Ytukyg

I' m trying to improve my android app. I have main app menu (with possible actions) in a GridView 3x3. And I decided to add ViewPager to separate my grid. Before I've added ViewPager, I had only one Activity with GridView. In my onCreate method, I calculated the window height with DisplayMetrics to understand, what height should I use for my GridView items.

Now I'm trying to use ViewPager with Fragments. I have my Activity with ViewPager, and 2 Fragments. Each Fragment has the same layout (GridView in LinearLayout). I'm trying to pass screen height into Fragment in this way:

public void onCreate(Bundle savedInstanceState) {

    super.onCreate(savedInstanceState);

    setContentView(R.layout.activity_main_grid_layout);



    pageHeight = getHeight();



    Log.d("HEIGHT", "Page height: "+pageHeight);



    ViewPager viewPager;

    viewPager = findViewById(R.id.main_menu_viewpager);

    src = new ArrayList<MainPageTableFragment>();



    /*Определяем количество страниц меню*/

    int pagesCount = 2;



    for (int i = 0; i < pagesCount; i++) {

        src.add(MainPageTableFragment.newInstance(i, pageHeight));

    }



    FragmentPagerAdapter adapter = new ScreenSlidePagerAdapter(getSupportFragmentManager(), src);

    viewPager.setAdapter(adapter);

    TabLayout tabLayout = (TabLayout) findViewById(R.id.tabDots);

    tabLayout.setupWithViewPager(viewPager, true);



}

So, each launch of onCreate method should recreate Fragments.

And in Fragment, I get my height in this way:

@Override

public View onCreateView(LayoutInflater inflater, ViewGroup container,

                         Bundle savedInstanceState) {

    ViewGroup rootView = (ViewGroup) inflater.inflate(

            R.layout.activity_main_grid_fragment, container, false);

    gridView = rootView.findViewById(R.id.main_menu_grid);

    //PROBLEM IS HERE...

    height = this.getArguments().getInt("containerHeight");

    pageNum = this.getArguments().getInt("pageNumber");

    populateGridItems(); //method to load items in gridview

    return rootView;

}

The problem is: when I rotate my device, all methods are called, but

height = this.getArguments().getInt("containerHeight");

uses old value. For instance, in first launch (vertical screen orientation), it is 690. When I rotate my device, in onCreate I calculate new height (382), but my Fragment takes old value (690).
I tried to call getArguments() in several places (onAttach, onCreate, onActivityCreated), but didn't help.

Can anybody explain me, where is the problem, and what should I do?

Thank you!

UPD: Code of my MainPageTableFragment

public static MainPageTableFragment newInstance(int pageNumber, int height) {



    Bundle args = new Bundle();

    args.putInt("pageNumber", pageNumber);

    args.putInt("containerHeight", height);

    MainPageTableFragment fragment = new MainPageTableFragment();

    fragment.setArguments(args);

    return fragment;

}



@Override

public View onCreateView(LayoutInflater inflater, ViewGroup container,

                         Bundle savedInstanceState) {

    ViewGroup rootView = (ViewGroup) inflater.inflate(

            R.layout.activity_main_grid_fragment, container, false);

    gridView = rootView.findViewById(R.id.main_menu_grid);

    height = getArguments().getInt("containerHeight");

    Log.d("HEIGHT", "Fragment height in onCreateView: "+height);

    pageNum = getArguments().getInt("pageNumber");

    populateGridItems();

    return rootView;

}



private void populateGridItems() {

    /*adding items in GridView*/



    gridView.setAdapter(new MenuGridAdapter(this.getContext(), items, height));

}

}

I'm not sure but i think it's because of supportFragmentManager and pagerAdapter.

First time in instantiateItem it creates a name for fragment and in destroyItem it's just detach fragment.
Then after rotating in instantiateItem it founds fragment by name and uses old instance instead of new. I think for optimization and so on.

As a solution, you can remove all fragments from supportFragmentManager or override instantiateItem/destroyItem to remove frgament as you need.

I found another way to do this. In my Activity, I've created public method to calculate height, and in onCreateView in my Fragment, I call this method. It works.
But for me, it's unknown problem: why recreation of the fragment took values of arguments from the old bundle.