Design篇

Notifications

DEVELOPER DOCS

Notifying the User

NOTIFICATIONS IN ANDROID 4.4 AND LOWER

VIDEO

DevBytes: Notifications in the Android L Developer Preview

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.

New in Android 5.0

In Android 5.0, notifications receive important updates: structurally, visually, and functionally:

• Notifications have undergone visual changes consistent with the new material design theme.
• Notifications are now available on the device lock screen, while sensitive content can still be hidden behind it.
• High-priority notifications received while the device is in use now use a new format called heads-up notifications.
• Cloud-synced notifications: Dismissing a notification on one of your Android devices dismisses it on the others, as well.

Note: Notification design in this version of Android is a significant departure from that of previous versions. For information about notification design in previous versions, see Notifications in Android 4.4 and lower.

Anatomy of a Notification

Base layout

At a minimum, all notifications consist of a base layout, including:

• The notification‘s icon. The icon symbolizes the originating app. It may also potentially indicate notification type if the app generates more than one type.
• A notification title and additional text.
• A timestamp.

Notifications created with Notification.Builder for previous platform versions look and work the same in Android 5.0, with only minor stylistic changes that the system handles for you. For more information about notifications on previous versions of Android, see Notifications in Android 4.4 and lower.

Base layout of a handheld notification (left) and the same notification on Wear (right), with a user photo and a notification icon

Expanded layouts

You can choose how much detail your app‘s notifications should provide. They can show the first few lines of a message or show a larger image preview. The additional information provides the user with more 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 to toggle between compact and expanded layouts. For single-event notifications, Android provides three expanded layout templates (text, inbox, and image) for you to use in your application. The following images show you how single-event notifications look on handhelds (left) and wearables (right).

Actions

Android supports optional actions that are displayed at the bottom of the notification. 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 focus on notifications that matter to them.

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 smallest number of actions possible by only including the most imminently important and meaningful actions.

Good candidates for actions on notifications are actions that:

• Are essential, frequent, and typical for the content type you‘re displaying
• Allow the user to accomplish tasks quickly

Avoid actions that are:

• Ambiguous
• The same as the default action of the notification (such as "Read" or "Open")

You can specify a maximum of three actions, each consisting of an action icon and name. Adding actions to a simple base layout makes 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, make sure that any action a user can invoke from a notification is available from within the associated application, as well.

Heads-up Notification

Example of a heads-up notification (incoming phone call, high priority) appearing on top of an immersive app

When a high-priority notification arrives (see right), it is presented to users for a short period of time with an expanded layout exposing possible actions.

After this period of time, the notification retreats to the notification shade. If a notification‘s priority is flagged as High, Max, or full-screen, it gets a heads-up notification.

Good examples of heads-up notifications

• Incoming phone call when using a device
• Alarm when using a device
• New SMS message
• Low battery

Guidelines

Make it personal

For notifications of items sent by another person (such as a message or status update), include that person‘s image usingsetLargeIcon(). Also attach information about the person to the notification‘s metadata (see EXTRA_PEOPLE).

Your notification‘s main icon is still shown, so the user can associate it with the icon visible in the status bar.

Notification that shows the person who triggered it and the content they sent.

Navigate to the right place

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 detailed view of a single data item such as a message, but it might also be a summary view if the notification is stacked. If your app takes the user anywhere below your app‘s top level, insert navigation into your app‘s back stack so that the user can press the system back button to return to the top level. For more information, see Navigation into Your App via Home Screen Widgets and Notifications in the Navigation design pattern.

Correctly set and manage notification priority

Android supports a priority flag for notifications. This flag allows you to influence where your notification appears, relative to other notifications, and helps ensure that users always see their most important notifications first. You can choose from the following priority levels when posting a notification:

How to choose an appropriate priority

DEFAULT, HIGH, and MAX are interruptive priority levels, and risk interrupting the user in mid-activity. To avoid annoying your app‘s users, reserve interruptive priority levels for notifications that:

• Involve another person
• Are time-sensitive
• Might immediately change the user‘s behavior in the real world

Notifications set to LOW and MIN can still be 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 the user will find valuable when they choose to look for notifications. Criteria for LOW and MIN priority notifications include:

• Don‘t involve other people
• Aren‘t time sensitive
• Contain content the user might be interested in but could choose to browse at their leisure

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.

Summarize your notifications

If a notification of a certain type is already pending when your app tries to send a new notification of the same type, combine them into a single summary notification for the app. Do not create a new object.

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 approach allows users to gain a better sense of which notifications are pending and if they are interesting enough to read in detail within the associated app.

Make notifications optional

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.

Use distinct icons

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.

Do

Use the proper notification icon style for small icons, and the Material Light action bar icon stylefor your action icons.

Do

Keep your icons visually simple, avoiding excessive detail that is hard to discern.

Don‘t

Place any additional alpha (dimming or fading) into your small icons and action icons; they can have anti-aliased edges, but because Android uses these icons as masks (that is, only the alpha channel is used), the image should generally be drawn at full opacity.

Don‘t

Use color to distinguish your app from others. Notification icons should only be a white-on-transparent background image.

Pulse the notification LED appropriately

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 white. Your notifications shouldn‘t use a different color unless the user has explicitly customized it.

Building Notifications That Users Care About

When to display a notification

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 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.

