rememberSaveable needs default saver [180042685]

Fixed

Bug

Status Update

No update yet.

Description

co...@gmail.com

created issue #1

Feb 11, 2021 10:33PM

Component used: Compose Version used: 1.0.0-alpha12 Devices/Android versions reproduced on: Pixel 4 Android 11

The recommended code to replace savedInstanceState{ 0 } is rememberSaveable { mutableStateOf(0) }

However, I've found this causes a crash whenever the app is minimized.

The exception thrown is

java.lang.RuntimeException: Parcel: unable to marshal value androidx.compose.runtime.SnapshotMutableStateImpl@5a847c2

After digging into the code I believe this is caused by the special version of rememberSaveable for MutableState objects doesn't have a default saver parameter so the normal version is used which doesn't know how to save a MutableState.

I think changing the rememberSaveable definition from

@Composable
fun <T> rememberSaveable(
    vararg inputs: Any?,
    stateSaver: Saver<T, out Any>,
    key: String? = null,
    init: () -> MutableState<T>
): MutableState<T> = rememberSaveable(
    inputs,
    saver = mutableStateSaver(stateSaver),
    key = key,
    init = init
)

@Composable
fun <T> rememberSaveable(
    vararg inputs: Any?,
    stateSaver: Saver<T, out Any> = autoSaver(),
    key: String? = null,
    init: () -> MutableState<T>
): MutableState<T> = rememberSaveable(
    inputs,
    saver = mutableStateSaver(stateSaver),
    key = key,
    init = init
)

would fix this.

Comments

da...@gmail.com <da...@gmail.com> #2Feb 11, 2021 10:57PM

It doesn't fix it (you can try it yourself by calling rememberSaveable(stateSaver = autoSaver()) { mutableStateOf(0) })

It seems that mutableStateSaver() will save a SnapshotMutableStateImpl which can't be save in a bundle. The responsible code seems to be this

co...@gmail.com <co...@gmail.com> #3Feb 12, 2021 01:08AM

Alright I think I have a working solution.

@Composable
fun <T : Any> rememberSaveable(
    vararg inputs: Any?,
    stateSaver: Saver<T, out Any> = autoSaver(),
    key: String? = null,
    init: () -> MutableState<T>
): MutableState<T> = rememberSaveable(
    *inputs,
    saver = mutableStateSaver(init, stateSaver),
    key = key,
    init = init
)

private fun <T : Any, K : Any> mutableStateSaver(
    init: () -> MutableState<T>,
    inner: Saver<T, K>
) =
    Saver<MutableState<T>, K>(
        save = { state ->
            with(inner) { save(state.value) }
        },
        restore = { value ->
            init().also { it.value = inner.restore(value)!! }
        }
    )

The original rememberSaveable also forgot to add the * operator to the inputs value it was passing which makes it initialize the value every time.

I wasn't sure about the inner.restore(value)!! line and if the type parameters need to be changed or something to be able to remove the !!.

cl...@google.com <cl...@google.com> Feb 12, 2021 11:50AM

Assigned to an...@google.com.

an...@google.com <an...@google.com> #4Feb 12, 2021 03:02PM

Thanks for reporting it!

The API we currently have is correct and we do want rememberSaveable { mutableStateOf(0) } to work automatically however it is indeed a bug that this not happens in some cases. I guess you are using Compose Navigation library and call rememberSaveable inside on of the navigation destinations?

The simple temporary workaround is using:

rememberSaveable(saver = stateSaver()) { mutableStateOf(0) }

where stateSaver() is

fun <T> stateSaver() = Saver<MutableState<T>, Any>(
    save = { state -> state.value ?: "null" },
    restore = { value ->
        @Suppress("UNCHECKED_CAST")
        mutableStateOf((if (value == "null") null else value) as T)
    }
)

da...@gmail.com <da...@gmail.com> #5Feb 12, 2021 06:23PM

Good guess I'm indeed using navigation. The above workaround fixes it for me.

co...@gmail.com <co...@gmail.com> #6Feb 12, 2021 09:31PM

I am also using navigation.

The provided workaround doesn't restore the mutation policy of the MutableState object.

an...@google.com <an...@google.com> #7Feb 16, 2021 05:33PM

This one will save/restore the mutation policy as well:

    fun <T> stateSaver() = listSaver<MutableState<T>, Any>(
        save = { state ->
            listOf(
                state.value ?: "null",
                when ((state as SnapshotMutableState).policy) {
                    structuralEqualityPolicy<T>() -> 0
                    referentialEqualityPolicy<T>() -> 1
                    neverEqualPolicy<T>() -> 2
                    else -> throw IllegalStateException("Mutation policy is not supported")
                }
            )
        },
        restore = {
            val value = it[0]
            val policy = when (it[1]) {
                0 -> structuralEqualityPolicy<T>()
                1 -> referentialEqualityPolicy<T>()
                else -> neverEqualPolicy<T>()
            }
            @Suppress("UNCHECKED_CAST")
            mutableStateOf((if (value == "null") null else value) as T, policy)
        }
    )

co...@gmail.com <co...@gmail.com> #8Feb 17, 2021 03:48PM

What did you think of my solution that uses the init() function passed to the rememberSaveable()? This prevents needing to save anything about the policy and would support any mutation policy.

