Changing local variable from anonymous nested inner class

Question

I need to return an object that was set in methodB(), I have tried a lot and searched also :

interface A{}
interface B{}

class Main{
  Object method(){
     Object o;

     new A(){
        methodA(){
            new B(){
                methodB(){
                    // how to use setters of o here?
                }
            }        
        }
    }

    return o;// o should contain the values set in methodB()
  }
}

My actual code

  public ImageUtil saveImagetoStorage() {
    final ImageUtil imageUtil[] = new ImageUtil[1];

    filepath.putFile(mPublishedImageUri).addOnCompleteListener(new OnCompleteListener<UploadTask.TaskSnapshot>() {
        @Override
        public void onComplete(@NonNull final Task<UploadTask.TaskSnapshot> task) {

                UploadTask uploadTask = FirebaseUtil.sStorageReference.child(thumbs)
                        .child(randomName + ".jpg").putBytes(thumbData);

                uploadTask.addOnSuccessListener(new OnSuccessListener<UploadTask.TaskSnapshot>() {
                    @Override
                    public void onSuccess(UploadTask.TaskSnapshot taskSnapshot) {

                        String downloadthumbUri = taskSnapshot.getDownloadUrl().toString();
                        imageUtil[0]=new ImageUtil();
                        imageUtil[0].setImgUrl(downloadUri);
                        imageUtil[0].setImgThumb(downloadthumbUri);
                    }
                });
        }
    });
    return imageUtil[0];
}

Am I missing anything? Thanks in advance.

where are `methodA()` and `methodB()` from ? Abstrat from A and B ? or inteface ? — azro, May 19 '18 at 21:25
correct @azro, those A and B are implementations of Interfaces. — GN Reddy, May 19 '18 at 21:28
o can be final and we can set it in methodB() @markspace, but when I return o, they are becoming null. — GN Reddy, May 19 '18 at 21:34
Your `saveImagetoStorage` method returns *before* the `onSuccess` method executes. Also, the `onSuccess` method will be executed by another thread, so your code needs to be made thread-safe too. Re-think the sequence of events. You can't return an `ImageUtil` before the download completes, and you don't wait for completion of the `UploadTask` task. — Andreas, May 19 '18 at 21:59
Just looking at your "actual code" I think perhaps `imageUtil[0]` is `null` because the downloading hasn't finished yet. It's asynchronous. — markspace, May 19 '18 at 21:59

Andreas · Answer 1 · 2018-05-19T22:00:16.647

1

Disclaimer: This answer was written before "actual code" was added to the question.

You can't, because o must be effectively final, whether you declare it so or not.

One way to get around that is to change code to

Object[] o = new Object[1];

new A() {
    methodA() {
        new B() {
            methodB() {
                o[0] = ...
            }
        }
    }
}

return o[0];

Of course, that won't work either unless you actually call methodB before reaching the return o[0] statement.

edited May 19 '18 at 22:00

answered May 19 '18 at 21:37

Andreas

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@GNReddy Define "did not work" (see [why “It’s not working” is not helpful](http://idownvotedbecau.se/itsnotworking/)). If you mean the returned value is `null`, then **(re)read the sentence at the end of the answer**. – Andreas May 19 '18 at 21:55

score 0 · Answer 2 · answered May 19 '18 at 22:10

Your method needs to wait for the file upload to complete.

Since there are two asynchronous calls involved, one way to do this is to use a CompletableFuture.

public ImageUtil saveImagetoStorage() {
    final CompletableFuture<ImageUtil> futureImageUtil = new CompletableFuture<>();

    filepath.putFile(mPublishedImageUri).addOnCompleteListener(new OnCompleteListener<UploadTask.TaskSnapshot>() {
        @Override
        public void onComplete(@NonNull final Task<UploadTask.TaskSnapshot> task) {

            UploadTask uploadTask = FirebaseUtil.sStorageReference.child(thumbs)
                    .child(randomName + ".jpg").putBytes(thumbData);

            uploadTask.addOnSuccessListener(new OnSuccessListener<UploadTask.TaskSnapshot>() {
                @Override
                public void onSuccess(UploadTask.TaskSnapshot taskSnapshot) {

                    String downloadthumbUri = taskSnapshot.getDownloadUrl().toString();
                    ImageUtil imageUtil = new ImageUtil();
                    imageUtil.setImgUrl(downloadUri);
                    imageUtil.setImgThumb(downloadthumbUri);
                    futureImageUtil.complete(imageUtil); // Make imageUtil available
                }
            });
        }
    });
    return futureImageUtil.get(); // wait (potentially forever) until image available
}

You should of course never assume asynchronous operations can fail, so you need to add failure-handlers too, otherwise the get() will wait forever, since complete(...) is never called.

Changing local variable from anonymous nested inner class

2 Answers2