react-native-device-screen-switcher

Testing your React Native UI layouts on different screen sizes can be quite time-consumning.

This library aims to make this much easier by allowing the run-time switching of the main app viewport to match the sizes of different devices.

This library requires React Native 0.43.0 or above. For versions older versions of React Native (from 0.34.0 up), use the 0.0.4 release.

GIF of the library in action

Usage

npm i -S react-native-device-screen-switcher

In your root-level component, wrap the root component returned by render() with <ScreenSwitcher>.

import ScreenSwitcher from 'react-native-device-screen-switcher';
 
class MyRoot extends Component {
  ...
  render() {
    return (
      <ScreenSwitcher>
        <MyRootComponent/>
      </ScreenSwitcher>
    )
  }
}

Run your app in Debug mode. For best results run on the iPhone 11 Pro Max simulator:

react-native run-ios --simulator="iPhone Pro Max"

You'll see a 'Switch' button at the bottom-right of the screen.
Tap this button to bring up a menu of the available screen sizes.
Make your selection.

The viewport is resized to the correct size.

Additionally, the app will render images using the density appropriate to the simulated device (@3x on iPhone 6 Plus, @2x on most others).

Notes: Dimensions.get('window') will now return the size of the simulated device. So long as you have followed React Native's documentation and not cached these values, your app will continue to render with the correct simulated sizes.

To hide the Switch button use the hideButton prop on ScreenSwitcher, e.g.

<ScreenSwitcher hideButton>
  ...
</ScreenSwitcher>

For scale screen down to fit physical device dimensions, use scaleToFit prop, e.g.

<ScreenSwitcher scaleToFit>
  ...
</ScreenSwitcher>

If you want to scale up to fill device screen, use 'scaleUp' prop with addition to scaleToFit, e.g.

<ScreenSwitcher scaleToFit scaleUp>
  ...
</ScreenSwitcher>

In Production

In production builds the <ScreenSwitcher> component simply passes through the child components without changing them using the same method as the react-redux <Provider> component.

This means it's not necessary to remove <ScreenSwitcher> from your root component for production builds.

Similar libraries

This library was inspired by https://github.com/machadogj/react-native-layout-tester, which performs a similar function by running your app on an iPad.

However, that library required that you did not use React Native's Dimensions system, but used their own alternative system. It also required you to set your iPhone app to be Universal in Xcode. Neither of these are the case here.