动作栏内还是下方的导航标签？

Question

I want to know if navigation tabs are inside action bar or below it. In a first (non-valid) approach I assume action bar is inside action bar in landscape and below it on portrait. Here it is the testing activity code:

public class TabTestActivity extends FragmentActivity implements
        ActionBar.TabListener {

    SectionsPagerAdapter mSectionsPagerAdapter;
    ViewPager mViewPager;
    private AlertDialog.Builder dialogBuilder;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_tab_test);
        dialogBuilder = new AlertDialog.Builder(this);
        dialogBuilder.setTitle("Tabs inside or below action bar?");
        dialogBuilder.setPositiveButton("OK", new DialogInterface.OnClickListener() {
            public void onClick(DialogInterface dialog, int which) {
            }
        });
        final ActionBar actionBar = getActionBar();
        actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
        mSectionsPagerAdapter = new SectionsPagerAdapter(
                getSupportFragmentManager());
        mViewPager = (ViewPager) findViewById(R.id.pager);
        mViewPager.setAdapter(mSectionsPagerAdapter);
        mViewPager
                .setOnPageChangeListener(new ViewPager.SimpleOnPageChangeListener() {
                    @Override
                    public void onPageSelected(int position) {
                        actionBar.setSelectedNavigationItem(position);
                    }
                });

        for (int i = 0; i < mSectionsPagerAdapter.getCount(); i++) {
            actionBar.addTab(actionBar.newTab()
                    .setText(mSectionsPagerAdapter.getPageTitle(i))
                    .setTabListener(this));
        }
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.tab_test, menu);
        return true;
    }

    @Override
    public void onTabSelected(ActionBar.Tab tab,
            FragmentTransaction fragmentTransaction) {
        mViewPager.setCurrentItem(tab.getPosition());
        AlertDialog notifyTabsLocationDialog = dialogBuilder.create();
        // First approach: assume that tabs are inside action bar in landscape
        // and below action bar in landscape, but they are always inside action
        // bar for my tablet
        if (getResources().getConfiguration().orientation == Configuration.ORIENTATION_PORTRAIT) {
            notifyTabsLocationDialog.setMessage("Tabs below action bar");
        } else {
            notifyTabsLocationDialog.setMessage("Tabs inside action bar");            
        }
        notifyTabsLocationDialog.show();
    }

    @Override
    public void onTabUnselected(ActionBar.Tab tab,
            FragmentTransaction fragmentTransaction) {
    }

    @Override
    public void onTabReselected(ActionBar.Tab tab,
            FragmentTransaction fragmentTransaction) {
    }

    public class SectionsPagerAdapter extends FragmentPagerAdapter {

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

        @Override
        public Fragment getItem(int position) {
            Fragment fragment = new DummySectionFragment();
            Bundle args = new Bundle();
            args.putInt(DummySectionFragment.ARG_SECTION_NUMBER, position + 1);
            fragment.setArguments(args);
            return fragment;
        }

        @Override
        public int getCount() {
            return 3;
        }

        @Override
        public CharSequence getPageTitle(int position) {
            Locale l = Locale.getDefault();
            switch (position) {
            case 0:
                return getString(R.string.title_section1).toUpperCase(l);
            case 1:
                return getString(R.string.title_section2).toUpperCase(l);
            case 2:
                return getString(R.string.title_section3).toUpperCase(l);
            }
            return null;
        }
    }

    public static class DummySectionFragment extends Fragment {
        public static final String ARG_SECTION_NUMBER = "section_number";

        public DummySectionFragment() {
        }

        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container,
                Bundle savedInstanceState) {
            View rootView = inflater.inflate(R.layout.fragment_tab_test_dummy,
                    container, false);
            TextView dummyTextView = (TextView) rootView
                    .findViewById(R.id.section_label);
            dummyTextView.setText(Integer.toString(getArguments().getInt(
                    ARG_SECTION_NUMBER)));
            return rootView;
        }

    }

}

Answer 1

From the ActionBar guide: Adding Navigation Tabs

The tabs provided by the ActionBar are ideal because they adapt to different screen sizes. For example, when the screen is wide enough the tabs appear in the action bar alongside the action buttons (such as when on a tablet, shown in figure 7), while when on a narrow screen they appear in a separate bar (known as the "stacked action bar", shown in figure 8). In some cases, the Android system will instead show your tab items as a drop-down list to ensure the best fit in the action bar.

And yes, your assumption is quiet right. But the parameter is not portrait or landscape, but is there enough or not enough room to merge the tabs with the actionbar.

Answer 2

I've found a workaraound using reflection to access a boolean field mHasEmbeddedTabs of ActionBar :

Class<?> actionBarClass = getActionBar().getClass();
Field mHasEmbeddedTabs = actionBarClass.getDeclaredField("mHasEmbeddedTabs");
mHasEmbeddedTabs.setAccessible(true);
if (mHasEmbeddedTabs.getBoolean(getActionBar())) {
    notifyTabsLocationDialog.setMessage("Tabs inside action bar");            
} else {
    notifyTabsLocationDialog.setMessage("Tabs below action bar");
}