Android | stop TabLayout reload/refresh my Fragments

Question

I've a similar tab layout, with 4 tabs.

When I go from tab 0 to tab 2 and then I come back to tab 0, Fragment0 is reloaded.. Same problem when I go from a tab to another "away" tab.
I would to load Fragment only first time and re-use them, without reloading.

This is a part of my code (I've using this tutorial):

MyActivity:

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

    toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);

    if(getSupportActionBar()!=null) {
        getSupportActionBar().setDisplayHomeAsUpEnabled(true);
    }

    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
        Window window = MyActivity.this.getWindow();
        window.addFlags(WindowManager.LayoutParams.FLAG_DRAWS_SYSTEM_BAR_BACKGROUNDS);
        window.clearFlags(WindowManager.LayoutParams.FLAG_TRANSLUCENT_STATUS);
        window.setStatusBarColor(ContextCompat.getColor(MyActivity.this, R.color.colorPrimaryDark));
    }

    viewPager = (ViewPager) findViewById(R.id.viewpager);
    setupViewPager(viewPager);

    tabLayout = (TabLayout) findViewById(R.id.tabs);
    tabLayout.setSelectedTabIndicatorColor(Color.parseColor("#FFFFFF"));
    tabLayout.setupWithViewPager(viewPager);
    setupTabIcons(); //I have only icon, not text.
}

private void setupViewPager(ViewPager viewPager) {
    ViewPagerAdapter adapter = new ViewPagerAdapter(getSupportFragmentManager());
    adapter.addFragment(MyFragment.newInstance(0));
    adapter.addFragment(MyFragment.newInstance(1));
    adapter.addFragment(new DifferentFragment());
    adapter.addFragment(new TestFragment());
    viewPager.setAdapter(adapter);
}

class ViewPagerAdapter extends FragmentPagerAdapter {
    private final List<Fragment> mFragmentList = new ArrayList<>();

    public ViewPagerAdapter(FragmentManager manager) {
        super(manager);
    }

    @Override
    public Fragment getItem(int position) {
        return mFragmentList.get(position);
    }

    @Override
    public int getCount() {
        return mFragmentList.size();
    }

    public void addFragment(Fragment fragment) {
        mFragmentList.add(fragment);
    }

    @Override
    public CharSequence getPageTitle(int position) {
        return null;
    }
}

my_activity.xml:

<?xml version="1.0" encoding="utf-8"?>
<android.support.design.widget.CoordinatorLayout 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="match_parent">

    <android.support.design.widget.AppBarLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar">

        <android.support.v7.widget.Toolbar
            android:id="@+id/toolbar"
            android:layout_width="match_parent"
            android:layout_height="?attr/actionBarSize"
            android:background="?attr/colorPrimary"
            app:layout_scrollFlags="scroll|enterAlways"
            app:popupTheme="@style/ThemeOverlay.AppCompat.Light" />

        <android.support.design.widget.TabLayout
            android:id="@+id/tabs"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            app:tabMode="fixed"
            app:tabGravity="fill"/>
    </android.support.design.widget.AppBarLayout>

    <android.support.v4.view.ViewPager
        android:id="@+id/viewpager"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        app:layout_behavior="@string/appbar_scrolling_view_behavior"  />
</android.support.design.widget.CoordinatorLayout>

Answer 1

As you can see in the Documentation setOffscreenPageLimit

Inside your function setupViewPager(ViewPager viewPager) add this:

viewPager.setOffscreenPageLimit(limitNumberOfPages); //before setAdapter
viewPager.setAdapter(adapter);

And the limitNumberOfPages is an int that contains the amount of pages that can be scrolled without reloading the fragments. If you have 4 tabs, you should use:

int limitNumberOfPages = 3;

The default number for this property is 1.

Answer 2

I solved it by myself Simple, use:

viewPager.setOffscreenPageLimit(numberOfPages);

From reference: Set the number of pages that should be retained to either side of the current page in the view hierarchy in an idle state.

In my case, I need 3 pages that should be retained.