Service Extension Ability Development

When to Use

ExtensionAbility is the base class of the new Extension component in the stage model. It is used to process missions without UIs. The lifecycle of an Extension ability is simple and does not involve foreground or background states. ServiceExtensionAbility is extended from ExtensionAbility.

You can customize a class that inherits from ServiceExtensionAbility and override the lifecycle callbacks in the base class to perform service logic operations during the initialization, connection, and disconnection processes.

Available APIs

Table 1 ServiceExtensionAbility lifecycle APIs

API	Description
onCreate(want: Want): void	Called for the initialization when `startAbility` or `connectAbility` is invoked for a given ability for the first time.
onRequest(want: Want, startId: number): void	Called each time `startAbility` is invoked for a given ability. The initial value of `startId` is `1`, and the value is incremented by one each time `startAbility` is invoked for that ability.
onConnect(want: Want): rpc.RemoteObject	Called when `connectAbility` is invoked for a given ability. This callback is not invoked for repeated calling of `connectAbility` for a specific ability. However, it will be invoked unless `connectAbility` is called after the ability has been disconnected using `disconnectAbility`. The returned result is a `RemoteObject`.
onDisconnect(want: Want): void	Called when `disconnectAbility` is called for a given ability. If the Extension ability is started by `connectAbility` and is not bound to other applications, the `onDestroy` callback will also be triggered to destroy the Extension ability.
onDestroy(): void	Called when `terminateSelf` is invoked to terminate the ability.

Constraints

OpenHarmony does not support creation of a Service Extension ability for third-party applications.

How to Develop

Declare the Service Extension ability in the module.json5 file by setting its type attribute to service. The following is a configuration example of the module.json5 file:

 "extensionAbilities":[{
     "name": "ServiceExtAbility",
     "icon": "$media:icon",
     "description": "service",
     "type": "service",
     "exported": true,
     "srcEnty": "./ets/ServiceExtAbility/ServiceExtAbility.ts"
 }]

Customize a class that inherits from ServiceExtensionAbility in the .ts file in the directory where the Service Extension ability is defined (entry\src\main\ets\ServiceExtAbility\ServiceExtAbility.ts by default) and override the lifecycle callbacks of the base class. The code sample is as follows:

import ServiceExtensionAbility from '@ohos.application.ServiceExtensionAbility'
import rpc from '@ohos.rpc'

class StubTest extends rpc.RemoteObject {
    constructor(des) {
        super(des);
    }
    onRemoteRequest(code, data, reply, option) {
    }
}

class ServiceExtAbility extends ServiceExtensionAbility {
    onCreate(want) {
        console.log('onCreate, want:' + want.abilityName);
    }
    onRequest(want, startId) {
        console.log('onRequest, want:' + want.abilityName);
    }
    onConnect(want) {
        console.log('onConnect , want:' + want.abilityName);
        return new StubTest("test");
    }
    onDisconnect(want) {
        console.log('onDisconnect, want:' + want.abilityName);
    }
    onDestroy() {
        console.log('onDestroy');
    }
}