ServiceAbility开发指导

场景介绍

基于Service模板的Ability（以下简称“Service”）主要用于后台运行任务（如执行音乐播放、文件下载等），但不提供用户交互界面。Service可由其他应用或Ability启动，即使用户切换到其他应用，Service仍将在后台继续运行。

接口说明

表1 Service中相关生命周期API功能介绍

接口名 描述
onStart?(): void 该方法在创建Service的时候调用，用于Service的初始化。在Service的整个生命周期只会调用一次，调用时传入的Want应为空。
onCommand?(want: Want, startId: number): void 在Service创建完成之后调用，该方法在客户端每次启动该Service时都会调用，开发者可以在该方法中做一些调用统计、初始化类的操作。
onConnect?(want: Want): rpc.RemoteObject 在Ability和Service连接时调用。
onDisconnect?(want: Want): void 在Ability与绑定的Service断开连接时调用。
onStop?(): void 在Service销毁时调用。Service应通过实现此方法来清理任何资源，如关闭线程、注册的侦听器等。

开发步骤

创建Service

  1. 重写Service的生命周期方法，来添加其他Ability请求与Service Ability交互时的处理方法。

    创建Service的代码示例如下：

    export default {
    onStart() {
        console.log('ServiceAbility onStart');
    },
    onCommand(want, startId) {
        console.log('ServiceAbility onCommand');
    },
    onConnect(want) {
        console.log('ServiceAbility OnConnect');
        return null;
    },
    onDisconnect(want) {
        console.log('ServiceAbility OnDisConnect');
    },
    onStop() {
        console.log('ServiceAbility onStop');
    },
}

  2. 注册Service。

    Service需要在应用配置文件config.json中进行注册，注册类型type需要设置为service。

     {
     "module": {
         "abilities": [         
             {    
                 "name": ".ServiceAbility",
                 "type": "service",
                 "visible": true
                 ...
             }
         ]
         ...
     }
     ...
 }

启动Service

Ability为开发者提供了startAbility()方法来启动另外一个Ability。因为Service也是Ability的一种，开发者同样可以通过将Want传递给该方法来启动Service。

开发者可以通过构造包含bundleName与abilityName的Want对象来设置目标Service信息。参数的含义如下：

  • bundleName：表示包名称。
  • abilityName：表示待启动的Ability名称。

启动本地设备Service的代码示例如下：

import featureAbility from '@ohos.ability.featureAbility';
let promise = featureAbility.startAbility(
    {
        want:
        {
            bundleName: "com.jstest.service",
            abilityName: "com.jstest.service.ServiceAbility",
        },
    }
);

执行上述代码后，Ability将通过startAbility() 方法来启动Service。

  • 如果Service尚未运行，则系统会先调用onStart()来初始化Service，再回调Service的onCommand()方法来启动Service。
  • 如果Service正在运行，则系统会直接回调Service的onCommand()方法来启动Service。

停止Service

Service一旦创建就会一直保持在后台运行，除非必须回收内存资源，否则系统不会停止或销毁Service。开发者可以在Service中通过terminateSelf()停止本Service。

连接本地Service

如果Service需要与Page Ability或其他应用的Service Ability进行交互，则须创建用于连接的Connection。Service支持其他Ability通过connectAbility()方法与其进行连接。

在使用connectAbility()处理回调时，需要传入目标Service的Want与IAbilityConnection的实例。IAbilityConnection提供了以下方法供开发者实现：onConnect()是用来处理连接Service成功的回调，onDisconnect()是用来处理Service异常死亡的回调，onFailed()是用来处理连接Service失败的回调。

创建连接本地Service回调实例的代码示例如下：

import prompt from '@system.prompt'

let mRemote;
function onConnectCallback(element, remote){
    console.log('onConnectLocalService onConnectDone element: ' + element);
    console.log('onConnectLocalService onConnectDone remote: ' + remote);
    mRemote = remote;
    if (mRemote == null) {
      prompt.showToast({
        message: "onConnectLocalService not connected yet"
      });
      return;
    }
    let option = new rpc.MessageOption();
    let data = new rpc.MessageParcel();
    let reply = new rpc.MessageParcel();
    data.writeInt(1);
    data.writeInt(99);
    mRemote.sendRequest(1, data, reply, option).then((result) => {
        console.log('sendRequest success');
        let msg = reply.readInt();
        prompt.showToast({
            message: "onConnectLocalService connect result: " + msg,
            duration: 3000
        });
    }).catch((e) => {
        console.log('sendRequest error:' + e);
    });

}

function onDisconnectCallback(element){
    console.log('ConnectAbility onDisconnect Callback')
}

function onFailedCallback(code){
    console.log('ConnectAbility onFailed Callback')
}

连接本地Service的代码示例如下：

import featureAbility from '@ohos.ability.featureAbility';
let connId = featureAbility.connectAbility(
    {
        bundleName: "com.jstest.service",
        abilityName: "com.jstest.service.ServiceAbility",
    },
    {
        onConnect: onConnectCallback,
        onDisconnect: onDisconnectCallback,
        onFailed: onFailedCallback,
    },
);

同时，Service侧也需要在onConnect()时返回IRemoteObject，从而定义与Service进行通信的接口。onConnect()需要返回一个IRemoteObject对象。OpenHarmony提供了IRemoteObject的默认实现，开发者可以通过继承rpc.RemoteObject来创建自定义的实现类。

Service侧把自身的实例返回给调用侧的代码示例如下：

import rpc from "@ohos.rpc";

let mMyStub;
export default {
    onStart() {
        class MyStub extends rpc.RemoteObject{
            constructor(des) {
                if (typeof des === 'string') {
                    super(des);
                }
                return null;
            }
            onRemoteRequest(code, data, reply, option) {
                console.log("ServiceAbility onRemoteRequest called");
                if (code === 1) {
                    let op1 = data.readInt();
                    let op2 = data.readInt();
                    console.log("op1 = " + op1 + ", op2 = " + op2);
                    reply.writeInt(op1 + op2);
                } else {
                    console.log("ServiceAbility unknown request code");
                }
                return true;
            }
        }
        mMyStub = new MyStub("ServiceAbility-test");
    },
    onCommand(want, startId) {
        console.log('ServiceAbility onCommand');
    },
    onConnect(want) {
        console.log('ServiceAbility OnConnect');
        return mMyStub;
    },
    onDisconnect(want) {
        console.log('ServiceAbility OnDisConnect');
    },
    onStop() {
        console.log('ServiceAbility onStop');
    },
}

连接远程Service（当前仅对系统应用开放）

说明：由于DeviceManager的getTrustedDeviceListSync接口仅对系统应用开放，当前连接远程Service仅支持系统应用。

如果Service需要与Page Ability或其他应用的Service Ability进行跨设备交互，则须创建用于连接的Connection。Service支持其他Ability通过connectAbility()方法与其进行跨设备连接。

在使用connectAbility()处理回调时，需要传入目标Service的Want与IAbilityConnection的实例。IAbilityConnection提供了以下方法供开发者实现：onConnect()是用来处理连接Service成功的回调，onDisconnect()是用来处理Service异常死亡的回调，onFailed()是用来处理连接Service失败的回调。

创建连接远程Service回调实例的代码示例如下：

import prompt from '@system.prompt'

let mRemote;
function onConnectCallback(element, remote){
    console.log('onConnectRemoteService onConnectDone element: ' + element);
    console.log('onConnectRemoteService onConnectDone remote: ' + remote);
    mRemote = remote;
    if (mRemote == null) {
      prompt.showToast({
        message: "onConnectRemoteService not connected yet"
      });
      return;
    }
    let option = new rpc.MessageOption();
    let data = new rpc.MessageParcel();
    let reply = new rpc.MessageParcel();
    data.writeInt(1);
    data.writeInt(99);
    mRemote.sendRequest(1, data, reply, option).then((result) => {
        console.log('sendRequest success');
        let msg = reply.readInt();
        prompt.showToast({
            message: "onConnectRemoteService connect result: " + msg,
            duration: 3000
        });
    }).catch((e) => {
        console.log('sendRequest error:' + e);
    });
}

function onDisconnectCallback(element){
    console.log('ConnectRemoteAbility onDisconnect Callback')
}

function onFailedCallback(code){
    console.log('ConnectRemoteAbility onFailed Callback')
}

目标Service的Want需要包含远程deviceId，该远程deviceId可通过deviceManager获取,具体示例代码如下：

import deviceManager from '@ohos.distributedHardware.deviceManager';