I'm not sure if the docs say anywhere that the init() function will only be called the first time and using it to restore the state would be incorrect.

I've been using my workaround fairly extensively and it has been great.

an...@google.com <an...@google.com> #9Feb 17, 2021 03:51PM

Yes, this also works. Feel free to use it until we provide the correct fix in the library

ap...@google.com <ap...@google.com> #10Feb 24, 2021 05:47PM

Marked as fixed.

Project: platform/frameworks/support
Branch: androidx-main

commit dd000ea5e6eb3a8f07b869595ca62aa2fb781d12
Author: Andrey Kulikov <andreykulikov@google.com>
Date: Mon Feb 22 19:42:13 2021

Fix for broken rememberSaveable { mutableStateOf(0) } with navigation-compose

Previously we were converting MutableState into a parcelable structure only for a direct child of the saving list. It was incorrect as SaveableStateHolder used in navigation is wrapping the state of the screen as a value into a Map. Now we will recursively iterate through List/Maps and covert all inner MutableState objects.

Fixes: 180042685
Fixes: 180701630
Test: new tests in ActivityRecreationTest
Relnote: Fix for broken rememberSaveable { mutableStateOf(0) } when used inside a destination of navigation-compose.
Change-Id: I1312b5b210dde32250945d164a2f3a1b574cb0a8

M compose/runtime/runtime-saveable/src/androidAndroidTest/AndroidManifest.xml
M compose/runtime/runtime-saveable/src/androidAndroidTest/kotlin/androidx/compose/runtime/saveable/ActivityRecreationTest.kt
M compose/runtime/runtime-saveable/src/commonMain/kotlin/androidx/compose/runtime/saveable/RememberSaveable.kt
M compose/ui/ui/src/androidMain/kotlin/androidx/compose/ui/platform/DisposableSaveableStateRegistry.android.kt

https://android-review.googlesource.com/1599261

an...@google.com <an...@google.com> #11Feb 24, 2021 06:12PM

Thanks for reporting. The fix will be released in beta02

ba...@gmail.com <ba...@gmail.com> #12Aug 3, 2021 04:14PM

It looks like this bug has been re-introduced in 1.0

an...@google.com <an...@google.com> #13Aug 3, 2021 04:38PM

Can you share more details?

el...@kroger.com <el...@kroger.com> #14Jan 24, 2023 07:08PM

Hi I am seeing this same issue using navigation-compose version 2.5.2, we tried the suggestions from this thread from 2021 but they did not work. The stack trace looks like this:

java.lang.RuntimeException: Parcelable encountered IOException writing serializable object (name = [Landroidx.compose.runtime.MutableState;)
    at android.os.Parcel.writeSerializable(Parcel.java:1833)
    at android.os.Parcel.writeValue(Parcel.java:1780)
    at android.os.Parcel.writeList(Parcel.java:1045)
    at android.os.Parcel.writeValue(Parcel.java:1729)
    at android.os.Parcel.writeMapInternal(Parcel.java:896)
    at android.os.Parcel.writeMap(Parcel.java:878)
    at android.os.Parcel.writeValue(Parcel.java:1694)
    at android.os.Parcel.writeMapInternal(Parcel.java:896)
    at android.os.Parcel.writeMap(Parcel.java:878)
    at android.os.Parcel.writeValue(Parcel.java:1694)
    at android.os.Parcel.writeList(Parcel.java:1045)
    at android.os.Parcel.writeValue(Parcel.java:1729)
    at android.os.Parcel.writeArrayMapInternal(Parcel.java:928)
    at android.os.BaseBundle.writeToParcelInner(BaseBundle.java:1584)
    at android.os.Bundle.writeToParcel(Bundle.java:1253)
    at android.os.Parcel.writeBundle(Parcel.java:997)
    at android.os.Parcel.writeValue(Parcel.java:1698)
    at android.os.Parcel.writeArrayMapInternal(Parcel.java:928)
    ...
    at android.app.IActivityTaskManager$Stub$Proxy.activityStopped(IActivityTaskManager.java:4505)
    at android.app.servertransaction.PendingTransactionActions$StopInfo.run(PendingTransactionActions.java:145)
    at android.os.Handler.handleCallback(Handler.java:883)
    at android.os.Handler.dispatchMessage(Handler.java:100)
    at android.os.Looper.loop(Looper.java:214)
    at android.app.ActivityThread.main(ActivityThread.java:7356)
    at java.lang.reflect.Method.invoke(Native Method)
    at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:492)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:930)
 Caused by: java.io.NotSerializableException: androidx.compose.runtime.ParcelableSnapshotMutableState
    at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1240)
    at java.io.ObjectOutputStream.writeArray(ObjectOutputStream.java:1434)
    at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1230)
    at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:354)
    at android.os.Parcel.writeSerializable(Parcel.java:1828)
    at android.os.Parcel.writeValue(Parcel.java:1780) 
    at android.os.Parcel.writeList(Parcel.java:1045) 
    at android.os.Parcel.writeValue(Parcel.java:1729) 
    at android.os.Parcel.writeMapInternal(Parcel.java:896) 
    at android.os.Parcel.writeMap(Parcel.java:878) 
    ...

