Posted past times Jingyu Shi, Developer Advocate, Partner DevRel
This is the minute inwards a serial of weblog posts inwards which outline strategies as well as guidance inwards Android amongst regard to power.
Notifications are a powerful channel y'all tin utilization to dice on your app's users connected as well as updated. Android provides Notification APIs to do as well as postal service notifications on the device, only quite oftentimes these notifications are triggered past times external events as well as sent to your app from your app server.
In this weblog post, we'll explicate when as well as how to generate these remote notifications to furnish timely updates to users as well as minimize battery drain.
Use FCM for remote notifications
We recommend using upgrade to FCM!
There are ii types of FCM messages y'all tin select from:
- Notification Messages, which simplify notification treatment as well as are high priority past times default.
- Data Messages, for when y'all desire to handgrip the FCM messages inside the customer app.
You tin gear upward the priority to either blog post on Firebase Blog.
FCM is optimized to operate amongst Android powerfulness administration Moar Power inwards P as well as the future".
To notify or not?
All of the notifications that y'all shipping should hold out well-structured as well as actionable, every bit good every bit furnish timely as well as relevant information to your users. We recommend that y'all follow these notification guidelines, as well as avoid spamming your users. No 1 wants to hold out distracted past times irrelevant or poorly-structured notifications. If your app behaves similar this, your users may block the notifications or fifty-fifty uninstall your app.
The When non to utilization a notification department of the Material Design documentation for notifications highlights cases where y'all should non shipping your user a notification. For example, a mutual utilization instance for a normal priority FCM Data Message is to tell the app when there's content cook for sync, which requires no user interaction. The sync should compass quietly inwards the background, amongst no demand for a notification, as well as y'all tin utilization the WorkManager1 or JobScheduler API to schedule the sync.
Post a notification first
If y'all are sending remote notifications, y'all should e'er postal service the notification every bit presently every bit possible upon receiving the FCM message. Adding whatsoever additional network requests earlier posting a notification volition Pb to delayed notifications for some of your users. When non handled properly, the notifications mightiness non hold out seen at all, come across the "avoid background service" department below.
⚠️ Avoid adding whatsoever additional network requests earlier posting a notification
Also dice on inwards heed that, depending on the the world of the device, user actions, as well as app behavior, 1 or many powerfulness saving features could hold out restricting your app's background work. As a result, your app's jobs as well as alarms mightiness hold out delayed, as well as its powerfulness to access the network mightiness hold out restricted.
For all of these reasons, to ensure timely delivery of the notification, y'all should e'er demo the notification promptly when the FCM message is received, earlier whatsoever other operate similar network fetch or scheduling jobs.
FCM message payload is your friend
To postal service a notification upon the receipt of an FCM message, y'all should include all the information needed for the notification inwards the FCM message payload.
The same applies to information sync--we recommend that your app shipping every bit much information every bit possible inwards the FCM payload and, if needed, charge the residual of the information when the app opens. On a well-performing network, there's a adept jeopardy that the information volition hold out synced past times the fourth dimension the user opens the app thence the spinner won't hold out shown to the user. If network connectivity is non good, a notification volition hold out sent to the user amongst the content inwards the FCM payload to inform the user inwards a timely manner. The user tin as well as thence opened upward the app to charge all the data.
You tin besides encrypt FCM messages end-to-end using libraries similar Capillary. The icon below shows a full general menses of how to handgrip FCM messages.
Need to a greater extent than data?
As convenient every bit FCM message payload is, it comes amongst a 4KB maximum limit. If y'all demand to shipping a rich notification amongst an icon attachment, or y'all desire to improve your user sense past times keeping your app inwards sync amongst media content, y'all may demand to a greater extent than than the 4KB payload limit. For this, nosotros recommend using FCM messages inwards combination amongst the WorkManager 1 or JobScheduler API.
If y'all demand to postal service a rich notification, nosotros recommend posting the notification first, amongst some of the content inwards the FCM message. Then schedule a chore to fetch the residual of the content. Once the chore is finished, update the notification if it is withal active. For example, y'all tin include a thumbnail or preview of the content inwards the FCM payload as well as postal service it inwards the notification first. Then schedule a chore to fetch the ease of the media files. Be aware that if you've scheduled jobs from the FCM message handler, it is possible that when the user launches the app, the scheduled chore won't have got finished yet. You should handgrip this instance gracefully.
