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 imp

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