I would like to load data from network into fragments. Inside the Activity I have a ViewPager and I am using a FragmentPagerAdapter to provide fragments to it. The problem is:
How can I detect from activity, that ALL fragments from ViewPager are created and ready to show data. How can I inform fragments, that there is a data inside activity, that should be shown?
How can I detect from activity, that ALL fragments from ViewPager are
created and ready to show data.
This sounds a bit strange to ask. You Activity doesn't need to know when all of the ViewPager fragments are initialized(as only one will actually be seen by the user(plus one on each side will be available if you don't mess with setOffScreenPageLimit()), it doesn't make sense to update the rest).
How can I inform fragments, that there is a data inside activity, that
should be shown?
You fragments could register themselves as listeners for an Activity data load event. The Activity will do it's job of getting the data and then call the update method on all of the registered fragments(which should be stored in WeakReferences to avoid holding on to them when we shouldn't). The main problem is you'll risk trying to update items
Another hacky approach is to use something like from the Activity:
// get the current fragment(add/subtract one for the available fragments on each side of the curently visible
Fragment f = getSupportFragmentManager().findFragmentByTag("android:switcher:" + R.id.ViewPagerId + ":" + mViewPager.getCurrentItem()); one.)
f.update();
The rest of the fragments will check for new data being available when they get recreated.
Related
I have an Activity that contains a ViewPager with four tabs .
each tab has a fragment.
When I click something in tab 4, I want tab 3 to refresh(or access a non-static method in tab 3 ) ..I've searched but all I found had this in it:
FragmentB fragment = (FragmentB)getFragmentManager().findFragmentByTag("FragmentB");
and I can't use it since I never set a tag on the fragment.
I also could call a function from fragment in another fragment but it has to be static , and I don't want that since everything inside it must be static too and that would mess things up for me..
is there a solution to this ?
First of all i think it's not a good practice to update a view which user cannot see on screen at the moment. It's much better to update your data when user navigates to screen. By the way it not our first concern now.
I'm not sure this is still a valid way to find Fragments in a ViewPager byTag but you can find them like below:
This method generates default Tag for a Fragment in ViewPager.
#NonNull
public static String generateViewPagerFragmentTag(int viewPagerId, int position) {
final StringBuilder tagBuilder = new StringBuilder();
tagBuilder.append("android:switcher:");
tagBuilder.append(viewPagerId);
tagBuilder.append(":");
tagBuilder.append(position);
return tagBuilder.toString();
}
Than you can use this tag to find your Fragment with findFragmentByTag method.
Also as mentioned in comments you can use an EventBus library to achieve what you want to do but be careful of Fragment Lifecycle states in ViewPager because the Fragment you want to communicate can be in onPause state an your changes canned be received. This depends on in which lifecycle method you subscribe and unsubscribe to bus. (If you are using OttoBus you can get no subscribers found for this event exception.) You can do same pattern with interfaces. You can create an interface and implement in your Fragments.
For an other solution, you can directly access our fragments in your ViewPager. Here's my answer for another question it.
Finally, as i mentioned at the beginning i think you should implement a solution which updates your data when user switched to specific tab of ViewPager. You can keep your data changes in a mem-cache and listen tab changes and update your view when user exactly navigated to that screen and ready to see data changes. You can check Repository pattern for a more complex solution.
I want to separate logic fragment from activity but the problem is I make api call and save data in fragment. And when user click a item in fragment. I need to send parcelable data to other fragment to show detail info about item.
Is launching fragment in fragment anti pattern for android ?
I would like to hear some opinion about this matter.
Yes, is totally an anti-pattern, remember that you need to see the Activity as a container and fragments as independent sub-screens, so is the Activity responsibility to manage the fragments. I.e.: If you have a Post activity you can have a PostText fragment, a PostImage fragment and all of that is manage by the activity, every fragment is attached to an Activity.
It is not a common practice to have a nested fragment inside a fragment even it can be done. However, it would be better to have an activity as the centric container for all your fragments. You can use EventBus (GreenRobot / Otto) to separate the concerns and do all the API calls in another class and send the results by subscribing to this event.
When viewpager displays one fragment, it will automatically load the fragment pages around it for performance reasons.
In my fragments, i have recycleviews with a popup menu to delete one item in the list.
I am facing a problem of deleting one item from one fragment, but that item still exists in the other preloaded fragments after I scroll to them.
It works only if I force the viewpager to reload the contents of its fragments by manually scrolling back and forth the fragments.
Is there a way to force reload the preloaded fragments by viewpager?
Your problem can be solved by using Interface. Google suggest using callbacks\listeners that are managed by your main Activity for communicating between fragments.You can use Interface which tells the other fragment to refresh its listview when you delete an item in current fragment.
