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How to keep informations in fragment after onBackPressed?

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.

Dealing with SavedInstances, and restoration of activity

basically my app has 2 activities.Say "A" and "B"
.
A launches B.
Activity B plays music and also has a notification.
Case 1:when the view is still on activity B` i press home button and then i click on the the notification, activity B is opened with its view intact and with its music playing (because in the manifest i am using android:launchMode= "singleTop" and hence another instance of the activity is not created) this part is as desired......
but
Case 2:when the view is on activity B and i press back button ,activity A appears and then i click on the the notification, activity B is opened with the view lost and music also stops(not desired)......i am making a guess that it happens because when i press the back button the activity is destroyed ,so i have to progamatically restore its view right??so to restore its view i override two methods .....
#Override
public void onSaveInstanceState(Bundle savedInstanceState) {
// Save UI state changes to the savedInstanceState.
// This bundle will be passed to onCreate if the process is
// killed and restarted.
savedInstanceState.putBoolean("boolMusicPlaying", boolMusicPlaying);
savedInstanceState.putInt("swapnumber", swapnumber);
savedInstanceState.putString("seekbarprogress", progress2);
savedInstanceState.putInt("position.seekbar",seekbar.getProgress());
savedInstanceState.putString("seekmaxString", max2);
savedInstanceState.putInt("seekmaxInt",seekMax);
savedInstanceState.putParcelableArrayList("songfetails",songdetails);
super.onSaveInstanceState(savedInstanceState);
}
//make a note ....even if i don't override onDestroy() and don't call on SaveInstanceState explicitly, then too i am not getting any desired effect.......
#Override
public void onDestroy()
{ Bundle savedState = new Bundle();
onSaveInstanceState(savedState);//because of this line....the app is crashing......
super.onDestroy();
}
but it didn't help.....
and in on create i am putting a check if saved instances is null or not....create view accordingly...(i.e from saved instances or from fresh) but it didn't help...
also this line is giving a crash ...onSaveInstanceState(savedState);
even if i don't override ondestroy() and kill the app manually from task killer,and then try to open activity B,then too the saved instances thing should work right,because the method OnSaveInstanceState will be automatically called then,right???please help

Basically if you have pressed a back button,restoration of activity should be done using shared preferences/or a database but if you haven't pressed the back button and then you want to restore the state of the activity (because the activity was destroyed by the system ) then the bundle savedinstances can be used ...

From Android documentation:
When your activity is destroyed because the user presses Back or the activity finishes itself, the system's concept of that Activity instance is gone forever because the behavior indicates the activity is no longer needed. However, if the system destroys the activity due to system constraints (rather than normal app behavior), then although the actual Activity instance is gone, the system remembers that it existed such that if the user navigates back to it, the system creates a new instance of the activity using a set of saved data that describes the state of the activity when it was destroyed. The saved data that the system uses to restore the previous state is called the "instance state" and is a collection of key-value pairs stored in a Bundle object.
To fix second problem you must restore data form some other source (service that plays music, restore info from application context or singleton, etc.)
For more info check this.

Task, Back Button, and onSaveInstanceSate method

Hello I am just a little confused after reading these materials on Tasks and Back Stack, Android Developer Guide:
It says:
When Activity A starts Activity B, Activity A is stopped, but the system retains its state (such as scroll position and text entered into forms). If the user presses the Back button while in Activity B, Activity A resumes with its state restored.
While in the APIs reference for onSaveInstanceState() method, it says:
One example of when onPause() and onStop() is called and not this method is when a user navigates back from activity B to activity A: there is no need to call onSaveInstanceState(Bundle) on B because that particular instance will never be restored, so the system avoids calling it.
The above two situations seem identical to me ("press the Back button to Activity A" and "navigate back from Activity B to Activity A"). But I don't understand why while the former says Activity A resumes with its previous state restored while the latter says the particular instance of Activity B will never be restored. Any explanations?
Thanks in advance!

I think the first one is saying that A will be saved so it can be restored, and the second one is saying that B will not be saved because it can't be restored.

How to pull string from bundle in onResume()?

I have an activity that is resumed after a user picks a contact. Now before the user picks a contact onSavedInstanceState is called and i put a string in the Bundle. Now, After the user selects the contact and the results are returned. onRestoreInstanceState doesnt get called. only onResume() gets called. So how would i go about pulling my string back out of the bundle once the activity is resumed?

Lets say you have two Activities A and B, and Activity A starts Activity B. If you want to pass information from A to B, you can pass information from A to B with:
Intent i = new Intent(this. ActivityB.class);
i.putExtra("Key","Value");
startActivity(i);
Then in Activity B you can get the string with
String value = this.getIntent().getExtras().getString("keyName");
However, if you want to pass information from B to A you have to use a different method. Instead of using startActivity you need to use startActivityForResult. A description of this method is found here: How to return a result (startActivityForResult) from a TabHost Activity?

