如何在应用启动时预加载Firestore数据？

Question

I am building an app that tracks the location of nearby coffee shops and allows users to view each shop's available products. I am using firestore to store all of the data for each product and showcasing this data to the user through a recyclerview + firestoreRecyclerAdapter. It works. However, the product data loads really slowly. Taking several seconds or even minutes to load the recyclerview. Even after the recycler is fully loaded, this problem persists.

Now, I think that it's because he reads from the database are overloading the main UI thread. So I have tried to perform these reads in an asyncTask, but I can't pull values from the asyncTask since it outputs data after the activity has requested it. Giving me an error.

I have tried decreasing the amount of data that is pulled from firestore. But that doesn't help either.

I am thinking about trying to load all of the product data from firestore to shared preferences, internal storage, or a package of some kind while the app is starting up. That way requests don't need to be sent to the server. In this way, the server can serve as a way to update this data rather than continuously attempt to retrieve it.

However, I am lost on how to do this. How can a load firestore data say a custom object, save that list of custom objects to an array, then provide some way for this data to be loaded in and accessed later?

Answer 1

Firestore database has offline persistence enabled for mobile platforms by default. It means it saves loaded data and what you have queried in cache. Try to read this https://firebase.google.com/docs/firestore/manage-data/enable-offline . Also do not try to save your data in shared preferences, it is designed to contain small chunks of data stored in Key/Value pair. To be more specific, I think the performance problem is in your code.

I would suggest few things: move realization of your code to your activity/fragment - from your adapter.(Just create interfaces with which you can operate to open new activity/fragment/onClick something etc with your items in adapter)

I also highly suggest to use Livedata + ViewModel, it helped me a lot to deal with performance problems. Check out this blog https://firebase.googleblog.com/2017/12/using-android-architecture-components.html . It helped me to understand the principles and implement it in my code. Good Luck!