@mythologi/react-native-linear-gradient

react-native-linear-gradient

A <LinearGradient> element for React Native

Table of Contents

• Installation
• Usage and Examples
• Props
• Example App
• Troubleshooting
• Other Platforms

Installation

Using Yarn

yarn add react-native-linear-gradient

Using npm

npm install react-native-linear-gradient --save

With React Native >= 0.60

Run npx pod-install

Linking (for React Native <= 0.59 only)

Note: If you are using react-native version 0.60 or higher you don't need to link react-native-linear-gradient.

Automatic

react-native link react-native-linear-gradient

Manual

iOS (with CocoaPods)

Add the following line to your Podfile:

pod 'BVLinearGradient', :path => '../node_modules/react-native-linear-gradient'

Run npx pod-install

iOS (without CocoaPods)

• Open your project in Xcode
• Right click on Libraries and click Add Files to "Your Project Name".
• Look under node_modules/react-native-linear-gradient/ios and add BVLinearGradient.xcodeproj. (Screenshot 1) (Screenshot 2).
• Add libBVLinearGradient.a to Build Phases -> Link Binary With Libraries (Screenshot 1) (Screenshot 2).
• Click on BVLinearGradient.xcodeproj in Libraries and go the Build Settings tab.
• Double click the text to the right of Header Search Paths and verify that it has $(SRCROOT)/../react-native/React - if it isn't, then add it. (Screenshot).

Android

In android/settings.gradle

include ':react-native-linear-gradient'
project(':react-native-linear-gradient').projectDir = new File(rootProject.projectDir, '../node_modules/react-native-linear-gradient/android')

In android/app/build.gradle add:

dependencies {
    ...
    implementation project(':react-native-linear-gradient')
}

In android/app/src/main/java/com/{YOUR_APP_NAME}/MainActivity.java for react-native < 0.29, or android/app/src/main/java/com/{YOUR_APP_NAME}/MainApplication.java for react-native >= 0.29 add:

// ...

import com.BV.LinearGradient.LinearGradientPackage; // <--- This!

// ...

@Override
protected List<ReactPackage> getPackages() {
  return Arrays.<ReactPackage>asList(
    new MainReactPackage(),
    new LinearGradientPackage() // <---- and This!
  );
}

Windows (WPF)

• in windows/MyApp.sln Add -> Existing Project: node_modules/react-native-linear-gradient/windows/LinearGradientWPF/LinearGradientWPF.csproj

• in windows/MyApp/MyAppWPF/MyAppWPF.csproj Add -> Reference -> LinearGradientWPF

• in windows/MyApp/MyAppWPF/AppReactPage.cs add: using LinearGradient; and

public override List<IReactPackage> Packages => new List<IReactPackage>
{
  ...
  new LinearGradientPackage()
}

Examples

react-native-login is a legacy component which showcases the use of <LinearGradient>.

Simple

The following code will produce something like this:

import LinearGradient from 'react-native-linear-gradient';

// Within your render function
<LinearGradient colors={['#4c669f', '#3b5998', '#192f6a']} style={styles.linearGradient}>
  <Text style={styles.buttonText}>
    Sign in with Facebook
  </Text>
</LinearGradient>

// Later on in your styles..
var styles = StyleSheet.create({
  linearGradient: {
    flex: 1,
    paddingLeft: 15,
    paddingRight: 15,
    borderRadius: 5
  },
  buttonText: {
    fontSize: 18,
    fontFamily: 'Gill Sans',
    textAlign: 'center',
    margin: 10,
    color: '#ffffff',
    backgroundColor: 'transparent',
  },
});

Horizontal gradient

Using the styles from above, set start and end like this to make the gradient go from left to right, instead of from top to bottom:

<LinearGradient start={{x: 0, y: 0}} end={{x: 1, y: 0}} colors={['#4c669f', '#3b5998', '#192f6a']} style={styles.linearGradient}>
  <Text style={styles.buttonText}>
    Sign in with Facebook
  </Text>
</LinearGradient>

Text gradient (iOS)

On iOS you can use the MaskedViewIOS to display text with a gradient. The trick here is to render the text twice; once for the mask, and once to let the gradient have the correct size (hence the opacity: 0):

