There are several principles to keep in mind while developing for the Apple Watch. This video explains the two-second rule, and discusses why keeping the background black and keeping your interface small and simple are important.
- [Instructor] There are several key points to keep in mind when writing Apple Watch apps. As we go through this course, and as you work on your own apps, you'll repeatedly find these principles illuminate how you as developers should design your applications. Apple kept it simple, so keep it simple. You'll find simplicity to be the theme of Watch Kit. While IOS might have far more complex and flexible methods and properties, Watch Kit will simplify code to the barest minimum.
You are also working in a very small space for your user interface. Layout and the controls you can use need minimal user interaction. While you do have scrolling abilities, leave the most important information and actions you want to express at the visible part of your watch face. The barely seen batch for the 100 move goals is not as important as the message. Less important information should be presented further down the scroll. Info on top, actions on bottom.
Think how people look and use their watch. They look for information on the top half of the watch. The finger from the opposite hand approaches the watch from the bottom up. Set your important info on top and then place your primary control towards the bottom of the watch interface. Black space is good. Keep your background black for almost all cases. Apple human interface guidelines want you to do this because the exterior bezel is black. Using a solid background color breaks the continuous edge to edge background, since the bevel edges can only be black.
Properties and actions are limited. Unlike Mac OS or IOS, you don't have a choice how to use Watch Kit properties and actions. Most properties on controls are read only and many exist only as attributes on the story board, not as properties. While you might be used to the sender argument in IBAction in IOS, most actions have no argument at all. A few return a value, but never the control. The five second rule.
There should be a very short time between a wrist raise or start of an app, and the app appearing on the watch. Ideally, this should be two seconds, but should never be over five. While Watch OS does a lot to make that happen, you as a developer should do your best to keep things simple. Minimize the amount of data the watch has to ask the phone. Communications between devices takes time. Keep image assets on the watch instead of the phone. Load your images when you add the app to the watch in the Watch Kit app and extension.
Avoid as much as possible the extension grabbing them. Add some leader time from the phone. As you go through the course, you'll find these principles visited over and over again. You'll find remembering them to be very useful while developing applications. The watch does not have the screen space or memory of an iPhone or iPad. Keeping things simple and fast will make the best user experience.
- Principles of watchOS development
- Adding buttons and labels to your app
- Connecting objects to code
- Testing a watchOS app
- Laying out WatchKit UI objects
- Adding navigation
- Using Interface Library elements such as inputs, pickers, and media players
- Creating tables
- Working with table data