Swipe Viewpager Tabs - alignment, icone color change, back to page 0 and shrink to Toolbar

Question

Hello, I made in the code below a Viewpager with Tabs: In the code of Main:

private TabLayout tabLayout;
private ViewPager viewPager;
SwipeRefreshLayout refresh;
ParseUser currentUser;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    getSupportActionBar().setDisplayHomeAsUpEnabled(false);


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

    tabLayout = (TabLayout) findViewById(R.id.tabs);
    tabLayout.setupWithViewPager(viewPager);

    tabLayout.getTabAt(0).setIcon(tabIcons[0]);
    tabLayout.getTabAt(1).setIcon(tabIcons[1]);
    tabLayout.getTabAt(2).setIcon(tabIcons[2]);
}

final int[] tabIcons = new int[]{
        R.drawable.mainazul,
        R.drawable.lupaazul,
        R.drawable.menuazul
};

private void setupTabIcons() {

}

private void setupViewPager(ViewPager viewPager) {
    ViewPagerAdapter adapter = new ViewPagerAdapter(getSupportFragmentManager());
    adapter.addFragment(new FragmentoMain());
    adapter.addFragment(new PesquisaFrag());
    adapter.addFragment(new Menu());
    viewPager.setAdapter(adapter);
}

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

In my xml:

<android.support.design.widget.AppBarLayout
    android:id="@+id/appbar"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"

    android:theme="@style/AppTheme.AppBarOverlay">



    <android.support.design.widget.TabLayout
        android:id="@+id/tabs"
        android:layout_width="match_parent"
        app:tabMode="fixed"
        android:background="@color/branca"
        android:layout_height="40dp"
        android:layout_gravity="bottom|fill_vertical"
        android:fillViewport="true" />

</android.support.design.widget.AppBarLayout>

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

Tabs are icon-only, no text.

It’s working fine, but I’m having the following questions:

1. When the phone is vertical, the icons are well distributed on the screen. When it is horizontal they align in the center. How to change this?

2.Icons are always the same color. You can change them as the page is selected.

3. When I’m on page 1 or 2 and I press the back button of the mobile phone, it leaves. I’d like it to go back to page 0, instead of leaving the application.

4. I found that with "app:layout_behavior="@string/appbar_scrolling_view_behavior"" the Toolbar (where the App name is) would shrink. But this is not happening. How to shrink Toolbar?

Thank you.