an...@google.com <an...@google.com> #15Jan 24, 2023 07:19PM

ParcelableSnapshotMutableState is Parcelable, not sure how it is possible that it can't be written to Parcel.

If you can file a new bug with the reproducible code sample we will be able to take a look

ga...@gmail.com <ga...@gmail.com> #16Jun 7, 2023 09:41AM

Hey, I'm also having same kinda problem:

E FATAL EXCEPTION: main
Process: com.example.animeapp, PID: 12273
java.lang.RuntimeException: Parcel: unable to marshal value Color(0.83137256, 0.75686276, 0.8156863, 1.0, sRGB IEC61966-2.1)
at android.os.Parcel.writeValue(Parcel.java:1885)
at android.os.Parcel.writeList(Parcel.java:1092)
at android.os.Parcel.writeValue(Parcel.java:1832)
at android.os.Parcel.writeList(Parcel.java:1092)
at android.os.Parcel.writeValue(Parcel.java:1832)
at android.os.Parcel.writeMapInternal(Parcel.java:943)
at android.os.Parcel.writeMap(Parcel.java:925)
at android.os.Parcel.writeValue(Parcel.java:1797)
at android.os.Parcel.writeMapInternal(Parcel.java:943)
at android.os.Parcel.writeMap(Parcel.java:925)
at android.os.Parcel.writeValue(Parcel.java:1797)
at android.os.Parcel.writeList(Parcel.java:1092)
at android.os.Parcel.writeValue(Parcel.java:1832)
at android.os.Parcel.writeArrayMapInternal(Parcel.java:975)
at android.os.BaseBundle.writeToParcelInner(BaseBundle.java:1620)
at android.os.Bundle.writeToParcel(Bundle.java:1303)
at android.os.Parcel.writeBundle(Parcel.java:1044)
at android.os.Parcel.writeValue(Parcel.java:1801)
at android.os.Parcel.writeArrayMapInternal(Parcel.java:975)
at android.os.BaseBundle.writeToParcelInner(BaseBundle.java:1620)
at android.os.Bundle.writeToParcel(Bundle.java:1303)
at android.os.Parcel.writeBundle(Parcel.java:1044)
at android.os.Parcel.writeValue(Parcel.java:1801)
at android.os.Parcel.writeArrayMapInternal(Parcel.java:975)
at android.os.BaseBundle.writeToParcelInner(BaseBundle.java:1620)
at android.os.Bundle.writeToParcel(Bundle.java:1303)
at android.app.IActivityTaskManager$Stub$Proxy.activityStopped(IActivityTaskManager.java:4389)
at android.app.servertransaction.PendingTransactionActions$StopInfo.run(PendingTransactionActions.java:145)
at android.os.Handler.handleCallback(Handler.java:938)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:223)
at android.app.ActivityThread.main(ActivityThread.java:7656)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:592)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:947)

an...@google.com <an...@google.com> #17Jun 7, 2023 11:05AM

Color is not automatically saveable, you need to write a custom Saver which will convert it to primitive and then back

ma...@marcardar.com <ma...@marcardar.com> #18Jun 25, 2023 11:24AM

Related to this issue, it would be useful to give more details in the log message, because when, for example, the object is a Set we have no idea what is the underlying type (the type of the items stored in the Set) and so have no idea where to look in the code:

