How to manage data in an offline Android app in kotlin?-CodePudding

I want to make an android app that works offline. For the data part, I want to have some data in a json file, and whenever my app is open firstly that JSON file is fetched, and from the fetched data I want to make tables entries in android room database(offline). So that, let say if user liked some quotes, then i can change the state of that quote as liked in room db, and when user clicked on Liked Quotes navigation, I can show those offline stored quotes which were liked (OfCourse when user delete the app that data will be lost). The problem I'm facing is where to fetch that data file and create entries in room db. If I do this in onCreate() then whenever user will open this app the duplicate entries will be created everytime. How to make those entries only ones?

CodePudding user response：

There's several ways to do it. One way is to include a random UUID in each element, and make that column in the DB have a UNIQUE constraint. Then re-adding it will fail (alternatively you can use an UPSERT and then it will automatically update the data in case the data changed).

Another way is to just not process the file if it already exists in onCreate. Your logic can be

if(network_exists) {
   copy_file_from_network()
}
else if(json file exists) {
   return
}
else {
  copy_file_from_assets()
}
process_json_file()

Actually I can see a good argument for doing both- that way if there are updates to existing rows you process them, but if there's no new data you don't waste your time.

As for a good place to put this- I'd be running this during your splash screen if you have one, so the user has an indication that you may be processing for a while.

CodePudding user response：

try using SQLite Database

https://developer.android.com/training/data-storage#db and https://documentation.alphasoftware.com/pages/HowTo/PhoneGap/SQLite.xml