Figure 1. Base layout of a handset notification
The notification system allows users to keep informed about relevant and timely events in your app, such as new chat messages from a friend or a calendar event. Think of notifications as a news channel that alerts the user to important events as they happen or a log that chronicles events while the user is not paying attention - and one that is synced as appropriate across all their Android devices.
In L, notifications receive an important structural visual and functional update:
At a minimum, all notifications consist of a base layout, including:
Figure 1. Base layout of a handset notification
Figure 2. The same notification on Wear, with a user photo and a notification icon
Notifications created with {@code Notification.Builder} for versions of Android earlier than L will look and work the same in L, with only minor stylistic changes that the system handles for you.
You have the option to provide more details on notifications. You can use this to show the first few lines of a message or show a larger image preview. This provides the user with additional context, and - in some cases - may allow the user to read a message in its entirety. The user can pinch-zoom or perform a single-finger glide in order to toggle between compact and expanded layouts. For single event notifications, Android provides three expanded layout templates (text, inbox, and image) for you to re-use in your application.
Figure 3. A text-focused notification, an inbox notification, and a photo-centric notification, shown expanded and contracted, and with Wear equivalents for the first two.
Android has supported optional actions that are displayed at the bottom of the notification, as far back as Jelly Bean. With actions, users can handle the most common tasks for a particular notification from within the notification shade without having to open the originating application. This speeds up interaction and, in conjunction with "swipe-to-dismiss", helps users to streamline their notification triaging experience.
Be judicious with how many actions you include with a notification. The more actions you include, the more cognitive complexity you create. Limit yourself to the fewest number of actions possible by only including the most imminently important and meaningful ones.
Good candidates for actions on notifications are actions that:
Avoid actions that are:
Figure 4. Calendar reminder notification with two actions
Figure 5. Gmail new message notification - the actions appear to the right of the main card on Wear devices
You can specify a maximum of three actions, each consisting of an action icon and an action name. Adding actions to a simple base layout will make the notification expandable, even if the notification doesn't have an expanded layout. Since actions are only shown for expanded notifications and are otherwise hidden, you must make sure that any action a user can invoke from a notification is available from within the associated application as well.
Additionally, notifications and their actions are bridged over to Wear devices by default. Developers have control to control which notifications from bridging from the phone to the watch and vice versa. And developers can control which actions bridge as well. If your app includes actions that can't be accomplished with a single tap, either hide these actions on your Wear notification or consider hooking them up to a Wear app to allow the user to finish the action on their watch.
Bridging notifications
Notifications that should be bridged
Don't bridge
Bridging actions
Actions to bridge
Actions not to bridge
Unique actions to define for Wear
[Asset needed: show one or more sample Wear notifications]
Heads-up Notification
When notifications with priority set to High (see below) arrives, it is presented to users for a short period of time on the device with an expanded layout with its actions exposed. After this period of time, it retreats back to the Notification shade. If a notification is flagged as High or Max or a full-screen takeover, it gets a HUN in L.
Figure 6. Example of a Heads-up notification (incoming phone call, high priority) coming in on top of an immersive app
Good examples of Heads-up notifications
Figure 7. Notification that shows the person who triggered it and the content they are sending you
For notifications of items sent by another person (such as a message or status update), include that person's image using setLargeIcon. Also attach information about the person to the notification's metadata (see EXTRA_PEOPLE).
Your notification's main icon will still be shown, so the user can associate it with the icon visible in the status bar.
When the user touches the body of a notification (outside of the action buttons), open your app to the place where the user can view and act upon the data referenced in the notification. In most cases this will be the detail view of a single data item such as a message, but it might also be a summary view if the notification is stacked (see Stacked notifications below) and references multiple items. If in any of those cases the user is taken to a hierarchy level below your app's top-level, insert navigation into your app's back stack to allow them to navigate to your app's top level using the system back button. For more information, see the chapter on System-to-app navigation in the Navigation design pattern.
