Android Kotlin抽象类二级构造函数

我无法为此抽象类创建二级构造函数

@SuppressLint("StaticFieldLeak")
abstract class BaseAndroidViewModel(
        application: Application,
        private val creditsGetByIdUseCase: CreditsGetByIdUseCase,
        private val videosGetByIdUseCase: VideosGetByIdUseCase,
        private val reviewGetByIdUseCase: ReviewGetByIdUseCase,
        private val addToFavoritesUseCase: AddToFavoritesUseCase,
        private val getFavoriteByIdUseCase: GetFavoriteByIdUseCase
) : AndroidViewModel(application) {

constructor(application: Application) : this(application) // There's a cycle in the delegation calls chain error

---

当您创建一个辅助构造函数，并且一个类具有非空的主构造函数时，您应该传递主构造函数具有的所有参数，例如：

abstract class BaseAndroidViewModel(
        application: Application,
        private val creditsGetByIdUseCase: String,
        private val videosGetByIdUseCase: String
) : AndroidViewModel(application) {

    constructor(application: Application) : this(application, 
            "creditsGetByIdUseCase", "videosGetByIdUseCase") // here we pass other necessary parameters
}

在您的情况下，可能是以下情况：

@SuppressLint("StaticFieldLeak")
abstract class BaseAndroidViewModel(
    application: Application,
    private val creditsGetByIdUseCase: CreditsGetByIdUseCase?,
    private val videosGetByIdUseCase: VideosGetByIdUseCase?,
    private val reviewGetByIdUseCase: ReviewGetByIdUseCase?,
    private val addToFavoritesUseCase: AddToFavoritesUseCase?,
    private val getFavoriteByIdUseCase: GetFavoriteByIdUseCase?
) : AndroidViewModel(application) {

    constructor(application: Application) : this(application, null, null, null, null, null)
}

或者，您可以使用默认参数创建主构造函数：

abstract class BaseAndroidViewModel(
        application: Application,
        private val creditsGetByIdUseCase: CreditsGetByIdUseCase? = null,
        private val videosGetByIdUseCase: VideosGetByIdUseCase? = null,
        private val reviewGetByIdUseCase: ReviewGetByIdUseCase? = null ,
        private val addToFavoritesUseCase: AddToFavoritesUseCase? = null,
        private val getFavoriteByIdUseCase: GetFavoriteByIdUseCase? = null
    ) : AndroidViewModel(application) { ... }

---

您可以像这样调用二级构造函数-

@SuppressLint("StaticFieldLeak") abstract class BaseAndroidViewModel : AndroidViewModel{
constructor(application: Application,
            creditsGetByIdUseCase: CreditsGetByIdUseCase,
            videosGetByIdUseCase: VideosGetByIdUseCase,
            reviewGetByIdUseCase: ReviewGetByIdUseCase,
            addToFavoritesUseCase: AddToFavoritesUseCase,
            getFavoriteByIdUseCase: GetFavoriteByIdUseCase) : super(application)

constructor(application: Application) : super(application) }

---

您在委派调用链错误中获得

周期的原因是

constructor(application: Application): this(application)

与java等效：

public MyClass(Application application){
    this(application)
}

这表示您正在递归调用构造函数


如中所述，您应该调用超级构造函数

constructor(application: Application): super(application)

这实际上相当于您的主构造函数：

BaseAndroidViewModel(application: Application): AndroidViewModel(application)

您可以假设这只是用
BaseAndroidViewModel
替换关键字
constructor
和
super
替换关键字
AndroidViewModel