react-native-units

A collection of useful units and a simple grid implementation for responsive layouts in React Native.

React Native uses density-independent pixels, or dp, as it's default unit. This will size elements so that they are roughly the same physical size on different devices. Whilst this is useful, I missed some of the units you have available in CSS.

Setup

Add the package from NPM. No react-native-link required.

yarn add react-native-units
- or - 
npm install react-native-units

Import the library where you need it:

import RNU from 'react-native-units'

Units

vw(x=1)

% of the screen width, e.g. RNU.vw(10) is equal to 10% of the screens width

vh(x=1)

% of the screen height, e.g. RNU.vh(10) is equal to 10% of the screen height

px(x=1)

Physical pixels based on device pixel ratio, e.g. RNU.px(1) is equal to 1 pixel on the device, handy for very thin lines!

su(x=1)

Scaled unit, similar to rem in CSS. You can set the scale using RNU.setScale(scale). This is useful for scaling fonts and layouts depending on the device e.g.

if(iPad) RNU.setScale(0.75) // RNU.su(10) > 7.5dp
if(iPhone5) RNU.setScale(1.5) // RNU.su(10) > 15dp

Grid

A simple way to create grids. First set your parameters:

RNU.setGrid({
	cols: 24, 
	padding: 20, 
	spacing: 10 
})

Then use the gr, gs & gp units to create your layout. I have made a snack here which will create the example below.

gr(x=1)

This unit is equal to one column's width, however it will also include any spacing it encompasses. In this example, if RNU.gr(1) is equal to 12dp then RNU.gr(2) will equal 34dp ((12*2)+10)

gs(x=1)

The grid spacing. In this example RNU.gs() is equal to 10dp

gp(x=1)

The grid padding. In this example RNU.gp() is equal to 20dp

Screen Rotation

As this library depends on the screen width and height to calculate units, when the screen rotates you need to call RNU.update(). The easiest way is to add an onLayout to your main app component e.g.

<View onLayout={() => { RNU.update() }>
	...
</View>