We often need to track our model class over the application lifecycle. We can do this easily using below class. No extra code needed. It's save the data in memory and retrieve from there.

ModelPersistHelper.kt

import android.content.Context
import android.util.Log
import com.google.gson.Gson
import java.io.File

class ModelPersistHelper<T>(
    private val context: Context,
    private val gson: Gson,
    private val clazz: Class<T>
) {
    private val jsonPath = context.filesDir.absolutePath + "/${clazz.simpleName}.json"

    suspend fun obtain(): T? {
        return try {
            val inputTxt = File(jsonPath).bufferedReader().use { it.readText() }
            gson.fromJson(inputTxt, clazz)
        }catch (ex:Exception){
            return null
        }
    }

    suspend fun save(
        model: T,
        onSuccess: (() -> Unit)? = null,
        onError: ((Throwable) -> Unit)? = null
    ) {
        try {
            File(jsonPath).also {
                it.writeBytes(gson.toJson(model).toByteArray())
            }
            onSuccess?.invoke()
        } catch (ex: Exception) {
            onError?.invoke(ex)
        }
    }

    fun delete() {
        File(jsonPath).delete()
    }

}