Feature request: Allow to provide a "TypeAdapter" for collections [69164099]

Fixed

Bug

Status Update

No update yet.

Description

de...@gmail.com

created issue #1

Nov 10, 2017 06:53PM

Component used: Room
Version used: 1.0
Devices/Android versions reproduced on: NA

I have one entity that contains a set of enums. For example:

@Entity
data class Person(
@field:PrimaryKey val id: Int,
val name: String,
val favouriteDays: Set<Day>)

enum class Day {
MONDAY,
TUESDAY,
WEDNESDAY,
THURSDAY,
FRIDAY,
SATURDAY,
SUNDAY
}

I want to store this entity in a single table. In many cases, especially with enums, we could use a single bit mask to save the list as a number in the database.

Here's one example of what I wanted to do:

object DayCollectionTypeConverter {
@JvmStatic
@TypeConverter
fun daysConverter(days: Set<Day>): Int {
var value = 0
for (day in days) {
value += (1 shl day.ordinal)
}
return value
}

@JvmStatic
@TypeConverter
fun daysConverter(value: Int): Set<Day> {
val set = mutableSetOf<Day>()
for (day in Day.values()) {
if (value and 1 shl day.ordinal != 0) {
set.add(day)
}
}
return set
}
}

That code doesn't work as intended because @TypeConverter would allow me to convert one Day object, but not a collection (or set, list, etc) of Days.

I suggest a new annotation is created so the developer can specify how to save a Collection into a single column in the same table.

Comments

fs...@gmail.com <fs...@gmail.com> #2Nov 11, 2017 12:03AM

Found the issue, ugh

Noticed that when I do the following:
transaction.addToBackStack(null)

When adding a Fragment with ViewPager2, the above issue occurs, although, idk if it's becaugh of gcFragments() anymore.

As soon as I un-comment that line, the issue disappears.

yb...@google.com <yb...@google.com> #3Nov 27, 2017 08:24PM

https://github.com/PenguinDan/ViewPagerCrash

Is the Sample application, to reproduce, move back really fast between page 2 -> 1 and vice versa (they are bottom buttons) a couple times.
Wait a couple seconds and page 1 (the black page) should turn white meaning the Fragment has been removed.

As soon as you comment line 40 on MainActivity, and attempt again, the error does not persist

de...@gmail.com <de...@gmail.com> #4Nov 27, 2017 09:50PM

Woops, sorry, If you guys had the previous ViewPagerCrash test app, I forgot to push (was exhasuted after debugging) I pushed one more time for the latest reproducible code

Poc.kt

1.4 KB

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output.txt

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yb...@google.com <yb...@google.com> #5Dec 15, 2017 09:39PM

We'll have a look, thanks for reporting and repro steps / sample app. Stay tuned for updates on this issue.

yb...@google.com <yb...@google.com> #6Dec 18, 2017 09:29PM

Status: Assigned (reopened)

Got to debug this now. Your sample indeed showcases an issue, so thanks for reporting and for the sample!

`transaction.addToBackStack(null)` adds the Fragment replacement transaction to the back stack, so you can go back to the previous state with the back button. Is that what you were looking to achieve? You said it works without it, which might help in the meantime.

Would you mind describing the use-case, so I better understand what you're trying to achieve? E.g. in the example, by switching between buttons 1 and 2 at some point you achieve multiple stack entries going back to the ViewPager2 Fragment.

yb...@google.com <yb...@google.com> #7Dec 18, 2017 10:17PM

Mostly for my notes, but the trace below explains what happens. Still need to work out why.

We have 5 instances of FragmentStateAdapter below.
Notice how in lines 36-39 4 different instances of FragmentStateAdapter perform a scheduled gc (after grace period expires).
Those don't have the Fragments bound to their ViewHolders as those were removed: lines 8, 16, 24, 32.

At the same time, com.test.myapplication.VPAdapter.createFragment(ViewPagerFragment.kt:161) only gets called once, so presumably all 5 have a reference to that same Fragment.

Needs more investigation as looks fishy.

