when is onRestoreInstanceState called?

Question

Sorry for my incomprehension, but I am new in the android development.

I have an application with activity A and activity B in it, and I go from activity A to activity B. When I left activity A, the onSaveInstanceState method was called, but when I went back to activity A (from activity B in the same application), the bundle in the onCreate method was null.

What can I do, to save the activity A's previous state? I only want to store the data for the application lifetime.

Can someone help me with this?

Here is my code for Activity A:

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    if (savedInstanceState != null)
    {
        Log.v("Main", savedInstanceState.getString("test"));
    }
    else
    {
        Log.v("Main", "old instance");
    }
}  

@Override
public void onSaveInstanceState(Bundle savedInstanceState) 
{
    Log.v("Main", "save instance");

    savedInstanceState.putString("test", "my test string");

    super.onSaveInstanceState(savedInstanceState);
}


public void buttonClick(View view)
{
    Intent intent = new Intent(this, Activity2.class);
    startActivity(intent);
}

Here is my code for Activity B, when I press a button to go back to activity A:

public void onBack(View view)
{
    NavUtils.navigateUpFromSameTask(this);
}

Octonary

post your code and lets see how you are saving the bundle. – Sirmons

check developer.android.com/reference/android/app/… – Perrotta

possible duplicate of #6554817 – Ambi

I just posted my code – Hoard

Answer 1

Saving and restoring state is meant to save the current temporary data that is obsolete when user exits the application. When you minimize or leave the Activity by opening next one it might be killed by the system due to lack of resources and restarted with savedInstanceState when you get back to it. So use onSaveInstanceState() only for saving minimize-restore session data or data that should be preserved on rotation.

So if you start a new Activity in front and get back to the previous one (what you are trying to do), the Activity A might not be killed (just stopped) and restarted without going being destroyed. You can force killing it and restoring by checking Don't keep activities in developer options menu.

If you call finish() or remove the Activity from recent task list the savedInstanceState will not be passed to onCreate() since the task was cleared.

If the value must be persistent consider using SharedPreferences.

Westernism

1. I tried, nothing changed, 2. if Activity A might not be restarted, should I get this log message: Log.v("Main", "old instance") ? – Hoard

What am I saying is that if onSaveInstanceState is called it does not guarantee that you will receive the bundle. onRestoreInstanceState will be called only if activity is was killed by the system previously. – Westernism

Can you give me some tip please how can I save values from my activity (that would be persistent only in my application lifetime) – Hoard

Just store the values as fields and add saving to onSaveInstanceState and restoring to onRestoreInstanceState and onCreate and you're done. – Westernism

Updated the answer with the example of what I mean. – Westernism

@Peter: Another way to say what Doctoror is saying is that, if you don't get a call to onRestoreInstanceState, you don't need it, because you haven't lost your state. – Wenz

I found some misleading info in my answer and edited to be more correct. – Westernism

Thank you so much for informing me about "Don't keep activities" It really helps me to debug the application better. Thank you for your help:) – Emblazonry

Answer 2

To answer your question, have a look at the android doc: https://developer.android.com/reference/android/app/Activity.html#onRestoreInstanceState(android.os.Bundle)

It says that onRestoreInstanceState is called after onStart() method in the activity lifecycle.

Saline

Thanks for answering the question asked in the title =) – Wildee

Answer 3

reference

onSaveInstanceState

... onPause()-> onSaveInstanceState() -> onStop() -> onDestory()

onRestoreInstanceState

onCreate()-> onStart()-> onRestoreInstanceState()-> onPostCreate(Bundle) ...

Or You can use LiveData. Save the states in it and observe.If the device rotates it'll update the views accordingly.

Fanechka

Answer 4

This happens because you are navigating the hard way. If you used the phone's default back button navigation, your onCreate would get the bundle passed in.

To circumvent this issue, I suggest you save your state to shared preferences as well as a back up. When the bundle is null, restore it from the shared preferences.

Hereinto

Answer 5

After onStart() which is after onCreate()

Cann

Answer 6

I used in this case a flag and SharedPreferences. This should work, and when you change the screen orientation.

Thiosinamine