Implementing tab button with ViewPager.

 @Override
    public Fragment getItem(int position) {

        Log.d("test","=====position====" + position);

        switch (position){
            case 0:
                fragement a = new a();
                return a;
            case 1:
                fragment b = new b();
                return bt;
            case 2:
                fragment c = new c();
                return c;
            case 3:
                fragment d = new d();
                return d;
            default:
                return null;
        }