Starting with Jelly Bean, Android supported a priority flag for notifications. It allows you to influence where your notification will appear in comparison to other notifications and help to make sure that users always see their most important notifications first. You can choose from the following priority levels when posting a notification:
|
Priority |
Use |
|
{@code MAX} |
Use for critical and urgent notifications that alert the user to a condition that is time-critical or needs to be resolved before they can continue with a particular task. |
|
{@code HIGH} |
Use high priority notifications primarily for important communication, such as message or chat events with content that is particularly interesting for the user. High priority notifications will get the Heads-Up Notification display starting in L. |
|
{@code DEFAULT} |
The default priority. Keep all notifications that don't fall into any of the other categories at this priority level. |
|
{@code LOW} |
Use for notifications that you still want the user to be informed about, but that rate low in urgency. LOW notifications will tend to show up at the bottom of the list, which makes them a good choice for things like pubic/undirected social updates: the user has asked to be notified about them, but they should never take precedence over urgent or direct communication. |
|
{@code MIN} |
Contextual/background information (e.g. weather information, contextual location information). Minimum priority notifications will not show in the status bar. The user will only discover them when they expand the notification shade. |
Default, High, and Max priority are interruptive priority levels and risk interrupting the user from what they are doing. This should not not be taken lightly, so these levels should be reserved for notifications that:
Notifications set to Low and Min can still be very valuable for the user. Many if not most notifications just don't need to command the user's immediate attention, or vibrate the user's wrist, yet contain information that they will find valuable when they choose to look for notifications. Criteria for Low and Min priority notifications:
If your notification falls into one of the predefined categories (see below), assign it accordingly. Aspects of the system UI such as the notification shade (or any other notification listener) may use this information to make ranking and filtering decisions.
|
{@code Notification.CATEGORY_CALL} |
Incoming call (voice or video) or similar synchronous communication request |
|
{@code Notification.CATEGORY_MESSAGE} |
Incoming direct message (SMS, instant message, etc.) |
|
{@code Notification.CATEGORY_EMAIL} |
Asynchronous bulk message (email) |
|
{@code Notification.CATEGORY_EVENT} |
Calendar event |
|
{@code Notification.CATEGORY_PROMO} |
Promotion or advertisement |
|
{@code Notification.CATEGORY_ALARM} |
Alarm or timer |
|
{@code Notification.CATEGORY_PROGRESS} |
Progress of a long-running background operation |
|
{@code Notification.CATEGORY_SOCIAL} |
Social network or sharing update |
|
{@code Notification.CATEGORY_ERROR} |
Error in background operation or authentication status |
|
{@code Notification.CATEGORY_TRANSPORT} |
Media transport control for playback |
|
{@code Notification.CATEGORY_SYSTEM} |
System or device status update. Reserved for system use. |
|
{@code Notification.CATEGORY_SERVICE} |
Indication of running background service |
|
{@code Notification.CATEGORY_RECOMMENDATION} |
A specific, timely recommendation for a single thing. For example, a news app might want to recommend a news story it believes the user will want to read next. |
|
{@code Notification.CATEGORY_STATUS} |
Ongoing information about device or contextual status |
If your app creates a notification while another of the same type is still pending, avoid creating an altogether new notification object. Instead, turn it into a summary notification for the app.
A summary notification builds a summary description and allows the user to understand how many notifications of a particular kind are pending.
Don't:
Do:
You can provide more detail about the individual notifications that make up a summary by using the expanded digest layout. This allows users to gain a better sense of which notifications are pending and if they are interesting enough to be read in detail within the associated app.
Figure 8. Expanded and contracted notification that is a summary (using InboxStyle)
Users should always be in control of notifications. Allow the user to disable your app's notifications or change their alert properties, such as alert sound and whether to use vibration, by adding a notification settings item to your application settings.
By glancing at the notification area, the user should be able to discern what kinds of notifications are currently pending.
Do
Look at the notification icons Android apps already provide and create notification icons for your app that are sufficiently distinct in appearance.
[asset: include some sample visuals of notification icons]
Do
Use the proper notification icon style for small icons, and the Material Light action bar icon style for your action icons. Do not place any additional alpha (dimming or fading) into your small icons and action icons; they can have anti-aliased edges, but because L uses these icons as masks (that is, only the alpha channel is used), the image should generally be drawn at full opacity.
[asset: show a zoomed example of how this should look]
Do
Keep your icons visually simple and avoid excessive detail that is hard to discern.
