differences, for example Android users may expect contextual menus on long
press, a convention which does not exist on iOS, where the same menu would
be displayed on another screen (see figure 9. 22 ).
Figure 9. 22 : Android and iOS screens from the same mobile app showing
different platform conventions
In general, for mobile devices and others that have established platform
conventions, following these conventions will make it much easier for users to
use your app even if it means some things are done in a different way than
they are on any specialized connected devices. A heating control app for iOS
must be a good iOS app as well as recognizably part of the heating service. It
does not have to be a skeuomorphic representation of a heating controller. But
this works both ways: a heating controller does not have to pretend to be an
iPhone just because it has an iPhone app. The goal is to ensure that interfaces
are appropriate to each device, yet also feel like parts of a coherent service.
Interaction elements such as buttons, menus and switches should be
recognizable according to the platform conventions of the device. An iOS
button should generally follow conventions for button styles on iOS rather
than trying to look like the physical button on an embedded device.
Most importantly, specific interaction controls should be optimized to the
platform. If a physical control uses a wheel, slider or handle, there is no need
to replicate this on a small touchscreen device where it could be harder and
more imprecise to use.
For example, the Nest thermostat incorporates a rotating bezel, which is used
(amongst other things) to increase and decrease the temperature. The bezel
makes a clicking noise as it is rotated. But the iOS app up/down controls are
arrows. The designers could have shown a representation of a bezel onscreen
for the user to tap and drag around. But the arrows are a much more efficient
and precise control on a touchscreen (see figure 9. 23 ). Adjustments to
domestic temperature are typically within a degree or two, so precision is
important to avoid overshooting.