I'll try to explain my problem:
all my fragments are using setRetainInstance(true)
In my activity onCreate I'm doing this:
if (savedInstanceState == null) {
fragment = onCreatePane();
fragment.setArguments(intentToFragmentArguments(getIntent()));
FragmentTransaction trans = getSupportFragmentManager().beginTransaction();
trans.add(R.id.root_container, fragment, getFragmentTag());
trans.commit();
} else {
FragmentTransaction trans = getSupportFragmentManager().beginTransaction();
if ( fragment == null ) {
fragment = getSupportFragmentManager().findFragmentByTag(getFragmentTag());
}
if (fragment == null) {
fragment = onCreatePane();
fragment.setArguments(intentToFragmentArguments(getIntent()));
}
trans.add(R.id.root_container, fragment, getFragmentTag());
trans.commit();
}
So when I create the activity and savedInstance is null I create the Fragment, I set it's arguments, I begin the transaction and add my fragment to the transaction with it's own tag (to get it back later).
The user interact with the activity and change the orientation. The activity is destroyed and recreated (as normal activity lifelycle). So now it enter the else, the fragment is null and I do a fragment = getSupportFragmentManager().findFragmentByTag(getFragmentTag()); that returns the correct Fragment holded by the fragmentManager.
The problem is that this fragment hold a reference to the old Activity that has been destoyed so if I do a fragment.getActivity it returns null. How can I update the fragment reference to the acitivy to the new re-created Activity?
UPDATE: To be more precise I'm on the SearchActivity that call the onNewIntent when it get a new Search. So the actual interaction is this-> user do a search -> search is displayed correctly -> user change orientation, result is displayed correctly (if user interact with results they are fine) -> user do a new search from the search button and this call the SearchActivity's onNewIntent that dispatch the new intent to the fragment that has the search logic. Here it crashes because the reference to the activity is null
When and where are you calling getActivity()? The activity reference does get updated automatically, but not immediately. You should be safe to access it after onActivityCreated() was called.
just remove null check from else part if ( fragment == null ) { fragment = getSupportFragmentManager( ...... let update fragment with new one created on orientation change ......
If setRetainInstance(true) -- yes, it's the solution (to find fragment by tag, because instantiate it again -- is the wrong way -- there could be background routines in progress). Otherwise, if you have setRetainInstance(false) the problem can be back.
I had the similar one. I my case -- because I used Loader (in background). Solution was simple: to destroy fragment's loaders in onDestroy() method of the fragment.
In your baseAcvivity you can override onSaveInstanceStat to resolve this problem :
#Override
protected void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
//solution of fragment.getActivity() is null
outState.remove("android:support:fragments");
}
Related
Given an Activity that acts as a Home page (it never closes) that launches various fragments, how to know when the Activity is visible to the user?
From what I have observed, when I open a fragment the lifecycle for the Activity never changes, onPause() is not called. And when I close the fragment, onResume() is not called on my Activity.
Here is how I am starting my fragments, I am using this method and passing the fragment I want to launch to it.
public void addFragment(int containerId, Fragment fragment, boolean addToBackStack) {
// Check if the fragment has been added already. If so, then
// don't add the fragment.
Fragment temp = mFragmentManager.findFragmentByTag(fragment.getClass().getName());
if(temp != null && temp.isAdded()) {
return;
}
FragmentTransaction ft = mFragmentManager.beginTransaction();
ft.add(containerId, fragment, fragment.getClass().getName());
if(addToBackStack)
ft.addToBackStack(null);
ft.commit();
}
What is the methodology for indicating that my Activity is visible again? Thanks in advance!
in the oncreate method of your home activity, call
mFragmentManager.addOnBackStackChangedListener(this) ;
and then define
#Override
public void onBackStackChanged() {
int backStackCount = mFragmentManager.getBackStackEntryCount();
if(backStackCount == 0) {} //back to home screen
}
Your Activity is always Visible even if thousand Fragments are showing at the same time, for the sake of understanding Fragments are just Custom-Views, and the Fragment gives a helping hand in handling your View, so onPause() on your activity does not need to called when a Fragment dies or is born,just like inflating a View.
Just like Sir #Tim Mutton said, you need to check your BackStack to know if you are back, or you can use the ViewGroup method ViewGroup.indexOfChild(View child) - this method will an int of value getChildCount()-1 which means its on top of its fellow sibblings..
Hope it helps
I have an Activity with a FrameLayout and need to show different fragments based on user input.
