20101121 – Apple, iPhone Human Interface Guidelines

CHAPTER 2 Human Interface Principles: Creating a Great User Interface A great user interface follows human interface design principles that are based on the way people—users—think and work, not on the capabilities of the device. A user interface that is unattractive, convoluted, or illogical can make even a great application seem like a chore to use. But a beautiful, intuitive, compelling user interface enhances an application's functionality and inspires a positive emotional attachment in users. Metaphors When possible, model your application's objects and actions on objects and actions in the real world. This technique especially helps novice users quickly grasp how your application works. Folders are a classic software metaphor. People file things in folders in the real world, so they immediately understand the idea of putting data into folders on a computer. Metaphors in iOS include iPod playback controls, tapping controls to make things happen, sliding on-off switches, and flicking through the data shown on picker wheels. Comments: This is inline with Nielsen's Heuristics: Match between system and the real world. Direct Manipulation Direct manipulation means that people feel they are controlling something tangible, not abstract. The benefit of following the principle of direct manipulation is that users more readily understand the results of their actions when they can directly manipulate the objects involved. iOS users enjoy a heightened sense of direct manipulation because of the Multi-Touch interface. Using gestures, people feel a greater affinity for, and sense of control over, the objects they see on screen, because they do not use any intermediate device (such as a mouse) to manipulate them. To enhance the sense of direct manipulation in your iPhone application, make sure that: ■ Objects on the screen remain visible while the user performs actions on them ■ The result of the user's action is immediately apparent See and Point An iPhone application is better than a person at remembering lists of options, commands, data, and so on. Take advantage of this by presenting choices or options in list form, so users can easily scan them and make a choice. Keeping text input to a minimum frees users from having to spend a lot of time typing and frees your application from having to perform a lot of error checking. Comments: Selecting choices/options is better than keying in text. Presenting choices to the user, instead of asking for more open-ended input, also allows them to concentrate on accomplishing tasks with your application, instead of remembering how to operate it. Feedback In addition to seeing the results of their actions, users need immediate feedback when they operate controls and status reports during lengthy operations. Your application should respond to every user action with some visible change. For example, make sure list items highlight briefly when users tap them. Audible feedback also helps, but it can't be the primary or sole feedback mechanism because people may use iOS-based devices in places where they can't hear or where they must turn off the sound. In addition, you don't want to compete with the iOS system sounds users already associate with system alerts. iOS automatically provides feedback when it's temporarily busy by displaying the activity indicator. During operations that last more than a few seconds, your application should show elapsing progress and, if appropriate, display an explanatory message. Animation is a great way to provide feedback to users, as long as it's both subtle and meaningful. Animation pervades iOS, even in nonimmersive applications. As a means of providing feedback, however, it is used to enhance the user's experience, not as the focus of the user's experience. Comments: Animation (such as progress bar) and audible sound are useful feedbacks when the user does an action (such as downloading, installing). User Control Allow users, not your application, to initiate and control actions. Keep actions simple and straightforward so users can easily understand and remember them. Whenever possible, use standard controls and behaviours that users are already familiar with. Provide ample opportunity to cancel operations before they begin, and be sure to get confirmation when the user initiates a potentially destructive action. Whenever possible, allow users to gracefully stop an operation that's underway. Comments: Use familiar or standardised controls. Get user's confirmation for destructive action (e.g. delete file). Make "Stop" button to enable user to terminate a certain process after process has commenced. Aesthetic Integrity Although the ultimate purpose of an application is to enable a task, even if that task is playing a game, the importance of an application's appearance should not be underestimated. This is because appearance has a strong impact on functionality: An application that appears cluttered or illogical is hard to understand and use. Aesthetic integrity is not a measure of how beautiful your application is. It's a measure of how well the appearance of your application integrates with its function. For example, a productivity application should keep decorative elements subtle and in the background, while giving prominence to the task by providing standard controls and behaviors. Be sure you design the user interface elements of such an application carefully, so that they provide an internally consistent experience. Comments: Aesthetics is also important to enhance usability. Source: Apple Inc (2001). iPhone Human Interface Guidelines: User Experience. Apple Inc, Cupertino, California. Pp 31-33