回收站视图不显示列表

Question

我的recyclerview 无法正常工作，并且没有显示我为其设置的列表。你能帮我找出问题吗？下面是我创建的Fragment 和Adapter。

片段类 ->

class HomeFragment : Fragment() {

    lateinit var recyclerViewHomeHome: RecyclerView
    lateinit var layoutManager: RecyclerView.LayoutManager

    private val restaurantsInfoList = arrayListOf<Restaurant>(
        Restaurant("rohh", "4.5", "560/person", R.id.imgLogoLogin),
        Restaurant("rohh", "4.5", "560/person", R.id.imgLogoLogin),
        Restaurant("rohh", "4.5", "560/person", R.id.imgLogoLogin),
        Restaurant("rohh", "4.5", "560/person", R.id.imgLogoLogin),
        Restaurant("rohh", "4.5", "560/person", R.id.imgLogoLogin),
        Restaurant("rohh", "4.5", "560/person", R.id.imgLogoLogin),
        Restaurant("rohh", "4.5", "560/person", R.id.imgLogoLogin)

    )

    lateinit var recyclerAdapter: HomeRecyclerAdapter

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

        val view = inflater.inflate(R.layout.fragment_home, container, false)
        recyclerViewHomeHome = view.findViewById(R.id.recyclerViewHomeHome)
        layoutManager = LinearLayoutManager(activity)
        recyclerAdapter = HomeRecyclerAdapter(activity as Context, restaurantsInfoList)

    }
return view
}

适配器类 ->

class HomeRecyclerAdapter(val context: Context, val itemList: ArrayList<Restaurant>) :
    RecyclerView.Adapter<HomeRecyclerAdapter.homeViewHolder>() {

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): homeViewHolder {

        val view = LayoutInflater.from(parent.context)
            .inflate(R.layout.recycler_view_single_row_item, parent, false)
        return homeViewHolder(view)
    }

    override fun getItemCount(): Int {
        return itemList.size
    }

    override fun onBindViewHolder(holder: homeViewHolder, position: Int) {
        val restaurant = itemList[position]
        holder.txtRestaurantNameSingle.text = restaurant.name
        holder.txtPriceSingle.text = restaurant.cost_for_one
        holder.imgRecyclerViewSingle.setBackgroundResource(restaurant.image_url)
        holder.ratingRecyclerViewSingle.text = restaurant.rating

    }

    class homeViewHolder(view: View) : RecyclerView.ViewHolder(view) {
        val txtRestaurantNameSingle: TextView = view.findViewById(R.id.txtRestaurantNameSingle)
        val txtPriceSingle: TextView = view.findViewById(R.id.txtPriceSingle)
        val ratingRecyclerViewSingle: TextView = view.findViewById(R.id.ratingRecyclerViewSingle)
        val imgRecyclerViewSingle: ImageView = view.findViewById(R.id.imgRecyclerViewSingle)
    }
}

Answer 1

你需要在RecyclerView上设置布局管理器和适配器：

    recyclerViewHomeHome = view.findViewById(R.id.recyclerViewHomeHome)
    layoutManager = LinearLayoutManager(activity)
    recyclerAdapter = HomeRecyclerAdapter(activity as Context, restaurantsInfoList)
    recyclerViewHomeHome.layoutManager = layoutManager
    recyclerViewHomeHome.adapter = recyclerAdapter

Answer 2

首先你应该重构你的代码，看看recyclerview

这是我在重构中提出的建议。您不需要在 HomeRecyclerAdapter 中包含上下文，因此只需将其删除即可。

所以它应该看起来像这样：

class HomeFragment : Fragment() {

    lateinit var recyclerViewHomeHome: RecyclerView
    lateinit var layoutManager: RecyclerView.LayoutManager
    lateinit var recyclerAdapter: HomeRecyclerAdapter

    private val restaurantsInfoList = arrayListOf<Restaurant>(
            Restaurant("rohh", "4.5", "560/person", R.id.imgLogoLogin),
            Restaurant("rohh", "4.5", "560/person", R.id.imgLogoLogin),
            Restaurant("rohh", "4.5", "560/person", R.id.imgLogoLogin),
            Restaurant("rohh", "4.5", "560/person", R.id.imgLogoLogin),
            Restaurant("rohh", "4.5", "560/person", R.id.imgLogoLogin),
            Restaurant("rohh", "4.5", "560/person", R.id.imgLogoLogin),
            Restaurant("rohh", "4.5", "560/person", R.id.imgLogoLogin)

    )

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

        val view = inflater.inflate(R.layout.fragment_home, container, false)
        recyclerViewHomeHome = view.findViewById(R.id.recyclerViewHomeHome)
        layoutManager = LinearLayoutManager(this)
        recyclerAdapter = HomeRecyclerAdapter(restaurantsInfoList)
        recyclerViewHomeHome.layout = layoutManager
        recyclerViewHomeHome.adapter = recyclerAdapter
        return view
    }

}

对于您的适配器，您可以使用大量的 kotlin 优势：

class HomeRecyclerAdapter(val itemList: ArrayList<Restaurant>) :
    RecyclerView.Adapter<HomeRecyclerAdapter.homeViewHolder>() {

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): homeViewHolder {
        homeViewHolder.from(parent)
    }

    override fun getItemCount(): Int = itemList.size

    override fun onBindViewHolder(holder: homeViewHolder, position: Int) {
        val restaurant = itemList[position]
        holder.bind(restaurant)
    }

    class homeViewHolder private constructor(view: View) : RecyclerView.ViewHolder(view) {
        val txtRestaurantNameSingle: TextView = view.findViewById(R.id.txtRestaurantNameSingle)
        val txtPriceSingle: TextView = view.findViewById(R.id.txtPriceSingle)
        val ratingRecyclerViewSingle: TextView = view.findViewById(R.id.ratingRecyclerViewSingle)
        val imgRecyclerViewSingle: ImageView = view.findViewById(R.id.imgRecyclerViewSingle)

        fun bind(item: Restaurant){
            txtRestaurantNameSingle.text = item.name
            txtPriceSingle.text = item.cost_for_one
            imgRecyclerViewSingle.setBackgroundResource(item.image_url)
            ratingRecyclerViewSingle.text = item.rating
        }

        companion object {
            fun from(parent: ViewGroup): ViewHolder {
                val view = LayoutInflater.from(parent.context).inflate(R.layout.recycler_view_single_row_item, parent, false)
                return homeViewHolder(view)
            }
        }

    }
}

Answer 3

我修好了。 你犯了一个简单的错误。 崩溃的问题是您错误地使用了充气机。我下载了你的项目并删除了所有不必要的方法和变量以突出问题。 我假设您是初学者，但这没关系，这就是我在 cmets 上提出一些提示的原因。

请注意，repo 仅包含 java 文件。

https://github.com/MicroRJ/BenzinpreiseApp-fixed

//Here was the problem 
@NonNull
@Override
public ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
    return new ViewHolder(LayoutInflater.from(parent.getContext()).inflate(R.layout.list_row_prices, parent, false));
}

如果您需要更多帮助，请告诉我。顺便说一句，该应用程序是做什么用的？看起来很酷。