Widget service doesn’t wait for data before trying to populate collection

Question

Well it seems I'm stuck again. I have my widget half working and I think I know why it's failing but I have no idea how to fix it.

In my widget service class, in the onDataSetChanged() method I make a call to get my data (asynchronously). But the system makes a call to getCount() before the data is loaded and therefore returns 0 for the size and never calls getViewAt().

If I create some fake data inside onDataSetChanged() instead of calling to get the real data from Firebase then it will display just fine. So I know it works apart from this.

I've tried all sorts of things to get it to work but no luck. I don't want to make this into a really long question so I'll try to keep it simple. My question is how does the system know when the data is ready? There doesn't seem to be a method I can call to notify it that the data is now there.

I could be totally wrong but I think that's what the problem is. The onDataSetChanged() method doesn't wait and I have no way to tell it to.

What makes this more confusing is that in my mockDebug version of the app where I use fake static data it actually works, even with the asynchronous call. My conclusion is that it must be loading so fast that it's ready by the time getCount() is called. But even more confusing is that for a short while it was also working in the prodDebug version and then didn't and hasn't ever since. As far as I know I hadn't changed anything in that time. In any case this is the only explanation I've been able to come up with. The reason is because I can see either with the debugger or logging that getCount() is called before the data is loaded when I get the data from Firebase, causing it to fail, but it's called after the data is loaded if I use static data, allowing it to succeed.

How do I make it wait? Or is there something else I may be doing wrong?

Thanks.

Answer 1

Ok, solution number 2: convert the asynchronous calls into a synchronous call with CountDownLatch.

With this I can get all the data from inside onDataSetChanged() as I was originally trying to with just a couple extra lines of code.

So far I've been able to populate the widget list and also add data to it.

http://docs.oracle.com/javase/1.5.0/docs/api/java/util/concurrent/CountDownLatch.html

Sync version of async method