What makes it its own discipline.
WHAT DIFFERS FROM WEB AND DESKTOP
The device is constrained: battery, memory, processor, storage
Connectivity is intermittent and metered Screens are small and touched, not pointed at The operating system can terminate your application at any time Distribution is controlled by a store Updates require approval and user action
WHAT THAT LAST POINT MEANS
A defect shipped may persist on devices for months.
WHY
Users do not update immediately, and some never do.
WHAT THAT REQUIRES
Care before release, and the ability to disable features remotely.
WHAT THE LIFECYCLE IMPOSES
Your application is suspended, resumed and terminated without warning.
WHAT THAT MEANS PRACTICALLY
State must be saved continuously, not on exit.
WHAT PERMISSION MODELS IMPOSE
Access to camera, location, contacts and storage must be requested and may be refused.
WHAT TO DESIGN FOR
Refusal, and the feature being unavailable.
WHAT MATTERS MOST LOCALLY
Application size, data consumption, and performance on modest devices.
