Singleton object is gone, My data is cleared

Question

There are several activities and fragments that need access to a specific data, so i created a singleton object to store data in that. The problem is after a long time that the app is in background, that singleton object will disapear and become null, so when i open my app again the app crashes and throws null pointer exception to that object. What should I do? How should i share that data between activities and fragments? Is it a good practice to store that data in database? Or bundle? or whatever?

This is my singleton:

public class Book {
private static Book ourInstance;
private int FLNB;

private Book() {
}

public static Book getInstance() {
    if (ourInstance == null) {
        ourInstance = new Book();
    }
    return ourInstance;
}

public void setFLNB(int FLNB) {
    this.FLNB = FLNB;
}

public int getFLNB() {
    return this.FLNB;
}
}

I set FLNB, and when singleton is gone, the value of FLNB is cleared and I need to access this value after re-initial singleton.

if it's null, you should create the instance. Is there something disallowing you to do that? That's how a singleton works :) — Claudio Redi, Nov 23 '16 at 20:01
there are the `onResume` and `onPause` lifecycle methods that you could use to handle the app behaviour when app goes to background and comes back. — donfuxx, Nov 23 '16 at 20:01
@ClaudioRedi my data is stored in singleton and since singleton is null my data is gone. I need my data back and must be restore it. — Hamidreza Shokouhi, Nov 23 '16 at 20:04
@HamidrezaShokouhi: could you should how you're implementing the singleton? — Claudio Redi, Nov 23 '16 at 20:06
You can check out this answer: http://stackoverflow.com/a/4878259/1697326 - it might be helpful. But just as Claudio wrote - show your implementation. It's hard to say what you do wrong without the code. — Paul, Nov 23 '16 at 20:48
You need to place null check on onPause on all activities that utilizes the singleton object and reinstantiate it if necessary. — muthuraj, Nov 23 '16 at 20:52

Singleton object is gone, My data is cleared

0 Answers0