1 {FragmentStateAdapter@11,288}.mItemIdToViewHolder will be modified at FragmentStateAdapter.<init>(FragmentStateAdapter.java:85). Current value = 'null'. New value = 'instance of androidx.collection.LongSparseArray(id=11289)'
2 {FragmentStateAdapter@11,288}.mItemIdToViewHolder will be accessed at FragmentStateAdapter.itemForViewHolder(FragmentStateAdapter.java:234)
3 {FragmentStateAdapter@11,288}.mItemIdToViewHolder will be accessed at FragmentStateAdapter.onBindViewHolder(FragmentStateAdapter.java:174)
4 {FragmentStateAdapter@11,288}.mItemIdToViewHolder will be accessed at FragmentStateAdapter.itemForViewHolder(FragmentStateAdapter.java:234)
5 {FragmentStateAdapter@11,288}.mItemIdToViewHolder will be accessed at FragmentStateAdapter.itemForViewHolder(FragmentStateAdapter.java:235)
6 {FragmentStateAdapter@11,288}.mItemIdToViewHolder will be accessed at FragmentStateAdapter.itemForViewHolder(FragmentStateAdapter.java:240)
7 {FragmentStateAdapter@11,288}.mItemIdToViewHolder will be accessed at FragmentStateAdapter.itemForViewHolder(FragmentStateAdapter.java:234)
8 {FragmentStateAdapter@11,288}.mItemIdToViewHolder will be accessed at FragmentStateAdapter.onViewRecycled(FragmentStateAdapter.java:391)
9 {FragmentStateAdapter@11,306}.mItemIdToViewHolder will be modified at FragmentStateAdapter.<init>(FragmentStateAdapter.java:85). Current value = 'null'. New value = 'instance of androidx.collection.LongSparseArray(id=11307)'
10 {FragmentStateAdapter@11,306}.mItemIdToViewHolder will be accessed at FragmentStateAdapter.itemForViewHolder(FragmentStateAdapter.java:234)
11 {FragmentStateAdapter@11,306}.mItemIdToViewHolder will be accessed at FragmentStateAdapter.onBindViewHolder(FragmentStateAdapter.java:174)
12 {FragmentStateAdapter@11,306}.mItemIdToViewHolder will be accessed at FragmentStateAdapter.itemForViewHolder(FragmentStateAdapter.java:234)
13 {FragmentStateAdapter@11,306}.mItemIdToViewHolder will be accessed at FragmentStateAdapter.itemForViewHolder(FragmentStateAdapter.java:235)
14 {FragmentStateAdapter@11,306}.mItemIdToViewHolder will be accessed at FragmentStateAdapter.itemForViewHolder(FragmentStateAdapter.java:240)
15 {FragmentStateAdapter@11,306}.mItemIdToViewHolder will be accessed at FragmentStateAdapter.itemForViewHolder(FragmentStateAdapter.java:234)
16 {FragmentStateAdapter@11,306}.mItemIdToViewHolder will be accessed at FragmentStateAdapter.onViewRecycled(FragmentStateAdapter.java:391)
17 {FragmentStateAdapter@11,313}.mItemIdToViewHolder will be modified at FragmentStateAdapter.<init>(FragmentStateAdapter.java:85). Current value = 'null'. New value = 'instance of androidx.collection.LongSparseArray(id=11314)'
18 {FragmentStateAdapter@11,313}.mItemIdToViewHolder will be accessed at FragmentStateAdapter.itemForViewHolder(FragmentStateAdapter.java:234)
19 {FragmentStateAdapter@11,313}.mItemIdToViewHolder will be accessed at FragmentStateAdapter.onBindViewHolder(FragmentStateAdapter.java:174)
20 {FragmentStateAdapter@11,313}.mItemIdToViewHolder will be accessed at FragmentStateAdapter.itemForViewHolder(FragmentStateAdapter.java:234)
21 {FragmentStateAdapter@11,313}.mItemIdToViewHolder will be accessed at FragmentStateAdapter.itemForViewHolder(FragmentStateAdapter.java:235)
22 {FragmentStateAdapter@11,313}.mItemIdToViewHolder will be accessed at FragmentStateAdapter.itemForViewHolder(FragmentStateAdapter.java:240)
23 {FragmentStateAdapter@11,313}.mItemIdToViewHolder will be accessed at FragmentStateAdapter.itemForViewHolder(FragmentStateAdapter.java:234)
24 {FragmentStateAdapter@11,313}.mItemIdToViewHolder will be accessed at FragmentStateAdapter.onViewRecycled(FragmentStateAdapter.java:391)
25 {FragmentStateAdapter@11,315}.mItemIdToViewHolder will be modified at FragmentStateAdapter.<init>(FragmentStateAdapter.java:85). Current value = 'null'. New value = 'instance of androidx.collection.LongSparseArray(id=11316)'
26 {FragmentStateAdapter@11,315}.mItemIdToViewHolder will be accessed at FragmentStateAdapter.itemForViewHolder(FragmentStateAdapter.java:234)
27 {FragmentStateAdapter@11,315}.mItemIdToViewHolder will be accessed at FragmentStateAdapter.onBindViewHolder(FragmentStateAdapter.java:174)
28 {FragmentStateAdapter@11,315}.mItemIdToViewHolder will be accessed at FragmentStateAdapter.itemForViewHolder(FragmentStateAdapter.java:234)
29 {FragmentStateAdapter@11,315}.mItemIdToViewHolder will be accessed at FragmentStateAdapter.itemForViewHolder(FragmentStateAdapter.java:235)
30 {FragmentStateAdapter@11,315}.mItemIdToViewHolder will be accessed at FragmentStateAdapter.itemForViewHolder(FragmentStateAdapter.java:240)
31 {FragmentStateAdapter@11,315}.mItemIdToViewHolder will be accessed at FragmentStateAdapter.itemForViewHolder(FragmentStateAdapter.java:234)
32 {FragmentStateAdapter@11,315}.mItemIdToViewHolder will be accessed at FragmentStateAdapter.onViewRecycled(FragmentStateAdapter.java:391)
33 {FragmentStateAdapter@11,317}.mItemIdToViewHolder will be modified at FragmentStateAdapter.<init>(FragmentStateAdapter.java:85). Current value = 'null'. New value = 'instance of androidx.collection.LongSparseArray(id=11318)'
34 {FragmentStateAdapter@11,317}.mItemIdToViewHolder will be accessed at FragmentStateAdapter.itemForViewHolder(FragmentStateAdapter.java:234)
35 {FragmentStateAdapter@11,317}.mItemIdToViewHolder will be accessed at FragmentStateAdapter.onBindViewHolder(FragmentStateAdapter.java:174)
36 {FragmentStateAdapter@11,306}.mItemIdToViewHolder will be accessed at FragmentStateAdapter.gcFragments(FragmentStateAdapter.java:221)
37 {FragmentStateAdapter@11,313}.mItemIdToViewHolder will be accessed at FragmentStateAdapter.gcFragments(FragmentStateAdapter.java:221)
38 {FragmentStateAdapter@11,315}.mItemIdToViewHolder will be accessed at FragmentStateAdapter.gcFragments(FragmentStateAdapter.java:221)
39 {FragmentStateAdapter@11,317}.mItemIdToViewHolder will be accessed at FragmentStateAdapter.gcFragments(FragmentStateAdapter.java:221)

yb...@google.com <yb...@google.com> Dec 19, 2017 11:43PM

Marked as fixed.