Expose onScrollStarted/onScrollStopped listeners in verticalScroll modifier [169509805]

Fixed

Bug

Status Update

No update yet.

Description

ya...@gmail.com

created issue #1

Sep 28, 2020 02:45PM

Component used: ScrollableColumn/verticalScroll modifier

Version used: alpha-03

Devices/Android versions reproduced on: Irrelevant

The scrollable modifier has onScrollStarted/onScrollStopped parameters, but the verticalScroll/horizontalScroll modifiers are not exposing those. Some type visibility like state.scrollableController make it impossible to use scrollable manually.

Would also be nice to have those on ScrollableColumn/ScrollableRow I guess.

Use case: I'd like to receive the event where the user stopped scrolling, and use the velocity to trigger a snap behavior.

I have the following page:

Stack {
    val collapsingToolbarExpandedSize = ...
    ScrollableColumn(){
       Spacer(modifier = Modifier.height(collapsingToolbarSize))
    }
    CollapsingToolbar {
          ....
    }
}

I want to be able to trigger a smooth scroll to a certain value (0 or collapsingToolbarSize) to snap the toolbar state.

Maybe there is a different way of doing this. I tried using the rawDragGestureFilter, but the onStop was always receiving a value of 0 for the offset. Maybe this is a bug?

Thanks.

Comments

so...@google.com <so...@google.com> Sep 28, 2020 03:46PM

Assigned to ma...@google.com.

ma...@google.com <ma...@google.com> #2Sep 28, 2020 05:14PM

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

ya...@gmail.com <ya...@gmail.com> #3Sep 28, 2020 09:06PM

Thanks for your response

Indeed waiting for the fling to end is bad for user experience.

Would this also expose the velocity? I feel like this solution would basically be the same thing than using rawDragGestureFilter with a less-weird api (except the gesture filter is not getting the velocity). If I'm wrong about it being the same kind of solution with a different API please correct me.

The issue with not having the velocity propagated is that the implementation is not great, since we don't know in which direction the scroll was occurring. So we can only snap depending on scrollState.value. This could be solved by saving the initial position when the drag starts and compare with the value when stopping, but it feels really hacky. So having this kind of information in the state (velocity, and thus direction by its sign, and also the initial value from drag started).

It does feel like the current implementation of the CollapsingToolbar view implementation. But I'm not sure I understood it completely

When ScrollableColumn hits the bound, dragging deltas will flow to the parent above What do you mean by "hits the bounds"?

Wouldn't the parent wrapping the ScrollableColumn always intercept the scroll events since higher in the hierarchy? I'm not sure how this would work, since it's not a huge priority, I don't mind waiting proper nested scrolling support. Though I'm not sure how this would solve the issue here, so would appreciate more details if you have time to spare :)

I do feel like snapping is a bit tricky to implement, maybe I should've opened a different feature request for this :)

Again thanks for the details

ap...@google.com <ap...@google.com> #4Oct 13, 2020 04:16PM

Marked as fixed.

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

commit 03b8c488e9eb8764bd36e30590f5171823f9560a
Author: Matvei Malkov <malkov@google.com>
Date: Thu Oct 08 18:19:09 2020

Add InteractionState to scrollable and corresponding containers, add animation observation to LazyList

This CL adds InteractionState to the ScrollableColumn/Row and Lazy lists to allow people to observe interactions that are happening on this element. While doing so, to make functionality on par, I added isAnimationRunning and stopAnimation is LazyState, so people won't miss this menthods while migrating from ScrollableColumn.

Change-Id: I815666e1b4544dcd5da9f253ec1b539fdd777529
Relnote: Added interactionState to Modifier.scrollable, ScrollableColumn and LazyColumnFor
Fixes: 169509805
Test: added

M compose/foundation/foundation/api/current.txt
M compose/foundation/foundation/api/public_plus_experimental_current.txt
M compose/foundation/foundation/api/restricted_current.txt
M compose/foundation/foundation/integration-tests/foundation-demos/src/main/java/androidx/compose/foundation/demos/ListDemos.kt
M compose/foundation/foundation/samples/src/main/java/androidx/compose/foundation/samples/ScrollerSamples.kt
M compose/foundation/foundation/src/androidAndroidTest/kotlin/androidx/compose/foundation/ScrollableTest.kt
M compose/foundation/foundation/src/androidAndroidTest/kotlin/androidx/compose/foundation/lazy/LazyColumnForTest.kt
M compose/foundation/foundation/src/commonMain/kotlin/androidx/compose/foundation/Scroll.kt
M compose/foundation/foundation/src/commonMain/kotlin/androidx/compose/foundation/gestures/Scrollable.kt
M compose/foundation/foundation/src/commonMain/kotlin/androidx/compose/foundation/lazy/LazyListState.kt

https://android-review.googlesource.com/1454897

ma...@google.com <ma...@google.com> #5Oct 19, 2020 01:27PM

As I mentioned above, I exposed InteractionState on the scrollable containers (and their states), so you are now able to understand whether fling or drag is happening and distinguish between them. This thought doesn't solve your issue, as you need to wait for a proper nested scrolling support, unfortunately.

Closing this as the main feature request of exposing ongoing scroll/fling is completed, please, follow the rest of the work here: b/162408885

Issue 169509805