I have got loader in fragment and it loads data on background. After data are loaded, I fill edittexts with that informations. Problem is that if user changes something in edittexts and rotate screen, onLoadFinished is called again and edittexts are replaced with loaded information. I solve this by adding help variable, if data was already loaded .. But when i replace this fragment with other, rotate screen back and forth and press back button, edittexts are empty. Fragment is set to retain instance true. It looks like views lost its state when fragment is on backstack. Anyone familiar with this?
You shouldn't use the retain state.
But the proper way to do so it to save the save using the Bundle and restore it when you recreate the activity (onCreate Bundle is not new).
Please review the link I've sent you it includes a very specific example.
from the android dev guide:
To properly handle a restart, it is important that your activity
restores its previous state through the normal Activity lifecycle, in
which Android calls onSaveInstanceState() before it destroys your
activity so that you can save data about the application state. You
can then restore the state during onCreate() or
onRestoreInstanceState().
Android Rotation Change
Related
I have FragmentX in a ViewPager. FragmentX has EditText's in it and a Button. The user presses the Button and FragmentY replaces FragmentX. The user then presses back and FragmentX has lost all of its input from the user.
How do you either:
a) Save the data in FragmentX before FragmentY appears then FragmentY is replaced by FragmentX retrieve the data and fill in the EditText's in FragmentX
(please don't reply with OnSaveInstanceState, as this does not work unless the Fragment is destroyed, which in this case it is not)
b) somehow keep the data in FragmentX so it is there when we go back to FragmentX from FragmentY..
Any suggestions?
Using addToBackStack() might help in your case.
If you return to a fragment from the back stack it does not re-create the fragment but re-uses the same instance and starts with onCreateView() in the fragment lifecycle, see Fragment lifecycle.
So if you want to store state you should use instance variables and not rely on onSaveInstanceState().
Check this out: Maintaining fragment states
I am now saving the data in FragmentX to SharedPreferences and overriding onBackPressed in the Activity, and have created a function in the Activity called popFromBackstack where the popBackStack() occurs.
In the functions in my Activity where i replace my Fragments i am now saving the data in FragmentX into SharedPrefs before the replace. I am also checking after the replace if the new Fragment is FragmentX and, if it is, i am filling the data into FragmentX from SharedPrefs.
I am also saving the data from FragmentX in onBackPressed in my Activity (if the current fragment is FragmentX), incase the user presses the back button.
I have also created a public static activity called popBackStack() in my Activity which i call from Fragments to pop the backstack. I am also saving the data from FragmentX here (if the current fragment being popped is FragmentX). Once the Fragment being popped is popped i am checking if the new Fragment is FragmentX, and filling in the data if it is...
Long winded approach but i couldn't figure out any other reliable way. This is working perfectly.
I suggest following guidelines that Google provides and implement an interface declared in your Fragment and save the Bundle or whatever object you want in the activity. Then, in your newInstace() static factory method pass that Bundle and recreate data as usual. Since you are using a ViewPager and it will always render the second fragment before the button is pushed (I assume your second fragment is in another tab) you still need to manage it via an interface. When the back button is pressed, the data will still be there, unless it is destroyed, and you still need to implement onSaveInstaceState() for that matter. You can also use setRetainInstance(boolean retain). See here for more details
I'm writing an app that loads user profiles and user's ratings for different places. The app uses fragments pervasively, and it's relatively easy to jump from a profile to a rated place.
As a user clicks a profile and gets to a rated place, they can click another profile on a rated place and go on and on.
The problem I'm having is memory related, when I'm looking at a ranked place and I click a profile, I switch from one Activity to the next. In both of these activities, after setContentView I load a fragment dynamically into layout space.
Now, as I shuttle between these activities, onSaveInstance state is almost always called, however since the Fragment displaying whatever was in the foreground before the activity switch, onDestroyView is not called.
What I would like is when onSaveInstanceState is called in these dynamic fragments, it to force onDestroyView to be called as well.
The only time onDestroyView seems to be called is when I add a Fragment to the back stack. When another activity comes to the foreground and this fragment is stopped, I'd like on DestroyView to be called as well.
The current workaround I want to implement is have an empty fragment with no view, and every time I call startActivity(Intent i), load this dummy fragment to destroy views and start the next activity. Then, when I come back, pop it off the back stack and restore the actual last fragment.
This however seems excessive. So, for a stopped fragment in a stopped activity with a new activity in front of it, how do I force it to destroy it's View?
First, you should not force or satisfy onDestroyView to fix your code, that's the job of the FragmentManager and the Android lifecyle # Pausing and Resuming an Activity. If you want to work with your existing code, use the other override methods onPause() or onStop().
Without posted code, I assume you're using the replace() method to display one fragment over another. This more or less forces you to manage the fragments yourself, some developers actually succeed in doing so with some struggle (look at other SO questions).
