How to show selected fragment in action bar tab

Question

I am facing one issue regarding tab swipe. My project is built on Android 3.2. I am implementing tab swipe using support library 4.0 (android-support-v4.jar). Everything implemented is working fine but when I deploy my app to an ICS device, then in portrait mode I am getting a spinner in action bar for tab selection. In portrait mode, the tab selection is not changing when swipe is done although content is changing, and everything is working fine in landscape mode.

final ActionBar actionBar = getActionBar();
actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
actionBar.setDisplayHomeAsUpEnabled(true);
// Set up the ViewPager with the sections adapter.
ViewPager mViewPager = (ViewPager) findViewById(R.id.pager);

mViewPager.setOnPageChangeListener(new ViewPager.SimpleOnPageChangeListener() {

    @Override
    public void onPageSelected(int position) {
        actionBar.setSelectedNavigationItem(position);
    }

});

I have tried putting breakpoint actionBar.setSelectedNavigationItem(position); on this line and even on portrait mode it's getting called but the selection is not changing.

Can anybody help with this?

EDITED: Found a similar problem but don't see exactly how it is solved and how to integrate it in my code.

Answer 1

Problem: Due to an insufficient real-state the platform uses collapsed navigation (i.e. Spinner). The system auto-determines NAVIGATION_MODE_TABS for landscape & NAVIGATION_MODE_LIST for portrait, changing the orientation from landscape to portrait updates the UI but for some reason does not update the navigation mode property to NAVIGATION_MODE_LIST and hence mActionView.setDropdownSelectedPosition(position) is not called. See the following code of ActionBarImpl : setSelectedNavigationItem

    public void setSelectedNavigationItem(int position) {
    switch (mActionView.getNavigationMode()) {
    case NAVIGATION_MODE_TABS:
        selectTab(mTabs.get(position));
        break;
    case NAVIGATION_MODE_LIST:
        mActionView.setDropdownSelectedPosition(position);
        break;
    default:
        throw new IllegalStateException(
                "setSelectedNavigationIndex not valid for current navigation mode");
    }
}

Workaround solution: Through reflection we can get the tab spinner object and call setSelection method.

private Spinner getTabSpinner()
{
    try
    {
        int id = getResources().getIdentifier("action_bar", "id", "android");
        View actionBarView = findViewById(id);

        Class<?> actionBarViewClass = actionBarView.getClass();
        Field mTabScrollViewField = actionBarViewClass.getDeclaredField("mTabScrollView");
        mTabScrollViewField.setAccessible(true);

        Object mTabScrollView = mTabScrollViewField.get(actionBarView);
        if (mTabScrollView == null) {
            return null;
        }

        Field mTabSpinnerField = mTabScrollView.getClass().getDeclaredField("mTabSpinner");
        mTabSpinnerField.setAccessible(true);

        Object mTabSpinner = mTabSpinnerField.get(mTabScrollView);
        if (mTabSpinner != null)
        {
            return (Spinner)mTabSpinner;
        }
    } 
    catch (Exception e) {
        return null;
    }

    return null;
}

Then call the above method in onPageSelected event.

        public void onPageSelected(int position) {
            actionBar.setSelectedNavigationItem(position);
            Spinner spinner = getTabSpinner();
            if (spinner != null) {
                spinner.setSelection(position);
            }
        }

Referred this post https://gist.github.com/2657485