React Native Simple Boxing Timer - From Scratch to the App Store

Ever wondered how easy it is to create your first app for iOS? It really isn’t. There are many pitfalls to consider. I’ll describe the process of developing your first app for iOS using React Native as it was actual in October, 2016.

Develop with React Native

It is quite easy to initialize React Native project and start to tackle the code. With provided CLI, it will run nicely and have a hot refresh on the emulator, along with browser debug console. Developing with React Native feels great in comparison with Phonegap that I’ve tried before
(there is the link to the app I wrote as a result) In comparison with web React.js, instead of DOM components, you use native components like <View/> and write a lot of inline styles. Otherwise, it’s a familiar React JS app where you can use your favorite libraries like Bluebird, Moment.js, etc., and of course, Redux/Mobx too. One exception – you cannot use the libraries working with DOM. Because there’s no DOM. I’ve chosen Mobx for data handling and I think it was a very good solution for concrete application objectives. It worked quite nicely with settings screen. That’s a topic in itself that I plan to write about in a future post.

Settings screen

React Native components which were used for this screen - View, Picker and Settings classes.

Version for old iOS

I wanted the app to be accessible as much as possible, including to the third-world countries. For this reason, I included iOS 7 support to the app (iPhone 4s and later). It brings additional considerations: React Native version 0.33.1 was the last version where iOS 7 was officially supported. Luckily, it wasn’t too old (it was released just a month ago) so I’ve decided to go with it. Of course, I’ve tried later versions initially, but they weren’t building well in xCode.

Design, Material UI

All apps need a design. When you’re a web developer without a visual design sense, you reach for a Bootstrap. However, since is no Bootstrap in mobile apps world, I’ve turned to Google Material Design rulebook. First, I’ve decided on the color scheme. It had to be roughly the same I used for my previous timer app, so I got an appropriate color combination from Material Design color guide.

Icons, buttons

Second, I needed some buttons. Library React Native Material Kit did the job. Third, I’ve needed some icons. For the web, you just get Font Awesome, and the good news is, they’re available on React Native too

Main screen

So now I had a design for my main screen.

Sleep control, sounds

The specifics of a timer application allow you to play sounds and have a control over screen sleeping. For sounds, I’ve used React Native Sound library. It was quite old at the time, but I haven’t found anything better. It did its job though and let me play the sounds.

Note that in order for some React Native libraries to work, you have to do additional settings in your iOS and Android projects.

What you’ll need to do is described in each library readme, but mostly running script `react-native link library-name` does the job automatically.

This is true for Material Kit, Icons lib, React Native Sound and Screen Sleep Control lib.

For screen sleep control, I used react-native-keep-awake. I do KeepAwake.activate() whenever timer is running and KeepAwake.deactivate() whenever timer is stopped. This way, the user won’t experience screen sleep in the middle of a training.

Rotation control, responsive font size

The challenging part was the reactive font size change, depending on screen rotation. Googling for screen rotation detection gave me a couple of deprecated and non-working libraries. The official React Native docs were quite vague on this matter. Eventually, in the depths of Stack Overflow, I found the answer, and now I’m sharing this Secret with you — use View’s onLayout callback function!

<View onLayout={(event) => {

where calculateWH is defined this way:

calculateWH(event) {
    const l = event ? event.nativeEvent.layout : Dimensions.get('window'); // for some reason, it doesn't always give the event
    return {
        vw: l.width / 100,
        vh: l.height / 100

so now you have vw and vh for reactively changing your fonts size, and also have re-rendered on screen rotation. Don’t forget to import Dimensions from react-native package.

App store

I found this part most time-consuming, in comparison with development itself.

App icons

First, you need a nice icon. I just fetched a couple of free ones from the Internet, glued them together in Photoshop, and added a gradient background. Another thing you’ll need is a lot of different sizes for the icon. I uploaded my icon to one of the free icon resizing services and got it in various sizes.

App Icon

App screenshots, UX testing

Second, in order to get your app published, you need screenshots. Usually, a couple is enough, but I wanted screenshots for all devices. As a result, with two app screens, I needed around 12 screenshots on 6 emulators. People who add internationalization in their app need screenshot packs for each language. For example, if I will be supporting 12 languages, I’ll require 144 screenshots. Better to be prepared for that, and automatize the process. For this and for beta testing / deployment, I used fastlane. Fastlane is a set of tools for automating several mobile development chores. It actually spared me a lot of clicks. I used its snapshot tool for taking screenshots. Before really using it, I needed to set up the tests in xCode. I did everything by the manual, but I ran into an issue: elements didn’t recognize testId property. So I’ve decided not to go with it, and record test with manual recording feature in xCode instead.

Here is my test code:

func testExample() {
      let app = XCUIApplication()
      let startButton = app.buttons[" Start  "]
      let stopButton = app.buttons[" Stop  "]

After running it in snapshot tool, I got 12 nice screenshots. Now I can use them for internationalization also.

Beta, signing, release

It was time to check the app in a real environment. By default, fastlane is set up for TestFlight, but TestFlight doesn’t work on old iOS that I had at the time, so I’ve reconfigured it to TestFairy service. After checking on the device, I’ve released it with fastlane deploy. This process has its moments (i.e. signing) but generally, fastlane automatize most of the chores for you.