在Firebase数据库中获取String值的正确方法是什么

Question

Good day!

I am having a problem in displaying the images.

Here is the code snippet:

final ArrayList<String> imgURLs = new ArrayList<>();

    String userUid = FirebaseAuth.getInstance().getCurrentUser().getUid();
    FirebaseDatabase firebaseDatabase = FirebaseDatabase.getInstance();
    DatabaseReference databaseReference = firebaseDatabase.getReference(userUid).child("WARDROBE");
    databaseReference.addListenerForSingleValueEvent(new ValueEventListener() {
        @Override
        public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
            for(DataSnapshot snapshot : dataSnapshot.getChildren()){
                imgURLs.add(snapshot.getValue().toString());
                Toast.makeText(Profile.this, (String)snapshot.getValue(), Toast.LENGTH_SHORT).show();
            }
        }

        @Override
        public void onCancelled(@NonNull DatabaseError databaseError) {

        }
    });

    imgURLs.add("https://assets.academy.com/mgen/58/20083458.jpg?is=500,500");
    imgURLs.add("https://assets.academy.com/mgen/61/20057861.jpg?is=500,500");
    imgURLs.add("https://assets.academy.com/mgen/65/20082765.jpg?is=500,500");
    imgURLs.add("https://ir0.mobify.com/project-burlington/1082/1922/https://cdn.burlingtoncoatfactory.com/FileLibrary/f4ee340d60f0421a8020b8ae05e6f36e/7854_SquareThumbnail.jpeg");
    imgURLs.add("https://qph.fs.quoracdn.net/main-qimg-5d9f95691aca6affb53dcae7fbeba61f-c");
    imgURLs.add("https://images.mattel.com/scene7//wcsstore/MattelCAS/05BUN14_Comfy_Space_PJs_and_Slippers_Girls_FMD28_FMD29_1?$ossmallindex$&storeId=10651&SKU=05BUN14");

My problem resides in the onDataChange. My target is to display the images I saved in the Firebase storage but first of all I created a Firebase Database with a child "Images" in it. It must be a list of all https://.

I created an example first. I created a sample with child Images. In it are the urls I added manually in my java code - which I got over the internet. In Toast view the displayed string are the same as the urls I added manually in my java code. The problem is that it doesnt display the images from the URL in the firebase, it displays only the manually added java urls.

What makes this happen?

Answer 1

Okay, I have had a mistake.

The solution relies in onDataChange. So, after the activity opened, the code is run from top to bottom and let's say the databaseReference was executed and onDataChange still takes time to take effect until there are changes.

so at the very bottom of my code there is setUpImageView() method and it was executed first before the onDataChange was finished. As a result, it doesnt display the image as wanted :D