So my suggestion for you is either:
Maintain your own states, and show the proper fragments based on the state.
Use the BackStack and let the Fragment management handle the stack/states.
I'm newbie in android and I'm working with fragments.
My problem:
I have two fragments, "A" and "B", my fragment "A" is a complex form, the user can add and remove products, set customer information, payment method and more. My fragment "B" just show the information that user set in the previous fragment.
But if user press back button, I'm losing all information that already set in the previous fragment.
How can i maintain this informations on fragment A?
Thanks.
you can save your data by using sharedpreferences
so that once you get back to the fragment you load your data from sharedpreferences
You should add android:id attribute to each View element of which state you want to save.
this explains in android documentation:
By default, the system uses the Bundle instance state to save information about each View object in your activity layout (such as the text value entered into an EditText object). So, if your activity instance is destroyed and recreated, the state of the layout is restored to its previous state with no code required by you. However, your activity might have more state information that you'd like to restore, such as member variables that track the user's progress in the activity.
Note: In order for the Android system to restore the state of the views in your activity, each view must have a unique ID, supplied by the android:id attribute.
To save additional data about the activity state, you must override the onSaveInstanceState() callback method. The system calls this method when the user is leaving your activity and passes it the Bundle object that will be saved in the event that your activity is destroyed unexpectedly. If the system must recreate the activity instance later, it passes the same Bundle object to both the onRestoreInstanceState() and onCreate() methods.
I have an Android project for which I am creating a custom tab view. I have structured the main Activity (FragmentActivity) in such a way that it has a tab bar at the bottom of the screen with a FrameLayout above it. Each option on the tab creates a new Fragment (relating to that option). Now, to prevent recreation of fragments each time an option is clicked, I store the fragment in an instance variable in the activity. So, when a tab option is clicked, I check if its fragment is already created, if it is not already created, I create and add it to the FrameLayout (and hide any existing fragment), otherwise, I just hide the existing fragment (stored in an instance variable called currentlyViewedFragment) and show the already created fragment that matches the clicked option.
Also when the onCreate() of the activity is called, I set the initial tab to be the home tab (one of the tabs).
This works great, except when the activity is recreated (due to orientation changes). Here, I think the instance variables (essentially pointers to already created fragments) loose their value and are set to null. This causes the home tab to be created and be overlayed on the restored view. I also know that you can save state using the bundle passed to onSaveInstanceState and restore it using onRestoreInstanceState. But the bundle needs to contain data which is serialisable. However, these instance variables are merely pointers! How do I restore their values?
NOTE: this problem is solved below in a comment posted by me.
Thanks.
The answer to your problem is using the bundle for state restoration. Create a class in where you can put the variables and is serializable so you can put the its object to the bundle. Or you may also use SharedPreferences to store the instance variables' value in the phone storage. I hope you got idea from my weird answer.
I realized that there are lots of question on this topic already asked on SO.
But I don't even know the basic when it comes to saving the state of an activity.
(Refer Screenshot Below) When app launches,
1) ScrollView item 1,2,3,4 are visible
2) table containd data which is populated due to Gainer button.
As showed in below screenshots, While app is running in PORTRAIT mode, I
1)scrolled down to ScrollView item 4,5,6
2)pressed the Loser button so accordingly data in the table below the button changes.
3)I'll even change content of graph dynamically(which I had not done yet).
Now I switch to LANDSCAPE Mode so
1)ScrollView is showing ScrollView item 1,2,3,4
2)table is showing data which is populated due to pressing Gainer button.
3)graph is as it is as I've not changed it yet(which I will change later).
So what happens is when I change the orientation, my activity is getting re-launched. So if user is performing some task in one orientation and he changes the orientation, then whole progress will be lost.
I know I need to save the state of the activity and Restore it when orientation changes.
But I don't know from where to start and what to save.
ANY HELP WILL BE LIFE-SAVER !
Option #1: Override onSaveInstanceState() of your Activity and put whatever information you want in the supplied Bundle. Your new activity instance will receive that Bundle in onRestoreInstanceState() (or onCreate()). Here is a sample project demonstrating this.
Option #2: Override onRetainNonConfigurationInstance() of your Activity and return some object that represents your state. Your new activity instance can call getLastNonConfigurationInstance() to retrieve that object, so the new activity can apply that information. Be careful, though, not to have the old activity return something in the object that holds a reference back to the old activity (e.g., a widget, an instance of a regular inner class). Here is a sample project demonstrating this.
Option #3: Convert this activity to a fragment. Have the fragment call setRetainInstance(true); on itself during its initial setup. Add the fragment dynamically to some activity via a FragmentTransaction. Now, when the configuration changes, the fragment is retained, so all your widgets and state are retained. Here is an overly-complex sample application demonstrating this.
Those are the three recommended approaches nowadays.