Help to migrate from Actionbar.Tabs to ViewPager because of API 21

Hello, first I'd like to tell you about my experience regarding Dynamic Fragments within ViewPager and I can tell you that is not a good idea. I have no idea how your app is but if it was good advice (rsrs) I would tell you to think about how most messaging apps work (hangouts, fb messenger, whatsapp, telegram, etc.), where there is a Fragment that list the conversations and another Fragment / Activity that shows the conversation. I also think about usability, for example: I have 10 Tabs / Conversations open and to be able to open the 9th I need to keep rolling the ViewPager until I get there O_o

But by clarifying how ViewPager works, you should think about the structure of it. First xml:

<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <com.astuetz.PagerSlidingTabStrip
        android:id="@+id/sliding_tabs"
        android:layout_width="match_parent"
        android:layout_height="?actionBarSize"
        android:layout_gravity="top"
        android:textSize="16sp"
        android:background="@color/color_primary"
        app:pstsIndicatorColor="@color/color_primary_darker"
        app:pstsTextAllCaps="false"
        app:pstsIndicatorHeight="2dp"
        app:pstsPaddingMiddle="false"/>

    <android.support.v4.view.ViewPager
        android:id="@+id/viewpager"
        android:layout_width="match_parent"
        android:layout_height="0px"
        android:layout_weight="1"
        android:background="@android:color/white"/>

</LinearLayout>

Very simple where you indicate where Tabs will be (title or any layout you want) and your ViewPager which is where all your Fragments will be added.

Next, in the Fragment / Activity you want to implement the ViewPager you should create an Adapter for it and set the ViewPager in SlidingTab:

mPager = (ViewPager) v.findViewById(R.id.viewpager);
mPagerTab = (PagerSlidingTabStrip) v.findViewById(R.id.sliding_tabs);
mPager.setAdapter(new ViewPagerAdapter(getActivity().getSupportFragmentManager(), tabtitles, mDrawable));
mPagerTab.setViewPager(mPager);

And a simple example of a FragmentPagerAdapter:

public class ViewPagerAdapter extends FragmentPagerAdapter {

    final int PAGE_COUNT = 3;
    private String titles[];

    public ViewPagerAdapter(FragmentManager fm, String[] titles) {
        super(fm);
        titles = titles;
    }

    @Override
    public Fragment getItem(int position) {
        switch (position) {
            case 0:
                return SampleFragment.newInstance();
            case 1:
                return SampleFragment.newInstance();
            case 2:
                return SampleFragment.newInstance();

        }
        return null;
    }

    public CharSequence getPageTitle(int position) {
        return titles[position];
    }

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

}

What determines the amount of Fragments in the ViewPager, in this case is the field PAGE_COUNT;

You can, of course, change the amount of Fragments in your Adapter so you have to create it by passing in as many Fragments as you want and a list of Fragments that you want to use. Or you can also create these methods within the Adapter, modify them, and inform the controller by the Adapter% method of%.

In this example I used the framework link