Why can we not pass a Serializable object to NavArguments?

Question

As I see in NavType docs, there is a sub-type called NavType.SerializableType which:

Is used for Serializable NavArguments.

The SerializableType's class constructor takes an argument of type Class<D?>? which should be a:

class that is a subtype of Serializable.

Now, I have the following class:

data class Product (
    var key: String? = null,
    //Other 15 different fields.
): Serializable

Here is how the NavHost looks like:

NavHost(
    navController = navController,
    startDestination = "Products"
) {
    composable(
        route = "Products"
    ) {
        ProductsScreen(
            navController = navController
        )
    }
    composable(
        route = "Product/{product}",
        arguments = listOf(
            navArgument("product") {
                type = NavType.SerializableType(Product::class.java)
            }
        )
    ) {
        val product = navController.previousBackStackEntry?.arguments?.getSerializable("product") as Product
        ProductScreen(
            navController = navController,
            product = product
        )
    }

And I navigate from inside the start destination (Products screen) to (Product screen) using inside the :

navController.currentBackStackEntry?.arguments?.putSerializable("product", product)
navController.navigate("Product/${product}")

I get a crash with this errror:

Serializables don't support default values.

However, if I change the above by removing /{product}:

NavHost(
    navController = navController,
    startDestination = "Products"
) {
    composable(
        route = "Products"
    ) {
        ProductsScreen(
            navController = navController
        )
    }
    composable(
        route = "Product",
        arguments = listOf(
            navArgument("product") { 
                type = NavType.SerializableType(Product::class.java)
            }
        )
    ) {
        val product = navController.previousBackStackEntry?.arguments?.getSerializable("product") as Product
        ProductScreen(
            navController = navController,
            product = product
        )
    }

And navigate as explained here:

navController.currentBackStackEntry?.arguments?.putSerializable("product", product)
navController.navigate("Product")

I get:

java.lang.IllegalArgumentException: Navigation destination that matches request NavDeepLinkRequest{ uri=android-app://androidx.navigation/Product } cannot be found in the navigation graph NavGraph(0x0) startDestination={Destination(0xb543811) route=Products}

How can I add a Serializable object of type Product to NavArguments and get back correctly? I don't want to transform the object to JSON String. Is this even possible?

the Jetpack Navigation team said that this is "just like the web", and therefore this is by design, and serialization to JSON (or similar format such as a byte array represented as base64) is unavoidable, and that you should URL-encode any strings because `&` or `/` or `$` breaks the nav args parser. You can define "custom parser strategy" but it will still rely on serialization to JSON (as is shown in their official docs and example). — EpicPandaForce, Jan 12 '22 at 14:40
@EpicPandaForce Thanks for commenting. So if you say that transforming the `Product` object into JSON **cannot** be avoided, then I'll go ahead with that. It's not what I want, but perhaps, that's the way it is... — Joan P., Jan 12 '22 at 14:44
Yeah, it's unfortunate, there is also docs on it here: https://developer.android.com/guide/navigation/navigation-kotlin-dsl#custom-types — EpicPandaForce, Jan 12 '22 at 14:48
@JoanP. I'd advice to avoid Jetpack Navigation alltogether. Use fragments as before, or if you really want to stay compose-only - use Voyager — Jakoss, Jan 12 '22 at 15:39
You shouldn't be passing a `Product` as an argument in *any* case: you should be passing the ID of your product, just like you would if you were building a RESTful website (where putting your entire model object in the URL is just as odd of a use case). Where is your `ProductRepository` that both destinations use as an observable single source of truth? — ianhanniballake, Jan 12 '22 at 17:05
@ianhanniballake I don't want to stop using Jetpack Navigation as Jakoss suggested. However, it's weird that I cannot send a Serializable object between screens. And yes, I can only send the product ID, but that means that I have to create another database call, in order to request that product. But that is actually not necessary, since I already have all the data inside the object that was clicked. That object I want to be passed to the next screen. It's also true I can send the value of each field separately, but there are some many of them. It's a pain to do that. — Joan P., Jan 13 '22 at 09:16
@ianhanniballake Is converting the `Product` object to `GSON` the only solution for this use-case? Thanks — Joan P., Jan 13 '22 at 09:16
@JoanP. Voyager is alternative navigation library, that makes use of kotlin types instead of relying on urls like Jetpack Navigation (https://github.com/adrielcafe/voyager). It's pragmatic, works like expected. As to sending objects - googlers seems to ignore the fact that we don't want to create a special table just to be able to pass object with 2-3 fields to another screen. We've tried that conversation, no luck there — Jakoss, Jan 13 '22 at 09:30
my Android app is not a RESTful web page, so I don't see why such limitations would need to apply. At this rate, we might also "serialize JSON to session storage I mean shared preferences" for data sharing soon. Anyways, if you use the library `Compose-Destinations`, they generate code that converts serializable/parcelable to Base64 and back. https://github.com/raamcosta/compose-destinations/blob/95d6154f932751703ec424ab968491d9dee6b7ad/compose-destinations/src/main/java/com/ramcosta/composedestinations/navargs/serializable/DefaultSerializableNavTypeSerializer.kt#L17-L23 — EpicPandaForce, Jan 13 '22 at 11:10
@EpicPandaForce After hours, and hours of research, I understand now why are you so angry on this type of navigation :| But hopefully, this will change, so we can have a way to simply pass a Serializable object to another screen. — Joan P., Jan 13 '22 at 11:17

Why can we not pass a Serializable object to NavArguments?

0 Answers0

Linked