ScrollView onScroll only fires once

[nick]

I have a component that looks something like this:

var ScrollTest = React.createClass({

  render() {
    return (
      <ScrollView onScroll={this.onScroll}>
        <View style={{ height: 2000 }} />
      </ScrollView>
    );
  },

  onScroll: function(e) {
    console.log("Scroll", e)
  }
});

Right now I'm only seeing the log message when I start a new scroll action. Is there a way to get that onScroll event to fire on every frame? I want the height of another component to depend on the scroll position of this ScrollView component. (trying to duplicate the behavior you see on the iOS Weather app when you scroll down).

[vjeux]

Hmm this is weird, you should receive an onScroll event every 200ms

https://phabricator.fb.com/diffusion/FBOBJC/browse/master/Libraries/FBReactKit/js/RKJSModules/Libraries/Components/ScrollViewPropTypes.js;ab0173e350a5d5a542bbbb1af82e36cb9e82609e$27

[nick]

If I set a value for throttleScrollCallbackMS then it works :-)

[frantic]

@vjeux - the comment in the code is misleading, looks like we don't default to 200ms. @nick you are right, to receive the event continuously, you have to explicitly tell how often it should fire. The design decision here was driven by perf considerations - we don't want to spam the bridge with commands you are not interested in. If you want to animate something when scrolling, set throttleScrollCallbackMS to 16ms or less.

[vjeux]

Just made a diff internally to add a warning. D1833444 (for tracking purposes)

[vjeux]

Warning is now in: dd78b09

[cleercode]

I set throttleScrollCallbackMS={16} and the warning doesn't show but I seem to still only get one event fired. Also only seeing one event logged in the UIExplorer example.

[ssssssssssss]

Don't work for listview

[nicklockwood]

The throttleScrollCallbacksMS property is now called scrollEventThrottle.

[nicklockwood]

Looks like the warning wasn't updated when the property name was changed.