React Native is a new technology that allows building real mobile apps using only JavaScript. It is a JavaScript framework for writing, debugging, and deploying both iOS and Android mobile applications with native experience. React-Native allows developers to share about 80% of code between iOS and Android which make the development is 5x faster than traditional means. React-Native libraries are created by Facebook released in March 2015. It was proven by many world-class mobile applications, such as Facebook, Facebook Ads Manager, TaskRabbit, QQ, Discord, SoundCloud, etc.

1. ITS485 Lecture 1:
React Native Introduction
Dr. Kobkrit Viriyayudhakorn
iApp Technology Limited
http://www.kobkrit.com

3. Course Outline

4. Course Outline

5. Grading Policy
• Quizzes: 10%
• At the beginning of the class (Always
be on time).
• Term Project: 20%
• Midterm exam: 35% (Open Books)
• Final exam: 35% (Open Books)

6. Term Project
• Making a 5-10 Screens Mobile Application.
• Group & Project Assignment after the midterm exam.
• Set up a group of three. (36/3 = 12 groups)
• 15% - Group scores - Usefulness, App Business
Model, UI, UX, Functionality, Code Style, and
Pitching.
• 5% - Individual scores - App development questions
target to each person during presentation.
• 10 minutes presentation: Pitching 3 minutes, Code
Explanation 2 minutes, Question & Answering 5
minutes.

7. Books & Reference
• https://facebook.github.io/reactnative/
• Bonnie Eisenman, Learning React Native Building
Native Mobile Apps with JavaScript, O'Reilly
Media, December 2015.
• https://github.com/jondot/awesome-react-native
• https://js.coach/react-native/

9. What is React Native?
• JavaScript framework for building iOS and Android
mobile apps.
• Based on popular JavaScript Web framework called
React.
• Created by Facebook. Firstly release iOS version on
March 2015 and Android version on September
2015
• Writing the app by using JavaScript and XML-esque
markup (JSX)
• React-Native bridges and invokes the Native
rendering API in Objective-C (iOS) and Java
(Android)

10. Approach of Mobile App Dev.
Approach Platform Logic UI UX Dev Time*
Native
Object C, Swift
(iOS), Java
(Android)
Native Native Smooth 6-24 weeks
HTML5
Hybrid
PhoneGap,
Cordova, Ionic
JS
HTML,
CSS
Laggy 2-8 weeks
Native
Hybrid
React Native,
NativeScript
JS Native Smooth 2-8 weeks
* 20-30 screens mobile apps approximated based on instructor experiences

11. Why React Native?
• Native Experience
• One language rules them all, JavaScript.
• Fast & Great Development Experience
• Don’t Waste Time Recompiling (Hot Reloading)
• 80% Share code between Android & iOS
• Great Debugging Tool using Chrome Developer Tools
• Be able to bridge with Native Code when we need to.

12. Native Experience

13. Hot Reloading

14. Debugging with Chrome Developer Tools

15. Why not React Native?
• React-Native is still relatively young compared with
Native iOS and Android Communities (Released on
2015)
• Some of Native API still are not supported. (But you
can use the native libraries through)
• Add one additional layer to mobile app project.

16. What is React?
• Declarative, Efficient,
and Flexible
JavaScript Library that
Building User
Interface on Website.
• React Native is rooted
from React.
• React treats every
thing as a Component.
A React Component

17. How React Native Works?
• Q: How a Web framework (React) can be improved and
become a Native Mobile Development Platform?
• A: Flexibility of React’s Virtual DOM
• React aimed to make Web application fast as much as
possible.
• DOM Changing (Changing the content of webpage)
dynamically is expensive step. Re-rendering DOM is
significant impact on performance.
• Rather than directly render change DOM in the page, React
compute the only diff that need to be render in memory by
Virtual DOM and re-renders the minimal amount necessary.

18. Virtual Dom, Technique of React => Root of React Native

19. Another Benefits of Virtual
DOM
• Performance benefits.
• Abstraction layers.
• FB Engineer: What if React could render to a target
other than the Web Browser’s DOM?
• Instead of rendering HTML/CSS to the browser’s
DOM. Why can’t we rendering mobile app by using
Objective-C APIs to render to iOS, and invokes
Java to render to Android.

21. Rendering Lifecycle
Mounting Component
Re-rendering Component

22. Async Rules
• Good benefits of JavaScript is their asynchronous
natures.
• React-Native is running on separated thread using
JavaScript asynchronous call via the event bridge
to invokes the host native platform’s underlying APIs
and UI elements. (Objective-C, Java)
• Since, React-Native don’t run on the main UI
rendering thread, it can do asynchronous call without
impact user’s experience (such as delay).

23. Android
Native
UI
Event Bridge
JS World Android World
Thread 1 Main Thread
AsyncCall
(Non-Blocking)

24. How React-Native Draw?
• React for the Web, render normal HTML elements
• React Native, render cross-platform (or platform-
specific) native UI component.
Cross Platform (iOS, Android) Platform Specific
<DatePickerIOS>

25. Example of Platform Specific
Components
<Switch>
<SwitchIOS><SwitchAndroid>

26. JSX
• Combining JavaScript and XML-markup syntax to create view.
• Single File Concept (Write down at Component Class), Not
Seperate Files (Split HTML, CSS, JS)
• Separation of concerns > Separation of technologies
JSX (Underlined) Rendered View

27. Styling
• In Web, We have CSS, necessary part of the Web.
• In React-Native, We have something similar to CSS,
called Flexbox Layout Model.
{ background-color : ‘white’}
{ backgroundColor : ‘white’}
CSS
Camel Case in React

29. React-Native Support
• Mac OS can develop
• iOS
• Android
• Windows OS can develop
• Only Android

30. HomeBrew Installation
• Open Terminal (Click on Find icon on the top right
of the screen)
• Type “Terminal”
• Enter $ /usr/bin/ruby -e "$(curl -fsSL https://
raw.githubusercontent.com/Homebrew/install/
master/install)"

31. Install React-Native in Mac
for iOS Development.

32. React-Native-Cli Command

33. Try
• $ react-native init sampleProject
• $ cd sampleProject
• $ react-native run-ios

34. IDE
• Any Text Editor is fine.
• Atom
• React
• React-Snippet
• Atom-React-Native-CSS
• Atom-React-Native-
Autocomplete
• Sublimes
• Visual Studio Code

35. Project Structure

36. Download Lecture Note
After Class & Video
http://www.kobkrit.com