Question

I’m trying to write an Android game and I would like to be able to pause the game even if the user wants to return to the main menu or the activity gets killed off by the system. onSaveInstanceState doesn’t seem to give me a whole lot of control as to when I can read the bundle back, plus from what I can tell, the bundle is only good for short periods of time. So I want to serialize a few ArrayLists that I have, then read them back. I don’t get any compile errors nor does the program crash. But, the data either never gets written or never gets read. I’m not sure which one. My serializeData method is called in onDestroy and the deserializeData is called from onCreate. Here’s my code for writing and reading the data:

public void serializeData(String filename, ArrayList<String>arrayList) {
    FileOutputStream fos;
    try {
        fos = openFileOutput(filename, Context.MODE_PRIVATE);
        ObjectOutputStream oos = new ObjectOutputStream(fos);
        oos.writeObject(arrayList); 
        oos.close();
    } catch (FileNotFoundException e) {
        e.printStackTrace();
    }catch(IOException e){
        e.printStackTrace();
    }
}

@SuppressWarnings("unchecked")
private void deserializeData(String filename, ArrayList<String>arrayList){
    try{
        FileInputStream fis = openFileInput(filename);
        ObjectInputStream ois = new ObjectInputStream(fis);
        arrayList = (ArrayList<String>)ois.readObject();
    } catch (FileNotFoundException e) {
        e.printStackTrace();
    }catch(IOException e){
        e.printStackTrace();
    }catch(ClassNotFoundException e){
        e.printStackTrace();
    }
}

Any help would be greatly appreciated! Thanks in advance!

Answer 1

Let me tell you one thing: never use the onDestroy() method to save your data. Use onPause() or onStop() instead. You should never count on the onDestroy() method to save data or call some functions.

Use onDestroy to close connections and finish using resources and the like. If you want to read more about this you should take a look here.

Other than that your code seems fine. Just add one more thing: put a oos.flush() just above oos.close().

And don’t forget to close the objectInputStream object.