"));

list.add(new Person("Hamid","Comedian"));

list.add(new Person("Harsh","Student"));

}