# 连接ServiceAbility


如果ServiceAbility需要与PageAbility或其他应用的ServiceAbility进行交互，则须创建用于连接的Connection。ServiceAbility支持其他Ability通过connectAbility()方法与其进行连接。PageAbility的connectAbility方法定义在featureAbility中，ServiceAbility的connectAbility方法定义在particleAbility中。连接ServiceAbility的规则详见[组件启动规则](component-startup-rules.md)章节。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。


  **表1** IAbilityConnection接口说明

| 接口名 | 描述 |
| -------- | -------- |
| onConnect() | 用于处理连接Service成功的回调。 |
| onDisconnect() | 用来处理Service异常死亡的回调。 |
| onFailed() | 用来处理连接Service失败的回调。 |


PageAbility创建连接本地ServiceAbility回调实例的代码以及连接本地ServiceAbility的示例代码如下：

```ts
import rpc from "@ohos.rpc"
import prompt from '@system.prompt'
import featureAbility from '@ohos.ability.featureAbility'

let option = {
  onConnect: function onConnectCallback(element, proxy) {
    console.info(`onConnectLocalService onConnectDone`)
    if (proxy === null) {
      prompt.showToast({
        message: "Connect service failed"
      })
      return
    }
    let data = rpc.MessageParcel.create()
    let reply = rpc.MessageParcel.create()
    let option = new rpc.MessageOption()
    data.writeInterfaceToken("connect.test.token")
    proxy.sendRequest(0, data, reply, option)
    prompt.showToast({
      message: "Connect service success"
    })
  },
  onDisconnect: function onDisconnectCallback(element) {
    console.info(`onConnectLocalService onDisconnectDone element:${element}`)
    prompt.showToast({
      message: "Disconnect service success"
    })
  },
  onFailed: function onFailedCallback(code) {
    console.info(`onConnectLocalService onFailed errCode:${code}`)
    prompt.showToast({
      message: "Connect local service onFailed"
    })
  }
}

let request = {
  bundleName: "com.example.myapplication",
  abilityName: "com.example.myapplication.ServiceAbility",
}
let connId = featureAbility.connectAbility(request, option)
```


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示例代码如下：

```ts
import rpc from "@ohos.rpc"

class FirstServiceAbilityStub extends rpc.RemoteObject {
  constructor(des: any) {
    if (typeof des === 'string') {
      super(des)
    } else {
      return
    }
  }

  onRemoteRequest(code: number, data: any, reply: any, option: any) {
    console.info(`onRemoteRequest called`)
    if (code === 1) {
      let string = data.readString()
      console.info(`string=${string}`)
      let result = Array.from(string).sort().join('')
      console.info(`result=${result}`)
      reply.writeString(result)
    } else {
      console.info(`unknown request code`)
    }
    return true
  }
}
```