Apple Issues Strict Rules for the First Watch Apps

The release of Apple’s WatchKit yields more insight into how the company is tackling smart-watch issues.

Millions of people use iPhones, and nobody has yet cracked the fast-growing smart-watch market.

This Tuesday Apple released WatchKit, a set of software tools, rules, and recommendations for developing apps for its forthcoming Apple Watch. The release sheds more light on the company’s vision for the device and its plans to work out some common challenges related to issues like power consumption, device navigation, and very small screen size. As with the iPhone before it, the popularity of the new device could depend, in large part, on the apps made for it.

the Apple Watch
Like the iPhone and iPad, the Apple Watch, which will be released next year, will be able to run apps made by outside developers.

Slated for release early next year (see “The Apple Watch May Solve the Usual Smart-Watch Annoyances”), the Apple Watch is the company’s first attempt to compete in the smart-watch market, where major players like Google and Samsung have so far failed to gain popularity. WatchKit shows Apple’s usual obsession with design details: it wants wearable apps that look clean, provide very easy access to information, and don’t bother users too much.

One criticism leveled at other smart watches is that they overwhelm the user with functionality (see “So Far, Smart Watches Are Pretty Dumb”). In its human-interface guidelines for the device, Apple writes that watch apps are meant to be used for quick interactions at the wrist and should “respect the context in which the wearer experiences them: briefly, frequently, and on a small display.”

Apple also wants to make sure that developers pay attention to how their apps work with corresponding iPhone apps—like most other smart watches, the Apple Watch requires a smartphone to function, in this case an iPhone. In the guidelines, the company stresses that any app on the wrist “complements your iOS app; it does not replace it.” This could encourage developers to think about how they can bring functions to Apple Watch apps that might be more appropriate on the wrist than on the smartphone screen, such as certain kinds of context-aware alerts.

Another obvious problem facing makers of smart watches is battery life. In its guidelines, Apple tells app makers to use black as the background color for apps, because it “blends seamlessly with the device bezel ands maintains the illusion of there being no screen edges.” But if the Apple Watch display is an OLED display, as suspected (see “Manufacturing Advances Mean Truly Flexible Devices Are on the Way”), this could also be a simple way to save power, since pixels in such displays glow individually rather than being lit up by a backlight.

And Apple’s WatchKit programming guidelines indicate that most of the actual computing work will be done on the iPhone, not on the watch. All Apple Watch apps will require an accompanying iPhone app that includes a WatchKit extension, Apple says. The Watch app will include “only the storyboards and resource files associated with your app’s user interface,” while the WatchKit extension includes the code for “managing a Watch app’s user interface and responding to user interactions.”

“The WatchKit extension is the brains of the operation,” Apple writes.

This is set to change in the not-so-distant future, though: Apple said in September that “later next year” it will let developers build native Apple Watch apps. This suggests they’ll be able to write code that is installed and run on the watch, as with a normal phone app, and it could make for faster or more capable apps.

Additionally, while the Apple Watch supports a number of touch-screen gestures, developers will not be able to add their own or incorporate multifinger gestures such as pinching or spreading to zoom in and out (though in September’s announcement it appeared that the physical dial on the side of the watch, which is used for scrolling, can be used for zooming). And when including an image of a map within an app, developers are warned not to let the map be any bigger than the Apple Watch display so the user can see it all without having to scroll.

When arranging these maps—and any other images—within apps, developers will also be working with slightly different screen resolutions for the two watch sizes Apple plans to release. The documentation indicates that the 38-millimeter Apple Watch display measures 340 pixels tall by 272 pixels across, while the 42-millimeter one measures 390 by 312 pixels.

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