将包含不可序列化对象的 HashMap 传递给另一个 Fragment

Question

Here is my non Serializable class:

class Foo(val foo: String)

When I try to put it as an arguments it won't compile:

MainFragment().apply {
    arguments = Bundle().apply {
        val foo = Foo("foo!")
        putSerializable("key", foo) // compile error
    }
}

But If I put it into a HashMap then I can put the HashMap as an argument:

MainFragment().apply {
    arguments = Bundle().apply {
        val foo = Foo("foo!")
        val hashMap = hashMapOf("foo" to foo)
        putSerializable("key", hashMap) // compile
    }
}

And when I try to get Foo instance from the HashMap during Fragment creation, I'm expecting an error like NotSerializableException because Foo class is not serializable, but it works fine:

override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
    super.onViewCreated(view, savedInstanceState)
    val hashMap = arguments?.getSerializable("key") as HashMap<String, Foo> // unchecked cast warning
    Log.d(TAG, "${hashMap["foo"]?.foo}") // It works fine without an exception
}

And it survives during the configuration changes as well. Why?

Answer 1

Self answer

It turns out my app got the RuntimeException when the app goes to the background.

java.lang.RuntimeException: Parcel: unable to marshal value com.example.serializationsample.ui.main.Foo@378ca1e
    at android.os.Parcel.writeValue(Parcel.java:1799)
    ...
    at android.app.IActivityTaskManager$Stub$Proxy.activityStopped(IActivityTaskManager.java:5112)
    at android.app.servertransaction.PendingTransactionActions$StopInfo.run(PendingTransactionActions.java:145)
    at android.os.Handler.handleCallback(Handler.java:883)
    at android.os.Handler.dispatchMessage(Handler.java:100)
    at android.os.Looper.loop(Looper.java:237)
    at android.app.ActivityThread.main(ActivityThread.java:8154)
    at java.lang.reflect.Method.invoke(Native Method)
    at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:496)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1100)

I guess the actual serialization is happened by the ActivityManager when an app goes to the background but not the fragment creation or the configuration changes. Because the ActivityManager handles the serialized Bundle via IPC technique to take care of the process death and re-creation of an app.