Question

I have this android fragment:

class MainFragment: BaseFragment(){

private val recyclerView by lazy { find<RecyclerView>(R.id.recyclerView) }
private val fab by lazy { find<FloatingActionButton>(R.id.fab) }

private val myLayoutManager by lazy { LinearLayoutManager(ctx, LinearLayoutManager.VERTICAL, false) }
private val myAdapter by lazy { MainCardAdapter(ctx, ArrayList<MainCardAdapterItem>(), R.layout.card_main_item) }

override val fragmentLayout = R.layout.fragment_main_layout

val DUMMY_TEXT = "Lorem ipsum dolor sit amet, consectetur adipiscing"

)

override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
    val view = super.onCreateView(inflater, container, savedInstanceState)
    setHasOptionsMenu(true)
    return view
}

override fun onViewCreated(view: View?, savedInstanceState: Bundle?) {
    Log.i("TAG", "onViewCreated")
    super.onViewCreated(view, savedInstanceState)
    (act as MainActivity).run { showWidgetStars(true) }

    recyclerView
            .linkToLayoutManager(myLayoutManager)
            .linkToAdapter(myAdapter)
            .addItemDecorator(removedSwipeLeftDecorator)
            .setOnItemChangedDuration(500)

    myAdapter.run {
        setAdapterItems(dummyList)
    }
}

override fun onCreateOptionsMenu(menu: Menu, inflater: MenuInflater) {
    inflater.inflate(R.menu.activity_main_context, menu)
    menu.findItem(R.id.action_secundary_menu).run {
        isVisible = true
        icon.setTintCompat(ctx, act.colorFromRes(R.color.appGreyDark))
    }
    super.onCreateOptionsMenu(menu, inflater)
}

override fun onOptionsItemSelected(item: MenuItem): Boolean {
    when(item.itemId){
        R.id.action_secundary_menu -> {
            act.showSnackBar("Clicked Secondary Menu!")
            return true
        }
        else -> return super.onOptionsItemSelected(item)
    }
  }
}

Everything works good except after i come back to this fragment (replaced in fragment manager by another, added to the backstack). When i return, i get an error saying: E/RecyclerView: No adapter attached; skipping layout. My bet is that its something to do with lazy properties but i can't figure it why. The fragment shows good on first run, only when going back it shows no recycler view items and display this message

Answer 1

因为我的属性被声明为lazy { find<View>(R.id.xxx}，这基本上意味着它们只会从布局中膨胀一次。如果片段的视图需要再次创建，则recyclerview属性将指向旧视图。

我不确定在这种情况下如何抛出空指针异常。只需将延迟更改为var，然后在onCreateView上重新分配。另一件事，如果我们想要使用相同的LayoutManager用于新的inflated recyclerview，我们必须从之前的recyclerview recyclerView.layoutManager = null中清除它，否则会抛出一个例外layoutManager已被绑定到另一个recyclerView。

kotlin android fragment empty recycler view after back

1 个答案: