CODEWITHSUNDEEP
androidsharedpreferenceskotlinpersistencemutable
Julian Torregrosa
Julian Torregrosa

Reputation: 861

Kotlin - Persist MutableList on SharedPreferences

I've been playing around with Kotlin for Android. I have a mutable list which is a list of objects. Now I want to persist them, but I don't know what's the best way to do it. I think it can be done with SharedPreferences but I don't know how to parse the objects to a plain format or something. The objects are actually coming from a data class, maybe that can be useful.

Thanks

Upvotes: 1

Views: 2688

Answers (5)

goofy
goofy

Reputation: 444

Feel free to use this Kotlin extension functions to store and edit your list to SharedPreferences. I think they are realy useful.

inline fun <reified T> SharedPreferences.addItemToList(spListKey: String, item: T) {
    val savedList = getList<T>(spListKey).toMutableList()
    savedList.add(item)
    val listJson = Gson().toJson(savedList)
    edit { putString(spListKey, listJson) }
}

inline fun <reified T> SharedPreferences.removeItemFromList(spListKey: String, item: T) {
    val savedList = getList<T>(spListKey).toMutableList()
    savedList.remove(item)
    val listJson = Gson().toJson(savedList)
    edit {
        putString(spListKey, listJson)
    }
}

fun <T> SharedPreferences.putList(spListKey: String, list: List<T>) {
    val listJson = Gson().toJson(list)
    edit {
        putString(spListKey, listJson)
    }
}

inline fun <reified T> SharedPreferences.getList(spListKey: String): List<T> {
    val listJson = getString(spListKey, "")
    if (!listJson.isNullOrBlank()) {
        val type = object : TypeToken<List<T>>() {}.type
        return Gson().fromJson(listJson, type)
    }
    return listOf()
}

Upvotes: 0

Marcel Skotnicki
Marcel Skotnicki

Reputation: 126

It is very easy to persist any data within SharedPreferences. All you need to do is get Gson implementation 'com.squareup.retrofit2:converter-gson:2.3.0' and then create class you would like to persist like this:

class UserProfile {

    @SerializedName("name") var name: String = ""
    @SerializedName("email") var email: String = ""
    @SerializedName("age") var age: Int = 10

}

and finally in your SharedPreferences

fun saveUserProfile(userProfile: UserProfile?) {
            val serializedUser = gson.toJson(userProfile)
            sharedPreferences.edit().putString(USER_PROFILE, serializedUser).apply()
        }


fun readUserProfile(): UserProfile? {
            val serializedUser = sharedPreferences.getString(USER_PROFILE, null)
            return gson.fromJson(serializedUser, UserProfile::class.java)
        }

Upvotes: 3

Norris Boateng
Norris Boateng

Reputation: 357

For lists it think using sqlite will provide you with better control of your data. Check out anko's sqlite wiki for more info.

Upvotes: 1

Hohenheim
Hohenheim

Reputation: 407

Shared Preferences are mostly used in storing data like settings or configs, it's not meant for storing large data though it can do it as long as you implement Parcable. If you think your data contained in your MutableList is large, best way is to make a database.

Upvotes: 0

HyunJin
HyunJin

Reputation: 336

You can also use Firebase too for data persistence, you can use SharedPreferences, but personally I find it more easy and comfortable using Firebase. I will leave a link here so you can take a look at disk persistence behavior of Firebase.
Hope this helps you!

Upvotes: 2

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