First, why onRestoreInstanceState isn't firing: According to the documentation, onRestoreInstanceState gets called after onStart(), which, according to the activity lifecycle diagram, only gets called after onCreate or onRestart. If your main activity isn't destroyed when the user goes to choose a contact, then onStart will never fire, and onRestoreInstanceState will never fire. The diagram shows this to be the case when "Another activity comes in front of the activity", and onPause is fired - From there your Activity will only be killed if the system needs more memory.
Second, how to get the data you saved before choosing a contact- A local variable should do it, since the activity is staying in memory. If you get to a point where the activity does not stay in memory, onRestoreInstanceState should fire.

How to handle activity coming to foreground again

The books I have are abysmal at explaining how to work with the lifecycle, there's a lot I'm missing that I'm hoping somebody can fill in.
My app structure is that when it's first started, it starts an activity full of legalbabble that the user has to accept. When he says 'ok', I start my main activity and then I call finish like this:
public void onClick(View view) { //as a result of "I accept"
Intent mainIntent = new Intent(mParent, EtMain.class);
startActivity(mainIntent); // Start the main program
finish();
}
Then in EtMain in the onCreate method, I've got some tabs and I instantiate some classes:
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
mTabHost = (TabHost)findViewById(android.R.id.tabhost);
SetupTabs.setMyTabs(mTabHost, this);
mComData = new ComFields(this); // Create the objects
mDepWx = new WxFields(this, DepArr.Departure);
mArrWx = new WxFields(this, DepArr.Arrival);
mDepVs = new DepFields(this);
mArrVs = new ArrFields(this);
mTabHost.setOnTabChangedListener(new OnTabChangeListener(){
}
Questions:
The 'finish' in the first fragment should terminate the legalbabble activity so it'll never be restarted, right? And the EtMain one will remain forever (until killed externally), even if my app gets pushed to the background, right?
The way it is now, when EtMain gets pushed and later brought to the foreground (by tapping on the icon), it goes through the legalbabble screen as though it's a complete start - that's what I'd like to prevent - going thru the legalbabble screen again.
It would seem that I'd want to override onRestart in the second code fragment and put something in there to restart the app, right? That's the part I'm unclear about.
My question then is what needs to be done in onRestart. Do I have to recreate all the tabs and data in the tabs and all my object instantiations? Or is the memory state of the app saved someplace and then is restored back to the state that it was in before something else was brought to the foreground in which case not much needs to be done because all the objects and listeners will still be there?

Yes after the first activity has ended you shouldn't have to view that activity again. You could also write to the shared preferences that the user has previously seen legal info.
If you're UI object creation is in the onCreate method, this should only be called once. Pausing or resuming will not call the onCreate method again.
Unless you explicitly remove your objects and tabChangedListeners in the onPause method, you should not have to touch them in the onRestart method.
Correct, the state of the app is saved automatically. You shouldn't have to touch the onRestart method.
Hope this helps!

I think the problem is that the launch activity in your manifest is the legalbabble activity, so when you click on the icon, the system launches another one. A better architecture would be to launch the legalbabble activity it from your EtMain activity in the onCreate method of the latter, using startActivityForResult. From the docs:
As a special case, if you call startActivityForResult() with a requestCode >= 0 during the initial onCreate(Bundle savedInstanceState)/onResume() of your activity, then your window will not be displayed until a result is returned back from the started activity.
When you get the result in onActivityResult, you can call finish() if the legal stuff was declined; otherwise everything will proceed normally.
This avoids the problem that the launch activity defined in your manifest finishes when the legal stuff is accepted.

EtMain will not remain forever, if the user backs out (by pressing the BACK key) the Activity will be finished (onPause, then onStop, then onDestroy will be called).
In general you can ignore onRestore until you are doing something complicated.
Once the user has exited your application and re-enters (or presses the icon on the Homescreen), onCreate (followed by onStart and onResume) will be called for your first activity, so you do not need any logic in onRestart, your code in onCreate will do the setting up for you as it did the first time. Because of this your legal babble will appear again when the user starts the app after exiting unless you store a preference (in SharedPreferences or a database or file) to indicate you have already displayed it - in which case finish it straight away and start the main activity.
onRestart is only called when the application goes from the stopped state (onStop has been called but not onDestroy) to the started state (onStart is called but onResume has not yet).
For saving data - some components save their state automatically (e.g. EditTexts remember the text in them, TabHosts remember the currently selected tab etc). Some components will not. If you wish to save extra data then make use of onSaveInstanceState and onRestoreInstanceState. You should only use these methods to restore the state of your application or temporary data, not important things, e.g. the id of the resource what the user was looking at, what zoom level they were at etc. For things like contacts or actual data you should commit these changes to a database, SharedPreferences or other permanent storage (e.g. file) when onPause is called.
I recommend taking a look at the Android Activity lifecycle if you are confused. Or ask more questions!