[Paging3] loading of data not fully triggered when using small pages. [169259468]

Fixed

Bug

Status Update

No update yet.

Description

jd...@xooloo.com

created issue #1

Sep 24, 2020 08:59AM

Component used: Paging3 Version used: alpha06 Devices/Android versions reproduced on: Android 7.1

I'm presenting a list of items using data from a room DB.

    fun getMessages(chat: Chat): Pager<Int, Message> {
        return Pager(
                PagingConfig(pageSize = 3, enablePlaceholders = true)
        ) {
            db.messages.getMessages(chat.id)
        }
    }

Note: The page size is intentionally low to try to debug paging issues, but is higher in production code.

The pager flow is used to produce PagingData passed to a PagingAdapter.

chats.getMessages(chat).flow.map {
  it.map { message -> getEntryForMessages(chatWithUsers, message) }
}.collect {
  adapter.submitList(it)
}

The RecyclerView uses a simple LinearLayoutManager.

Everything work mostly fine except that that latest entry may never be loaded while scrolling (especially when scrolling slowly). The PagingData properly provides a placeholder that is shown in the list, but it never trigger the loading of the last data, and so never replace the placeholder when reaching the end of the list.

Comments

du...@google.com <du...@google.com> #2Sep 24, 2020 01:16PM

Project: platform/frameworks/support
Branch: androidx-master-dev

commit c60f33e229e31ab328ef6b59dab63b264954831c
Author: Alexandre Elias <aelias@google.com>
Date: Fri Jul 10 16:23:09 2020

Semantics no-op cleanups

Partly in response to lmr's broad code review, I did a pass of
superficial API/implementation cleanup. The main changes are:

- I changed each Boolean SemanticsProperty where false is equivalent to
not being present to take "Unit" instead. This is conceptually
clearer: it avoids questions like "can I cancel out a semantics from a
merged child by setting it to false?" Because "property = Unit" looks
weird, I also changed the style of these to "property()".

- I moved the Semantics id generator closer to where it's used, in
SemanticsModifierCore. I made it internal and an AtomicInt.
(Note that integer ids are heavily used in the Android
AccessibilityNodeInfo APIs so I can't simply remove them entirely.)

- I deleted dead code. Some examples include SemanticsHintOverrides,
a public API not connected to anything, and SemanticsPropertyKey
merge() open method which is never called. (In both cases I have
a different plan in mind for accessibility.)

Fixes: 145951226
Fixes: 145955412
Test: existing tests
Relnote: "Single-value semantics properties now use a calling style.
For example, 'semantics { hidden = true }' is now written as:
'semantics { hidden() }'."

Change-Id: Ic1afd12ea22c926babc9662f1804d80b33aa0cfc

M ui/integration-tests/benchmark/src/androidTest/java/androidx/ui/benchmark/test/LayoutNodeModifierBenchmark.kt
M ui/ui-core/api/0.1.0-dev15.txt
M ui/ui-core/api/current.txt
M ui/ui-core/api/public_plus_experimental_0.1.0-dev15.txt
M ui/ui-core/api/public_plus_experimental_current.txt
M ui/ui-core/api/restricted_0.1.0-dev15.txt
M ui/ui-core/api/restricted_current.txt
M ui/ui-core/src/androidAndroidTest/kotlin/androidx/ui/graphics/vector/VectorTest.kt
M ui/ui-core/src/androidAndroidTest/kotlin/androidx/ui/semantics/SemanticsTests.kt
M ui/ui-core/src/androidMain/kotlin/androidx/ui/core/AndroidActuals.kt
M ui/ui-core/src/androidMain/kotlin/androidx/ui/core/AndroidComposeView.kt
M ui/ui-core/src/androidMain/kotlin/androidx/ui/core/AndroidComposeViewAccessibilityDelegateCompat.kt
M ui/ui-core/src/androidMain/kotlin/androidx/ui/core/AndroidPopup.kt
M ui/ui-core/src/commonMain/kotlin/androidx/ui/core/Expect.kt
M ui/ui-core/src/commonMain/kotlin/androidx/ui/core/semantics/SemanticsConfiguration.kt
D ui/ui-core/src/commonMain/kotlin/androidx/ui/core/semantics/SemanticsHintOverrides.kt
M ui/ui-core/src/commonMain/kotlin/androidx/ui/core/semantics/SemanticsModifier.kt
M ui/ui-core/src/commonMain/kotlin/androidx/ui/core/semantics/SemanticsNode.kt
M ui/ui-core/src/commonMain/kotlin/androidx/ui/core/semantics/SemanticsOwner.kt
M ui/ui-core/src/commonMain/kotlin/androidx/ui/core/semantics/SemanticsWrapper.kt
M ui/ui-core/src/commonMain/kotlin/androidx/ui/semantics/SemanticsProperties.kt
M ui/ui-foundation/api/0.1.0-dev15.txt
M ui/ui-foundation/api/current.txt
M ui/ui-foundation/api/public_plus_experimental_0.1.0-dev15.txt
M ui/ui-foundation/api/public_plus_experimental_current.txt
M ui/ui-foundation/api/restricted_0.1.0-dev15.txt
M ui/ui-foundation/api/restricted_current.txt
M ui/ui-foundation/src/main/java/androidx/ui/foundation/Clickable.kt
M ui/ui-foundation/src/main/java/androidx/ui/foundation/Dialog.kt
M ui/ui-foundation/src/main/java/androidx/ui/foundation/Scroller.kt
M ui/ui-foundation/src/main/java/androidx/ui/foundation/selection/Selectable.kt
M ui/ui-foundation/src/main/java/androidx/ui/foundation/selection/Toggleable.kt
M ui/ui-foundation/src/main/java/androidx/ui/foundation/semantics/FoundationSemanticsProperties.kt
M ui/ui-material/src/androidTest/java/androidx/ui/material/ButtonTest.kt
M ui/ui-material/src/androidTest/java/androidx/ui/material/CardTest.kt
M ui/ui-material/src/androidTest/java/androidx/ui/material/CheckboxScreenshotTest.kt
M ui/ui-material/src/androidTest/java/androidx/ui/material/RadioButtonScreenshotTest.kt
M ui/ui-material/src/androidTest/java/androidx/ui/material/ScaffoldTest.kt
M ui/ui-material/src/androidTest/java/androidx/ui/material/SnackbarTest.kt
M ui/ui-material/src/androidTest/java/androidx/ui/material/SurfaceTest.kt
M ui/ui-material/src/androidTest/java/androidx/ui/material/ripple/RippleIndicationTest.kt
M ui/ui-material/src/androidTest/java/androidx/ui/material/textfield/TextFieldScreenshotTest.kt
M ui/ui-material/src/main/java/androidx/ui/material/AppBar.kt
M ui/ui-material/src/main/java/androidx/ui/material/TextFieldImpl.kt
M ui/ui-test/src/androidTest/java/androidx/ui/test/AssertsTest.kt
M ui/ui-test/src/androidTest/java/androidx/ui/test/CallSemanticsActionTest.kt
M ui/ui-test/src/androidTest/java/androidx/ui/test/ErrorMessagesTest.kt
M ui/ui-test/src/androidTest/java/androidx/ui/test/FindersTest.kt
M ui/ui-test/src/androidTest/java/androidx/ui/test/PrintToStringTest.kt
M ui/ui-test/src/androidTest/java/androidx/ui/test/ScrollToTest.kt
M ui/ui-test/src/androidTest/java/androidx/ui/test/TextActionsTest.kt
M ui/ui-test/src/main/java/androidx/ui/test/Actions.kt
M ui/ui-test/src/main/java/androidx/ui/test/Filters.kt
M ui/ui-text/api/0.1.0-dev15.txt
M ui/ui-text/api/current.txt
M ui/ui-text/api/public_plus_experimental_0.1.0-dev15.txt
M ui/ui-text/api/public_plus_experimental_current.txt
M ui/ui-text/api/restricted_0.1.0-dev15.txt
M ui/ui-text/api/restricted_current.txt
M ui/ui-text/src/commonMain/kotlin/androidx/ui/text/CoreTextField.kt
M ui/ui-text/src/commonMain/kotlin/androidx/ui/text/TextSemanticsProperties.kt

https://android-review.googlesource.com/1360099

jd...@xooloo.com <jd...@xooloo.com> #3Sep 28, 2020 10:17AM

You can clone this:

https://github.com/Jean-Daniel/MyPager.git

Run the Main Activity, scroll to the end of the list: I join a screen of the issue.

Screenshot_20200928-120938.png

58 KB

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du...@google.com <du...@google.com> #4Sep 28, 2020 10:04PM

Accepted by du...@google.com.

Thanks for providing a sample project! Looks like this is an issue with how we conflate item accesses when triggering prefetch.

ap...@google.com <ap...@google.com> #5Oct 1, 2020 07:51PM

Marked as fixed.

Project: platform/frameworks/support
Branch: androidx-master-dev

commit 190a76ec743552627310e024976fd5896e989acb
Author: Dustin Lam <dustinlam@google.com>
Date: Mon Sep 28 13:54:08 2020

Prioritize hints from more recent presenter state

Currently we only use itemsPresentedAfter, which only accounts for the
placeholderOffset from the last page, but this value is insufficient to
determine which hint loads more items in cases where the last/first
pageOffset changes on presenter side.

As a result, we'll drop hints that would load more items in favor of
hints that came from a past presenter state that was scroll further into
placeholders.

This change fixes the above by always prioritizing new incoming hints if
the first/last pageOffset of presenter state changes.

RelNote: "N/A"
Fixes: 169259468
Test: ./gradlew paging:paging-common:test
Change-Id: Iffda3a0eb7abe162045893367b4781daf75adb01

M paging/common/api/current.txt
M paging/common/api/public_plus_experimental_current.txt
M paging/common/api/restricted_current.txt
M paging/common/src/main/kotlin/androidx/paging/PageFetcherSnapshot.kt
M paging/common/src/test/kotlin/androidx/paging/PageFetcherSnapshotTest.kt

https://android-review.googlesource.com/1441095

Issue 169259468

Description

Issue summary

Comments

du...@google.com <du...@google.com> #2Sep 24, 2020 01:16PM

jd...@xooloo.com <jd...@xooloo.com> #3Sep 28, 2020 10:17AM

du...@google.com <du...@google.com> #4Sep 28, 2020 10:04PM

ap...@google.com <ap...@google.com> #5Oct 1, 2020 07:51PM

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