Develop Reference

How to call methods in 1st class to 2nd class with passing values

I have MainActivity and SecondActivity. in main activity implemented a viewpager and in my SecondActivity i have button. when i click on button in SecondActivity
move to main activity and jump to spacific viewpager page.
Please provide suitable examples.

In your code on button click write this line,
startActivity(new Intent(CurrentActivity Name, TargetActivity.class).putExtras(tempBundle)
tempBundle is a Bundle argument for identify which position of the pager you want to display at current.
Then in your target Activity get the Bundle information, and set your ViewPager.
viewPager.setCurrentItem(0); //You can set your Bundle information 0 or 1 or 3
That time your ViewPager can set according to given position.

We have Two ways
Use Static Methods OR
Use interface to communicate between activities and fragments also
Communication through Interface

How can I get fragment by tag?

I've found a lot of questions about that, but none of these can help me.
I have a "MainActivity" which have 4 fragments.
I need to access to one of these fragments, called "my_fragment", in an other simple activity, let's call "SecondActivity".
So, I try to put a property android:tag="my_fragment" in the LinearLayout markup XML of "my_fragment".
And after that, I do that in "SecondActivity":
Fragment frg = getFragmentManager().findFragmentByTag("my_fragment");
... in order to get my fragment. But frg is always null.
I try a lot of others ways, but in vain. This one seems better and easier to do, but perhaps I'm wrong.
Any help would be appreciate. Thank you in advance.
Fabien
EDIT
Since your answers that indicate that's isn't possible, I want to specify what I need.
I just want to get this fragment for reload it. I found something like that on an other subject on Stackoverflow:
frg= getFragmentManager().findFragmentByTag(my_fragment);
final FragmentTransaction ft = getFragmentManager().beginTransaction();
ft.detach(frg);
ft.attach(frg);
ft.commit();
By the way, I just try to get the fragment in the fragment himself and it's still return null. With the method :
findFragmentById(R.layout.my_fragment)
it's the same result.
And after, I did :
findFragmentById(this.getId())
But it's make an infinite looper, I don't understand the reason...
EDIT2
Alright, let’s give some details :
I have MainActivity with ViewPager with 4 fragments. It’s not fragments at the xml sense. Sorry if I’m confused, I was training to Android very recently and somethings are not clear for me again. So, before yesterday and the read of #Bruce edit, I was thinking that fragments were the components of a ViewPager. So, #Bruce, this is why I can’t use your solution. I was trying to use findFragmentByTag with the tag applicate on my principal LinearLayout markup of my fragment - that is not, I repeat, an xml markup fragment.
This is my approach :
In my MainActivity, I click on the third fragment. I make a research for find some points around me. After an action of the user, still from the third fragment, I open the SecondActivity for authentification and on the user connection, I close this SecondActivity. Now, I need to reload the fourth fragment that will adapt his components in terms of the user situation, while keeping the same state on the third fragment, with points loaded. It’s why can’t use your solution #menion.asamm : I can’t reinstantiate the MainActivity, even if I simulate a click on the third fragment because it will come back in his initial state, without points loaded.
Thank you both of you #Bruce and #menion.asamm for your time in helping me !

Fragments are always owned by one activity, so you cannot directly access a different activity's fragments. The call you are making is looking for fragments within your SecondActivity.
Why do you want to do this? Once some UI is off screen (MainActivity), you usually don't want to do anything with those UI objects, because Android may have removed them from memory. If there is data in "my_fragment" that is needed by SecondActivity, one approach might be to save the data in SharedPreferences or a database in my_fragment, and then load it in SecondActivity.
EDIT
I'm not sure you're getting that it is important which activity you are running in. Here are two options for how to proceed:
If you just want to run the SAME instance of your fragment that was already running inside MainActivity, then maybe what you want to do is finish your SecondActivity to return to MainActivity.
If you want a NEW copy of the same fragment inside SecondActivity, then you can include the fragment inside SecondActivity's layout (or add it to some container later).
Also, notice that for your call to findFragmentById, the ID needs to be the ID that was specified in the layout file as the value of android:id (not the R.layout.my_fragment). It might be better to use a fragment tag, which you can either specify in your layout file or when you add the fragment.
Mainly I think you need to read Google's guide on fragments.
EDIT2:
Ah, I see, I have a similar fragment-refresh situation in my app. You basically need to get data from SecondActivity back to the fragment inside MainActivity. The approach I use is this:
Save the data from SecondActivity in storage (DB or SharedPreferences).
Finish SecondActivity so that MainActivity and your fragment are shown again.
Override onResume in your fragment to fetch the data you saved in SecondActivity.
Another option is to launch SecondActivity using startActivityForResult, and then process the results in MainActivity, passing them to its fragment.
Regarding how to find the fragment by tag, you first need to set the fragment's tag. If you are declaring your fragment in a layout XML, then you can do it there (and you can also declare
<fragment class="com.xyz.MyFragment"
android:tag="MyFragment"
android:id="#+id/my_fragment"
android:layout_width="match_parent"
android:layout_height="match_parent"
/>
Now from inside MainActivity you can either do findFragmentById(R.id.my_fragment) or findFragmentByTag("MyFragment").
If you are NOT declaring the fragment in XML, but adding it directly, you can set the fragment's tag as part of the add call:
FragmentTransaction ft = fm.beginTransaction();
ft.add(R.id.frag_parent, new MyFragment(), tag);
EDIT3: Ah, you're using ViewPager to hold fragments. Now I understand better. They're still fragments, but getting access to them is indeed tricky, because Android constructs a fragment tag in some internal code. Here is another SO question on this issue:
Retrieve a Fragment from a ViewPager

Hmm if you really need just refresh of fragment attached to different activity, I suggest:
first activity start second activity with
startActivityForResult(intent, MY_CODE);
second activity when wants to refresh fragment in first activity, finish it's state with
Intent data = new Intent();
data.putExtra("REFRESH_FRAGMENT", true);
setResult(RESULT_OK, data);
finish();
back in first activity, you may catch this result by
#Override
public void onActivityResult(int requestCode, int resultCode, Intent data) {
// check request code
if (requestCode == MY_CODE) {
// check result
if (resultCode == RESULT_OK) {
// check data
if (data != null && data.getBooleanExtra("REFRESH_FRAGMENT", false)) {
refreshFragment();
}
}
}
}
Possible?

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

Call Fragments onCreateView in context with Tabs

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.