Fatal Exception: java.lang.RuntimeException: Parcelable encountered IOException writing serializable object (name = java.util.LinkedHashSet)
       at android.os.Parcel.writeSerializable(Parcel.java:2178)
       at android.os.Parcel.writeValue(Parcel.java:1944)
       at androidx.compose.runtime.ParcelableSnapshotMutableState.writeToParcel(ParcelableSnapshotMutableState.kt:30)
       at android.os.Parcel.writeParcelable(Parcel.java:1965)
       at android.os.Parcel.writeValue(Parcel.java:1871)
       at android.os.Parcel.writeList(Parcel.java:1153)
       at android.os.Parcel.writeValue(Parcel.java:1893)
       at android.os.Parcel.writeMapInternal(Parcel.java:1004)
       at android.os.Parcel.writeMap(Parcel.java:986)
       at android.os.Parcel.writeValue(Parcel.java:1858)
       at android.os.Parcel.writeMapInternal(Parcel.java:1004)
       at android.os.Parcel.writeMap(Parcel.java:986)
       at android.os.Parcel.writeValue(Parcel.java:1858)
       at android.os.Parcel.writeList(Parcel.java:1153)
       at android.os.Parcel.writeValue(Parcel.java:1893)
       at android.os.Parcel.writeMapInternal(Parcel.java:1004)
       at android.os.Parcel.writeMap(Parcel.java:986)
       at android.os.Parcel.writeValue(Parcel.java:1858)
       at android.os.Parcel.writeList(Parcel.java:1153)
       at android.os.Parcel.writeValue(Parcel.java:1893)
       at android.os.Parcel.writeArrayMapInternal(Parcel.java:1036)
       at android.os.BaseBundle.writeToParcelInner(BaseBundle.java:1620)
       at android.os.Bundle.writeToParcel(Bundle.java:1304)
       at android.os.Parcel.writeBundle(Parcel.java:1105)
       at android.os.Parcel.writeValue(Parcel.java:1862)
       at android.os.Parcel.writeArrayMapInternal(Parcel.java:1036)
       at android.os.BaseBundle.writeToParcelInner(BaseBundle.java:1620)
       at android.os.Bundle.writeToParcel(Bundle.java:1304)
       at android.os.Parcel.writeBundle(Parcel.java:1105)
       at android.os.Parcel.writeValue(Parcel.java:1862)
       at android.os.Parcel.writeArrayMapInternal(Parcel.java:1036)
       at android.os.BaseBundle.writeToParcelInner(BaseBundle.java:1620)
       at android.os.Bundle.writeToParcel(Bundle.java:1304)
       at android.os.Parcel.writeBundle(Parcel.java:1105)
       at android.os.Parcel.writeValue(Parcel.java:1862)
       at android.os.Parcel.writeArrayMapInternal(Parcel.java:1036)
       at android.os.BaseBundle.writeToParcelInner(BaseBundle.java:1620)
       at android.os.Bundle.writeToParcel(Bundle.java:1304)
       at android.os.Parcel.writeBundle(Parcel.java:1105)
       at android.os.Parcel.writeValue(Parcel.java:1862)
       at android.os.Parcel.writeArrayMapInternal(Parcel.java:1036)
       at android.os.BaseBundle.writeToParcelInner(BaseBundle.java:1620)
       at android.os.Bundle.writeToParcel(Bundle.java:1304)
       at android.os.Parcel.writeBundle(Parcel.java:1105)
       at android.os.Parcel.writeValue(Parcel.java:1862)
       at android.os.Parcel.writeArrayMapInternal(Parcel.java:1036)
       at android.os.BaseBundle.writeToParcelInner(BaseBundle.java:1620)
       at android.os.Bundle.writeToParcel(Bundle.java:1304)
       at android.os.Parcel.writeBundle(Parcel.java:1105)
       at android.os.Parcel.writeValue(Parcel.java:1862)
       at android.os.Parcel.writeArrayMapInternal(Parcel.java:1036)
       at android.os.BaseBundle.writeToParcelInner(BaseBundle.java:1620)
       at android.os.Bundle.writeToParcel(Bundle.java:1304)
       at android.os.Parcel.writeBundle(Parcel.java:1105)
       at android.os.Parcel.writeValue(Parcel.java:1862)
       at android.os.Parcel.writeArrayMapInternal(Parcel.java:1036)
       at android.os.BaseBundle.writeToParcelInner(BaseBundle.java:1620)
       at android.os.Bundle.writeToParcel(Bundle.java:1304)
       at android.os.Parcel.writeBundle(Parcel.java:1105)
       at android.os.Parcel.writeValue(Parcel.java:1862)
       at android.os.BaseBundle.dumpStats(BaseBundle.java:1690)
       at android.os.BaseBundle.dumpStats(BaseBundle.java:1727)
       at android.app.servertransaction.PendingTransactionActions$StopInfo.run(PendingTransactionActions.java:150)
       at android.os.Handler.handleCallback(Handler.java:938)
       at android.os.Handler.dispatchMessage(Handler.java:99)
       at android.os.Looper.loopOnce(Looper.java:226)
       at android.os.Looper.loop(Looper.java:313)
       at android.app.ActivityThread.main(ActivityThread.java:8751)
       at java.lang.reflect.Method.invoke(Method.java)
       at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:571)
       at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1135)

il...@google.com <il...@google.com> #19Jun 26, 2023 06:09PM

Re comment#18 - Due to type erasure, generic types (e.g., the type stored inside your Set) aren't a thing at runtime.