The code I use for showing a fragment is this:
private void showFragment(Fragment fragment, Bundle args, boolean addToBackStack) {
if (args != null) {
fragment.setArguments(args);
}
FragmentManager fragmentManager = getSupportFragmentManager();
FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
fragmentTransaction.setCustomAnimations(R.anim.activity_open_translate, R.anim.activity_close_scale);
fragmentTransaction.replace(R.id.main_frame, fragment);
if (addToBackStack) {
fragmentTransaction.addToBackStack(fragment.getClass().getName());
}
fragmentTransaction.commit();
}
This is called as :
if (contactPickFragment == null) {
contactPickFragment = new ContactPickFragment();
}
showFragment(contactPickFragment, args, true);
All this works fine. Now if the user goes into one fragment presses back and returns back to the same fragment, all my views inside stay the same. For example, I have an EditText inside the fragment and the user edits something inside. If the user comes back to the fragment, the same text persists. I do not want this to happen. How do I reset everything in the view?
I have added code within the Fragment's onCreateView() to clear the text, and from debugging I see that this is being called, but the text never gets cleared. What am I doing wrong here?
If you don't want the data from the previous instance to appear, simply create a new instance of ContactPickFragment each time you show it.
Clearing data in onCreateView() has no effect because view state is restored AFTER onCreateView(). Your Fragment has no view before onCreateView() and so Android cannot possibly apply the previous state any earlier. Values set on the views during onCreateView() will be overwritten by their previous values.
As a general answer, there is no way to "refresh" the view of a Fragment, other than replacing the fragment with another instance of itself (possibly initialized with the parameters that you want to refresh/update).
You can reuse your fragments and refresh the state of your views. You just can't do it from onCreateView as #antonyt correctly points out.
Instead, override onViewStateRestored and set up the state of your views the way you'd like from there.
Something like:
#Override
public void onViewStateRestored(Bundle savedInstanceState) {
super.onViewStateRestored(savedInstanceState);
View view = getView();
// Code to call view.findViewById to grab the views you want
// and set them to a specific state goes here
}
There are advantages to reusing fragments. Not the least of which is that if you have a memory leak with your fragment (which is easier than you may think to accomplish,) you will exacerbate the problem by creating myriads of them.
First, some background information. I have an Activity that hosts several Fragments; these are hidden and shown such that only one Fragment is visible at a time. Each Fragment hosts several custom Views that I call IncrementCounters. Those views display a number and increment that number by 1 when tapped.
Each of the Fragments has setRetainInstance(true) called on it when it is created in my Activity. When the Activity is created, I check to see if the Fragments exist; if they do, I store a reference to them; if not, I create a new instance, like this:
autonFragment = (AutonomousScoutingFragment) getFragmentManager()
.findFragmentByTag("auton");
teleopFragment = (TeleoperatedScoutingFragment) getFragmentManager()
.findFragmentByTag("teleop");
postMatchFragment = (PostMatchScoutingFragment) getFragmentManager()
.findFragmentByTag("post_match");
FragmentManager fm = getFragmentManager();
FragmentTransaction ft = fm.beginTransaction();
if (autonFragment == null) {
Log.d("onCreate", "autonFragment is null!");
autonFragment = new AutonomousScoutingFragment();
autonFragment.setRetainInstance(true);
ft.add(R.id.scouting_fragment_container, autonFragment, "auton")
.hide(autonFragment);
}
if (teleopFragment == null) {
Log.d("onCreate", "teleopFragment is null!");
teleopFragment = new TeleoperatedScoutingFragment();
teleopFragment.setRetainInstance(true);
ft.add(R.id.scouting_fragment_container, teleopFragment, "teleop")
.hide(teleopFragment);
}
if (postMatchFragment == null) {
Log.d("onCreate", "postMatchFragment is null!");
postMatchFragment = new PostMatchScoutingFragment();
postMatchFragment.setRetainInstance(true);
ft.add(R.id.scouting_fragment_container, postMatchFragment,
"post_match").hide(postMatchFragment);
}
ft.commit();
One problem I have is that after every orientation change, it seems as though the Fragments aren't actually being retained, as ever time I see debug prints stating that they are all null. This may be realted to my bigger problem; I'm not sure.
I am trying to figure out how to maintain the value of the number stored in each IncrementCounter across configuration changes, specifically rotation. I have overridden onSaveInstanceState() and onRestoreInstanceState() in IncrementCounter. When I rotate my device, I see that onSaveInstanceState() is called on all of the IncrementCounters I have in my Fragments. However, the corresponding onRestoreInstanceState() is never called, and my IncrementCounters do not have their states restored. What is the proper way to handle something like this? I've been banging my head against my desk for hours about this problem.
Since the Fragments have the setRetainInstance(true), they will not be destroyed on a rotation. The Activity will be destroyed, and the Fragments will be detached until a new Activity is created. However, the Fragments will go through the onCreateView() method again, so you would need to restore their IncrementCounters.
Also, you can save state in onSaveInstanceState(), and then restore it in onCreate(), onCreateView(), and several other methods that are all passed that same bundle as a parameter.
I have this activity where I run an asynctask that gathers a series of data. This data can be represented in several ways, for the sake of simplicity let's say there's two ways. I want the user to be able to switch between these two representations (listview and graphical view).
