public class MainActivity extends AppCompatActivity {

    public static MainActivity instance;
    private FirstFragment fragmentOne;
    private SecondFragment fragmentTwo;
    private ThirdFragment fragmentThree;
    private TabLayout allTabs;
    ImageView add;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        getAllWidgets();
        bindWidgetsWithAnEvent();
        setupTabLayout();

    }
    public static MainActivity getInstance() {
        return instance;
    }
    private void getAllWidgets() {
        allTabs = (TabLayout) findViewById(R.id.simpleTabLayout);
        add = findViewById(R.id.addButton);
    }
    private void setupTabLayout() {
        fragmentOne = new FirstFragment();
        allTabs.addTab(allTabs.newTab().setText("ONE"),true);
        add.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                allTabs.addTab(allTabs.newTab().setText("NEW_TAB"),true);
                bindWidgetsWithAnEvent();
            }
        });
    }
    private void bindWidgetsWithAnEvent()
    {
        allTabs.setOnTabSelectedListener(new TabLayout.OnTabSelectedListener() {
            @Override
            public void onTabSelected(TabLayout.Tab tab) {
                setCurrentTabFragment(tab.getPosition());
            }
            @Override
            public void onTabUnselected(TabLayout.Tab tab) {
            }
            @Override
            public void onTabReselected(TabLayout.Tab tab) {
            }
        });
    }
    private void setCurrentTabFragment(int tabPosition)
    {
        replaceFragment(fragmentOne);
    }
    public void replaceFragment(Fragment fragment) {
        FragmentManager fm = getSupportFragmentManager();
        FragmentTransaction ft = fm.beginTransaction();
        ft.replace(R.id.simpleFrameLayout, fragment);
        ft.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_OPEN);
        ft.commit();
    }
}