When the FragmentPagerAdapter adds a fragment to the FragmentManager, it uses a special tag based on the particular position that the fragment will be placed. FragmentPagerAdapter.getItem(int position) is only called when a fragment for that position does not exist. After rotating, Android will notice that it already created/saved a fragment for this particular position and … Read more
When you add the fragment in your transaction you should use a tag. fragTrans.replace(android.R.id.content, myFragment, “MY_FRAGMENT”); …and later if you want to check if the fragment is visible: MyFragment myFragment = (MyFragment)getSupportFragmentManager().findFragmentByTag(“MY_FRAGMENT”); if (myFragment != null && myFragment.isVisible()) { // add your code here } See also http://developer.android.com/reference/android/app/Fragment.html
To correctly save the instance state of Fragment you should do the following: 1. In the fragment, save instance state by overriding onSaveInstanceState() and restore in onActivityCreated(): class MyFragment extends Fragment { @Override public void onActivityCreated(Bundle savedInstanceState) { super.onActivityCreated(savedInstanceState); … if (savedInstanceState != null) { //Restore the fragment’s state here } } … @Override public … Read more
Please check my answer here. Basically I just had to : @Override protected void onSaveInstanceState(Bundle outState) { //No call for super(). Bug on API Level > 11. } Don’t make the call to super() on the saveInstanceState method. This was messing things up… This is a known bug in the support package. If you need … Read more
I solved in this way override onBackPressed in the Activity. All the FragmentTransaction are addToBackStack before commit: @Override public void onBackPressed() { int count = getSupportFragmentManager().getBackStackEntryCount(); if (count == 0) { super.onBackPressed(); //additional code } else { getSupportFragmentManager().popBackStack(); } }
#1 & #2 what are the purposes of using a fragment & what are the advantages and disadvantages of using fragments compared to using activities/views/layouts? Fragments are Android’s solution to creating reusable user interfaces. You can achieve some of the same things using activities and layouts (for example by using includes). However; fragments are wired … Read more
You can use getActivity(), which returns the activity associated with a fragment. The activity is a context (since Activity extends Context).
If Android decides to recreate your Fragment later, it’s going to call the no-argument constructor of your fragment. So overloading the constructor is not a solution. With that being said, the way to pass stuff to your Fragment so that they are available after a Fragment is recreated by Android is to pass a bundle … Read more
How to determine when Fragment becomes visible in ViewPager You can do the following by overriding setUserVisibleHint in your Fragment: public class MyFragment extends Fragment { @Override public void setUserVisibleHint(boolean isVisibleToUser) { super.setUserVisibleHint(isVisibleToUser); if (isVisibleToUser) { } else { } } }
Experts will tell you: “When I see the UI, I will know whether to use an Activity or a Fragment“. In the beginning this will not have any sense, but in time, you will actually be able to tell if you need Fragment or not. There is a good practice I found very helpful for … Read more