Android Save Instance State

Question

I have created two activities A and B. In the Activity A, using onSaveInstanceState method I am saving bundle value ex(outState.putString("selectSaveDate", this.CalSelectedDate)) and going to the Activity B. When I hit back button to the Activity A , In the oncreate method the bundle value is null. I am unable to get my saved value in the oncreate method.

@Override
protected void onSaveInstanceState(Bundle outState) {
    super.onSaveInstanceState(outState);
    outState.clear();
    Log.i("bundleSave", "tester1" + this.CalSelectedDate);
    outState.putString("selectSaveDate", this.CalSelectedDate);
   }
    @Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
            if(savedInstanceState != null){
            Log.i("todolist", "dsa" + savedInstanceState.getString("selectSaveDate"));
        }
    }

Answer 1

You only store data in a bundle in the OnSaveInstanceState method to persist data when your activity is destroyed and re-created (such as when rotating the screen or when the android os may decide to kill your activity if it is low on resources). When you launch activity B on top of your currently executing activity A, A is put in to a stopped state (therefore, your A activity is not destroyed). Also, when you come back from onStop, the next method that is called is onStart() (technically onRestart() is called be before onStart() but I find that callback is rarely ever implemented.

In conclusion, if your trying to keep persist data between launching an activity on top of your currently executing activity, you can just store that data in instance variables for that activity. If your trying to persist data between app launches then your going to want to look into storing data in Android's built in sqllite database or Android's SharedPreferences.

You should also obtain a real good understanding of the Activity lifecycle (its tricky but needed to code successfully in android):

http://developer.android.com/training/basics/activity-lifecycle/index.html

Answer 2

please try to Override onSaveInstanceState(Bundle savedInstanceState) and write the application state values you want to change to the Bundle parameter like this:

@Override
public void onSaveInstanceState(Bundle savedInstanceState) {
  super.onSaveInstanceState(savedInstanceState);
  // Save UI state changes to the savedInstanceState.
  // This bundle will be passed to onCreate if the process is
  // killed and restarted.
  savedInstanceState.putDouble("myDouble", 1.9);
  savedInstanceState.putInt("MyInt", 1);
  savedInstanceState.putString("MyString", "How are you");
  // etc.
}

it will get passed in to onCreate and also onRestoreInstanceState where you'd extract the values like this:

@Override
public void onRestoreInstanceState(Bundle savedInstanceState) {
  super.onRestoreInstanceState(savedInstanceState);
  // Restore UI state from the savedInstanceState.
  // This bundle has also been passed to onCreate.
  double myDouble = savedInstanceState.getDouble("myDouble");
  int myInt = savedInstanceState.getInt("MyInt");
  String myString = savedInstanceState.getString("MyString");
} 


 or follow activity life cycle for better understanding.