Question

我有这样的存储库设置

 //EXAMPLE
 let heightMeters = Measurement(value: 16.99, unit: UnitLength.meters)

 let heightCentimeters = heightMeters.converted(to: UnitLength.centimeters)

 //EXTRACT CM FROM METERS BY EVALUATING THE DECIMAL PART
 let cm = ceil((heightMeters.value - floor(heightMeters.value))*100)

 // GET METERS WITHOUT CM
 let meters = floor(heightMeters.value)

 let heightInches = heightMeters.converted(to: UnitLength.inches)
 let heightFeet = heightMeters.converted(to: UnitLength.feet)

 //EXTRACT INCHES FROM FT BY EVALUATING THE DECIMAL PART
 let inches = ceil((heightFeet.value - floor(heightFeet.value))*12)

 // GET FT WITHOUT INCHES
 let feet = floor(heightFeet.value)

然后我有一个像这样的视图模型调用此仓库

class ServerTimeRepo @Inject constructor(private val retrofit: Retrofit){
    var liveDataTime = MutableLiveData<TimeResponse>()
    fun getServerTime(): LiveData<TimeResponse> {
        val serverTimeService:ServerTimeService = retrofit.create(ServerTimeService::class.java)
        val obs = serverTimeService.getServerTime()
        obs.subscribeOn(Schedulers.io()).observeOn(AndroidSchedulers.mainThread()).unsubscribeOn(Schedulers.io())
                .subscribe(object : Observer<Response<TimeResponse>> {
                    override fun onComplete() {

                    }

                    override fun onSubscribe(d: Disposable) {

                    }

                    override fun onNext(t: Response<TimeResponse>) {
                        val gson = Gson()
                        val json: String?
                        val code = t.code()
                        val cs = code.toString()
                        if (!cs.equals("200")) {
                            json = t.errorBody()!!.string()
                            val userError = gson.fromJson(json, Error::class.java)
                        } else {

                            liveDataTime.value = t.body()
                        }

                    }

                    override fun onError(e: Throwable) {

                    }

                })
        return liveDataTime
    }
}

然后我有一个活动，其中有一个onClickListener，用于观察实时数据，就像这样

class ServerTimeViewModel @Inject constructor(private val serverTimeRepo: ServerTimeRepo):ViewModel() {

    fun getServerTime(): LiveData<TimeResponse> {
        return serverTimeRepo.getServerTime()
    }
}

我不知道这有什么问题。谁能指出我正确的方向？谢谢。

Answer 1

问题是，每次您的 ClickListener 被解雇时，您就会一次又一次地观察到LiveData。因此，您可以按照以下解决方案来解决该问题：

在您的MutableLiveData内私下放置一个ViewModel对象，并以LiveData的身份观察。

class ServerTimeViewModel @Inject constructor(private val serverTimeRepo: ServerTimeRepo):ViewModel() {

    private val serverTimeData = MutableLiveData<TimeResponse>() // We make private variable so that UI/View can't modify directly

    fun getServerTime() {
        serverTimeData.value = serverTimeRepo.getServerTime().value // Rather than returning LiveData, we set value to our local MutableLiveData
    }

    fun observeServerTime(): LiveData<TimeResponse> {
        return serverTimeData //Here we expose our MutableLiveData as LiveData to avoid modification from UI/View
    }
}

现在，我们在LiveData外部直接观察到此ClickListener，我们只是通过按钮点击调用API方法，如下所示：

//Assuming that this code is inside onCreate() of your Activity/Fragment
//first we observe our LiveData
serverTimeViewModel.observeServerTime().observe(this@HomeScreenActivity, Observer {
        //In such case, we won't observe multiple LiveData but one
})
//Then during our ClickListener, we just do API method call without any callback.
tvPWStart.setOnClickListener {
    serverTimeViewModel.getServerTime()
}

在Android的onClickListener中多次观察到LiveData

1 个答案: