How to load fragment data only when its tab is clicked in PagerSlidingTabStrip

android, android-fragments, android-viewpager, pagerslidingtabstrip

Solution

You could override `setUserVisibleHint` event of the fragment to know if its visible to the user and then load your data. something like following:

boolean _areLecturesLoaded = false;

@Override
 public void setUserVisibleHint(boolean isVisibleToUser) {
     super.setUserVisibleHint(isVisibleToUser);
     if (isVisibleToUser && !_areLecturesLoaded ) {
      loadLectures(); 
      _areLecturesLoaded = true;
     }
 }

Problem

I am using `PagerSlidingTabStrip` in my project and am showing data in fragments. Its a great library which works great. Each Fragment consists of a scholar's lectures which are loaded from a web service. The code to access the web service is in `onCreateView` method of the Fragment. Currently all the fragment's data is loaded at the same time when they are added to `ViewPager`. I was wondering if there is any way of loading the Fragment's data only when a user clicks/swipes to a specific tab. Not everything at a time. Current code is pretty standard, I took help from the provided example [android solution].1 Pager Adapter is as follows: ``` public class ScholarDetailPagerAdapter extends FragmentPagerAdapter { private final String[] TITLES = { "Scholar Info", "Lectures"}; Scholar _scholar; public ScholarDetailPagerAdapter(FragmentManager fm, Scholar scholar) { super(fm); _scholar = scholar; } @Override public CharSequence getPageTitle(int position) { return TITLES[position]; } @Override public Fragment getItem(int arg0) { if(arg0 == 0) return ScholarsInfoFragment.netInstance(_scholar.Name, _scholar.Information, _scholar.ThumbnailUrl); else return ScholarLecturesFragment.newInstance(_scholar.ScholarId); } @Override public int getCount() { return TITLES.length; } } ``` It returns TWO fragments, Info and Lectures. Lectures fragment calls a web service to get a scholar's lectures. Activity code is: ``` @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); // set the Above View setContentView(R.layout.tabbed_view); Scholar scholar = getScholar(getIntent()); _tabs = (PagerSlidingTabStrip) findViewById(R.id.tabs); _pager = (ViewPager) findViewById(R.id.pager); _adapter = new ScholarDetailPagerAdapter(getSupportFragmentManager(), scholar); _pager.setAdapter(_adapter); final int pageMargin = (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, 4, getResources() .getDisplayMetrics()); _pager.setPageMargin(pageMargin); _tabs.setViewPager(_pager); } ``` I tried adding `_tabs.setOnPageChangeListener(this);` and ended up having `onPageSelected(int arg0)` in my activity as well. I thought It would be easy now. Then I modified `public Fragment getItem(int arg0)` in `ScholarDetailPagerAdapter` above and returned `null` instead of returning two fragments. But that raised an exception. I thought It would render empty views in pager .. but of course I was wrong. To make sure Fragment loads data when its respective tab is clicked and is visible, I also have tried overriding its following events and wrote the data loading call in them: `onResume()` Not worked. Still loads data when added in activity Tried overriding onHiddenChanged ``` @Override public void onHiddenChanged(boolean hidden) { super.onHiddenChanged(hidden); if(!hidden){ loadLectures(); } ``` } This did not work too. No data loaded as if this event is not fired at all. How do I do that? I simply want to load a fragment when user clicks on a tab. Thanks in advance

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