For an overview http://developer.android.com/training/basics/fragments/communicating.html
Also a good question about this How to pass data between fragments
First create an interface to detect changes in your RecyclerView:
public interface MyRecyclerViewChangeListener(){
void onRecyclerViewDataChanged(int id);
}
Create a static variable in your Fragment or Activity which contains your viewpager:
public static List<MyRecyclerViewChangeListener> mListeners = new ArrayList();
Implement your interface to your ViewPagerFragments and do what you want in method you implemented.
In your fragment's onResume register your listener to mListeners like blow to detect changes:
MyFragmentOrActivity.mListeners.add(this);
And in your fragment's onPause unregister your listener:
MyFragmentOrActivity.mListeners.remove(this);
Finally notify your listeners when your recyclerview data changed:
for(MyRecyclerViewChangeListener listener : mListeners){
listener.onRecyclerViewDataChanged(id);
}
Edit : If you are changing your recyclerview's data after an async task result such as a web api call, you can register your listener in fragment's onCreateView method and un register in onDestroyView method. So you can catch changes in your fragments.
I am not sure if i'm getting your question right but i think this should do it.
YourViewpager.setOffscreenPageLimit(0);
Now the fragment should be destroyed if it is not active and will be recreated if you open it again.So the data change should be recognized.
Hope I could help
Try setting mViewPager.setOffscreenPageLimit(1) such that it will not pre-cache any fragment or you could use FragmentStatePagerAdapter inside viewPager to achieve what you want.
Edit 1:
So Conclusion is :
1) Use local broadcast mechanism to update the fragments present in ViewPager adapter
2) Use handler mechanism to refresh these fragments
3) if you want to blindly update these fragments once they are visible to users then do it inside onPageChangeListener of view pager method.
The answers helped me find the solution.
For future reference, I used a callback every time I used deleteItem(), and took a list of the loaded frags by using the method [FragmentHostingViewPager].getChildFragmentManager().getFragments()
Then I iterated through each fragment as long as each fragment was not null, and called a refresh() method on them.
So I currently have an app that has 4 tabs (fragments). They are fragments A,B,C,D, in that order.
Fragment A is the first view opened (along with B because viewPager loads the view before and after the current view).
When I click a button in Fragment A, it sends Data back to MainActivity and then sends that data out to Fragments B and C.
However, this is where the issue comes into play. Since Fragment B was already called, the View isn't updated once I click the button and send the data over, but Fragment C is because the view wasn't called before.
Is there any way that I can remedy this?
You can do it a few ways right.
Just set the data to the fragment and have it update its views
Have all the fragments like B and C register themselves to recieve data from the MainActivity and when MainActivity gets it's data set you tell all the registered receivers of the new data
Recreate the fragment
Use an event bus and tell all subsribers of the new data and MainActivity, Fragment B would get notified of new data. Fragment C would get its data when created by MainActivity
I think this list is pretty endless tbh
The key here is the fragments need to fetch the data from the actvitiy aswell as be updated by the activity. In which case you need to break your UI update behaviour out of onCreateView and into its own updateUI() function. updateUI(MyData) can then be called from onCreateView and also called in a setMyData() on the fragment. Just make sure you check the isAdded flag in setMyData.
This pretty much says it all:
http://developer.android.com/training/basics/fragments/communicating.html
I used a simple fragment communicator that allows the activity to call the fragment, and the same for a fragment to talk to the activity.
You can change the views with the new data based on calling the method from within the activity. The way I do it is set the fragments in the activity then pass them into the page adapter this way I can call the methods within the fragment and implement the fragmentcommunicator interface on the fragments.
You can honestly even avoid the interface if you want, but if you are going to include the same method in all the fragments to talk to them it is easiest.
If you show code, I can show you a quick example.
I have 2 fragments which are called from the action bar of an activity. Both are gridviews, the first one displays applications with a dedicated adapter, and the second one displays a file list with another adapter. My problem is that when I launch a file then when I back to my activity I switch from one fragment to another, when I come back to the previous one, its content disappears. And when I rotate tablet I have the some problem, because my Fragment restart so for this I think that removing fragment give the possibility to create a new Fragment up to date. How can I save and reload data in my fragment.
How can I manage to update the content of the first fragment while coming back from the second one ? And how to remove fragment after the rotation in order to recreate the Action with new Fragment? I asked this questions but I don't have any responses. the code is given below
If your data is just strings or integers, you can make use of shared preferences to store and retrieve data.
Solution to your first problem -how to save fragment state
Use setRetainInstance(true) in you fragments onCreate() *it prevents your fragment from destroying and hence recreating.
Add your fragment to back stack
declare your adapter globally in fragment and resuse it when you get back.
when, you get back to fragment its onCreateView() method will be called directly. hence initialize your adapter in onCreate() method and use it in onCreateView().
Solution to your second problem -how to update fragment content
For this you can use interface. create interface in your second fragment and implement it in your first fragment. prefer this doc for this,
http://www.vogella.com/tutorials/AndroidFragments/article.html#fragments_activitycommunication