Kotlin Android Library, that makes preference usage simple and fun.

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This library is younger brother of KotlinPreferences.

With PreferenceHolder, you can define different preference fields this way:

object Pref: PreferenceHolder() {
    var canEatPie: Boolean by bindToPreferenceField(true)

And use it this way:

if(Pref.canEatPie) //...

Here are other preference definition examples: (see full example and usage)

object UserPref: PreferenceHolder() {
    var canEatPie: Boolean by bindToPreferenceField(true)
    var allPieInTheWorld: Long by bindToPreferenceField(0)

    var isMonsterKiller: Boolean? by bindToPreferenceFieldNullable()
    var monstersKilled: Int? by bindToPreferenceFieldNullable()
    // Property with backup is reading stored value in the first usage, 
    // and saving it, in background, each time it is changed.
    var experience: Float? by bindToPropertyWithBackup(-1.0F) 
    var className: String? by bindToPropertyWithBackupNullable()

    // Any type can used if serializer is set. See: Gson serialization
    var character: Character? by bindToPreferenceFieldNullable()
    var savedGame: Game? by bindToPreferenceFieldNullable()

    // Single level collections are also supported if serializer is set. See: Gson serialization
    var longList: Map<Int, Long> by bindToPreferenceField(mapOf(0 to 12L, 10 to 143L))
    var propTest: List<Character>? by bindToPropertyWithBackupNullable()
    var elemTest: Set<Elems> by bindToPreferenceField(setOf(Elems.Elem1, Elems.Elem3))

There must be application Context added to PreferenceHolder companion object. Example:

class App : Application() {

    override fun onCreate() {

It it suggested to do it in project Application class. As an alternative, there can also be added PreferenceHolderApplication as an name in application in AndroidManifest: (example)


Unit testing components

Library also include test mode:

PreferenceHolder.testingMode = true

When it is turned on, then all properties are acting just like normal properties without binding to preference field. This allows to make unit tests to presenters and use cases that are using instance of PreferenceHolder.


To add PreferenceHolder to the project, add in build.gradle file:

dependencies {
    compile "com.marcinmoskala.PreferenceHolder:preferenceholder:1.5"

While library is located on JitPack, remember to add on module build.gradle (unless you already have it):

repositories {
    maven { url '' }

Gson serialization

To use Gson serializer, we need to add following dependency:

dependencies {
    compile "com.marcinmoskala.PreferenceHolder:preferenceholder-gson-serializer:1.5"

And specify GsonSerializer as PreferenceHolder serializer:

PreferenceHolder.serializer = GsonSerializer(Gson())

Since then, we can use all types, even one not supported by SharedPreference (like custom objects Character and Game, or collections)


Copyright 2017 Marcin MoskaƂa

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
See the License for the specific language governing permissions and
limitations under the License.
compile "com.github.MarcinMoskala:PreferenceHolder:1.5"

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