Navigation component, argument type and sealed class

If you use Navigation component you are familiar with code snippet like this:


<navigation>
....
    <fragment ...>
        <argument
            android:name="name"
            app:argType="string" />
    </fragment>
....

In here we have navigation, fragment and fragment has one String argument called „name”. All supported argument types can be found in documentation. Navigation component also supports custom parcelable types.

Subclass of a sealed class


sealed class Animal {
    ....
    @Parcelize
    data class Cat(val name: String) : Animal(), Parcelable
}

But what to do if we have sealed class and we want to specify only one subclass as argument type? For example, we have fragment which only takes Cat class as argument.

Probably you would to do it as normal:


<argument
    android:name="cat"
    app:argType="com.example.app.Animal.Cat" />

but you would encounter ClassNotFoundException. So what’s wrong?

Solution

Actually, the problem is in „Animal (dot) Cat” part. You have to replace dot with $ sign.


<argument
    android:name="cat"
    app:argType="com.example.app.Animal$Cat" />

Now everything should look good and work. There is no info about that in documentation so please be aware! Also if you have another nested sealed class in sealed class, use $ as separator.