Dealing with Physical Constraints
There are some well-known constraints we must take into consideration when designing and developing mobile apps—mostly surrounding a device’s form factor and physical user interface. Thus, the type of device on which a mobile app will run is a major design consideration. One nice aspect of designing apps for the iPhone is that the device’s form factor and physical user interface are standardized and well known. Plus, you can market your app and people can buy it using the familiar user interface of the iPhone app store.
However, when designing apps for other brands of mobile devices, you’ll need to deal with significant variability in their screen sizes, form factors, and physical user interfaces. For example, a Blackberry phone may have a small screen with a physical QWERTY keyboard, as on the Blackberry Curve, or it may have a larger touchscreen and a virtual keyboard like the Blackberry Storm. Consequently, the interaction design for each of these devices must be quite different. The Storm requires large buttons to facilitate touchscreen interaction, while the Curve requires smaller navigation elements, so they’ll fit on the smaller screen. For this reason, it’s important to specify the mobile devices on which you intend your app to run when defining requirements.
The Mobile Space Is Not the Web
Many of the assumptions about user interactions that drive Web design do not hold true for the mobile space. It’s essential to recognize that your users will not be sitting at a desk and looking at a big screen for substantial amounts of time, in a relatively peaceful environment. Instead, your users will be mobile—perhaps walking down the street, sitting on a train, or waiting for a latte at a coffee shop—using your app in environments where they will be surrounded by stimuli. So rather than running in a quiet office, library, or home, your app must compete with countless, extremely compelling external stimuli such as the constant movement of people and vehicles around them, as well as interactions with other people. Also, because your app runs on such a small screen and carries less auditory impact, it is not as immersive and is less able to hold users’ attention than a desktop or Web application. Therefore, it is essential that users be able to open your app quickly, accomplish what they hope to accomplish, then exit quickly and return their attention to the outside world. Accomplishing this type of lightning-fast engagement is essential for the success of an application in the mobile space.
One of the easiest ways of achieving the kind of quick engagement the mobile space requires is to streamline your app’s functionality. This means restraining any form of feature proliferation. Single-function or limited-function apps have a definite advantage when it comes to quick engagement. Google provides a great example of this philosophy with their Google Maps mobile app, which is separate from the Google search app. Thus, they can provide various capabilities, while limiting the functionality they incorporate into a single mobile app. This approach offers several advantages. First, it allows users to understand the utility of each app easily—enabling them to more quickly choose the app they need among the collection of apps on their phone, as well as to quickly make a purchase decision when buying a new app. It also makes it easier for users to organize their apps by function, especially now that more smartphones are incorporating file structures as a way of dealing with app proliferation on devices. Finally, single-function apps have simpler user interfaces, which reduces screen clutter and lets users access key functionality quickly and easily, while also minimizing the impact of distractions by reducing the amount of attention using an app requires.
In a real-world environment, a mobile app must overcome competition for a user’s attention, which goes far beyond just overcoming a competing app’s claims on a user’s attention, as on the Web. For example, if you are developing a news delivery app, it’s important to take into consideration why a user would use your app rather than just grab the newspaper sitting next to him at the local coffee shop. Navigation apps have done a great job of competing for users’ attention. Their competition includes traditional maps, printed directions, and dedicated navigation devices. Traditional maps don’t provide position tracking or turn-by-turn directions. Printed directions don’t provide positional information either, so are not helpful if you miss a turn and can’t generate updated directions when you are mobile. Dedicated navigation devices can’t incorporate other functionality like making phone calls, checking your email, or updating your Facebook status, so they add device clutter. A mobile navigation app offers significant advantages over each of the competing methods of completing the same objectives. Your mobile app should offer similar advantages to help ensure its success.
It is also important to take into account the reality that users may be engaging in simultaneous activities that not only require their attention, but may also take up the use of one hand. For instance, a person may be trying to use your mobile app while also trying to carry groceries, walk a dog, or carry a cup of coffee. If users discover that it is difficult to use your mobile app in such situations, they may avoid using it unless they can devote their full attention to it. Thus, single-handed operation is a major consideration for mobile apps.