Serializable in Kotlin

Question

In my Android app, I had a TreeMap that I could happily add to the Bundle , for example

 bundle.putSerializable("myHappyKey", myHappyTreeMap); 

but now when I port my application to Kotlin, Android Studio complains that Serializable! is required Serializable! but instead he finds Map .

How can I handle this?

EDIT The warning seems to disappear if I drop the card on Serializable . Is it so?

EDIT 2 I declare and initialize myHappyTreeMap as

 var myHappyTreeMap: Map<Int, Double> = mapOf() 

The documentation says that maps initialized with mapOf() are serializable. If the documents say so ...

Answer 1

TreeMap and various other Map implementations implement Serializable , but the Map interface itself does not extend Serializable .

I see several options:

• Make sure that myHappyTreeMap not just a Map , but a TreeMap or some other Map subtype that extends / implements Serializable . eg:.

   val myHappyTreeMap: TreeMap = ... 

• Copy your Map instance as Serializable (recommended only if you know the type of Map instance implements Serializable , otherwise you will get a ClassCastException ). eg:.

   bundle.putSerializable("myHappyKey", myHappyTreeMap as Serializable) 

• Check your Map instance, and if it is not Serializable , then create a copy of it using the Map implementation. eg:.

   bundle.putSerializable("myHappyKey", when (myHappyTreeMap) { is Serializable -> myHappyTreeMap else -> LinkedHashMap(myHappyTreeMap) })