Fix excessive toggles on the Switch component

[rurikoaraki]

Summary

In Windows, if you clicked on a Switch component to toggle it, you could see it "shimmy" back and forth once before settling. The native Switch ends up toggling three times every time it's invoked.

Switch.js prevents the native switch from toggling to the new value by explicitly setting the switch to this.props.value when it receives an onChange event. The re-setting of the value wasn't fast enough to prevent the Switch from starting to toggle, causing the visual shimmy.

The solution is taken from TextInput. TextInput.js stores _lastNativeText when it receives an onChange event. In componentDidUpdate, it puts this.props.text back on the native textbox if the value of this.props.text isn't the same as _lastNativeText, which is how it ensures that it is a controlled component. Porting this to the Switch results in only one toggle happening per invoke, removing the shimmy, while preserving the controlled component behavior.

This bug is not visible on Android or iOS, only Windows, however the code causing the bug was in Switch.js and it seems reasonable to avoid changing the value of the native switch excessively.

Changelog

[General] [Fixed] - Fix excessive toggles on the Switch component

Test Plan

Used RNTester on Android and iOS to test the Switch component and made sure that all scenarios behave as expected visually. Also ensured through the debugger that the value of the native switch is only being changed once, instead of three times.

Ruriko Araki
Microsoft Corp.

[facebook-github-bot]

Thank you for your pull request and welcome to our community. We require contributors to sign our Contributor License Agreement, and we don't seem to have you on file. In order for us to review and merge your code, please sign up at https://code.facebook.com/cla. If you are contributing on behalf of someone else (eg your employer), the individual CLA may not be sufficient and your employer may need the corporate CLA signed.

If you have received this in error or have any questions, please contact us at cla@fb.com. Thanks!

[facebook-github-bot]

Thank you for signing our Contributor License Agreement. We can now accept your code for this (and any) Facebook open source project. Thanks!

[JoshuaGross]

This seems reasonable to me. I'll import to test internally.

[facebook-github-bot]

@JoshuaGross has imported this pull request. If you are a Facebook employee, you can view this diff on Phabricator.

[JoshuaGross]

Thanks for fixing this @rurikoaraki!

[react-native-bot]

This pull request was successfully merged by @rurikoaraki in b782934.

^{When will my fix make it into a release? | Upcoming Releases}