Don't
Use color to distinguish your app from others. Notification icons should only be a white-on-transparent background image.
Many Android devices contain a notification LED, which is used to keep the user informed about events while the screen is off. Notifications with a priority level of MAX, HIGH, or DEFAULT should cause the LED to glow, while those with lower priority (LOW and MIN) should not.
The user's control over notifications should extend to the LED. When you use DEFAULT_LIGHTS, the LED will glow with a white color. Your notifications shouldn't use a different color unless the user has explicitly customized it.
To create an app that users love, it is important to design your notifications carefully. Notifications embody your app's voice, and contribute to your app's personality. Unwanted or unimportant notifications can annoy the user or make them resent how much attention the app wants from them, so use notifications judiciously.
To create an application that people enjoy using, it's important to recognize that the user's attention and focus is a resource that must be protected. While Android's notification system has been designed to minimize the impact of notifications on the user's attention, it is nonetheless still important to be aware of the fact that notifications are interrupting the user's task flow. As you plan your notifications, ask yourself if they are important enough to warrant an interruption. If you are unsure, allow the user to opt into a notification using your apps notification settings or adjust the notifications priority flag to Low or Min to avoid distracting the user while they are doing something else.
While well behaved apps generally only speak when spoken to, there are some limited cases where an app actually should interrupt the user with an unprompted notification.
Notifications should be used primarily for time sensitive events, and especially if these synchronous events involve other people. For instance, an incoming chat is a real time and synchronous form of communication: there is another user actively waiting on you to respond. Calendar events are another good example of when to use a notification and grab the user's attention, because the event is imminent, and calendar events often involve other people.
Figure 8. Time sensitive notification examples
There are however many other cases where notifications should not be used:
Figure 9. Anti-examples of notifications
Notifications are indicated by icons in the status bar and can be accessed by opening the notification drawer.
Touching a notification opens the associated app to detailed content matching the notification. Swiping left or right on a notification removes it from the list.
Ongoing notifications keep users informed about an ongoing process in the background. For example, music players announce the currently playing track in the notification system and continue to do so until the user stops the playback. They can also be used to show the user feedback for longer tasks like downloading a file, or encoding a video. Ongoing notifications cannot be manually removed from the notification drawer.
Figure 10. Ongoing notification due to music playback
The L lockscreen doesn't show transport controls for RCC (RemoteControlClient)s anymore. But the lockscreen does show notifications, so each app's playback notification is now the primary way for users to control playback from a locked state. This gives apps more control over which buttons to show and in what way, while providing a consistent experience for the user whether on the lockscreen or unlocked.
Your app should not create a dialog or toast if it is not currently on screen. Dialogs and Toasts should only be displayed as the immediate response to the user taking an action inside of your app. For further guidance on the use of dialogs and toasts, refer to Confirming & Acknowledging.
Ranking and ordering
Notifications are "news" and so they are essentially shown in reverse-chronological order, with special consideration given to the app's stated notification priority.
In L, notifications are now a key part of the lockscreen, and are featured prominently every time the device display comes on. Because space on the lockscreen is tight, it is more important than ever to identify the most urgent or relevant notifications.
Therefore, L has a more sophisticated sorting algorithm for notifications, taking into account:
To best take advantage of this sorting, developers should focus on the user experience they want to create rather than aiming for any particular spot on the list.
An example:
Figure 11. Gmail notifications are default priority, so they normally sort below messages from an instant messaging app like Hangouts, but Gmail will get a temporary bump when new messages come in.
Give the user choices: about whether to have notifications at all, whether they should vibrate or make sound.
On the lockscreen
Starting in L, notifications are visible on the lockscreen, and so we must consider the user's privacy. Notifications often contain sensitive information, and we must take care when showing it to anyone who picks up the device and turns on the display.
Figure 12. Notifications on the lockscreen followed by the Pattern Unlock when the user attempts to unlock the phone.
The user decides what shows on the secure lockscreen
When setting up a secure lockscreen, the user can choose to conceal sensitive details from atop the secure lockscreen. In this case the SystemUI considers the notification's visibility level to figure out what can safely be shown.
To control the visibility level, call {@code android.app.Notification.Builder.setVisibility()} and specify one of these values: