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StyleSheet

A StyleSheet is an abstraction similar to CSS StyleSheets.

Code quality tips:

  • By moving styles away from the render function, you're making the code easier to understand.
  • Naming the styles is a good way to add meaning to the low level components in the render function, and encourage reuse.
  • In most IDEs, using StyleSheet.create() will offer static type checking and suggestions to help you write valid styles.

Reference

Methods​

compose()​

static compose(style1: Object, style2: Object): Object | Object[];

Combines two styles such that style2 will override any styles in style1. If either style is falsy, the other one is returned without allocating an array, saving allocations and maintaining reference equality for PureComponent checks.

create()​

static create(styles: Object extends Record<string, ViewStyle | ImageStyle | TextStyle>): Object;

An identity function for creating styles. The main practical benefit of creating styles inside StyleSheet.create() is static type checking against native style properties.

flatten()​

static flatten(style: Array<Object extends Record<string, ViewStyle | ImageStyle | TextStyle>>): Object;

Flattens an array of style objects, into one aggregated style object.

setStyleAttributePreprocessor()​

WARNING: EXPERIMENTAL. Breaking changes will probably happen a lot and will not be reliably announced. The whole thing might be deleted, who knows? Use at your own risk.

static setStyleAttributePreprocessor(
  property: string,
  process: (propValue: any) => any,
);

Sets a function to use to pre-process a style property value. This is used internally to process color and transform values. You should not use this unless you really know what you are doing and have exhausted other options.

Properties​

absoluteFill​

A very common pattern is to create overlays with position absolute and zero positioning (position: 'absolute', left: 0, right: 0, top: 0, bottom: 0), so absoluteFill can be used for convenience and to reduce duplication of these repeated styles. If you want, absoluteFill can be used to create a customized entry in a StyleSheet, e.g.:

absoluteFillObject​

Sometimes you may want absoluteFill but with a couple tweaks - absoluteFillObject can be used to create a customized entry in a StyleSheet, e.g.:

hairlineWidth​

This is defined as the width of a thin line on the platform. It can be used as the thickness of a border or division between two elements. Example:

This constant will always be a round number of pixels (so a line defined by it can look crisp) and will try to match the standard width of a thin line on the underlying platform. However, you should not rely on it being a constant size, because on different platforms and screen densities its value may be calculated differently.

A line with hairline width may not be visible if your simulator is downscaled.