无法使用 Kotlin 协程解析回收器视图中的数据

如何解决无法使用 Kotlin 协程解析回收器视图中的数据

我正在从服务器获取数据并尝试使用协程在回收器视图中解析它。虽然数据已成功获取，但我无法从嵌套的 json 中解析特定键。

这是 JSON 响应：

{
"status": "200","message": "Success","result": [
    {
        "_id": "60f516fa846e059e2f19c50c","category": "Shirts","sku": [
            {
                "name": "Oxford shirt","brand": "John players","price": "25","color": "Blue","img": "https://firebasestorage.googleapis.com/v0/b/koovs-1ff31.appspot.com/o/shi1.jpg?alt=media&token=64779194-e3b5-484f-a610-c9a20648b64c"
            },{
                "name": "Buttoned down","brand": "Gap originals","price": "45","color": "Pink","img": "https://firebasestorage.googleapis.com/v0/b/koovs-1ff31.appspot.com/o/shi2.jpg?alt=media&token=0b207b90-f1bc-4771-b877-809648e6bdc1"
            },{
                "name": "Collared","brand": "Arrow","price": "30","color": "White","img": "https://firebasestorage.googleapis.com/v0/b/koovs-1ff31.appspot.com/o/shi3.jpg?alt=media&token=2c1bb3f8-e739-4f09-acbc-aa11fed795e3"
            },{
                "name": "Printed","color": "Olive green","img": "https://firebasestorage.googleapis.com/v0/b/koovs-1ff31.appspot.com/o/shi4.jpg?alt=media&token=666f94bf-4769-44fe-a909-3c81ca9262f7"
            },{
                "name": "Hoodie","brand": "Levis","price": "44","color": "Yellow","img": "https://firebasestorage.googleapis.com/v0/b/koovs-1ff31.appspot.com/o/shi5.jpg?alt=media&token=65fccef4-a882-4278-b5df-f00eb2785bf1"
            }
        ]
    },{
        "_id": "60f51c37846e059e2f19c50f","category": "Shoes","sku": [
            {
                "name": "Sneakers","brand": "Puma","price": "35","color": "Black and white","img": "https://firebasestorage.googleapis.com/v0/b/koovs-1ff31.appspot.com/o/sho1.jpg?alt=media&token=d078988d-9e85-4313-bb4a-c9d46e09f0b9"
            },{
                "name": "Running shoe","brand": "Nike","price": "99","color": "Multicolor","img": "https://firebasestorage.googleapis.com/v0/b/koovs-1ff31.appspot.com/o/sho2.jpg?alt=media&token=ed2e7387-3cf6-44df-9f7d-69843eb0bcdf"
            },{
                "name": "Yezzy","brand": "Adidas","price": "349","color": "Gray","img": "https://firebasestorage.googleapis.com/v0/b/koovs-1ff31.appspot.com/o/sho3.jpg?alt=media&token=2c37ef76-37bb-4bdd-b36c-dea32857291f"
            },{
                "name": "Sneakers","price": "79","color": "Black","img": "https://firebasestorage.googleapis.com/v0/b/koovs-1ff31.appspot.com/o/sho4.jpg?alt=media&token=4acd763e-8b93-47cd-ba45-92f34af4cf83"
            },{
                "name": "Joyride running","price": "80","img": "https://firebasestorage.googleapis.com/v0/b/koovs-1ff31.appspot.com/o/sho5.jpg?alt=media&token=e3780dcc-52cb-49d5-9791-e0a44870716c"
            }
        ]
    
       }
    ]
}

我想获取类别。

下面是数据类

Product.kt

data class Product(
  val message: String,val result: List<Result>,val status: String
)

结果.kt

data class Result(
  val _id: String,val category: String,val sku: List<Sku>
)

ApiService.kt

interface ApiService {

  @GET("getProducts")
  suspend fun getCategories(): Response<Product>
}

CategoriesViewModel.kt

class CategoriesViewModel: ViewModel() {

private var categoryList: MutableLiveData<List<Result>> = MutableLiveData()

fun getAllCategory(): LiveData<List<Result>> {

    viewModelScope.launch(Dispatchers.IO) {

        val retrofit = RetrofitClient.getRetrofitClient().create(ApiService::class.java)
        val response = retrofit.getCategories()

        if (response.isSuccessful) {
            categoryList.postValue(response.body()!!.result)
        }
    }
    return categoryList
  }
}

CategoryAdapter.kt

class CategoryAdapter(private val context: Context,private val categories:List<Result>): RecyclerView.Adapter<CategoryAdapter.ViewHolder>() {

override fun onCreateViewHolder(parent: ViewGroup,viewType: Int): CategoryAdapter.ViewHolder {
   return ViewHolder(ParentRowBinding.inflate(LayoutInflater.from(parent.context),parent,false))
}

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

    val model = categories[position]
    holder.binding.catTitle.text = model.category
}

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

class ViewHolder(val binding:ParentRowBinding): RecyclerView.ViewHolder(binding.root)
}

