Sharing an adapter between two fragments - android

I have two fragments nested within another fragment. One is a list view, and one is a ViewPager, with the viewpager's content being details of a selected list view item. Obviously, they both use the same adapter. The contents of the adapter is refreshed every, say, 5 seconds, so I need to keep the adapter used by both fragments in sync.
What would be the best way to go about keeping the adapter in sync between the two fragments?
I was thinking of storing the adapter in a retained non-ui fragment, making all the update calls within this fragment. This would however require I constantly make pass the updated adapter to the child fragments and call notifyDataSetHasChanged in each fragment

Related

Adding Fragment as a List Item

I am having a situation in which as a List Item I want to inflate a Fragment, but It seems like a bad approach. As Fragments are processed/managed by Activity's FragmentManager or by child FragmentManager and list item views are by ListView & ListAdapter.
Any comments and research regarding this would be highly appreciated.
Thanks
Here are my views and questions in mind on your problem.
You want to use ListView with fragments, since you already have a fragment which does that job and you dont want code to become redundant.
Though you can definitely use fragment, but i suppose its not the best practice. Fragments have their own life cycle and you are not going to use fragment life cycle methods (I suppose). Thus semantically it would not fit into this usecase.
And also your adapter will always be dependent on activity to retrieve fragments. (could there be any problems with orientation change again?)
List items and adapters are finetuned to work really well with scrolling really long lists. While the list view items get recycled when using view holder pattern, while scrolling, does any of fragment lifecycle methods come in between? would that cause performance impact. (I suppose yes. Havent tested it out yet)
You can instead have your view code in different layout file and include this layout in both fragment and also list adapter.
<include layout="#layout/YOUR_COMMON_VIEW_CODE"/>
and have utility class which takes the context and this layout container. Have all the functionality exposed inside that utility class.
You can't use fragment as list item views because the API doesn't allow you - View and Fragment aren't even related so there's no way you can use it like that. Make custom views and use adapter getViewTypeCount and getView to use different list item behavior.
Fragment are managed by Activity's FragmentManager or by other Fragments child FragmentManager; while list item views are managed by ListView & ListAdapter. You can use ListViews in Fragments, but not the other way around.
I googled and got this.

Passing Data Between RecyclerView inside Fragments

I have a ViewPager with 2 Fragments, FragA and FragB. Inside each Fragment I have a RecyclerView. When a user presses a button inside the RecyclerView in FragB I would like to remove the respective Object from that RecyclerView's ArrayList and add it to the RecyclerView contained in FragA.
Can I directly pass the Object from one RecyclerView's Adapter to the other? Or do I need to pass the Object from the RecyclerView Adapter to FragB then to the Activity containing the ViewPager then to FragA before finally passing to the RecyclerView inside FragA?
Your fragments and activity is just to present data.
I think the best solution is to use good design, like MVC pattern, or at least some model class (model-view kind of pattern), wich will have referens to both lists and can have public method for moving object between lists.
Giving both lists to both fragments so they can move objects is bad design choise IMHO.
This question is not for adapter solution at all.

Custom CursorAdapter loads data from db every time fragment switched

I have an Activity with ViewPager and three Fragments with-in. One Fragment contains ListView with custom CursorAdapter which loads data from database.
I've noticed that my cursor adapter loads data every time I switch Fragments in ViewPager. I think that it's normal and is due to the fact that every Fragment has its own lifecycle.
Regarding this it will be great pleasure for me if the users of the stackoverflow explain about their experience or best practices at all.
Thanks!
ViewPagers maintain the state of only certain number of fragments, which defaults to 1 for both sides of the current selected fragment. For example, if you have 3 fragments, when the first is selected, only first two fragments will be instantiated and have the listview data loaded. Alternatively, if you have the second fragment selected, the first and the third will be instantiated. If you switch to the third fragment, the second fragment will be retained, but the first one will be lost. However, you can set the number of fragments to be retained with calling setOffscreenPageLimit method on viewPager with any number of fragments to retain you need. Though you should remember, that setting the number too high may cause your app to consume too much memory.
For example, if you want your fragment to not reload listview content from db while switching fragments and you have 3 framents in your viewPager, you may write the following code:
ViewPager mViewPager;
mViewPager.setOffscreenPageLimit(2);

Iterate over all currently loaded fragments in a ViewPager

I have a ViewPager. It has Fragments. When those Fragments are created, they load data from the server. When the user selects a menu item, I want to tell those fragments to filter their data without reloading from the server.
To do this, I have a subclass of FragmentPagerAdapter which keeps a List to hold a reference to each Fragment as it is created. When the menu item is selected, I simply iterate over that collection and call a method on each Fragment.
The problem arises when the device is rotated. The framework automatically restores the fragments to their parent view, without calling the getItem method of my adapter, meaning that my List is empty.
How can I either repopulate that List when the device is rotated, or obtain a list of all of the ViewPager's child Fragments without keeping a list?
EDIT: It may be important to note that my ViewPager lives in a Fragment, and that Fragment gets hot swapped via a side navigation menu. In other words, my ViewPager is not owned by an Activity, and there are some known issues about ViewPager not cleaning up its child fragments correctly which may be exacerbating the problem.
Check this link Get Current visible fragment in ViewPager
The author basically suggests 2 similar approaches which are to attach tags on fragment creation and keep track of it.
getSupportFragmentManager().beginTransaction().add(myFragment, "Some Tag").commit();
Then retrieve the tag like so:
int index = mViewPager.getCurrentItem();
String tag = mPageReferenceMap.get(index);
Fragment myFragment = getSupportFragmentManager().findFragmentByTag(tag);

How to add 'listview rows' from fragment 1 to fragment 2 with SQL?

I have several custom list views set up inside each separate fragment. What is the way to save a specific list row from fragment 1 and immediately retrieve it into a dedicated (favorites) fragment? The user should also be able to delete (unfavorite) the list rows that have been populated in the favorites fragment.
And since each list row has a specific onItemClick action associated with them, will this stay consistent when the row is accessed from the favorites fragment?
After modifying the data in one fragment, update the data in your database, and tell the other fragments to reload the data. In order to do that register a BroadcastReciever in all fragments that listens to the action when the database have been updated. Maybe it is faster to do it directly between the fragments, but this way you can garantee the consecvency of the UI and the DB.

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