So I created a FragmentActivity with my ListFragment and my GraphicFragment.
How do you switch between these two so that user can go back and forth? I tried using replace but then the previous fragment gets destroyed which is not of my interest since its reference has the data passed by my Activity. (i.e. I don't want to recreate the fragment each times the user switches between views).
I also tried hiding and showing but I can't get it to work, one of the fragments is not showing.
Also, when I rotate I guess the fragments get destroyed because I get a nullpointerexception when trying to access them.
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main_layout);
pBar = (ProgressBar) findViewById(R.id.analyzingProgress);
// However, if we're being restored from a previous state, then don't
// create the fragment again (please)
if (savedInstanceState == null) {
firstFragment = new DirListFragment();
secondFragment = new GraphViewFragment();
getSupportFragmentManager().beginTransaction().add(R.id.fragment_container, secondFragment).commit();
fragments= new ArrayList<IFragment>();
fragments.add(firstFragment);
fragments.add(secondFragment);
}
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
if(item.getItemId() == R.id.listView){
FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
/*transaction.hide(secondFragment);
transaction.show(firstFragment);*/
transaction.replace(R.id.fragment_container, firstFragment);
transaction.addToBackStack(null);
transaction.commit();
}
else if(item.getItemId() == R.id.graph){
FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
/*transaction.hide(firstFragment);
transaction.show(secondFragment);*/
transaction.replace(R.id.fragment_container, secondFragment);
transaction.addToBackStack(null);
transaction.commit();
}
return true;
}
The problem comes when I try to access the fragment fields to update their data:
for(IMyFragment frag: fragments){
frag.updateData(data);
}
I get a NullPointerException after rotating the screen.
Also when switching fragmenents, their data is not updated (i.e. I start with list fragment, it's showing the proper data, then switch to graphic, no data is shown, switch back to list, no data again.)
If the fields are null when using setRetainInstance(true);, then you are recreating them (the fragments) in your activity. Make sure you are setting something in onSaveInstanceState() in your activity so in onCreate(), savedInstanceState will not be null, it can even be an empty bundle or useless variable, ex:
#Override
public void onSaveInstanceState(Bundle outstate){
super.onSaveInstanceState(outstate);
outstate.putBoolean("stateChanged", true);
}
Just make sure you call super before adding your arguments.
On another note, I personally have never stored my fragments in an array. I use a FrameLayout as a fragment container in my activities, just like you, and if I need to update something I just call: getSupportFragmentManager().findFragmentById(R.id.fragment_container).setWhatINeed(); This way I always get the visible fragment.
Let me know how the update goes and I'll update this post with any information I can.
Can I use savedInstanceState() to save the state when removing a fragment, then restore the state when I pop the fragment off the back stack? When I restore the fragment from the back stack, savedInstanceState bundle is always null.
Right now, the app flow is: fragment created -> fragment removed (added to back stack) -> fragment restored from back stack (savedInstanceState bundle is null).
Here is the relevant code:
public void onActivityCreated(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
Bundle bundle = getArguments();
Long playlistId = bundle.getLong(Constants.PLAYLIST_ID);
int playlistItemId = bundle.getInt(Constants.PLAYLISTITEM_ID);
if (savedInstanceState == null) {
selectedVideoNumber = playlistItemId;
} else {
selectedVideoNumber = savedInstanceState.getInt("SELECTED_VIDEO");
}
}
public void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
outState.putInt(Constants.SELECTED_VIDEO, selectedVideoNumber);
}
I think the problem is that onSavedInstanceState() is never called when being removed and being added to back stack. If I cant use onsavedInstanceState(), is there another way to fix this?
onSaveInstanceState is (unfortunately) not called in normal back-stack re-creation of a fragment. Check out http://developer.android.com/guide/components/fragments.html#Creating and the answer on How can I maintain fragment state when added to the back stack?
I like to store the View I return in onCreateView as a global variable and then when I return I simply check this:
if(mBaseView != null) {
// Remove the view from the parent
((ViewGroup)mBaseView.getParent()).removeView(mBaseView);
// Return it
return mBaseView;
}
The problem is that the fragment needs to have an Id or Tag associated with it in order for the FragmentManager to keep track of it.
There are at least 3 ways to do this:
In xml layout declare an Id for your fragment:
android:id=#+id/<Id>
If your fragments container View has an Id, use FragmentTransaction:
FragmentTransaction add (int containerViewId, Fragment fragment)
If your fragment is not associated with any View (e.g. headless fragment), give it a Tag:
FragmentTransaction add (Fragment fragment, String tag)
Also, see this SO answer.
FWIW, I hit this as well, but in my case onSaveInstanceState was called properly and I pushed in my state data when a new activity fragment was brought up on the smartphone. Same as you, the onActivityCreated was called w/ savedInstanceState always null. IMHO, I think it's a bug.
I worked around it by creating a static MyApplication state and putting the data there for the equivalent of "global variables"...