我应该何时将数据保存到我的Android应用程序中的SQLite中？

Question

I was watching one of Google's app reviews and they were ripping into this guys' app who had a save button and if you didn't save before leaving it would pop up a dialog. They said an android app should just save and not bother the user.

I have a fragment and have several fields and need to determine when to save the data into a SQLite database. I was thinking of saving on exit of each field via the onFocusChange event? Or maybe that's too often? Perhaps the fragment's onPause event? When should I save (specific event please)?

Answer 1

Fragments are much like the activities when it comes to lifecycle. So onPause() is the right place to save persistent state, later after onPause() it may be too late and can lead to data loss. Google recommends to use "edit in place" user model. That is, save edits immediately, in your case saving data when the user switches between input fields is good approach. This prevents data loss if your Fragment / Activity is killed by the system. If you think it can take few seconds to save your state you can use also IntentService in onPause() . In your scenario I would execute AsyncTask updating your database when the user switches between input fields, maybe with detecting if change really occured.

Edit: If you are using ContentProvider than consider using AsyncQueryHandler instead of AsyncTask .

Answer 2

public void onDestroy()

Called when the fragment is no longer in use. This is called after onStop() and before onDetach().

I would probably use that; it would mean the user is done using that fragment. I don't know of any cons in doing it that way or your way.