From iPhone App to Apple Watch App
When the iPhone SDK came out in 2008, developers struggled to find the right balance. They had Mac apps with tons of great features, but not all of those features made sense on iPhones of the time. Apple gave some guidance, suggesting to developers that they aggressively pare down their apps’ feature sets in the transition from OS X to iOS. As time went on, iOS apps became more full-featured than those initial apps, especially with the introduction of the iPad, but OS X apps are still, by nature, more complex.
The Apple Watch and its WatchKit SDK bring us to another such point in time. Not every single feature makes sense to bring from your iPhone app to its WatchKit extension, and some just flat out don’t belong. If your app is an RSS reader, for instance, your users aren’t going to be reading long-form think pieces on their wrists during their morning commute; they’ll just pull out their iPhones for that. That doesn’t mean that an RSS reader shouldn’t have a WatchKit extension, though—users might want to skim headlines on their watches, saving interesting ones to their reading lists or marking uninteresting articles as read. Other app types might want to bring every feature to the watch if every feature makes sense. So the question is how you pare down the features of an existing iPhone app to those that make sense on the watch.
Finding the Right Features
Think about your app in the context of the watch. Do you have features that would excel on a smaller screen? Quick, easy-to-navigate pieces of information are key here. If your app does light messaging, an inbox is a perfect addition to it. If your app is an RSS reader, on the other hand, full-length feeds aren’t as compelling. Focus your effort on the parts of your app that can save your users time—that’s why they bought the watch in the first place.
Often, it’s a good idea to incorporate only the best-fitting part of your app’s features in the watch app. If your app allows its users to change the temperature in their homes as well as schedule recurring temperature changes, consider showing only the controls for adjusting the current temperature. Since you know users can do more advanced changes on their iPhones, it’s a great way to focus and make a more streamlined interface.
After the watch’s announcement, you may have started to consider using the device’s hardware capabilities. It has a microphone for Siri, an accelerometer, and a heart rate sensor. While the first version of WatchKit didn’t include access to any of this hardware, apps built for watchOS 2 can take full advantage of these hardware features and use them to create more engaging apps. You’re not limited to simple taps and finger gestures on the watch, so get creative!
Integrating Important Watch Features
A simple messaging app could definitely be ported to WatchKit without losing features, but one feature in particular could make all the difference in the world: actionable notifications. Instead of just showing a user that she has a new message, the developer of a messaging app could create an actionable notification with the option to reply. Now the user doesn’t even have to be using that watch app to get value out of it. When the message comes in, she hits Reply, dictates a response, and sends it. This is one of the watch’s real strengths: it allows the user to spend the minimum amount of time doing something. Instead of digging out her phone and opening the app to respond, she just needs to move her wrist a little. More on actionable notifications in a later chapter.
Sometimes, despite your watch app’s best efforts, users will need to do something on their iPhones. Suppose you have an app for ordering cake to be delivered. On the watch, the user can select a cake to order, pick which color frosting, and even dictate a short phrase to be written on top of the cake. Sounds delicious! But then she goes to place the order and notices that her delivery address is the apartment she just moved out of. Now she’s stuck; she just used the watch to make these selections, but without a keyboard on the watch, it’s going to be tough to enter a new address. This is a job for Handoff.
Handoff is a feature of both iOS and OS X that allows your app to tell your user’s other devices what she’s doing. For more information on Handoff, read the Handoff Programming Guide.[3] You describe the type of activity the user is engaged in, and the system displays an icon for this activity on the iOS lock screen. In the cake example, you’d describe the user’s activity as “ordering a cake” and include with it information about the cake that she entered on the watch. From there, the user would open the app on her iOS device through the Handoff icon on the lock screen, and the app would open directly to the cake-ordering screen, allowing the user to change the delivery address to her new apartment and get her cake ordered successfully.
Even though the user in this scenario isn’t able to do everything on the watch, it’s important to save her work so she doesn’t feel like it’s a waste. In that same scenario without Handoff, the user would need to start over on her iPhone, selecting the cake she wants from scratch. By making the user redo everything, you run the risk of alienating her from using the watch app; after all, if she might have to redo it, why not just start on the iPhone?
Providing Information at a Glance
When an Apple Watch user swipes up on the watch face, she sees a list of Glances. A Glance is a miniature version of a watch app; it’s one screen of content that she can access quickly, without even opening your watch app. To that end, think about the information in your app that’s the most timely to the user: her next meeting, the boarding pass for her flight, or her friends with birthdays today. Put that information in your Glance. When the user taps it, she can go right to that piece of information in your watch app, giving her a shortcut to something she needs to access quickly.
Making It Beautiful
Once you know what features you’re going to implement in your WatchKit extension and its Glance, put on your designer hat (or hire a designer) and think about your app’s user interface. Apple strongly recommends having a dark background. Though Apple hasn’t said as much officially, common wisdom suggests that the OLED screens in the watch use less power for black pixels than for white. Since battery life is paramount for the watch, black backgrounds are a good idea. Having said that, color is one of the best ways to make your branding consistent between iPhone and Apple Watch. Try to avoid a black screen full of plain, white labels and stock buttons. Avoid a stark white background, too: be bold with your color choices and try to make your app stand out from the crowd, but aim for color as a highlight on top of a dark background.
Animations are among the coolest things you can do on the watch. Some animations on the watch are simply image sequences, animating like a flipbook. If you can’t display a screen immediately—if you need to go out to the network, for instance—use an image sequence animation to indicate that. If a button begins a long-running task like charging a battery, you can add an animation to indicate that’s happening. In a small way it can make an otherwise-boring app lively and fresh. Other animations can move user interface elements around, fade them in or out, and perform other small tasks to spice up the app a little.