Kotlin Singleton Application Class

Question

So in android i want to make my application class a singleton.

Making it like this:

object MyApplication: Application(){} 

won't work. Following erros is thrown at runtime:

java.lang.IllegalAccessException: private com....is not accessible from class android.app.Instrumentation. 

Doing this is also not possible:

class MyApp: Application() {      private val instance_: MyApp      init{         instance_ = this     }      override fun onCreate() {         super.onCreate()         if (BuildConfig.DEBUG) {             Timber.plant(Timber.DebugTree());         }     }      companion object{         fun getInstance() = instance_              } } 

So how can i get an instance of my application class everywhere in my app, would like to use MyApp.instance() instead of (applicationContext as MyApp).

Also an explanation why i want this: I have classes in my app, for example, a SharedPreference Singleton which is initialised with a context, and as its a singleton, can't have arguments.

Answer 1

You can do the same thing you would do in Java, i.e. put the Application instance in a static field. Kotlin doesn't have static fields, but properties in objects are statically accessible.

class MyApp: Application() {      override fun onCreate() {         super.onCreate()         instance = this     }      companion object {         lateinit var instance: MyApp             private set     } } 

You can then access the property via MyApp.instance.