Is there some way I get already created currently displayed same instance of fragment in my activity. I DON'T to use
findFragmentById(int id), simply I never created that
findFragmentByTag(String tag), because I am not adding tag in every fragment .offcourse due to some requirement.
getFragment(Bundle bundle, String key), because I never am putting in bundle.
Although I may look like fool to mention that, but I want something like this. Is activity keep some fragment instance somewhere.??
What can be the best approach I can take to achieve this requirement.
UPDATE
Okay, so let me tell you why I can't use above methods. If I am adding various fragment in one activity, where I always want to come back to one fragment when back is clicked. (As we have in navigation drawer, u know). And unless there are inner fragment. so for that I don't want to add in the back stack.
Now even if I have the tag associated with my fragments, I cant say for 8 fragment if- else-if-else for getting the tag. That I know is not correct. So first two ways goes out of my option. Now third one. I exactly don't know where to keep it. And even if I keep it where will I get the bundle and key every time I just want my fragment.
You can get from fragment Manager
List<Fragment> fragList=fManager.getFragments();
for(Fragment fr: fragList){
String fragClassName = fr.getClass().getName();
if(fragClassName.equals(Abc.class.getName())){
Log.i("Fragment:","Abc");
}else if (fragClassName.equals(Xyz.class.getName())) {
Log.i("Fragment:","Xyz");
}
}
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 have v4.ViewPager inside Activity and use SlidingTabLayout from google's examples SlidingTabBasics. The problem I encounter is that each fragment retrieved from getItem(position) in v4.FragmentPagerAdapter has to refresh activity title. I have already learnt the hard way that FragmentPagerAdapter causes fragments to have really weird life callbacks so I can't probably use onResume or onStart. I noticed though that onCreateOptionsMenu(menu,inflater) gets called exactly when I want to refresh activity title. Is there a callback to supply actions when ViewPager has settled the fragment and it should change activity title?
Setting callback on ViewPager.onPageSelected(position) is inconvenient because I want this information to be propagated from fragment, not to fragment.
Currently I 'steal' onCreateOptionsMenu(menu,inflater) to do the work for me but it causes optimisation issues when no menu should be inflated but I still want the fragment to be able to affect activity title.
Have you tried this code in your fragment:
if(getActivity() != null){
getActivity().setTitle("new title");
}
Take into consideration that getActivity() will be null if the fragment is not yet attached to the activity.
Godspeed.
You can do this in different ways.
You can use interfaces in fragments that can be implemented by activity. But the drawback is, if you do have large number of fragments you must implement all of them.
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?
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
I have an application where whenever I exit the application via the home hardware button, it should return to the last state the application is in. However, when I launch the application again, the application shows a white screen with only my header bar. And when I click on the header bar's button, the application crashes with the IllegalStateException where the application cannot find the method for the button clicked.
I am currently implementing with Sherlocks Fragment, where the header bar is an action bar. I'm also using HTC Rhyme, Version 2.3 (Gingerbread). The following is the codes for the addition of fragments into my main app.
Codes to add the fragments within the onCreate method in the activity:
FragmentTransaction trans = getSupportFragmentManager().beginTransaction();
Bundle bMain = getIntent().getExtras();
String statusCheck = "";
if (bMain != null) {
statusCheck = bMain.getString("statusCheck");
}
if (statusCheck.equals("web")) {
MyWebViewFragment webfrag = new MyWebViewFragment();
trans.add(R.id.container,webfrag, "WebViewFragment");
} else if(statusCheck.equals("traveloguelist")) {
MyTravelogueListFragment travelfrag = new MyTravelogueListFragment();
trans.add(R.id.container,travelfrag, "TravelogueListFragment");
}
trans.commit();
This is the codes when I change a fragment:
MyTravelogueListFragment travelfrag = new MyTravelogueListFragment();
getSupportFragmentManager().beginTransaction().replace(R.id.container, travelfrag).addToBackStack(null).commit();
[Edit]
I realized after much reading and running that the main issuei have is that upon resuming the application, the activity is actually created again. Thus, some of the parameters i passed in does not get registered, resulting in the wrong display. I THINK this is the error that is causing that to happen:
Previously focused view reported id "myresID" during save, but can't be found during restore.
However, I don't know how you force the application to remember the previous state of the fragment? Or is there any other way around this problem?
I'm still very stuck with this problem. Will really appreciate it if someone can help me!
After much trial and error and many readings, I finally found a way to sort of solve my problem.
From what I understand, this problem will occur due to the Activity's life cycle. The comment by Tseng in this forum was quite comprehensive:
http://forum.unity3d.com/threads/127794-Android-Apps-crashing-on-resume
It seems that during the time when other applications are invoked when a certain activity is onPause/onStop, Android might free up some of its memory the activity is currently holding on to if there is insufficient memory required. In this case, all the current objects or variable the paused activity is having will be destroyed. Thus, when the activity is back on focus, the onCreate is actually invoked again. Thus, the activity will have no idea which fragment I am currently require.
However, I realized that it will always call the saveInstanceState which is essentially a bundle object. So I did the following:
onSaveInstanceState method
#Override
public void onSaveInstanceState(Bundle bundle) {
//activityFrag is a string object that tells me which fragment i am in currently
bundle.putString("statusCheck", activityFrag);
}
onCreate method
if (savedInstanceState != null) {
getSupportFragmentManager().popBackStack(null, getSupportFragmentManager().POP_BACK_STACK_INCLUSIVE);
//return;
statusCheck = savedInstanceState.getString("statusCheck");
} else {
statusCheck = b.getString("statusCheck");
}
What I have done is to remove all the fragments I have stacked thus far to remove any issues where there is missing information needed. So this is like starting anew again. The status check just determine which fragment the user has last visited.
After much testing, it seems like it does solve my problem. though I wouldn't say it is perfect. One of the main downfall I have is that whenever I change my fragment, I have to update and change my statusCheck to make sure the correct fragment will be called. However, I have to admit this way is a little unorthodox and might not be very correct.
If any of you have any better ideas, please feel free to share!
You can try to implement following:
Use putFragment to save all fragments, currently located in FragmentManager, into bundle in onSaveInstanceState;
And then you can use getFragment to get all previously stored fragments back from bundle in onRestoreInstanceState.
Also... you'll probably need some HashMap that will help to determine the hierarchy of the fragments (in case you have containers and contained fragments) to be saved into bundle as well.
Also... when restoring from bundle you'll need to know keys for all fragment you've put there earlier. Probably, the easiest way is simply to organize an array of keys and put them into bundle when saving the fragment into instance.
This way your saving and restoring will be complete and centralized.