ShadowView - invoke onScrollChanged after internal var update

[MikeEA0]

Overview

ShadowView - invoke onScrollChanged after internal var update

Proposed Changes

Original View.java first sets member attributes (mScrollX, mScrollY) before listener is called. In that way, when listener accesses these variables, they are correctly set.

[hoisie]

Thanks for the PR. I agree that the way Robolectric fakes scrolling is really bad.

If you want realistic scrolling, set the system property robolectric.useRealScrolling to 'true'. This will use the real Android scrolling code. I would highly recommend using it.

https://github.com/robolectric/robolectric/blob/master/shadows/framework/src/main/java/org/robolectric/shadows/ShadowView.java#L1093-L1095

I would be OK with a PR that uses real scrolling by default, unless robolectric.useRealScrolling is set to false.

[utzcoz]

@hoisie IMO, we can accept PRs to improve legacy non-real scrolling logic if someone can do it like this PR. For a normal user, we can recommend them to use useRealScrolling branch.

[hoisie]

@utzcoz overall I agree, I will test this PR and check for any compatibility issues.

In the past I have attempted to make some improvements to this fake scrolling behavior and have always run into compatibility issues. The number of tests that inadvertently depend on the broken scrolling logic is quite surprising.

[utzcoz]

@MikeEA0 Please run tests locally and fix failed tests.

[hoisie]

This is the failure:

2024-02-20T04:55:01.6710780Z org.robolectric.shadows.ShadowViewTest > setScrolls_firesOnScrollChanged[19] FAILED
2024-02-20T04:55:01.6711883Z     value of: access$200(...)
2024-02-20T04:55:01.6712395Z     expected: 122
2024-02-20T04:55:01.6712812Z     but was : 453
2024-02-20T04:55:01.6713707Z         at org.robolectric.shadows.ShadowViewTest.setScrolls_firesOnScrollChanged(ShadowViewTest.java:763)
2024-02-20T04:55:01.6714546Z 
2024-02-20T04:55:01.6715067Z org.robolectric.shadows.ShadowViewTest > setScrolls_firesOnScrollChanged[21] FAILED
2024-02-20T04:55:01.6716003Z     value of: access$200(...)
2024-02-20T04:55:01.6716458Z     expected: 122
2024-02-20T04:55:01.6716845Z     but was : 453
2024-02-20T04:55:01.6717722Z         at org.robolectric.shadows.ShadowViewTest.setScrolls_firesOnScrollChanged(ShadowViewTest.java:763)
2024-02-20T04:55:01.6718564Z 
2024-02-20T04:55:01.6719075Z org.robolectric.shadows.ShadowViewTest > setScrolls_firesOnScrollChanged[34] FAILED
2024-02-20T04:55:01.6719974Z     value of: access$200(...)
2024-02-20T04:55:01.6720426Z     expected: 122
2024-02-20T04:55:01.6720798Z     but was : 453
2024-02-20T04:55:01.6721937Z         at org.robolectric.shadows.ShadowViewTest.setScrolls_firesOnScrollChanged(ShadowViewTest.java:763)