In short, utilization the information inwards the FCM message payload to postal service a notification as well as dice on your app content updated first. If y'all withal demand to a greater extent than data, as well as thence schedule jobs amongst APIs similar WorkManager 1 or JobScheduler API.
Avoid background services
One mutual pitfall is using a background service to fetch information inwards the FCM message handler, since background service volition hold out stopped past times the organization per recent changes to Google Play Policy (Starting belatedly 2018, Google Play volition require a minimum target API bird ).
Android nine Pie volition besides impose background execution limits when battery saver is on. Starting a background service volition Pb to IllegalStateException from a normal priority FCM message. High priority messages do grant y'all a curt whitelist window that allows y'all to start a background service. However, starting a background service amongst a network telephone call back volition seat the service at risk of getting terminated past times the system, because the curt execution window is solely intended to hold out used for posting a notification.
You should avoid using background services only utilization WorkManager 1 or JobScheduler API instead to perform operations inwards the background.
Power & message priority
Android six Marshmallow introduced Doze. FCM is optimized to operate amongst Doze, as well as y'all tin utilization high priority FCM messages to notify your users immediately. In Doze mode, normal priority messages are deferred to a maintenance window. This enables the organization to relieve battery when a device is idle, only withal ensure users have time-critical notifications. Consider an instant messaging app that sends users messages from friends or incoming telephone calls or a domicile monitoring app sends users alert notifications. These are some of the acceptable examples where y'all tin utilization high priority FCM messages.
In addition, Android nine Pie introduced App Standby Buckets as well as App Restrictions.
The tabular array below shows how diverse power-management features bear upon message delivery behaviors.
| High priority message delivery | Normal priority message delivery | |
| App inwards Foreground | Immediate, unless app is restricted (see below) | Immediate, unless app is restricted (see below) |
| App inwards Background | ||
| Device inwards Doze (M+) as well as Doze "on the go" (N+) | Immediate | Deferred until maintenance window |
| App Standby Buckets (P+) | May hold out restricted | No restriction |
| App Restrictions (P+) | All messages dropped (see below) | All messages dropped (see below) |
| Battery Saver | No restriction | No restriction |
★ Note: Starting Jan 2019, App Restrictions (in Battery Setting) volition include restrictions on FCM messages. You tin discovery out if your app is inwards the restricted the world amongst the isBackgroundRestricted API. Once your app is inwards the restricted state, no FCM messages volition hold out delivered to the app at all. This volition apply to both high as well as normal priority FCM messages as well as when app is inwards either foreground or background.
App Standby Buckets impose unlike levels of restrictions based on the app's standby bucket. Based on which bucket your app belongs to, in that place mightiness hold out a cap for the expose of high priority messages y'all are allowed to shipping per day. Once y'all attain the cap, whatsoever subsequent high priority messages volition hold out downgraded to normal priority. See to a greater extent than details inwards the power administration restrictions.
High priority FCM messages are designed to shipping remote notifications or trigger actions that involve user interactions. As long every bit y'all e'er utilization high priority messages for these purposes, your high priority messages volition hold out delivered forthwith as well as remote notifications volition hold out displayed without delay. In addition, when a notification from a high priority message causes a user to opened upward your app, the app gets promoted to the active bucket, which exempts it from FCM caps. The illustration below shows an instant messaging app moving to the active bucket afterwards the user taps on a notification triggered past times a high priority FCM message.
However, if y'all utilization high priority messages to shipping notifications to the blocked notification channels or tasks which do non involve user interactions, y'all volition run the risk of wasting the high priority messages allocated inwards your app's bucket. Once reaching the cap, y'all won't hold out able to shipping urgent notifications anymore.
In summary, y'all should solely utilization high priority FCM messages to deliver immediate, time-critical notifications to users. Doing thence volition ensure these messages as well as subsequent high priority messages attain your users without getting downgraded. You should utilization normal priority messages to trigger events that do non require immediate execution, such every bit a notification that is non time-sensitive or a information sync inwards the background.
Test amongst Android 9!
We highly recommend that y'all blog.
Thank y'all for helping motion the ecosystem forward, making ameliorate Android apps, as well as saving users' batteries!
Acknowledgements: This weblog posts is inwards articulation collaboration amongst FCM as well as Android teams.
1 WorkManager is the recommended solution for background processing in 1 lawsuit it's stable.
