This document provides an overview of WatchKit applications for the Apple Watch. It discusses that WatchKit applications rely on the WatchKit framework and run on the Apple Watch, responding to user interaction. The Watch app works with the WatchKit extension on the iPhone to load interface controllers and pass data back and forth as the user interacts. Key parts of a WatchKit app include WKInterfaceController objects that manage views and respond to lifecycle methods like awakeWithContext, willActivate, and didDeactivate.

1. WatchKit API
BJIT Ltd.
Updated by: Md Saidul Islam Ziku
December 29, 2015

2. Contents
Apple watch application Introductory
Native Applications
WatchKit Applications
Watch App Architecture
Way to launch an app
Watch App Life Cycle
WatchKit Anatomy
WKInterfaceController LifeCycle
Recap

3. Apple watch application Introductory
Apple Watch applications are,
- Watch Kit applications
- Native Apple Watch applications
The main difference is the application
architecture.

4. Native Applications
• Native applications will be able to run without
an extension running on a paired iPhone.
• Haven’t introduced yet.

5. WatchKit Applications
• WatchKit application
completely relies on the
WatchKit Framework.
• The WatchKit application
runs on the Apple Watch
and is in charge of two
things:
① presenting the user
interface
② responding to user
interaction

6. Watch App Architecture
• Interactions with app on Apple
Watch lead to the launching of
WatchKit extension on the
appropriate device.
• The Watch app and WatchKit
extension then work together to
run the interface until the user
stops interacting with it.
• Watch app and WatchKit pass
information back and forth until
the user stops interacting with
the app.

7. Way to launch an app
• By tapping on Home
Screen icon.

8. Way to launch an app(Cont.)
• By tapping on Glances.

9. Way to launch an app(Cont.)
• By tapping on
Notifications.

10. Watch App Life Cycle
• WatchKit automatically loads the
storyboard scene that is
appropriate for the current
interaction.
• WKExtensionDelegate will call for
the corresponding
WKInterfaceController Objcets.
• WatchKit asks the WatchKit
extension to create the
corresponding interface
controller object.

11. Watch App Life Cycle(cont.)
• Very Similar to iOS app UIApplicationDelegate, a WKExtensionDelegate would
responsible for the watch app target.
• Three Basic Delegate method for WKExtensionDelegate
① - (void)applicationDidFinishLaunching
 Called Once on Lunch
 Perform app initialization
 Setup notifications objervers
 Not yet been active
② - (void)applicationDidBecomeActive
 Each time app become visually active
 Update any states
③ - (void)applicationWillResignActive
 Prepare to be inactive
 Call before going to background
 Disable running service, timers etc

12. WatchKit Anatomy
• Watch app contains a minimized user
interface and features of the main
application.
– WKInterfaceController
• Notification views are used to handle
push or local notifications of the
application.
– WKUserNotificationInterfaceController
• A glance is another optional
interface. It should provide the most
relevant data for app users.
– WKInterfaceController
• Complication is related for data
source.
– CLKComplicationDataSource
Interface
Resources
Watch
App
Code
Resources
Watch
App
Extension

13. WKInterfaceController LifeCycle
WKInterfaceController has three
important lifecycle methods:
• - awakeWithContext
– to prepare the controller for use.
– The context object is provided by the
previous controller to exchange the
data.
– If it is the root view controller, the
context object will be nil.
• - willActive
– to notify that interface is onscreen.
– It’s similar to viewDidLoad.
• - didDeactivate
– for cleaning app the controller
– when the interface is no longer
onscreen.
– didDeactivate is similar to overriding
dealloc.

14. Recap
• So far this session we’ve covered the very
basics of WatchKit application development.
• We’ve covered the watch app lifecycle.
• Also covered the WKinterfaceController
lifecycle with a simple example project.