ArrayList resets itself

Question

I have an ArrayList of strings that I use to store image URLs. Inside a for loop, I add a value to the ArrayList each time but after the for loop, the ArrayList seems to reset itself.

for (int i = 0; i < imageUris.size(); i++) {
    imageFilePath = storageReference.child(imageUris.get(i).getLastPathSegment());

    StorageReference finalImageFilePath = imageFilePath;
    imageFilePath.putFile(imageUris.get(i)).addOnSuccessListener(taskSnapshot -> {
        finalImageFilePath.getDownloadUrl().addOnSuccessListener(uri -> {

            String imageUrl = uri.toString();
            imageUrls.add(imageUrl); // Here I'm adding to the ArrayList

            Log.d("test1", String.valueOf(imageUrls.size())); // the size is 1

        });
}


Log.d("test2", String.valueOf(imageUrls.size())); // the size is 0

EDIT:

I can't answer my own question so here is the solution (can see in comments): the problem here is that I update the list in an addOnSuccessListener, since this function works on another thread, the code keeps running, therefor it prints the list in it's first form (before adding urls to it).

You add to `imageUrls` in a success listener; but the final `Log.d` line is executed immediately. You need to wait until everything is successful. — Andy Turner, Mar 29 '21 at 13:41
As @Andy Turner the success listener is executed on another thread or in a later update tick of the main looper (After your method is already done). So the list is empty when you call 'Log.d("test2", String.valueOf(imageUrls.size()));' — IntoVoid, Mar 29 '21 at 13:43
`imageUrls` ArrayList would be local in your code and so resulting in this. — Swapnil Padaya, Mar 29 '21 at 13:48
@IdoBarnea - I suggest you either post the solution as an answer or delete the question if you think not useful to anyone in the future. — Arvind Kumar Avinash, Mar 29 '21 at 14:14

score 0 · Answer 1 · answered Mar 29 '21 at 14:10

0

Make sure your imageUrls variable instance variable not a local variable. If it is a local variable then keep it outside the specific method.

answered Mar 29 '21 at 14:10

Priyanka

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score 0 · Answer 2 · answered Mar 29 '21 at 14:25

0

maybe you put this array as local so before oncrate put this code ArrayList<String> imageUrls=new ArrayList<>(); now the variable is global and if you want ArrayList is saved until the application is closed just make array static

answered Mar 29 '21 at 14:25

Mohsen El Sayed

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ArrayList resets itself

2 Answers2