Question

这是我的项目的简化版。假设我在text view上方有一个recycler view，像下面的图片一样位于nested scroll view内

这是我的项目的XML：

<androidx.core.widget.NestedScrollView
        xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:app="http://schemas.android.com/apk/res-auto" xmlns:tools="http://schemas.android.com/tools"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:background="@android:color/white" android:id="@+id/nestedScrollView_user_control">

    <androidx.constraintlayout.widget.ConstraintLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content" android:id="@+id/constraintLayout_profile">

        <TextView
                android:text="TextView"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content" android:id="@+id/textView3"
                app:layout_constraintTop_toTopOf="parent"
                app:layout_constraintStart_toStartOf="parent"
                app:layout_constraintEnd_toEndOf="parent"/>


        <androidx.recyclerview.widget.RecyclerView
                android:layout_width="0dp"
                android:layout_height="wrap_content"
                android:scrollbars="vertical"
                android:nestedScrollingEnabled="false"
                app:layout_constraintBottom_toBottomOf="parent" app:layout_constraintEnd_toEndOf="parent"
                app:layout_constraintStart_toStartOf="parent"
                app:layout_constraintTop_toBottomOf="@id/textView3"
                tools:listitem="@layout/item_general_event" android:id="@+id/recyclerView_attended_event_user_control"
                android:layout_marginTop="120dp">
        </androidx.recyclerview.widget.RecyclerView>

        <ProgressBar
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:id="@+id/progressBar_user_control"
                app:layout_constraintEnd_toEndOf="parent"
                app:layout_constraintStart_toStartOf="parent"
                app:layout_constraintBottom_toBottomOf="parent"
                app:layout_constraintTop_toTopOf="parent"
                android:visibility="gone"/>

    </androidx.constraintlayout.widget.ConstraintLayout>

</androidx.core.widget.NestedScrollView>

以下是我的应用问题的视频：https://drive.google.com/file/d/1E6N0xGDp8sBPrLgwfctTEWeSfyPHevyj/view

如您所见，它位于tab中的最后一个bottom navigation view中。当我第一次点击该选项卡时（完全关闭应用程序后），第二个小部件的行为类似于：

text view将立即出现
然后progress bar将显示（从服务器中获取数据）
recycler view最终会出现。

但是，当我从bottom navigation视图中的最后一个选项卡切换时，先说第一个选项卡，然后再返回到最后一个选项卡，这会使我的应用看起来很滞后。 textView将不会立即显示。它会等待，甚至progressBar也不会显示，并且会与recyclerView同时显示。

似乎recyclerView正在设置项目并同时获取数据（不确定原因），这使我的应用看上去很滞后。

我想在点击bottom navigation view中的标签后立即显示文本视图

下面是我使用的代码：

    class UserControlFragment : Fragment(), EasyPermissions.PermissionCallbacks {

    lateinit var nestedScrollView: NestedScrollView
    lateinit var progressBar : ProgressBar
    lateinit var fragmentView : View
    lateinit var recyclerView : RecyclerView

    lateinit var sharedPrefManager : SharedPreferenceManager
    lateinit var userControlAdapter : GeneralEventRecyclerViewAdapter

    private var attendedEvents = ArrayList<Event>()
    private var userData : User? = null


    lateinit var mContext : Context
    lateinit var mActivity : FragmentActivity

    override fun onAttach(context: Context) {
        super.onAttach(context)

        mContext = context
        activity?.let { mActivity = it }

    }

    override fun onCreateView(
        inflater: LayoutInflater, container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View? {

        fragmentView = inflater.inflate(R.layout.fragment_user_control, container, false)
        sharedPrefManager = SharedPreferenceManager.getInstance(mContext)
        setUpViewsDeclaration()


        getUserData()
        initRecyclerView()
        getAttendedEvents()

        return fragmentView
    }



    private fun setUpViewsDeclaration() {

        nestedScrollView = fragmentView.findViewById(R.id.nestedScrollView_user_control)
        progressBar = fragmentView.findViewById(R.id.progressBar_user_control)
        recyclerView = fragmentView.findViewById(R.id.recyclerView_attended_event_user_control)



    }


    private fun getUserData() {
        userData = sharedPrefManager.loadUserData()

    }




    private fun initRecyclerView() {

        userControlAdapter = GeneralEventRecyclerViewAdapter(mContext)
        val layoutManager = LinearLayoutManager(mContext, RecyclerView.VERTICAL,false)
        recyclerView.adapter = userControlAdapter
        recyclerView.layoutManager = layoutManager
        nestedScrollView.isNestedScrollingEnabled = false

        userControlAdapter.setOnItemClickListener(object: OnEventKMListener {

            override fun eventKMClicked(position: Int) {
                val selectedEvent = attendedEvents[position]
                val eventDetailDestination = UserControlFragmentDirections.actionGlobalDestinationEventDetail(selectedEvent)
                Navigation.findNavController(fragmentView).navigate(eventDetailDestination)
            }

        })



    }


    private fun getAttendedEvents() {

        val user = userData ?: return


        progressBar.visibility = View.VISIBLE


        FirestoreKMClient.getRecommendedEvents(user.domicile) { errorMessage, events ->

            progressBar.visibility = View.GONE

            errorMessage?.let {
                mActivity.toast(it)
            } ?: run {

                val eventList = events ?: ArrayList()
                attendedEvents = eventList
                userControlAdapter.submitList(eventList)

            }

        }


    }


 }

这是我用于适配器的代码：

class GeneralEventRecyclerViewAdapter(val mContext: Context): ListAdapter<Event, RecyclerView.ViewHolder>(DIFF_CALLBACK) {

    lateinit var mOnEventKMListener : OnEventKMListener

    fun setOnItemClickListener(listener: OnEventKMListener) {
        mOnEventKMListener = listener
    }


    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): RecyclerView.ViewHolder {
        val itemView = LayoutInflater.from(parent.context).inflate(R.layout.item_general_event, parent, false)
        return GeneralEventViewHolder(itemView, mOnEventKMListener)
    }

    override fun onBindViewHolder(holder: RecyclerView.ViewHolder, position: Int) {

        val currentEvent = getItem(position)
        val generalEventViewHolder = holder as GeneralEventViewHolder

        Glide.with(mContext).load(currentEvent.thumbnailDownloadPath)
            .apply(RequestOptions.bitmapTransform(BlurTransformation(25, 3)))
            .into(generalEventViewHolder.blurThumbnailImageView)

        Glide.with(mContext).load(currentEvent.thumbnailDownloadPath).into(generalEventViewHolder.thumbnailImageView)


        generalEventViewHolder.eventNameTextView.text = currentEvent.title
        generalEventViewHolder.eventVenueTextView.text = currentEvent.venue
        generalEventViewHolder.eventDateTimeTextView.text = DateTimeService.changeDateToString("EEEE, d MMMM. HH:mm zzz",currentEvent.dateTimeStart)

    }


    companion object {

        private val DIFF_CALLBACK = object : DiffUtil.ItemCallback<Event>() {
            override fun areItemsTheSame(oldItem: Event, newItem: Event): Boolean {
                return oldItem.eventID == newItem.eventID
            }

            override fun areContentsTheSame(oldItem: Event, newItem: Event): Boolean {
                return oldItem == newItem
            }


        }
    }


}

Java代码很好

为什么底部导航视图的选项卡中的片段无法立即显示？

0 个答案: