Problem

You must provide an easily discovered display of the status of important hardware features such as battery level and network connections.

Annunciator row features are provided by the OS, but you may usually modify or suppress it within applications.

Solution

Annunciators are lights, gauges, or sounds that indicate system status. Annunciator lights and panels date to The dawn of electrical devices.

The term was carried over to electronic, and then to mobile OS design. Though the same feature is often referred to as a "status bar," this typically implies some overlap with the concept of Notifications, which I will discuss in the next pattern instead.

A bar is displayed along the top of every screen with a series of iconic representations of the status of the device. You should always use common representations and placement of icons, so your users can understand the key indicators on any device without having to learn the specifics of every device.

Variations

The Annunicator Row is present on all screens. It may only disappear or be of lower prominence when other controls disappear as for full-screen gameplay or video playback.

Certain devices may not require using the space for constant reminders of system status messages. Appliances, such as eReaders do not necessarily need an Annunicator Row as the battery life is very long, and network access is only needed intermittently. The status messages will still be needed, and this may be solved with something like the Notification repurposed to display such information when it becomes critical instead. See that pattern for details on this functionality.

Kiosks and other devices where the user does not have full control of the device also may not need to display an Annunicator Row to general users.

Interaction Details

Annunciators are notifiers only. You should generally not allow direct interaction with the items.

For touch and pen devices, it may be desirable to allow the user to select the Annunciator Row as a whole, in order to get more information, or to provide access to settings. This may also be accomplished by combining with the Notifications area.

Presentation Details

You should plan on displaying the default Annunicator Row on every screen. Make a careful, deliberate choice whenever hiding to regain screen real estate or declutter the screen. Hiding the status icons is generally appropriate for video playback, most games, and many slideshows or similar interfaces. Browsers and readers of eBooks, PDFs and the like may also benefit from hiding the Annunicator Row once reading or scrolling begins.

The Annunicator Row is generally displayed as a row of icons laid out on a strip of color, gradient or other background imagery to separate them from other, generally interactive, display elements. Scrollbars do not intrude into the Annunicator Row as it does not move, but remains fixed at the top of the viewport.

Many devices allow the Annunicator Row to be modified. In general, you should restrict these modifications to display changes, such as switching out the background color, and changing icons to match. You can also use this modification as a half-measure, when completely hiding the status messages might not be the best option. For example, camera applications often use great amounts of battery, so you could display the battery icon, but no others in order to leave more room for the live preview. If you do this, use the conventional position of the battery icon, simply leaving out all others.

Within the row the status messages are displayed as icons, with as few words or numbers as possible. Use common, universally-understand or industry-standard icons whenever available.

Icons do not indicate the presence of a feature, but the status of that feature. No display means it is not functional, and displaying the icon means it is enabled. Optionally, disabled features may be displayed as "grayed-out" icons. This can be beneficial to communicate the availability of some features. Use caution that these are clearly disabled, under all lighting conditions.

Whenever possible, you can add additional status messages to the icon, such as bars of signal, or of battery level. Use simple changes and well-understood signaling such as tall=more and red=bad.

For certain features, whose presence is assumed, explicit measures of their disabling or failure must be included. For example, when no signal is available, the mobile network will have an error "X" in place of the bars of signal.

Items are grouped by basic functionality. A conventional order has arisen, from left to right:

• Radios:
  • Mobile networks.

  • WiFi.

  • Bluetooth enabled, and activity.
  • NFC or contactless payment enabled.
  • IrDA or other non-wired networking as available.
  • Airplane mode.

• Input & Output:

  • Volume, vibrate or silent modes.
  • Screen or keyboard locks enabled.
  • Network activity.
  • Network speed.

  • Message Waiting Indicator for voicemail, unless this is displayed by the Notification Area instead.

  • Synch status or activity.
  • Location services enabled. May or may not indicate when GPS is active.
  • USB cable connected.
• Power:
  • Usually a single item, which changes based on charge level, and state (e.g. being charged).
  • Those now rare devices with outboard (piggyback) or secondary batteries may display a second battery indicator.

The time of day (and sometimes the date) is also present, but may be in any of several places in the row. The most common is centered, followed by right aligned. Time is always displayed, even on those few devices without an otherwise permanently visible annunciator row.

Naturally, features not included with the device are not given space in the display. Some items may share space, and the highest priority feature or the one with the most important message is displayed.

Antipatterns

Don't let the order or size of the row, or the details of the icons change with different screens. Use one layout and one type of icon in all situations.

Don't reinvent the wheel. Re-use existing good design concepts, so users do not have to re-learn your icons.

Except when notifying of special conditions in places where the rest of the bar is suppressed (e.g. battery on a camera screen), do not pick and choose which items to show. Always show the same set in the same manner.

Avoid explanations that are jargon-laden. Percentage of battery is not nearly as useful as an estimate (even a bad one) of time remaining on a battery.

Avoid animations as sole explanations. Mobiles, and especially the status area, are often only glanced at. Blinks will instead be seen as solid on or off at a glance.

Next: Notifications

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