开始时选择Android Design Support Library选项卡

Question

I am using the Android Design Support Library to implement the swiping tab feature in my app that holds 3 tabs. I want to know what you need to do to set the middle tab as the one that shows when the app starts up.

public class TabFragmentContainer extends Fragment {

    // Create the FragmentPagerAdapter that will provide and manage tabs for each section.
    public static MyFragmentPagerAdapter myFragmentPagerAdapter;

    public static TabLayout tabLayout;

    // The ViewPager is a layout widget in which each child view is a separate tab in the layout.
    // It will host the section contents.
    public static ViewPager viewPager;

    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {

        // Inflate tab_layout_fragment_container view and setup views for the TabLayout and ViewPager items.
        View view = inflater.inflate(R.layout.tab_layout_fragment_container, null);

        tabLayout = (TabLayout) view.findViewById(R.id.tabs);

        // Set up the ViewPager with the sections adapter.
        viewPager = (ViewPager) view.findViewById(R.id.viewpager);

        // Instantiate the adapter that will return a fragment for each of the three sections of the main activity
        myFragmentPagerAdapter = new MyFragmentPagerAdapter(getActivity(), getChildFragmentManager());

        // Set up the adapter for the ViewPager
        viewPager.setAdapter(myFragmentPagerAdapter);

        // Runnable() method required to implement setupWithViewPager() method
        tabLayout.post(new Runnable() {
            @Override
            public void run() {
                tabLayout.setupWithViewPager(viewPager);
            }
        });

        // Return the created View
        return view;
    }

}





public class MyFragmentPagerAdapter extends FragmentPagerAdapter {

    // The context to be passed in when the adapter is created.
    private Context mContext;
    // The number of tabs in the layout.
    public static int numberOfTabs = 3;

    /**
     * Default constructor that accepts a FragmentManager parameter to add or remove fragments.
     *
     * @param context         the context from the activity using the adapter.
     * @param fragmentManager the FragmentManager for managing Fragments inside of the TabFragmentContainer.
     */
    public MyFragmentPagerAdapter(Context context, FragmentManager fragmentManager) {
        super(fragmentManager);
        mContext = context;
    }

    /**
     * Method to return the relevant fragment for the selected tab.
     */
    @Override
    public Fragment getItem(int position) {
        switch (position) {
            case 0:
                return new SettingsFragment();
            case 1:
                return new InboxRouteFragment();
            case 2:
                return new FriendsFragment();
        }
        return null;
    }

    /**
     * Method that gets the number of tabs in the layout.
     *
     * @return the number of tabs in the layout.
     */
    @Override
    public int getCount() {
        return numberOfTabs;
    }

    /**
     * Method that returns the title of each tab in the layout.
     */
    @Override
    public CharSequence getPageTitle(int position) {
        Locale locale = Locale.getDefault();
        switch (position) {
            case 0:
                return mContext.getString(R.string.title_section1).toUpperCase(locale);
            case 1:
                return mContext.getString(R.string.title_section2).toUpperCase(locale);
            case 2:
                return mContext.getString(R.string.title_section3).toUpperCase(locale);
        }
        return null;
    }
}

Answer 1

尝试使用： viewPager.setCurrentItem(1, false)