PreferencesDelegate

Android SharedPreference delegate with kotlin flow

How to use

Create some preference class

class SomePreferences (
    private val context: Context
) {
    companion object {
        private const val SOME_KEY = "SOME_KEY"
    }

    private val somePref =
        context.getSharedPreferences("SomePreference", Context.MODE_PRIVATE)

  //The place for preferences delegates

}

1. Use for simple value

var someValue: String by PreferencesDelegate<String, String>(
        preferences = userPref,
        name = SOME_KEY,
        defValue = ""
    )

2. Use for object

var someObject: SomeObject? by PreferencesDelegate<SomeObject?, String>(
        preferences = userPref,
        name = "SOME_KEY",
        defValue = null,
        onDifficultTypeTransform = {   // Transform the object to a string to write to preferences
            it?.let {
                Gson().toJson(someObject)
            } ?: ""
        },
        onPrimitiveTypeTransform = {   // Transform the string back to an object
            if (it.isEmpty()) {
                null
            } else {
                Gson().fromJson(it, SomeObject::class.java)
            }
        }
    )

3. Use with kotlin flow

private val _someValueFlow = MutableSharedFlow<String>(replay = 1)

/**
 * Returns the flow.
 */
val someValueFlow: SharedFlow<String> = _usersFlow

var someValue: String by PreferencesDelegate<String, String>(
        preferences = userPref,
        name = SOME_KEY,
        defValue = "",
        prefFlow = _someValueFlow
    )

Sample

Download the project to see an sample of using PreferencesDelegate + RecyclerView + user list + flow

To get a Git project into your build

Add it in your root build.gradle at the end of repositories

allprojects {
	repositories {
		...
		maven { url 'https://jitpack.io' }
	}
}

Add the dependency

dependencies {
	implementation 'com.github.AndroidLab:PreferencesDelegate:Tag'
}