更改片段get IllegalStateException在Kotlin中不能为null

Question

嗨，我正在从程序中从网络获取一些信息，其中包含协程。接收信息时，我更改了片段。在这种情况下，程序崩溃并且Null错误采用以下选项

progress.isIndeterminate = false
adapter = CircularAdapter(itemsData, this@CircularFragment)
rc.adapter = adapter
adapter.notifyDataSetChanged()
swipe_refresh.visibility = View.VISIBLE
lyt_progress.visibility = View.GONE
swipe_refresh.isRefreshing = false

这是我的代码，我什至在OnDestroyView中取消了作业，但仍然出现错误

 private var job: Job = Job()
    override val coroutineContext: CoroutineContext
        get() = Dispatchers.Main + job
    launch {
                val operation = async(Dispatchers.IO) {
                   try {
                       ...
                       for (myTable in table) {
                           val rows: Elements = myTable.select("tr")
                           activity?.runOnUiThread{
                               progress.isIndeterminate = false
                           }
                           for (i in 1 until rows.size) {
                               progress.progress = i                               
                               itemsData.add(...)

                           }
                       }
                   }catch (e: Exception){
                       activity?.runOnUiThread{
                           val navController = Navigation.findNavController(activity!!, R.id.nav_host_fragment)
                           navController.navigate(R.id.noVPNFragment)
                       }
                   }
                }
                operation.await() // wait for result of I/O operation without blocking the main thread

                // update views
                activity?.runOnUiThread{
                    adapter = CircularAdapter(itemsData, this@CircularFragment)
                    rc.adapter = adapter
                    adapter.notifyDataSetChanged()
                    swipe_refresh.visibility = View.VISIBLE
                    lyt_progress.visibility = View.GONE
                    swipe_refresh.isRefreshing = false
                }
            }

    override fun onDestroy() {
            super.onDestroy()
            job.cancel()
        }

        override fun onDestroyView() {
            super.onDestroyView()
            job.cancel()
        }

更新：logcat：

02-21 12:52:48.268 16218-16218/ir.mahdi.circulars.test E/AndroidRuntime: FATAL EXCEPTION: main
    Process: ir.mahdi.circulars.test, PID: 16218
    java.lang.IllegalStateException: progress must not be null
        at ir.mahdi.circulars.Fragments.CircularFragment$getCirculars$1$operation$1$1.run(CircularFragment.kt:118)
        at android.os.Handler.handleCallback(Handler.java:739)
        at android.os.Handler.dispatchMessage(Handler.java:95)
        at android.os.Looper.loop(Looper.java:135)
        at android.app.ActivityThread.main(ActivityThread.java:5254)
        at java.lang.reflect.Method.invoke(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:372)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)

Answer 1

尝试一下，您需要使用findviewbyid

 lateinit var recyclerView: RecyclerView
override fun onCreateView(
        inflater: LayoutInflater,
        container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View? {
        val view: View = inflater!!.inflate(R.layout.some_fragment, container, false)

        recyclerView = view.findViewById(R.id.rc)

        return view
    }

对您所有的元素都执行此操作，我以前曾遇到过此问题，并已通过此方法对其进行了修复

Answer 2

从您的堆栈跟踪来看，似乎progress.isIndeterminate = false 是错误的原因。似乎progress尚未初始化。也许您忘记了findViewById()或用于视图绑定的任何东西。