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The Beauty Of React Native: Building Your First iOS App With JavaScript (Part 2)
Quick Summary
In part 1 of this tutorial we started building our iOS app from scratch. We started out by setting up a blank React Native project. Then we pulled data from the Unsplash.it API. Because downloading data takes time, we built a loading screen.
In the process we went over positioning UI elements with flexbox and styling them using CSS-like properties. Towards the end of part 1 we downloaded and included a third-party Swiper component from GitHub, which allowed us to display wallpaper data in a swipeable container.
Table of Contents
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In part 1 of this tutorial, we started building our iOS app from scratch. We started out by setting up a blank React Native project. Then we pulled data from the Unsplash.it API.
Because downloading data takes time, we built a loading screen. In the process we went over positioning UI elements with flexbox and styling them using CSS-like properties. Towards the end of part 1 we downloaded and included a third-party Swiper component from GitHub, which allowed us to display wallpaper data in a swipeable container.
Further Reading on SmashingMag:
It doesn’t do much yet but that’s all about to change. In this part of the tutorial we will start by replacing the photographer’s name with the actual wallpaper image along with proper credits. During this process you’ll learn how to link a library in Xcode, as well as more on general styling and positioning of UI elements. Then we will go over building a custom double-tap listener using the PanResponder API and a little bit of math. Toward the end you will learn how to save pictures to the Camera Roll and also how to run your app on a physical device. To apply all your newly learned React Native skills there is a challenge waiting for you at the end.
Just like the first part, this article has five sections. Completing each section takes us a step closer to finishing our app.
1. Displaying Wallpapers And Credits
Let’s take a look at the data each wallpaper object holds. Consider the following sample data.
Since we’re able to construct a URL for the image, we can add an Image component with proper source attribute.
But let’s not get ahead of ourselves. Wallpapers that we pull from Unsplash are high quality and may take time to load. If we simply use React Native’s Image component we will leave our users staring at a blank screen while the wallpaper loads. We need a progress bar-like component here – luckily, there is a component for just that.
Head over to the project directory from terminal and run the following two commands:
npm install --save react-native-image-progress
npm install --save react-native-progress
Let’s import these into our index.ios.js file. Add the following two lines right below the use strict; statement:
var NetworkImage = require('react-native-image-progress');
var Progress = require('react-native-progress');
Since our wallpaper images cover the whole viewport, we will need to know the width and height of the viewport. To do that add:
var {width, height} = React.Dimensions.get('window’);
outside the class declaration and right below the import statements. If you have been following carefully you’ll of course know that we can substitute React.Dimensions with Dimensions by adding a new line to the React import code block.
var {
AppRegistry,
StyleSheet,
Text,
View,
Component,
ActivityIndicatorIOS,
/***/
Dimensions // Add this line
/***/
} = React;
Just saving a couple of keystrokes, y’know.
Now, we will use the NetworkImage component in renderResults.
Notice the value that uri holds inside NetworkImage’s source attribute. This is one of ES2015’s new features called template strings. Template strings allow you to include variables right inside the string using ${variableName} instead of concatenating them again and again using +.
I’ll tell you again. ES2015 is pretty cool!
Add the following style definition to the styles variable:
Refresh the simulator and you should end up with a bunch of errors. Don’t worry, we didn’t break anything. The compiler is just complaining about a library it needs and cannot find. Let’s help the compiler out.
Taking a closer look at the code we just added, notice one of the NetworkImage’s properties is indicator and it holds the value of Progress.Circle. As mentioned in the component’s docs on GitHub (don’t tell me you didn’t read the docs) Progress.Circle requires ReactART, which is a library to draw vector graphics using React. We don’t need to download anything new here, just include it in our project, this time through Xcode.
Clicking on any of the images below will point you to a larger version of that image, which will give you a better idea of what’s going on.
Concentrate and pay close attention here.
Head to the following path from the root of the project: node_modules/react-native/Libraries/ART/
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