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React and React Native

You're reading from   React and React Native Build cross-platform JavaScript apps with native power for mobile, web and desktop

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Product type Paperback
Published in Mar 2017
Publisher Packt
ISBN-13 9781786465658
Length 500 pages
Edition 1st Edition
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Author (1):
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Adam Boduch Adam Boduch
Author Profile Icon Adam Boduch
Adam Boduch
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Toc

Table of Contents (27) Chapters Close

Preface 1. Why React? FREE CHAPTER 2. Rendering with JSX 3. Understanding Properties and State 4. Event Handling – The React Way 5. Crafting Reusable Components 6. The React Component Lifecycle 7. Validating Component Properties 8. Extending Components 9. Handling Navigation with Routes 10. Server-Side React Components 11. Mobile-First React Components 12. Why React Native? 13. Kickstarting React Native Projects 14. Building Responsive Layouts with Flexbox 15. Navigating Between Screens 16. Rendering Item Lists 17. Showing Progress 18. Geolocation and Maps 19. Collecting User Input 20. Alerts, Notifications, and Confirmation 21. Responding to User Gestures 22. Controlling Image Display 23. Going Offline 24. Handling Application State 25. Why Relay and GraphQL? 26. Building a Relay React App

Resizing images

The width and height style properties of Image components determine the size of what's rendered on the screen. For example, you'll probably have to work with images at some point that have a larger resolution than you want displayed in your React Native application. Simply setting the width and height style properties on the Image is enough to properly scale the image.

Let's look at some code that lets you dynamically adjust the dimensions of an image using a control:

import React, { Component } from 'react'; 
import { 
  AppRegistry, 
  View, 
  Text, 
  Image, 
  Slider, 
} from 'react-native'; 
import { fromJS } from 'immutable'; 
 
import styles from './styles'; 
 
class ResizingImages extends Component { 
  // The initial state of this component includes 
  // a local image source, and the width/height 
  // image dimensions. 
  state = { 
    data: fromJS({ 
      source: require('./images/flux.png'), ...
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