在活动之间进行切换时保存和还原RecyclerView

Question

I have HomeActivity contain recyclerView show data load from Firebase, but when click items and back HomeActivity then app reload data from Firebase. I want holder data when back HomeActivity (list data put into CustomAdapter).

Answer 1

If you are accessing the Homeactivity again via startActivity() , or calling finish() or onDestroy() in the Homeactivity There are 3 options:

1. You need to save the data in a database with the help of SqliteOpenHelper . Display data by extracting it from the database instead of Firebase
2. Save data in cache. Cached data can be re-accessed without storing it. Cache duration and size would have to be determined by you.
3. Store data in a shared preference which can be accessed when the activity is opened again.

When using any of the three methods, you need to specify when the app should connect with firbase to get new data. You can set up a gcm notification to tell the app new data is available or schedule a time after which the app will try to check if new data is available and try to download it.

HomeActivity will by default be in the activityStack, so if a backpress is pressed in NextActivity, HomeActivity will open as such.

savedInstanceState works for configuration change (ie rotation etc.). You will need to override OnSaveInstanceState , to prevent OnCreate to from removing all the data. But if you are accessing the Homeactivity again via startActivity() , or calling finish() or onDestroy() inside HomeActivity then this data is lost.