Datasheet

20
Part I: Getting Started
Engaging the user
While I’m on the subject of users, here are two more aspects of a compelling
application: direct manipulation and immediate feedback.
✓ Direct manipulation makes people feel more in control. On the desk-
top, that meant a keyboard and mouse; on the iPhone, the Multi-Touch
interface serves the same purpose. In fact, using fingers gives a user a
more immediate sense of control; there’s no intermediary (such as a
mouse) between the user and the object onscreen. To make this effect
happen in your application, keep your onscreen objects visible while the
user manipulates them, for example.
✓ Immediate feedback keeps the users engaged. Great applications
respond to every user action with some visible feedback — such as
highlighting list items briefly when users tap them.
Because of the limitations imposed by using fingers — especially some-
what pudgy fingers — applications need to be very forgiving. For example,
although the iPhone doesn’t pester the user to confirm every action, it also
won’t let the user perform potentially destructive, non-recoverable actions
(such as deleting all contacts or restarting a game) without asking, “Are you
sure?” Your application should also allow the user to easily stop a task that’s
taking too long to complete.
Notice how the iPhone uses animation to provide feedback. (I especially
like the flipping transitions in the Weather application when I touch the Info
button.) But keep it simple; excessive or pointless animation interferes with
the application flow, reduces performance, and can really annoy the user.
An app may have an infrastructure the size of Texas behind it, but to the
user, it should always appear to be just me and my app.
How the iPhone Makes This All Real
The iPhone’s unique software and hardware allow you to create an applica-
tion that enables the user to do something that may not be practical — or
even possible — with a laptop computer. Although the iPhone is a smaller,
mobile personal computer, it isn’t a replacement for one. It isn’t intended to
produce documents, proposals, or research. The iPhone has the capability
to be an extension of the user, seamlessly integrated into his or her everyday
life, and able to accomplish a singly focused task, or step in a series of tasks,
in real time, based on where he or she is.
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