Backstack and memory leakage

Question

I have developed a small API for dialog fragments based on Google support library with very simple requirements:

API could add (or replace) a modal dialog
API could dismiss dialog programmatically or user can dismiss dialog by pressing button

Does my API creates a memory leakage by constantly adding fragments to backstack?

public class DialogFragmentUtils {

private static final String DIALOG_TAG = "dialogTag";

public static void showDialogFragment(@Nullable Activity activity, @NotNull Fragment fragment) {
    if (activity instanceof FragmentActivity) {
        FragmentActivity fragmentActivity = (FragmentActivity) activity;
        FragmentManager fm = fragmentActivity.getSupportFragmentManager();
        FragmentTransaction ft = fm.beginTransaction();
        Fragment prev = fm.findFragmentByTag(DIALOG_TAG);
        if (prev != null && prev.isAdded()) {
            ft.remove(prev);
        }
        ft.add(fragment, DIALOG_TAG);
        ft.addToBackStack(null);
        ft.commit();
    }
}

public static void dismissDialogFragment(@Nullable Activity activity) {
    if (activity instanceof FragmentActivity) {
        FragmentActivity fragmentActivity = (FragmentActivity) activity;
        FragmentManager fm = fragmentActivity.getSupportFragmentManager();
        DialogFragment dialog = (DialogFragment) fm.findFragmentByTag(DIALOG_TAG);
        if (dialog != null) {
            dialog.dismiss();
        }
    }
}
}

How many dialogs are we talking about since your concerned about memory leak? — Warpzit, Jul 29 '13 at 17:20
Why won't you just check? Create several dialogs and dismiss them in various ways (back/ok). Then run a heap dump using Eclipse MAT and search the heap for instances of your dialog. — talkol, Jul 29 '13 at 21:05

score 4 · Accepted Answer · edited May 23 '17 at 11:59

4

Yes, its prone to low memory, not memory leak though. All back stack Fragment are kept in memory with hard references. So if you are keeping a ridiculous amount of Fragments in back stack then you will get out of memory.

Have a look here: When a Fragment is replaced and put in the back stack (or removed) does it stay in memory?

UPDATE: I see your DIALOG_TAG is not changing so you are keeping only one Fragment in backstack at a time, because you remove old one if it exists. In this case you might not have the issue of low memory.

edited May 23 '17 at 11:59

Community

1
1

answered Jul 31 '13 at 21:40

M-Wajeeh

17,204
10
66
103

Where is he removing the old one? `dismiss()`ing it is not the same as removing it! I'm reasonably sure the backstack just grows in this case. – Delyan Aug 01 '13 at 15:48
Look at his `showDialogFragment()` method where he calls `ft.remove(prev);`. He removes previous one before adding. – M-Wajeeh Aug 01 '13 at 16:51
Oops, sorry, missed it the first time. – Delyan Aug 01 '13 at 17:38

score 3 · Answer 2 · answered Jul 30 '13 at 20:30

3

I believe it wont leak but to be sure you need to test it. As talkol said, you should use Eclipse MAT to analyse this issue. There is a good guide by vogel here and a good guide on the Android blog here. Create and close a bunch of dialogs and see if it makes a difference.

On a side note why do you use ft.close() instead of prev.dismiss() in your showDialogFragment() method. The correct way of closing dialogs is dismiss().

answered Jul 30 '13 at 20:30

Warpzit

27,966
19
103
155

I do not use ft.close(). I use ft.remove() to remove from back stack. – Nulldevice Aug 02 '13 at 00:04

Backstack and memory leakage

2 Answers2

Linked