I am currently working on an application with ActionBar tabs inside one of its fragments (main navigation is NavigationDrawer). The fragment's onCreate():
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
actionBar = activity.getActionBar();
actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
Resources r = getResources();
//(…) tabNames initialization
adapter = new CustomTabAdapter(getFragmentManager());
}
and onCreateView():
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment, container, false);
viewPager = (ViewPager) rootView.findViewById(R.id.pager);
viewPager.setAdapter(adapter);
viewPager.addOnPageChangeListener(this);
for (String tabName : tabNames) {
actionBar.addTab(actionBar.newTab()
.setText(tabName)
.setTabListener(this));
}
return rootView;
}
There are 4 tabs, each of them with its own Fragment and layout. CustomTabAdapter returns new instance of proper fragment in its getItem(int). There are 4 tabs.
And now my problem is:
I start the application.
I choose this tab fragment from NavigationDrawer list. Everything is working just fine.
I choose another fragment from NavigationDrawer list which means that tab fragment is replaced with it.
I choose tab fragment again. And fragment related to tab that was selected before choosing another fragment from NavigationDrawer list, and one's adjacent to it are not recreated (blank screen under ActionBar tabs). I checked and onCreateView(…) methods of those fragment are not called. So after changing device orientation, or choosing tab not adjacent and this one again proper layout is shown.
How can I make it work as it should (showing proper layout on reentering tab fragment from NavigationDrawer list instead of blank space)? I run out of ideas.
Finally, I found a solution. My CustomTabAdapter was extension of FragmentPagerAdapter. I changed it to be extension of FragmentStatePageAdapter, and now fragments are recreated.
More details in this answer by #Louth.
It takes fragments from cache without recreation
I'm creating an application with a CustomPagerAdapter that can be controlled by ActionBar tabs or horizontal swipe. When you select a tab, a fragment corresponding to that tab is displayed on the screen. When the app is created and when any tab is selected, the adjacent tabs, fragments are loaded into memory. I do not want this to happen. I would like it so that when a tab is selected only that selected tab's fragment is loaded into memory. Is there a way to do this?
Edit: The code I'm currently having trouble with is as follows:
public class fragA extende Fragment
{
private VideoView videoViewA;
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
{
View rootView = inflater.inflate(R.layout.fragment_A, container, false);
videoViewA = (VideoView) rootView.findViewById(R.id.videoViewA);
return rootView;
}
#Override
public void setUserVisibleHint(final boolean isVisibleToUser)
{
super.setUserVisibleHint(isVisibleToUser)
if (isVisibleToUser)
{
videoViewA.setVideoURI(LINK);
videoViewA.start();
}
else
{
videoViewA.stopPlayback();
}
}
}
The error I'm receiving is at the videoViewA.setVideoURI(LINK); line. Mind you, the link is actually there, but for privacy reasons I cannot post it.
Edit 2: It's ajava.lang.NullPointerException.
Edit 3: Sorry, but I'm doing this all the hard way. The code now reflects what I have actually written.
Try loading your videos within setUserVisbleHint(), which gets fired by the FragmentPageAdapter upon showing the fragment.
http://developer.android.com/reference/android/support/v4/app/Fragment.html#setUserVisibleHint(boolean)
If that doesn't work for you, you can also try to do check onHiddenChanged(boolean hidden).
http://developer.android.com/reference/android/app/Fragment.html#onHiddenChanged(boolean)
I have ActionBar Tabs setup. It consists of 4 tabs. Everything is fine until I navigate away from TabbedFragment and returning back.
