How to set default font family in React Native?

Question

Is there an equivalent to this CSS in React Native, so that the app uses the same font everywhere ?

body {
  font-family: \'Open Sans\';
}

Answer 1

You can override Text behaviour by adding this in any of your component using Text:

let oldRender = Text.prototype.render;
Text.prototype.render = function (...args) {
    let origin = oldRender.call(this, ...args);
    return React.cloneElement(origin, {
        style: [{color: 'red', fontFamily: 'Arial'}, origin.props.style]
    });
};

Edit: since React Native 0.56, Text.prototypeis not working anymore. You need to remove the .prototype :

let oldRender = Text.render;
Text.render = function (...args) {
    let origin = oldRender.call(this, ...args);
    return React.cloneElement(origin, {
        style: [{color: 'red', fontFamily: 'Arial'}, origin.props.style]
    });
};

Answer 2

Add this function to your root App component and then run it from your constructor after adding your font using these instructions. https://medium.com/react-native-training/react-native-custom-fonts-ccc9aacf9e5e

import {Text, TextInput} from 'react-native'

SetDefaultFontFamily = () => {
    let components = [Text, TextInput]

    const customProps = {
        style: {
            fontFamily: "Rubik"
        }
    }

    for(let i = 0; i < components.length; i++) {
        const TextRender = components[i].prototype.render;
        const initialDefaultProps = components[i].prototype.constructor.defaultProps;
        components[i].prototype.constructor.defaultProps = {
            ...initialDefaultProps,
            ...customProps,
        }
        components[i].prototype.render = function render() {
            let oldProps = this.props;
            this.props = { ...this.props, style: [customProps.style, this.props.style] };
            try {
                return TextRender.apply(this, arguments);
            } finally {
                this.props = oldProps;
            }
        };
    }
}

Answer 3

Add

"rnpm": {
  "assets": [
 "./assets/fonts/"
  ]
}

in package.json then run react-native link

Answer 4

Super late to this thread but here goes.

TLDR; Add the following block in your AppDelegate.m

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{

 ....
    // HERE: replace "Verlag" with your font
  [[UILabel appearance] setFont:[UIFont fontWithName:@"Verlag" size:17.0]];
  ....
}

Walkthrough of the whole flow.

A few ways you can do this outside of using a plugin like react-native-global-props so Ill walk you though step by step.

Adding fonts to platforms.

How to add the font to IOS project

First let's create a location for our assets. Let's make the following directory at our root.

```

ios/
static/
       fonts/

```

Now let's add a "React Native" NPM in our package.json

  "rnpm": {
    "static": [
   "./static/fonts/"
    ]
  }

Now we can run "react-native link" to add our assets to our native apps.

Verifying or doing manually.

That should add your font names into the projects .plist (for VS code users run code ios/*/Info.plist to confirm)

Here let's assume Verlag is the font you added, it should look something like this:

     <dict>
   <plist>
      .....
      <key>UIAppFonts</key>
      <array>
         <string>Verlag Bold Italic.otf</string>
         <string>Verlag Book Italic.otf</string>
         <string>Verlag Light.otf</string>
         <string>Verlag XLight Italic.otf</string>
         <string>Verlag XLight.otf</string>
         <string>Verlag-Black.otf</string>
         <string>Verlag-BlackItalic.otf</string>
         <string>Verlag-Bold.otf</string>
         <string>Verlag-Book.otf</string>
         <string>Verlag-LightItalic.otf</string>
      </array>
      ....    
</dict>
</plist>

Now that you mapped them, now let's make sure they are actually there and being loaded (this is also how you'd do it manually).

Go to "Build Phase" > "Copy Bundler Resource", If it didn't work you'll a manually add under them here.

Get Font Names (recognized by XCode)

First open your XCode logs, like:

Then you can add the following block in your AppDelegate.m to log the names of the Fonts and the Font Family.

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    .....


  for (NSString* family in [UIFont familyNames])
  {
    NSLog(@"%@", family);
    for (NSString* name in [UIFont fontNamesForFamilyName: family])
    {
      NSLog(@" %@", name);
    }
  }

  ...
}

Once you run you should find your fonts if loaded correctly, here we found ours in logs like this:

2018-05-07 10:57:04.194127-0700 MyApp[84024:1486266] Verlag
2018-05-07 10:57:04.194266-0700 MyApp[84024:1486266]  Verlag-Book
2018-05-07 10:57:04.194401-0700 MyApp[84024:1486266]  Verlag-BlackItalic
2018-05-07 10:57:04.194516-0700 MyApp[84024:1486266]  Verlag-BoldItalic
2018-05-07 10:57:04.194616-0700 MyApp[84024:1486266]  Verlag-XLight
2018-05-07 10:57:04.194737-0700 MyApp[84024:1486266]  Verlag-Bold
2018-05-07 10:57:04.194833-0700 MyApp[84024:1486266]  Verlag-Black
2018-05-07 10:57:04.194942-0700 MyApp[84024:1486266]  Verlag-XLightItalic
2018-05-07 10:57:04.195170-0700 MyApp[84024:1486266]  Verlag-LightItalic
2018-05-07 10:57:04.195327-0700 MyApp[84024:1486266]  Verlag-BookItalic
2018-05-07 10:57:04.195510-0700 MyApp[84024:1486266]  Verlag-Light

So now we know it loaded the Verlag family and are the fonts inside that family

• Verlag-Book
• Verlag-BlackItalic
• Verlag-BoldItalic
• Verlag-XLight
• Verlag-Bold
• Verlag-Black
• Verlag-XLightItalic
• Verlag-LightItalic
• Verlag-BookItalic
• Verlag-Light

These are now the case sensitive names we can use in our font family we can use in our react native app.

Got -'em now set default font.

Then to set a default font to add your font family name in your AppDelegate.m with this line

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{

 ....
    // ADD THIS LINE (replace "Verlag" with your font)

  [[UILabel appearance] setFont:[UIFont fontWithName:@"Verlag" size:17.0]];
  ....
}

Done.

Answer 5

Set in package.json

"rnpm": {
  "assets": [
     "./assets/fonts/"
  ]
}

And link react-native link

Answer 6

The recommended way is to create your own component, such as MyAppText. MyAppText would be a simple component that renders a Text component using your universal style and can pass through other props, etc.

https://facebook.github.io/react-native/docs/text.html#limited-style-inheritance