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React Native: Building the "Shoes" App

Random | 20 Oct 2016
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Overview

I was recently experimenting building a react native app. After digging a bit deeper into hybrid development, I have got attracted to the concept of producing a native code, in contrast to the web view approach in most of hybrid apps.

So here's what we've got. Setting it up:

If you go to https://facebook.github.io/react-native/docs/getting-started.html you'll get some instructions how to set it up.

Android installation

JDK can be installed using this link:
http://www.oracle.com/technetwork/java/javase/downloads/index-jsp-138363.html

Android SDK can be installed using:
brew install android-sdk

After finishing these 3 steps, we would need to install some android packages.

Open Android package manager:

android

These packages will be required to run the android simulator:

You would also require to download IntelHAXM.dmg file, which you can do from:

https://software.intel.com/en-us/android/articles/intel-hardware-accelerated-execution-manager

Run the installation file after download dmg.

At this point we would like to create an android virtual device (AVD):

# launching avd manager
android avd

Click "Create" and choose the following options for your AVD:

screen-shot-2016-10-18-at-11-13-16-pm

Now your AVD is created and you can start your emulator using:

emulator -avd 
# in our example: emulator -avd reactnative

iOS installation

iOS emulator will be installed automatically as part of Xcode installation. You can install Xcode from the the app store and choose the particular emulator to start from within Xcode.

Installation

Before proceeding let's make sure that we have the following tools in place:

Check out the installation post for more information about how to install these tools.

# install the react native cli
npm install -g react-native-cli

Run this script to create your first app (our app is called "Shoes"):

react-native init Shoes

At any point throughout this tutorial, you can run your app using these commands:

# run your app on iOS
react-native run-ios

# run your app on Android
react-native run-android

It's time for fun now, let's start coding to build our beautiful shoe app !

The "Shoes" App

Everything is in place now, time to start the work!

Let's navigate to the directory where we initialized the shoe app:

cd Shoes

# directory  listing
ls -F

screen-shot-2016-10-19-at-10-13-29-pm

We have got several files here. T0 give possibility to distinguish the code based on the version used, we have 2 entry scripts: index.ios.js and index.android.js which will be parsed and executed based on the corresponding app platform.

This is how the default index.ios.js script would look like:

/**
 * Sample React Native App
 * https://github.com/facebook/react-native
 * @flow
 */

import React, { Component } from 'react';
import {
 AppRegistry,
 StyleSheet,
 Text,
 View
} from 'react-native';

export default class Shoes extends Component {
 render() {
 return (
 
 
 Welcome to React Native!
 
 
 To get started, edit index.ios.js
 
 
 Press Cmd+R to reload,{'\n'}
 Cmd+D or shake for dev menu
 
 
 );
 }
}

const styles = StyleSheet.create({
 container: {
 flex: 1,
 justifyContent: 'center',
 alignItems: 'center',
 backgroundColor: '#F5FCFF',
 },
 welcome: {
 fontSize: 20,
 textAlign: 'center',
 margin: 10,
 },
 instructions: {
 textAlign: 'center',
 color: '#333333',
 marginBottom: 5,
 },
});

AppRegistry.registerComponent('Shoes', () => Shoes);

We can notice here that our script consists from several sections.

In the top we are importing couple of components which will be needed to run the script. Some components are imported from react, while others from react native modules.

You will notice also that the default class has render() function which is supposed to return the objects to be parsed and rendered in the native app.

Notation used in return statement of render function() is called JSX - a Javascript syntax extension which make it look like XML. Of course you don't have to write using JSX and can use a plain javascript, however JSX will be much more comfortable.

You can read more about JSX here:

https://facebook.github.io/react/docs/jsx-in-depth.html

As mentioned in the previous section, we will use the following command to run our code as we developer:

react-native run ios

Building the Home Page

We will start by creating a folder called src in our project root.

screen-shot-2016-10-19-at-10-34-33-pm

Within the src/ folder we will place our Home page script called home.js. In addition, let's create a file called shoes.js which will be our root components which can be used both within index.ios.js and index.android.js. This is what I expected to have at this point:

src/
|__  src/shoes.js
|__  src/home.js

Let's start working on our beautiful home page. At this point I would like to achieve a blank page with some text in the middle, let's say "Hello world!". This won't be a great achievement in comparison to what was already generated in index.ios.js, however it will give as an ideas about how to better organize the code and wrap the default components into more complex reusable components.

This is how my home.js file would look like at this point:

screen-shot-2016-10-19-at-10-51-29-pm

 

In the shoes.js file we would like to refer to import home.js file and import it:

screen-shot-2016-10-19-at-10-51-52-pm

At this point we have got the Shoes components ready and it's using the Home component. Placing tags within the Shoes component indicates that rendering Shoes component, will require to instantiate and render Home components. All we want to do now in index.ios.js is to include the Shoes component and set it as an entry point to our app.

screen-shot-2016-10-19-at-10-51-38-pm

Now, try to run using:

react-native run-ios

screen-shot-2016-10-19-at-10-52-08-pm

Great ! First step accomplished, we got something working!