为什么作者将localCacheBillingClient设计为LateInit？

Question

代码A来自项目play-billing-samples，您可以看到它。

我不知道作者为什么将localcachebillingclient设计为lateinit，这是因为代码不太复杂，如果(::localcachebillingclient.isinitializal==false){...}被多次调用。

我认为代码B可以很好地工作，对吗？

class BillingRepository private constructor(private val application: Application) :
        PurchasesUpdatedListener, BillingClientStateListener {

     lateinit private var localCacheBillingClient: LocalBillingDb


    val subsSkuDetailsListLiveData: LiveData<List<AugmentedSkuDetails>> by lazy {
        if (::localCacheBillingClient.isInitialized == false) {
            localCacheBillingClient = LocalBillingDb.getInstance(application)
        }
        localCacheBillingClient.skuDetailsDao().getSubscriptionSkuDetails()
    }

    val inappSkuDetailsListLiveData: LiveData<List<AugmentedSkuDetails>> by lazy {
        if (::localCacheBillingClient.isInitialized == false) {
            localCacheBillingClient = LocalBillingDb.getInstance(application)
        }
        localCacheBillingClient.skuDetailsDao().getInappSkuDetails()
    }

   fun startDataSourceConnections() {
        Log.d(LOG_TAG, "startDataSourceConnections")
        instantiateAndConnectToPlayBillingService()
        localCacheBillingClient = LocalBillingDb.getInstance(application)
    }
    ...
}

代码B

class BillingRepository private constructor(private val application: Application) :
        PurchasesUpdatedListener, BillingClientStateListener {

    private val localCacheBillingClient: LocalBillingDb by lazy {
         LocalBillingDb.getInstance(application)
    }

    val subsSkuDetailsListLiveData: LiveData<List<AugmentedSkuDetails>> by lazy {
        localCacheBillingClient.skuDetailsDao().getSubscriptionSkuDetails()
    }


    val inappSkuDetailsListLiveData: LiveData<List<AugmentedSkuDetails>> by lazy {
        localCacheBillingClient.skuDetailsDao().getInappSkuDetails()
    }

   fun startDataSourceConnections() {
        Log.d(LOG_TAG, "startDataSourceConnections")
        instantiateAndConnectToPlayBillingService()        
    }
    ...
}

Answer 1

Kotlin-使用“by lazy”与“lateinit”进行属性初始化

我相信答案就在这条线上，就在这一点下面。

lateinit var可以从任何可以看到对象的地方初始化，例如从框架代码内部初始化，对于单个类的不同对象可以使用多种初始化方案。by lazy{...}反过来为该属性定义唯一的初始值设定项，只能通过在子类中重写该属性来更改该初始值设定项。如果希望从外部以事先可能未知的方式初始化属性，请使用LateInit。