IssueTracker

Thanks for the report and the example code. I understand your perspective when you say "the change is never delivered to the Adapter due to the behavior of StableIdKeyProvider".

StableIdKeyProvider is a SCOPE_CACHED style KeyProvider, and as such can't answer questions about detached items. It seems we might be able to replace OnChildAttachStateChangeListener#onChildViewDetachedFromWindow with RecyclerListener#onViewRecycled as the callback in which we clear cached information.

Shep, can you confirm that a ViewHolder's position remains valid until the holder is recycled?

Docs appear to indicate this:

        /**
         * This method is called whenever the view in the ViewHolder is recycled.
         *
         * RecyclerView calls this method right before clearing ViewHolder's internal data and
         * sending it to RecycledViewPool. This way, if ViewHolder was holding valid information
         * before being recycled, you can call {@link ViewHolder#getBindingAdapterPosition()} to get
         * its adapter position.
         *
         * @param holder The ViewHolder containing the view that was recycled
         */

nam.eneim, in the mean time you can work around the problem by switching to a SCOPE_MAPPED KeyProvider. (a provider that knows the id of an item even when not attached to RecyclerView).

Thanks for the update. I will try using the SCOPE_MAPPED KeyProvider. It's worth noting that there is so little document about how we can use this library efficiently. I notice that the v2 is under development. Really hope it brings a lot more to the RecyclerView ecosystem.

One quick question about using the `RecyclerListener#onViewRecycled`, AFAIK, RecyclerView only allows us to set one RecyclerListener. So if the selection library needs that, does that mean the consumer App, or 3rd party library should not use its own? (This is my observation for the version I used up until now, 1.1.x or something). Or the RecyclerView has a plan to allow multiple RecyclerListener as well (which will be really helpful).

Thanks.

Have you read the package summary?

https://developer.android.com/reference/androidx/recyclerview/selection/package-summary

There is fairly extensive javadoc included in the public classes as well.

I also recall the developer relations team wrote up an article on how to use lthe selection lib, but can't seem to find it right now :)

> I notice that the v2 is under development. Really hope it brings a lot more to the RecyclerView ecosystem.

Q: Are there specific features you're looking for?

The 2.0 release is being planned largely to make some breaking API changes, e.g. remove SelectionTracker.Builder#withGestureTooltypes and SelectionTracker.Builder#withPointerTooltypes.

The main new feature I'm planning on adding in 2.0 is proper stylus support.

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

commit a938a74a5ecb72f8e74bcc9a1722ac6bc07b89a2
Author: Steve McKay <smckay@google.com>
Date:   Wed Jul 29 11:38:24 2020

    StableIdKeyProvider improvements.
   
    Fix bug where key/position mapping in KeyProvider was lost while entry was not yet recycled.
    - In order to achieve adequate unit test coverage I added a new abstraction on-top of RecyclerView, the "ViewHost".
    - Note testing could be facilitated with fewer back-flips if selection lib was in the same package as RecyclerView.
    - In order to listen to recycle events we use the single use setRecyclerListener method. TODO: Add support for multiple listeners (or possibly just add a new method to OnChildAttachStateChangeListener.
    Update TestAdapter to support setting setHashStableIds prior to registration of internal AdapterDataObserver.
    Add some missing @NonNull, @Nullable, and @Override annotations.
    Added a new single-select, stable-id based demo app.
    Updated demo apps to use getAbsoluteAdapterPosition.
    Remove unnecessary fancy stuff from the "Simple" demo app.
   
    Bug: 145767095
    Test: Updated StableIdKeyProviderTest to actually test stuff :)
    Change-Id: If8ff8256cff49d0cbf12f2175af3c3ca62b7c68b

