在Tablayout中选择选项卡时IndexOutOfBoundsException

Question

I get IndexOutOfBoundsException error when i want selecting the tab in the TabLayout : This is the initTablayout function , that called in the onCreate method:

       //======================================== Init Tablayout and view pager
            private void initTabLayout() {
                mainActivityViewPager = (ViewPager) findViewById(R.id.view_pager_main_activity);


                mainActivityTabLayout = (TabLayout)findViewById(R.id.tab_layout_main_activity);
                TabLayout.Tab tab = mainActivityTabLayout.getTabAt(1);
                tab.select();

                FragmentManager manager = getSupportFragmentManager();
                MainActivityPagerAdapter adapter = new MainActivityPagerAdapter(manager);
                mainActivityViewPager.setAdapter(adapter);
                mainActivityTabLayout.setupWithViewPager(mainActivityViewPager);
                mainActivityViewPager.addOnPageChangeListener(new TabLayout.TabLayoutOnPageChangeListener(mainActivityTabLayout));
                mainActivityTabLayout.setTabsFromPagerAdapter(adapter);
            }

I got this error where i choose index of selected tab on the getTabAt(1) method , i have three tab on the PagerAdapter class :

public class MainActivityPagerAdapter extends FragmentStatePagerAdapter {

        //============================================ Constructor

        public MainActivityPagerAdapter(FragmentManager fm) {
            super(fm);
        }

        //============================================ GetItem Method ()
        @Override
        public Fragment getItem(int position) {
            Fragment frag = null;
            switch (position) {
                case 0:
                    frag = new Fragment_one();
                    break;
                case 1:
                    frag = new Fragment_two();
                    break;
                case 2:
                    frag = new Fragment_three();
                    break;

            }
            return frag;
        }

        //============================================= GetCount Method ()
        @Override
        public int getCount() {
            return 3;
        }

        //============================================= GetPageTitle

        @Override
        public CharSequence getPageTitle(int position) {
            String title = "";
            switch (position) {
                case 0:
                    title = "اول ";
                    break;
                case 1:
                    title = "دوم ";
                    break;
                case 2:
                    title = "سوم ";
                    break;

            }

            return title;
        }
    }

Complete error is :

 java.lang.IndexOutOfBoundsException: Invalid index 0, size is 0

Answer 1

It seem like you forget to addTab to your mainActivityTabLayout so your TabLayout will have 0 item. Therefore, you got IndexOutOfBoundsException when you access to tab1

mainActivityTabLayout.addTab(tabLayout.newTab().setText("1"));
mainActivityTabLayout.addTab(tabLayout.newTab().setText("2"));
mainActivityTabLayout.addTab(tabLayout.newTab().setText("3"));

Answer 2

Select tab3

Do following :

mainActivityTabLayout.addTab(tabLayout.newTab().setText("3"),true);