动作栏内还是下方的导航标签？

Question

我想知道导航选项卡是在操作栏中还是在其下方。 在第一种（无效）方法中，我假设动作栏在横向时位于动作栏内，而在纵向时位于其下方。 这是测试活动代码：

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

从ActionBar指南： 添加导航选项卡

ActionBar提供的选项卡非常理想，因为它们可以适应不同的屏幕尺寸。 例如，当屏幕足够宽时，选项卡将显示在操作栏中的动作按钮旁边（例如，在平板电脑上，如图7所示），而在狭窄的屏幕上，它们将出现在单独的栏中（称为“堆叠的动作栏”，如图8所示。 在某些情况下，Android系统会改为将您的标签项显示为下拉列表，以确保最适合操作栏。

是的，您的假设是正确的。 但是参数不是纵向或横向，而是有足够或不足的空间来合并选项卡和操作栏。

Answer 2

我发现了一个使用反射来访问ActionBar的布尔字段mHasEmbeddedTabs ：

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");
}