//dmClass具体实现请参考：相关实例 分布式Demo 章节中的实现
let dmClass;

function getRemoteDeviceId() {
    if (typeof dmClass === 'object' && dmClass != null) {
        let list = dmClass.getTrustedDeviceListSync();
        if (typeof (list) == 'undefined' || typeof (list.length) == 'undefined') {
            console.log("MainAbility onButtonClick getRemoteDeviceId err: list is null");
            return;
        }
        console.log("MainAbility onButtonClick getRemoteDeviceId success:" + list[0].deviceId);
        return list[0].deviceId;
    } else {
        console.log("MainAbility onButtonClick getRemoteDeviceId err: dmClass is null");
    }
}

连接远程Service的代码示例如下：

import featureAbility from '@ohos.ability.featureAbility';
let connId = featureAbility.connectAbility(
    {
        deviceId: getRemoteDeviceId(),
        bundleName: "ohos.samples.etsDemo",
        abilityName: "ohos.samples.etsDemo.ServiceAbility",
    },
    {
        onConnect: onConnectCallback,
        onDisconnect: onDisconnectCallback,
        onFailed: onFailedCallback,
    },
);

在跨设备场景下，需要向用户申请数据同步的权限。具体示例代码如下：

import abilityAccessCtrl from "@ohos.abilityAccessCtrl";
import bundle from '@ohos.bundle';
async function RequestPermission() {
  console.info('RequestPermission begin');
  let array: Array<string> = ["ohos.permission.DISTRIBUTED_DATASYNC"];
  let bundleFlag = 0;
  let tokenID = undefined;
  let userID = 100;
  let appInfo = await bundle.getApplicationInfo('ohos.samples.etsDemo', bundleFlag, userID);
  tokenID = appInfo.accessTokenId;
  let atManager = abilityAccessCtrl.createAtManager();
  let requestPermissions: Array<string> = [];
  for (let i = 0;i < array.length; i++) {
    let result = await atManager.verifyAccessToken(tokenID, array[i]);
    console.info("verifyAccessToken result:" + JSON.stringify(result));
    if (result == abilityAccessCtrl.GrantStatus.PERMISSION_GRANTED) {
    } else {
      requestPermissions.push(array[i]);
    }
  }
  console.info("requestPermissions:" + JSON.stringify(requestPermissions));
  if (requestPermissions.length == 0 || requestPermissions == []) {
    return;
  }
  let context = featureAbility.getContext();
  context.requestPermissionsFromUser(requestPermissions, 1, (data)=>{
    console.info("data:" + JSON.stringify(data));
  });
  console.info('RequestPermission end');
}

同时，Service侧也需要在onConnect()时返回IRemoteObject，从而定义与Service进行通信的接口。onConnect()需要返回一个IRemoteObject对象。OpenHarmony提供了IRemoteObject的默认实现，开发者可以通过继承rpc.RemoteObject来创建自定义的实现类。

Service侧把自身的实例返回给调用侧的代码示例如下：

import rpc from "@ohos.rpc";

class FirstServiceAbilityStub extends rpc.RemoteObject{
    constructor(des) {
        if (typeof des === 'string') {
            super(des);
        } else {
            return null;
        }
    }
    onRemoteRequest(code, data, reply, option) {
        console.log("ServiceAbility onRemoteRequest called");
        if (code === 1) {
            let op1 = data.readInt();
            let op2 = data.readInt();
            console.log("op1 = " + op1 + ", op2 = " + op2);
            reply.writeInt(op1 + op2);
        } else {
            console.log("ServiceAbility unknown request code");
        }
        return true;
    }
}

export default {
    onStart() {
        console.info('ServiceAbility onStart');
    },
    onStop() {
        console.info('ServiceAbility onStop');
    },
    onConnect(want) {
        console.log("ServiceAbility onConnect");
        try {
            let value = JSON.stringify(want);
            console.log("ServiceAbility want:" + value);
        } catch(error) {
            console.log("ServiceAbility error:" + error);
        }
        return new FirstServiceAbilityStub("first ts service stub");
    },
    onDisconnect(want) {
        console.log("ServiceAbility onDisconnect");
        let value = JSON.stringify(want);
        console.log("ServiceAbility want:" + value);
    },
    onCommand(want, startId) {
        console.info('ServiceAbility onCommand');
        let value = JSON.stringify(want);
        console.log("ServiceAbility want:" + value);
        console.log("ServiceAbility startId:" + startId);
    }
};

相关实例

针对ServiceAbility开发，有以下相关实例可供参考：