HomeFragment.kt

class HomeFragment : Fragment() {

private var binding: FragmentHomeBinding? = null
private lateinit var adapter: CategoryAdapter

override fun onCreateView(
    inflater: LayoutInflater,container: ViewGroup?,savedInstanceState: Bundle?
): View? {
    // Inflate the layout for this fragment
    binding = FragmentHomeBinding.inflate(inflater,container,false)

    binding!!.parentRecycler.setHasFixedSize(true)
    binding!!.parentRecycler.layoutManager = LinearLayoutManager(activity)

    val viewModel = ViewModelProvider(this).get(CategoriesViewModel::class.java)

    viewModel.getAllCategory().observe(viewLifecycleOwner,Observer { t ->

        val len = t.size

        if(len > 0){

            for(i in 0 until len){
                Log.d("hell",t[i].category.toString())
            }
        }
    })

    return binding!!.root
}

override fun onDestroy() {
    super.onDestroy()
    binding = null
}
}

在这里，我以某种方式获取了类别，但我不知道如何将其传递给适配器，以便我可以在 recyclerview 中显示它。

解决方法

您必须为 Adapter 观察者内的 RecyclerView 分配一个 getAllCategory，如下所示

viewModel.getAllCategory().observe(viewLifecycleOwner,Observer {
    if(!it.isNullOrEmpty()){
        binding!!.parentRecycler.adapter = CategoryAdapter(requireContext(),it)
        // This will bind the Result list received to the recycler view
    }
})

在您的 HomeFragment 中，您需要将适配器设置为 RecyclerView

 binding!!.parentRecycler.adapter= CategoryAdapter(requireContext(),t)

HomeFragment 的完整代码如下

class HomeFragment : Fragment() {

private var binding: FragmentHomeBinding? = null
private lateinit var adapter: CategoryAdapter

override fun onCreateView(
    inflater: LayoutInflater,container: ViewGroup?,savedInstanceState: Bundle?
): View? {
    // Inflate the layout for this fragment
    binding = FragmentHomeBinding.inflate(inflater,container,false)

    binding!!.parentRecycler.setHasFixedSize(true)
    binding!!.parentRecycler.layoutManager = LinearLayoutManager(activity)

    val viewModel = ViewModelProvider(this).get(CategoriesViewModel::class.java)

    viewModel.getAllCategory().observe(viewLifecycleOwner,Observer { t ->

        val len = t.size

        if(len > 0){
            //add this line
            binding!!.parentRecycler.adapter= CategoryAdapter(requireContext(),t) 

            for(i in 0 until len){
                Log.d("hell",t[i].category.toString())
            }
        }
    })

    return binding!!.root
}

override fun onDestroy() {
    super.onDestroy()
    binding = null
}
}

我想最好的方法是从 ListAdapter 继承您的适配器。因为与 RecyclerView.Adapter 不同，它内置支持提交新列表。

这更高效、更快捷，并且不需要创建新的适配器对象或完全更新 RecyclerView 中的所有项目。由于 DiffUtil，只有实际更改的项目才会更新。

所以你CategoryAdapter应该变成：

class CategoryAdapter : ListAdapter<Result,CategoryAdapter.ViewHolder>(DIFF_CALLBACK) {

    companion object {
        val DIFF_CALLBACK = object : DiffUtil.ItemCallback<Result>() {
            override fun areItemsTheSame(oldItem: Inspection.Type,newItem: Inspection.Type) = oldItem._id == newItem._id
            override fun areContentsTheSame(oldItem: Inspection.Type,newItem: Inspection.Type) = oldItem == newItem
        }
    }

override fun onCreateViewHolder(parent: ViewGroup,viewType: Int): CategoryAdapter.ViewHolder {
   return ViewHolder(ParentRowBinding.inflate(LayoutInflater.from(parent.context),parent,false))
}

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

    val model = getItem(position)
    holder.binding.catTitle.text = model.category
}

class ViewHolder(val binding:ParentRowBinding): RecyclerView.ViewHolder(binding.root)
}

在你的 onCreateView 中：

override fun onCreateView(
    inflater: LayoutInflater,false)

    binding!!.parentRecycler.setHasFixedSize(true)
    binding!!.parentRecycler.layoutManager = LinearLayoutManager(activity)
    adapter = CategoryAdapter()
    binding!!.parentRecycler.adapter = adapter

    val viewModel = ViewModelProvider(this).get(CategoriesViewModel::class.java)

    viewModel.getAllCategory().observe(viewLifecycleOwner,Observer { categories ->
        adapter.submitList(categories)
    })

    return binding!!.root
}

请注意，在上面的代码中，您根本没有创建适配器实例，也没有将其分配给回收者。所以它根本不会显示任何东西。

在我的示例中，我在 onCreateView 中创建了一个适配器并将其分配给回收者。在 Observer 中，我们将从 ViewModel 接收到的数据传递给适配器。

是的，正如@dhiraj-uchil 所提到的，这里的问题不是设置缺少的适配器。我也会使 binding 延迟或本地。我也会提取 context，并在其他地方使用它。

 val binding = FragmentHomeBinding.inflate(inflater,false)
 val context = requireContext()
 binding.parentRecycler.adapter= CategoryAdapter(context,t)

关于从 JSON 制作数据类对象，我制作了一个工具，其中包括生成这样的类：

https://kt.academy/json

无法使用 Kotlin 协程解析回收器视图中的数据

如何解决无法使用 Kotlin 协程解析回收器视图中的数据

解决方法

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