Examples of time-sensitive notification

While well-behaved apps generally only speak when spoken to, a few cases do merit an app‘s interrupting the user with an unprompted notification.

Use notifications primarily for time-sensitive events, especially if these synchronous events involve other people. For instance, an incoming chat is a real-time and synchronous form of communication: Another user actively waiting on your response. 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.

When not to display a notification

In many other cases, notifications aren‘t appropriate:

• Avoid notifying the user of information that is not directed specifically at them, or information that is not truly time-sensitive. For instance, the asynchronous and undirected updates flowing through a social network generally do not warrant a real-time interruption. For the users who do care about them, allow them to opt-in.
• Don‘t create a notification if the relevant new information is currently on screen. Instead, use the UI of the application itself to notify the user of new information directly in context. For instance, a chat application should not create system notifications while the user is actively chatting with another user.
• Don‘t interrupt the user for low-level technical operations, like saving or syncing information, or updating an application if the app or system can resolve the issue without involving the user.
• Don‘t interrupt the user to inform them of an error if it is possible for the application to recover from the error on its own without the user taking any action.
• Don‘t create notifications that have no true notification content and merely advertise your app. A notification should provide useful, timely, new information and should not be used merely to launch an app.
• Don‘t create superfluous notifications just to get your brand in front of users. Such notifications frustrate and likely alienate your audience. The best way to provide small amounts of updated information and keep them engaged with your app is to develop a widget that they can choose to place on their home screen.

Interacting with Notifications

Touching a notification opens the associated app to detailed content that matches the notification. Swiping left or right on a notification removes it from the drawer.

Ongoing notifications

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. Ongoing notifications can also show the user feedback for longer tasks like downloading a file, or encoding a video. A user cannot manually remove an ongoing notification from the notification drawer.

Media playback

In Android 5.0, the lock screen doesn‘t show transport controls for the deprecated RemoteControlClient class. But it does show notifications, so each app‘s playback notification is now the primary way for users to control playback from a locked state. This behavior gives apps more control over which buttons to show, and in what way, while providing a consistent experience for the user whether or not the screen is locked.

Dialogs and toasts

Your app should not create a dialog or toast if it is not currently on screen. A dialog or toast should only be displayed as an 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 are essentially shown in reverse-chronological order, with special consideration given to the app‘s stated notification priority.

Notifications are a key part of the lock screen, and are featured prominently every time the device display comes on. Space on the lock screen is tight, so it is more important than ever to identify the most urgent or relevant notifications. For this reason, Android has a more sophisticated sorting algorithm for notifications, taking into account:

• The timestamp and application‘s stated priority.
• Whether the notification has recently disturbed the user with sound or vibration. (That is, if the phone just made a noise, and the user wants to know "What just happened?", the lock screen should answer that at a glance.)
• Any people attached to the notification using EXTRA_PEOPLE, and, in particular, whether they are starred contacts.

To best take advantage of this sorting, focus on the user experience you want to create, rather than aiming for any particular spot on the list.

On the lock screen

Because notifications are visible on the lock screen, user privacy is an especially important consideration. Notifications often contain sensitive information, and should not necessarily be visible to anyone who picks up the device and turns on the display.

• For devices that have a secure lock screen (PIN, pattern, or password), the interface has public and private parts. The public interface can be displayed on a secure lock screen and therefore seen by anyone. The private interface is the world behind that lock screen, and is only revealed once the user has signed into the device.

User control over information displayed on the secure lock screen

Notifications on the lock screen, with contents revealed after the user unlocks the device.

When setting up a secure lock screen, the user can choose to conceal sensitive details from the secure lock screen. In this case the System UI considers the notification‘s visibility level to figure out what can safely be shown.

To control the visibility level, callNotification.Builder.setVisibility(), and specify one of these values:

• VISIBILITY_PUBLIC. Shows the notification‘s full content. This is the system default if visibility is left unspecified.
• VISIBILITY_PRIVATE. On the lock screen, shows basic information about the existence of this notification, including its icon and the name of the app that posted it. The rest of the notification‘s details are not displayed. A couple of good points to keep in mind are as follows:
  • If you want to provide a different public version of your notification for the system to display on a secure lock screen, supply a replacement Notification object in theNotification.publicVersion field.
  • This setting gives your app an opportunity to create a redacted version of the content that is still useful but does not reveal personal information. Consider the example of an SMS app whose notifications include the text of the SMS and the sender‘s name and contact icon. This notification should be VISIBILITY_PRIVATE, but publicVersion could still contain useful information like "3 new messages" without any other identifying details.
• Notification.VISIBILITY_SECRET. Shows only the most minimal information, excluding even the notification‘s icon.

Notifications on Android Wear

Bridging notifications and actions

A connected device, such as a phone, can bridge notifications to a Wear device, so that the notifications are displayed there. Similarly, it can bridge actions, so that the user can act on the notifications right from the Wear device.

Bridge

• New instant messages
• Single-tap actions such as +1, Like, Heart

Don‘t bridge

• Notifications of newly arrived podcasts
• Actions that map to features that aren‘t possible on the watch

Unique actions to define for Wear

There are some actions that you can perform only on Wear. These include the following:

• Quick lists of canned responses such as "Be right back"
• Open on the phone
• A "Comment" or "Reply" action that brings up the speech input screen
• Actions that launch Wear-specific apps