Question

class HomeFragment : Fragment(), CardStackListener {


val cardStackView = card_stack_view

val manager = CardStackLayoutManager(getActivity(), this)

private val adapter by lazy { CardStackAdapter(createSpots()) }

override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
    val homeFragmentView : View = inflater!!.inflate(R.layout.fragment_home, container, false)


    cardStackView.layoutManager = manager
    setupCardStackView()
    setupButton()
    return homeFragmentView
}

*错误消息是“ cardStackView不能为空” 错误出现在“ cardStackView.layoutManager = manager”中我该怎么办才能解决这个问题... *

Answer 1

在cardStackView之后添加问号，如下所示：

cardStackView?.layoutManager = manager

我想cardStackView是可以为空的，IDE表示此行可能会导致NullPointerException

Answer 2

您可以添加您正在使用哪个CardStackView吗？有几种实现这种视图的库（其中一些具有很好的文档，例如https://github.com/yuyakaido/CardStackView和https://github.com/loopeer/CardStackView）。

您可以查找CardStackView for Android being used on Stack Overflow的示例或使用Google。

更新该问题可能是由于manager字段可能为空引起的。如果您完全在函数中进行初始化会怎样？

val manager = CardStackLayoutManager()
val adapter = CardStackAdapter()

val cardStackView = findViewById<CardStackView>(R.id.card_stack_view)
cardStackView.layoutManager = manager
cardStackView.adapter = adapter

CardStackView null

2 个答案: