Call Fragments onCreateView in context with Tabs - android

I have 2 Tabs and 2 Corresponding Fragments. On calling the LAUNCH Activity both Tabs were added and then the first one added will be shown. Thus the first Fragments onCreateView is called the second Fragments ones not.
In my case this is an issue because the first Fragment has to call methods on the second Fragment. Inside the second Fragment there is an Objectreference which will be set by calling the onCreateView in the second Fragment.
Therefore I used following code snippet to solve this
actionBar.setSelectedNavigationItem(1);
actionBar.setSelectedNavigationItem(0);
It works but in my opinion there must be another possibility to solve this issue. Like calling the onCreateView of the second Fragment?
Here is the relevant code snippet. The listener is implemented as in android-dev Sample only with small changes not affecting my issue.
simplexFragment corresponds to the first Fragment
graphicFragment corresponds to the second Fragment
// adds two tabs
actionBar.addTab(actionBar.newTab().setText("Input").setTabListener(new TabListener(null, "input_fragment")));
graphicFragment = new GraphicFragment();
actionBar.addTab(actionBar.newTab().setText("Graphic").setTabListener(new TabListener(graphicFragment, "graphic_fragment")));
simplexFragment.setGraphics(graphicFragment); // sets the internal reference!
actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
// selects the Tab so the GraphicFragments onCreateView will be called
actionBar.setSelectedNavigationItem(1);
actionBar.setSelectedNavigationItem(0);
Thanks for support.

In my case this is an issue because the first Fragment has to call methods on the second Fragment.
This is not how Fragments are meant to work. The idea is a Fragment should be self-contained and re-usable and one Fragment shouldn't know that another exists (or at least shouldn't rely the existence any other Fragment).
For example, suppose you have 3 Fragments and ActivityA uses FragmentA and FragmentB but you have another Activity (ActivityB) which uses FragmentA and FragmentC. In that case, FragmentA doesn't know what the other Fragment is (B or C) and shouldn't even expect there to be another Fragment at all.
The way to achieve what you want is to use callback methods on the Activity and have it perform the actions on any other Fragments (if they exist). It can do this by either calling public methods on the other Fragments or by passing data in the 'arguments' Bundle when it creates the other Fragments.

Related

Refreshing a fragment view from MainActivity

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.

how to save my fragment content? how to refresh my fragment?

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

How do I dynamically update a fragment in a FragmentPagerAdapter

I'm writing a simple Fragment Activity with a FragmentPagerAdapter and two Fragments, where I need to show certain data in tab2 related to my selection in tab1. But the data in tab2 is never updated. Is there any common procedure for this?
You'll need a common holder for data, Activity object is most suitable, since it is parent of both fragments. All fragments can use getActivity() in onCreate(). You can call a method of Activity object to get selected data. The other fragment can similarly, call a method of Activity object to set selected data.
Solved. I just created one instance of each Tab and added an update() method on tab 2 which I called from Tab 1. I couldn't find a built in solution so I did it my way.

Communicating between fragments in Android

Based on the example from http://developer.android.com/training/basics/fragments/communicating.html I tried to reproduce the communication between two fragments which are sub fragments of a larger fragment.
In the example, AB activity contains A fragment and B fragment. But I am trying to achieve the same but in my case AB Fragment contains A fragment and B fragment.
The problem is the overridden method in the AB Fragment never gets called. Does this not work because the containing component is a Fragment and not a Activity like in the example? Am I missing out something here?
If you are referring to onClick() or some other onSomething() handler, then these always get called in the Activity class, not the fragment. So in the example you linked, the onArticleSelected() must remain in the Activity, even if you have nested fragments.
To pass info on to the fragment, you have a few options. One, you can keep a reference to the fragment within the activity. This might be lost if your activity recreates (settings event for example).
The second and better way would be to tag your fragments, and then use findFragmentByTag.
When you add your fragment (notice the parameter "my_fragment" which is the tag I gave to the fragment):
getSupportFragmentManager().beginTransaction().add(R.id.fragment_container, myFragment, "my_fragment").commit();
Or when you replace one fragment with another:
getSupportFragmentManager().beginTransaction().replace(R.id.fragment_container, myFragment, "my_fragment").comit();
Then, when you want to do something in the fragment from within your onArticleSelected of the activity:
Fragment fragment = getSupportFragmentManger().findFragmentByTag("my_fragment");
if (fragment != null) {
fragment.articleSelected(articleId);
}
You can always use an Interface to communicate between fragments. It is the safest way to do so.

How to make call backs between Fragments of the same Ativity

I have 4 tabs in an Activity.
Each of them is a Fragment. And every Fragment has a ListView.
So, if i change the ListView in Fragment, it must change the ListView in all other Fragments ie.., Tabs.
The problem i face is while creating the interface instance.
It takes it's own onClick() method.
In case i want a callback to the parent activity i could have done that by overriding onAttach. But how to make a callback to a Fragment?
From Developers site:
Often you will want one Fragment to communicate with another, for example to change the content based on a user event. All Fragment-to-Fragment communication is done through the associated Activity. Two Fragments should never communicate directly.
So, make a callback to the Activity which in turn makes a callback to other fragments??
Thank You
It's pretty simple,all You need is steps below:
1) From onClick method in your first fragment make a function call of activity:
((IYourActivityInterface) getActivty()).activityMethod();
2) In your activity find fragment by tag or id and run it's method:
public void activityMethod(){
Fragment tabFragment = getFragmentManager().findFragmentByTag("second_fragment");
// or Fragment tabFragment = getFragmentManager().findFragmentById(R.id.frag);
if (tabFragment!=null){
((IFragmentInterface) tabFragment).fragmentMethod();
}
}
Hope this is what you are looking for.)

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