M       recyclerview/recyclerview-selection/src/androidTest/java/androidx/recyclerview/selection/DefaultSelectionTrackerTest.java
M       recyclerview/recyclerview-selection/src/androidTest/java/androidx/recyclerview/selection/DefaultSelectionTracker_SingleSelectTest.java
M       recyclerview/recyclerview-selection/src/androidTest/java/androidx/recyclerview/selection/StableIdKeyProviderTest.java
M       recyclerview/recyclerview-selection/src/androidTest/java/androidx/recyclerview/selection/testing/TestAdapter.java
M       recyclerview/recyclerview-selection/src/androidTest/java/androidx/recyclerview/selection/testing/TestHolder.java
M       recyclerview/recyclerview-selection/src/main/java/androidx/recyclerview/selection/DefaultSelectionTracker.java
M       recyclerview/recyclerview-selection/src/main/java/androidx/recyclerview/selection/ItemDetailsLookup.java
M       recyclerview/recyclerview-selection/src/main/java/androidx/recyclerview/selection/StableIdKeyProvider.java
M       samples/Support7Demos/src/main/AndroidManifest.xml
M       samples/Support7Demos/src/main/java/com/example/android/supportv7/widget/selection/fancy/DemoAdapter.java
M       samples/Support7Demos/src/main/java/com/example/android/supportv7/widget/selection/fancy/DemoDetailsLookup.java
M       samples/Support7Demos/src/main/java/com/example/android/supportv7/widget/selection/fancy/DemoHeaderHolder.java
M       samples/Support7Demos/src/main/java/com/example/android/supportv7/widget/selection/fancy/DemoHolder.java
M       samples/Support7Demos/src/main/java/com/example/android/supportv7/widget/selection/fancy/DemoItemHolder.java
M       samples/Support7Demos/src/main/java/com/example/android/supportv7/widget/selection/fancy/FancySelectionDemoActivity.java
M       samples/Support7Demos/src/main/java/com/example/android/supportv7/widget/selection/simple/DemoAdapter.java
M       samples/Support7Demos/src/main/java/com/example/android/supportv7/widget/selection/simple/DemoHolder.java
M       samples/Support7Demos/src/main/java/com/example/android/supportv7/widget/selection/simple/SimpleSelectionDemoActivity.java
M       samples/Support7Demos/src/main/java/com/example/android/supportv7/widget/selection/single/DemoAdapter.java
M       samples/Support7Demos/src/main/java/com/example/android/supportv7/widget/selection/single/DemoDetailsLookup.java
M       samples/Support7Demos/src/main/java/com/example/android/supportv7/widget/selection/single/DemoHolder.java
A       samples/Support7Demos/src/main/java/com/example/android/supportv7/widget/selection/single/SingleStableIdSelectionDemoActivity.java
M       samples/Support7Demos/src/main/res/values/strings.xml

https://android-review.googlesource.com/1380276

Unfortunately, due to the reliance of the fix (https://android-review.googlesource.com/1380276) on setRecyclerListener (which supports a single listener only), the change opens the door to potential bugs where the selection library or app author overwrite the others' registered RecyclerListener.

https://r.android.com/1381078 adds support to RecyclerView for multiple RecyclerListeners, and https://r.android.com/1384002 updates Selection lib to use the new addRecyclerListener API. But the selection lib's rc release cannot depend on an API that is not also RC or above. Given the fact that there's a work around (SCOPE_MAPPED provider, see comment#2) will not include a fix for this issue in the 1.1.0-rc02 release.

Will leave this bug open to track inclusion in future release.

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

commit 66c5c69e735df7a0540ac621e0c084ac87be0cb1
Author: Steve McKay <smckay@google.com>
Date:   Fri Jul 31 14:42:15 2020

    Update StableIdKeyProvider to use addRecyclerListener.
   
    Bug: 145767095
    Test: All tests passing, manual testing via demo app.
    Change-Id: I21df99af34c2d34b720303858785eddb2a5314f6

M       recyclerview/recyclerview-selection/src/main/java/androidx/recyclerview/selection/StableIdKeyProvider.java

https://android-review.googlesource.com/1384002

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

commit ce1b333030414b89b1980fa2327774af1b5416dc
Author: Steve McKay <smckay@google.com>
Date:   Thu Jul 30 09:33:41 2020

    Add support for multiple RecyclerListeners.
   
    This feature is necessitated by RecyclerView-Selection dependency on listening
    to recycle events.
   
    Bug: 162504379
    Test: Added new coverage.
    Relnote: Add support for multiple RecyclerListeners as necessitated to fix b/145767095 affecting RecyclerView-Selection.
    Change-Id: I70ad8f9bcf25c2c00fbf5f71d5a991287bef1606

M       leanback/leanback/api/current.txt
M       leanback/leanback/api/public_plus_experimental_current.txt
M       leanback/leanback/api/restricted_current.txt
M       recyclerview/recyclerview/api/current.txt
M       recyclerview/recyclerview/api/public_plus_experimental_current.txt
M       recyclerview/recyclerview/api/restricted_current.txt
A       recyclerview/recyclerview/src/androidTest/java/androidx/recyclerview/widget/RecyclerListenerTest.java
M       recyclerview/recyclerview/src/main/java/androidx/recyclerview/widget/RecyclerView.java

https://android-review.googlesource.com/1381078

Planning on the fix being released in 1.2. Should be available in 1.2.0-alpha01 in the next few weeks. No telling for sure how long it will take to get 1.2.0 to stable.