<MaskedViewIOS maskElement={<Text style={styles.text} />}>
  <LinearGradient colors={['#f00', '#0f0']} start={{ x: 0, y: 0 }} end={{ x: 1, y: 0 }}>
    <Text style={[styles.text, { opacity: 0 }]} />
  </LinearGradient>
</MaskedViewIOS>

Animated Gradient

Check out Examples/AnimatedGradient (git clone this project, cd into it, npm install, open in Xcode and run) to see how this is done:

This gif was created using licecap - a great piece of free OSS

Transparent Gradient

The use of transparent color will most likely not lead to the expected result. transparent is actually a transparent black color (rgba(0, 0, 0, 0)). If you need a gradient in which the color is "fading", you need to have the same color with changing alpha channel. Example:

// RGBA

<LinearGradient colors={['rgba(255, 255, 255, 0)', 'rgba(255, 255, 255, 1)']} {...otherGradientProps} />

// Hex

<LinearGradient colors={['#FFFFFF00', '#FFFFFF']} {...otherGradientProps} />

Props

In addition to regular View props, you can also provide additional props to customize your gradient look:

colors

An array of at least two color values that represent gradient colors. Example: ['red', 'blue'] sets gradient from red to blue.

start

An optional object of the following type: { x: number, y: number }. Coordinates declare the position that the gradient starts at, as a fraction of the overall size of the gradient, starting from the top left corner. Example: { x: 0.1, y: 0.1 } means that the gradient will start 10% from the top and 10% from the left.

end

Same as start, but for the end of the gradient.

locations

An optional array of numbers defining the location of each gradient color stop, mapping to the color with the same index in colors prop. Example: [0.1, 0.75, 1] means that first color will take 0% - 10%, second color will take 10% - 75% and finally third color will occupy 75% - 100%.

<LinearGradient
  start={{x: 0.0, y: 0.25}} end={{x: 0.5, y: 1.0}}
  locations={[0,0.5,0.6]}
  colors={['#4c669f', '#3b5998', '#192f6a']}
  style={styles.linearGradient}>
  <Text style={styles.buttonText}>
    Sign in with Facebook
  </Text>
</LinearGradient>

useAngle / angle / angleCenter

You may want to achieve an angled gradient effect, similar to those in image editors like Photoshop. One issue is that you have to calculate the angle based on the view's size, which only happens asynchronously and will cause unwanted flickr.

In order to do that correctly you can set { useAngle: true, angle: 45, angleCenter: { x: 0.5, y: 0.5} }, to achieve a gradient with a 45 degrees angle, with its center positioned in the view's exact center.

useAngle is used to turn on/off angle based calculation (as opposed to start/end). angle is the angle in degrees. angleCenter is the center point of the angle (will control the weight and stretch of the gradient like it does in photoshop.

An example app

You can see this component in action in brentvatne/react-native-login.

Troubleshooting

iOS build fails: library not found, "BVLinearGradient" was not found in the UIManager

• Ensure you have followed the installations steps correctly. (react-native link for React Native < 0.60 and npx pod-install instead for > 0.60).
• Ensure pod 'BVLinearGradient', :path => '../node_modules/react-native-linear-gradient' is present in your ios/Podfile
• Ensure you use ios/**.xcworkspace file instead of ios./**.xcodeproj

Invariant Violation: Element type is invalid

Ensure you import the LinearGradient correctly:

// Like that:
import LinearGradient from 'react-native-linear-gradient';

// Not like that:
import { LinearGradient } from 'react-native-linear-gradient';

Other

Clearing build caches and reinstalling dependencies sometimes solve some issues. Try next steps:

• Reinstalling node_modules with rm -rf node_modules && yarn
• Clearing Android Gradle cache with (cd android && ./gradlew clean)
• Reinstalling iOS CocoaPods with (cd ios && rm -rf ./ios/Pods/**) && npx pod-install
• Clearing Xcode Build cache (open Xcode and go to Product -> Clean Build Folder)

For other troubleshooting issues, go to React Native Troubleshooting

Other platforms

• Web: react-native-web-community/react-native-web-linear-gradient

License

MIT