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

//基础布局在手机的通知（左）和同样的通知在wear（右）上，同时有一个用户图片和通知图标。

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

Don't

Do

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

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

Pulse the notification LED appropriately //适当得使用通知LED灯

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 //建立用户关心的通知

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.

When to display a notification //何时显示通知

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 //何时不显示通知

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 //通知交互

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 that matches the notification. Swiping left or right on a notification removes it from the drawer.

Ongoing notifications //持续通知

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 //媒体播放

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 //对话框和Toast

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 //等级和排序

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 //在锁屏界面

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 //在可穿戴设备上的通知

Notifications and their actions are bridged over to Wear devices by default. Developers can control which notifications bridge from the phone to the watch, and vice-versa. Developers can also 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, thus allowing the user to finish the action on their watch.

Bridging notifications and actions //桥接通知和动作

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 //为wear定义惟一的动作

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