ScrollView contentOffset bug

[vivalaakam]

Hi! in RN 0.48.1 doesn`t work contentOffset when component is initialized. Here is example for reproduction https://github.com/vivalaakam/rn_issue

In this example after initialize i will be see second screen, named 'Welcome to screen #2'

In version 0.47.2 it work as well

1. react-native -v

   react-native-cli: 2.0.1
   react-native: 0.48.1

2. node -v

   v8.4.0

3. npm -v

   5.4.0

4. yarn --version

   0.27.5

[stage88]

This is probably related to 1d22f8fb27e9432e357401ce6f6cede4d710472c, the scenario the commit addresses doesn't apply to me so i have replaced line 319 in node_modules/react-native/React/Views/RCTScrollView.m with

// self.contentOffset = CGPointMake(
//   MAX(0, MIN(originalOffset.x, fullContentSize.width - boundsSize.width)),
//   MAX(0, MIN(originalOffset.y, fullContentSize.height - boundsSize.height)));
self.contentOffset= originalOffset;

That fixes my negative offset with refresh control problem, it will have to do until the issue is fixed.

[shergin]

Well, the problem with this issue is that contentOffset prop should not exist in the first place. (And it does not exist on Android.) Could we use scrollTo method instead?

[janicduplessis]

@shergin I think we should try landing https://github.com/facebook/react-native/pull/15670 to fix that regression

[krizpoon]

I have similar problem and solved it with:

self.contentOffset = CGPointMake(
    MAX(-contentInset.left, MIN(originalOffset.x, fullContentSize.width - boundsSize.width)),
    MAX(-contentInset.top, MIN(originalOffset.y, fullContentSize.height - boundsSize.height)));

[pull-bot]

@facebook-github-bot no-template

[facebook-github-bot]

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[henrikra]

@shergin Could you explain more why contentOffset prop should not exists? For example now on Android I have to do weird hacks to init scroll view's position to something that I want.

[shergin]

@henrikra It was discussed here several times. And yes, it is kinda controversial; we will not introduce breaking change before we have a consensus, but I pesonally think this prop should be removed. The problem with this props is that it is unclear when (at which stage) we have to enforce/apply the offset, it causes bugs and unexpected behaviors. (And, I assume, the situation became much worse with async Fiber.) Such kind of momentum values should be represented as methods, not props.

[henrikra]

@shergin Okay so what would be ideal api for this? Do you have suggestions? Since we have to do the offsetting on native level so there isn't any flickering like now :/