How to recover data after closing another application

Question

I'm developing an Android application and I need to open pdf files and return to same activity when back button is pressed.

Problem

I correctly open pdf file (from ActivityOne) using an intent and starting activity, but when I press back button, all data that I had in the ActivityOne (and previous activities) have been lost.

Here is my code of starting activity for showing pdf:

File file = new File(Environment.getExternalStorageDirectory().getAbsolutePath() 
            +"/"+ myApplication.getUsuarioActual().getFacturaActual().getPdf());
Intent intent = new Intent(Intent.ACTION_VIEW, Uri.fromFile(file));
intent.setType("application/pdf");
startActivity(intent);

What do I have to do to solve that? Same occurs when I open another application and close it: when return to my app, it shows an error saying that all data is null.

EDIT

After reading that question, as @TheCharliemops recommended me, I know it is what I need, but I have another question related to that.

I have a class myApplicationthat extends Application to maintain global application state where I save all data that I read/write in different Activities.

My question is if I have to save all data I have in myApplication in every activity using onSaveInstanceState or there is some easiest manner to do it.

score 1 · Accepted Answer · edited May 23 '17 at 10:27

Firts of all, welcome to SO!!

Here, @reto-meier explains how to save the activity state in Android. I think that could fix your problem. I put his code here for future people with similar problem.

He says that you must override onSaveInstanceState(Bundle savedInstanceState) and onRestoreInstanceState(Bundle savedInstanceState) as following code shows:

Reto Meier said:

@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.putBoolean("MyBoolean", true);
  savedInstanceState.putDouble("myDouble", 1.9);
  savedInstanceState.putInt("MyInt", 1);
  savedInstanceState.putString("MyString", "Welcome back to Android");
  // etc.
}

The Bundle is essentially a way of storing a NVP ("Name-Value Pair") map, and 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.
  boolean myBoolean = savedInstanceState.getBoolean("MyBoolean");
  double myDouble = savedInstanceState.getDouble("myDouble");
  int myInt = savedInstanceState.getInt("MyInt");
  String myString = savedInstanceState.getString("MyString");
}

I hope this helps you.

Regards!

How to recover data after closing another application

1 Answers1