Background Service

Introduction

Prior to Zepp OS version 3.0, once a JS Mini Program was exited, the Mini Program was destroyed, and if it needed to save the associated state, it needed to rely on file system-related capabilities and could not be run in the background for scenarios such as continuous monitoring of sensor data.

In Zepp OS 3.0, Mini Programs support the new feature of background services, which differentiate services in terms of runtime, divided into long services and short services.

Long services, started in the Mini Program page via the start method in the @zos/app-service module, are allowed to reside in the background and are automatically loaded upon restart until the service is stopped using the stop method.

Short services, i.e. services that run for a short period of time and are forcibly shut down if they are started beyond a certain time. Analogous to callback functions, they are triggered by specific events, such as the new series of module APIs added to Zepp OS that support calling short services.

• @zos/alarm
  • Timed wake-up, support for waking up short services
• @zos/notification
  • OS notifications, evoking short services
• app-event System Events
  • Listening to system events and calling up short services when an event is thrown

Configure backend services

You need to add the app.json to the Mini Program configuration. In addition, the background service has permission restrictions, so you need to declare the relevant permissions in permissions.

{
  "permissions": [
    "device:os.notification",
    "device:os.bg_service",
    "event:os.health.heart_rate_abnl"
  ],
  "module": {
    "app-service": {
      "services": ["app-service/long_service"]
    },
    "app-event": {
      "path": "app-event/short-service"
    }
  }
}

A Mini Program can configure multiple app-services to start long services, which need to be manually controlled by start and stop APIs to start and stop

A Mini Program can only configure one short service to listen to system events, and the path of the service is specified by path of app-event, when the system event we listen to is triggered, the system will call the short service and close the service after a certain time

Register for background services

Use AppService register background service.

Ability Limits

Calling JS methods in the backend service cannot affect the frontend application, and only the following API calls are supported

• showToast of the @zos/interaction module
• @zos/sensor
• @zos/fs
• @zos/ble
• @zos/router
• @zos/alarm
• @zos/app-service
• @zos/notification
• The rest of the module has a series of get methods

Short Service System Events

The system events that the Mini Program needs to listen to also need to be configured in the app.json permissions field, which currently supports the following event listeners

System Events	Description
event:os.health.heart_rate_abnl	Abnormal heart rate
event:os.health.spo2_low	Low blood oxygen
event:os.weather.sun_rise	Sunrise
event:os.weather.sun_rise	Sunset
event:os.weather.moon_rise	Moonrise
event:os.weather.moon_set	Moonset

The short service that listens to system events also needs to be configured in the app-event field in app.json

"app-service": {
  "services": ["app-service/long_service"]
},
"app-event": {
  "path": "app-event/short_service"
}

info

More system events are still being improved, so stay tuned!

Full example

We provide a backend service demo in the Github Sample repository to demonstrate this feature, please refer to os-3.0show