I've added the [PagerSlidingTabStrip library](https://github.com/astuetz/PagerSlidingTabStrip) to my project, following the guide but the strip under the tabs doesn't slide (I'm referring to have something like what you can see in the Google Play app). 
Here is my MainActivity:

```
    mViewPager = (ViewPager) findViewById(R.id.pager);
    mViewPager.setAdapter(mCollectionPagerAdapter);

    PagerSlidingTabStrip tabs = (PagerSlidingTabStrip) findViewById(R.id.tabs);
    tabs.setViewPager(mViewPager);
    mViewPager.setOnPageChangeListener(new ViewPager.SimpleOnPageChangeListener() {

        @Override

        public void onPageSelected(int position) {
            actionBar.setSelectedNavigationItem(position);
        }

    });
    for (int i = 0; i < mCollectionPagerAdapter.getCount(); i++) {
        actionBar.addTab(actionBar.newTab()
                .setText(mCollectionPagerAdapter.getPageTitle(i))
                .setTabListener(this));

    }

```

**EDIT**:

activity\_main.xml:

```
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent">

<com.astuetz.PagerSlidingTabStrip
    android:id="@+id/tabs"
    android:layout_width="match_parent"
    android:layout_height="48dip"/>

<android.support.v4.view.ViewPager
    android:id="@+id/pager"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    tools:context=".MainActivity" />

</RelativeLayout>

```

MainActivity:

```
public class MainActivity extends FragmentActivity implements
    ActionBar.TabListener, android.app.ActionBar.TabListener {
CollectionPagerAdapter mCollectionPagerAdapter;
ViewPager mViewPager;
SharedPreferences mPrefs;
final String welcomeScreenShownPref = "welcomeScreenShown";

public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    requestWindowFeature(Window.FEATURE_INDETERMINATE_PROGRESS);
    setProgressBarIndeterminateVisibility(true);
    setProgressBarIndeterminateVisibility(false);
    setContentView(R.layout.activity_main);

    mCollectionPagerAdapter = new CollectionPagerAdapter(
            getSupportFragmentManager());

    final android.app.ActionBar actionBar = getActionBar();
    assert actionBar != null;
    actionBar.setDisplayShowTitleEnabled(true);
    actionBar.setDisplayUseLogoEnabled(false);
    actionBar.setHomeButtonEnabled(false);
    actionBar.setIcon(R.drawable.ic_action_icon3);
    actionBar.setTitle(R.string.app_name2);
    actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);

    mViewPager = (ViewPager) findViewById(R.id.pager);
    mViewPager.setAdapter(mCollectionPagerAdapter);

    PagerSlidingTabStrip tabs = (PagerSlidingTabStrip) findViewById(R.id.tabs);
    tabs.setViewPager(mViewPager);

}

```

**EDIT2**
tabs\_background.xml:

```
<item android:state_pressed="true" android:drawable="@drawable/tab_selected_pressed_example" />
<item android:state_focused="true" android:drawable="@drawable/tab_selected_focused_example"/>
<item android:drawable="@color/tab_color"/>

```

MainActivity:

```
actionBar.setDisplayShowTitleEnabled(true);
    actionBar.setDisplayUseLogoEnabled(false);
    actionBar.setHomeButtonEnabled(false);
    actionBar.setIcon(R.drawable.ic_action_icon3);
    actionBar.setTitle(R.string.app_name2);

    mViewPager = (ViewPager) findViewById(R.id.pager);
    mViewPager.setAdapter(mCollectionPagerAdapter);

    PagerSlidingTabStrip tabs = (PagerSlidingTabStrip) findViewById(R.id.tabs);
    tabs.setViewPager(mViewPager);
    tabs.setIndicatorColor(android.R.color.white);

```

activity\_main.xml:

```
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="match_parent">

<com.astuetz.PagerSlidingTabStrip
    android:id="@+id/tabs"
    android:layout_width="match_parent"
    android:layout_height="48dip"
    app:pstsIndicatorColor="@android:color/white"
    app:pstsUnderlineColor="@color/tab_color"
    app:pstsDividerColor="@color/tab_color"
    app:pstsTabBackground="@drawable/tabs_background"/>

<android.support.v4.view.ViewPager
    android:id="@+id/pager"
    android:layout_below="@+id/tabs"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    tools:context=".MainActivity" />

</RelativeLayout>

```