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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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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

Lazy image loading

Sometimes, you don't necessarily want an image to load at the exact moment that it's rendered. For example, you might be rendering something that's not yet visible on the screen. Most of the time, it's perfectly fine to fetch the image source from the network before it's actually visible. But if you're fine-tuning your application and discovering that loading lots of images over the network causes performance issues, you can lazily load the source.

I think the more common case in a mobile context is handling a scenario where you've rendered one or more images where they're visible, but the network is slow to respond. In this case, you will probably want to render a placeholder image so that the user sees something right away, rather than empty space.

To do this, we'll implement an abstraction that wraps the actual image that we want to show once it's loaded. Here's the code:

import React, { Component, PropTypes } from...
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