I create tabs like this:
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
final ActionBar actionBar = getActionBar();
tabs = Lists.newArrayList();
tabs.add(new TabDefinition<>("Tab 1"));
tabs.add(new TabDefinition<>("Tab 2"));
tabs.add(new TabDefinition<>("Tab 3"));
tabs.add(new TabDefinition<>("Tab 4"));
for (TabDefinition tab : tabs) {
actionBar.addTab(actionBar.newTab()
.setText(tab.text)
.setTag(tab.tag)
.setTabListener(this));
}
}
And initialize adapter like this:
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
return inflater.inflate(R.layout.paging_tab_container, container, false);
}
#Override
public void onViewCreated(View view, Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
viewPager = (ViewPager) view.findViewById(R.id.pager);
viewPager.setAdapter(new FragmentStatePagerAdapter(getFragmentManager()) {
#Override
public Fragment getItem(int position) {
return tabs.get(position).fragment;
}
#Override
public int getCount() {
return tabs.size();
}
});
viewPager.setOnPageChangeListener(new ViewPager.SimpleOnPageChangeListener() {
#Override
public void onPageSelected(int position) {
getActionBar().setSelectedNavigationItem(position);
}
});
viewPager.setCurrentItem(getActionBar().getSelectedNavigationIndex(), true);
}
When returning back to TabbedFragment selected tab and 1 next to it would not have any content. Just empty view. But if I select current + 2 fragment content is loaded. And then returning to that first fragment content is reloaded.
For example I have A, B, C, D tabs. Before leaving TabbedFragment I had selected tab A.
When returning to TabbedFragment I still am at tab A, but it's empty. So is tab B.
But when selecting tab C it is created and loaded. Returning to tab A it is recreated.
What could be the problem here?
After a while ran into the same problem again, so updating this question.
If you're using FragmentStatePagerAdapter you should provide FragmentManager via getChildFragmentManager() instead of getFragmentManager(). See Issue 55068: ViewPager doesn't refresh child fragments when back navigation via backstack
Okay so When using a FragmentStatePagerAdapter your fragments will be destroyed when you navigate anymore than one fragment Away since by default offScreenPageLimit is set to 1 by default just as mentioned above.
Typically this Class is used for an activity that has a very large set of Fragments, i.e have to scroll through a large amount of views. If your application does not need more than say 3-4 tabs I would suggest using FragmentPagerAdapter instead, and then specifying your offScreenPageLimit to something like 3, so if you get to the 4th Tab, all 3 tabs before will still be in memory.
Here is some Sample Code for a project on github that i created illustrating how to dynamically load the fragments if you don't want to add this offScreenPageLimit.
https://github.com/lt-tibs1984/InterfaceDemo/blob/master/src/com/divshark/interfacedemo/InterfaceDemoMain.java
Walk through all this code in this Class, and you will see how I'm dynamically loading the fragments, each time my ViewPager is slid over. Most notably at the bottom.
You can download this code, and use it as a test base for what you want to do.
Try adding the setOffScreenPageLimit(2) in the onCreate() method for the viewPager and notice the different behavior. To check the behavior, edit the text in fragment 1. Navigate Away and navigate back, with this set or not. You will see when it is set, the fragment's text remains what you change it to, since the fragment is never recreated.
Please provide additional questions if you have them.
GoodLuck
UPDATE
private static final String [] fragmentClasses = {"com.example.project.YourFragment1","com.example.project.YourFragment2","com.example.project.YourFragment3"};
viewPager.setAdapter(new FragmentStatePagerAdapter(getFragmentManager()) {
#Override
public Fragment getItem(int position) {
Fragment fragmentAtPosition = null;
// $$$$ This is the Important Part $$$$$
// Check to make sure that your array is not null, size is greater than 0 , current position is greater than equal to 0, and position is less than length
if((fragmentClasses != null) && (fragmentClasses.length > 0)&&(position >= 0)&& (position < fragmentClasses.length))
{
// Instantiate the Fragment at the current position of the Adapter
fragmentAtPosition = Fragment.instantiate(getBaseContext(), fragmentClasses[position]);
fragmentAtPosition.setRetainInstance(true);
}
return fragmentAtPosition;
}
#Override
public int getCount() {
return fragmentClasses.length;
}
});
The problem exists in the Fragments you use as tabs, I think. They seem to not show anything when they are resumed (see Fragment lifecycle). The "weird" issue that only the currently selected +/-1 tab is empty, is because the offScreenPageLimit of your ViewPager is 1 by default. All tabs above this threshold are re-created.
Therefore, increasing the value will -- in your case -- cause all your tabs to appear empty after resuming. Check in your Fragment code which lifecycle methods you use to inflate your layout, set adapters and so forth, because that's what's causing your trouble.
I guess this happens because while loading fragment android loads current and current+1, if you debug you would not see onPause getting called for the immediate next fragment.
You can reload content programmatically in onTabChanged() method of TabHost.OnTabChangeListener.
After doing much research, this worked for me.
I have a complex layout with 3 tabs in a fragment, that gets switched out for other fragments. I realized that the ViewpagerAdapter will retain state, even if you press the home button. My problem was switching back and forth would null out the child fragment UI view elements and crash. The key is to not new out your ViewPagerAdapter. Adding the null check for the Adapter worked for me. Also, be sure to allocate setOffscreenPageLimit() for your needs. Also, from what I understand setRetainInstance(true); should not be used for fragments that have UI, it is designed for headless fragments.
In the fragment that holds your Tabs:
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
View view = inflater.inflate(R.layout.fragment_tab, container, false);
tabLayout = (TabLayout) view.findViewById(R.id.tablayout);
viewPager = (ViewPager) view.findViewById(R.id.viewPager);
//Important!!! Do not fire the existing adapter!!
if (viewPagerAdapter == null) {
viewPagerAdapter = new ViewPagerAdapter(getChildFragmentManager());
viewPagerAdapter.addFragments(new AFragment(), "A");
viewPagerAdapter.addFragments(new BFragment(), "B");
viewPagerAdapter.addFragments(new CFragment(), "C");
}
//Allocate retention buffers for three tabs, mandatory
viewPager.setOffscreenPageLimit(3);
tabLayout.setupWithViewPager(viewPager);
viewPager.setAdapter(viewPagerAdapter);
return view;
}
Or more simply when navigating back to tabbedfragment (assuming you use an intent and the fragment is within an activity) use:
intent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
This keeps the original activity and moves it to the top of the stack rather than recreating it, thus you never need to recreate the viewPager.
Just created a new project in the newest ADT release in Eclipse and found that it will setup up certain environments for you to get things started. I choose Tabs + Swipe.
It has this code I have question on:
public static class DummyFragment extends Fragment {
public DummyFragment () {
}
public static final String ARG_SECTION_NUMBER = "section_number";
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
TextView textView = new TextView(getActivity());
textView.setGravity(Gravity.CENTER);
Bundle args = getArguments();
textView.setText(Integer.toString(args.getInt(ARG_SECTION_NUMBER)));
return textView;
}
}
Both tabs refer to this same fragment. All it does is switch the content on the TextView that has the tab position number on it (1,2, or 3).
The more advanced question first: I want two different Fragments that the tab switches to. In the example code, it points to the same fragment. Where does this change take place? and can I see brief code example?
Easier question: I have two pre-defined XML layouts I'd like to set each tab (or Fragment) with. Do I do this in the actual Fragment? And if so, where? setContentView does't seem to be working in the onCreateView method?
Not really sure what this question is asking exactly, but if I understand correctly the TabHost (or whatever you are using to manage the Fragment tabs) is instantiating multiple instances of the DummyFragment and then attaching each to the screen when a tab is clicked. This is all done behind the scenes... all you need to worry about is implementing the Fragment and telling the TabHost when it should be instantiated/displayed.
Fragments don't have a setContentView method. You should inflate your Fragment's layout from xml in onCreateView. For instance with,
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
return inflater.inflate(R.layout.fragment_layout, container, false);
}
I made a program that uses FragmentTabs for implementing ActionBar Tabs.
I was wondering how it is possible to add a widget to a inflated Fragments in Tabs. It's more complicated than normal because the fragment is returning only an onCreateView to the TabListener, so how would I add in functioning widgets? I don't need specific code, just the logic please!
Here is a sample Fragment being inflated when a Tab is clicked (inside of which I need widgets):
public class IdFragment extends Fragment{
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
{
// Inflate the layout for this fragment
return inflater.inflate(R.layout.id_layout, container, false);
}
}