ViewPager

Migrate from ViewPager to ViewPager2
https://developer.android.com/training/animation/vp2-migration

ViewPager2
https://developer.android.com/reference/androidx/viewpager2/widget/ViewPager2

FragmentStateAdapter
https://developer.android.com/reference/androidx/viewpager2/adapter/FragmentStateAdapter

Frag1.java, Frag2.java, Frag3.java

public class Frag1 extends Fragment {
    private View view;

    public static Fragment newInstance() {
        return new Frag1();
    }

    @Nullable
    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        return inflater.inflate(R.layout.fragment1, container, false);
    }
}

ViewPagerAdapter.java

public class ViewPagerAdapter extends FragmentPagerAdapter {

    public ViewPagerAdapter(@NonNull FragmentManager fm, int behavior) {
        super(fm, behavior);
    }

    @NonNull
    @Override
    public Fragment getItem(int position) {
        switch (position) {
            case 0:
                return Frag1.newInstance();
            case 1:
                return Frag2.newInstance();
            case 2:
                return Frag3.newInstance();
            default:
                return null;
        }
    }

    @Override
    public int getCount() {
        return 3;
    }

    @Nullable
    @Override
    public CharSequence getPageTitle(int position) {
        switch (position) {
            case 0:
                return "Monday";
            case 1:
                return "Tuesday";
            case 2:
                return "Wednesday";
            default:
                return null;
        }
    }
}

MainActivity.java

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        
        ViewPager viewPager = findViewById(R.id.viewPager);
        FragmentPagerAdapter fragmentPagerAdapter = new ViewPagerAdapter(getSupportFragmentManager(), FragmentPagerAdapter.BEHAVIOR_RESUME_ONLY_CURRENT_FRAGMENT);

        TabLayout tabLayout = findViewById(R.id.tabLayout);
        viewPager.setAdapter(fragmentPagerAdapter);
        tabLayout.setupWithViewPager(viewPager);
    }
}

fragment1.xml, fragment2.xml, fragment3.xml

<TextView
    android:id="@+id/textView"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:textSize="36sp"
    android:text="안녕하세요. 1"
    app:layout_constraintBottom_toBottomOf="parent"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toTopOf="parent" />

activity_main.xml

<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">

    <com.google.android.material.tabs.TabLayout
        android:id="@+id/tabLayout"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent">

        <com.google.android.material.tabs.TabItem
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Monday" />

        <com.google.android.material.tabs.TabItem
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Tuesday" />

        <com.google.android.material.tabs.TabItem
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Wednesday" />
    </com.google.android.material.tabs.TabLayout>

    <androidx.viewpager.widget.ViewPager
        android:id="@+id/viewPager"
        android:layout_width="0dp"
        android:layout_height="0dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/tabLayout" />
</androidx.constraintlayout.widget.ConstraintLayout>

안드로이드 앱 만들기 #35 뷰페이저 (ViewPager androidx ver)
https://www.youtube.com/watch?v=YWjyAfEacT8

홍드로이드 깃헙
https://github.com/hongdroid94/35_ViewPager