Create complications for Apple Watch

Timelines

• Representation of your complication’s data over time

• Enables ClockKit to query your app once and get all information needed

• Extend or invalidate as necessary to ask ClockKit to re-query your app

• Your complication will show an entry until the date of the next one

Complication building blocks

• There are dozens of watchOS families

• Ideally you will want to support as many complication families as you can

• For each family there are multiple templates

• All templates inherit from CLKComplicationTemplate

Providing data

• When providing a timeline, we’re giving WatchKit a list of CLKComplicationTimelineEntry instances.

• These will populate your complications

• Each entry represents what your complications should look like at a certain point in time.

• Each entry has two properties:

  • Date, which is the date that this entry should be visible

  • Complication template, which is the template containing the data you want to display for this entry

• Your main interaction with ClockKit is through an object you create that conforms to CLKComplicationDatasource.

• There’s only one required method in this protocol:

class ComplicationController: NSObject, CLKComplicationDataSource {
    func getCurrentTimelineEntry(
        for complication: CLKComplication, 
        withHandler handler: @escaping (CLKComplicationTimelineEntry?) -> Void) {
        // Call the handler with the current timeline entry
        handler(createTimelineEntry(forComplication: complication, date: Date()))
    }
}

• This function is used to get the current entry only, if we can/want to provide future entries as well, we will need to implement the following methods as well:

extension ComplicationController {

    // Specifies how far in the future you can provide entries 
    func getTimelineEndDate(
        for complication: CLKComplication, 
        withHandler handler: @escaping (Date?) -> Void) {
        handler(timeline(for: complication)?.endDate)
    }

    // lets you provide as many entries as is appropriate up to the limit after the given date
    func getTimelineEntries(
        for complication: CLKComplication, 
        after date: Date, 
        limit: Int, 
        withHandler handler: @escaping ([CLKComplicationTimelineEntry]?) -> Void) {
       handler(timeline(for: complication)?.entries(after: date, limit: limit))
    }
}

Reloading complications

• Call reloadTimeline(for:) on the .sharedInstance() CLKComplicationServer to invalidate the current timeline (and trigger an update session to reload it)

• Call extendTimeline(for:) on the .sharedInstance() CLKComplicationServer to let ClockKit know we can now provide more entries

Data Providers

• Provided by ClockKit to adapt the display of the same data/values in different templates or families of complications.

• CLKDateTextProvider will take care of displaying a date for you

let longDate: Date = DateComponents(year: 2020, month: 9, day: 23).date ?? Date()
let units: NSCalendar.Unit = [.weekday, .month, .day]
let textProvider = CLKDateTextProvider(date: longDate, units: units)

• CLKRelativeDateTextProvider will take care of displaying relative time/intervals

let timerStart: Date = …
let units: NSCalendar.Unit = [.hour, .minute, .second]
let textProvider = CLKRelativeDateTextProvider(date: timerStart, style: .timer, units: units)

• and many others including image and gauge providers

Multiple complications

• New in WatchOS 7

• Declared via our CLKComplicationDatasource implementation via getComplicationDescriptors(handler:)

• We will use a CLKComplicationDescriptor to define each complication

• If you want to update the complications your app offer, call reloadComplicationDescriptors() on the .sharedInstance() CLKComplicationServer

• Note that if you remove support for a complication that is currently on a user watch face, WatchKit will continue to ask you for timeline entries for that complication

Getting information back to your app

• Tapping a complication launches your app

• Based on the CLKComplicationDescriptor description define above, the app will be launched with:

  • A userActivity

  • A userInfo dictionary

• Either way, WatchKit will pass more data in the userInfo dictionary (passed also within the userActivity) such as the CLKLaunchedTimelineEntryDateKey and CLKLaunchedComplicationIdentifierKey