Fragment中的RecyclerView未填充

Question

我已经纠结了好几天了，我需要一些帮助。我已经使这个代码在一个活动中工作，但后来我把它移动到一个片段，它不工作。

使用带有工作活动的调试器，行

apiService = retrofit.create<HomeJsonApiService>(HomeJsonApiService::class.java)

转到getItemCount()。然而，在片段中，它直接进入片段中的onCreateView。我在下面附上了我的代码。提前感谢您的帮助!温柔一点。我还是新手:)

第一个是my fragment:

class TabHomeActivity : Fragment() {
val itemList = ArrayList<HomeCards>()
lateinit var adapter: HomeCardsAdapter
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
var binding = FragmentTabHomeActivityBinding.inflate(layoutInflater)
adapter = HomeCardsAdapter()
var rv = binding.rvHomeCards
rv.adapter = adapter
loadData()
}
override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?,savedInstanceState: Bundle?): View? {
return inflater.inflate(R.layout.cards_home, container, false)
}
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
}
private fun loadData() {
ApiManager.getInstance().service.listHeroes()
.enqueue(object : Callback<ResponseData<List<HomeCards>>> {
override fun onResponse(
call: Call<ResponseData<List<HomeCards>>>,
response: Response<ResponseData<List<HomeCards>>>
) {
val listData: List<HomeCards> = response.body()!!.data
// updating data from network to adapter
itemList.clear()
itemList.addAll(listData)
adapter.updateData(itemList)
adapter.notifyDataSetChanged()
}
override fun onFailure(call: Call<ResponseData<List<HomeCards>>>, t: Throwable) {
}
})
}
}

HTTP请求:

data class ResponseData<T> (
val code: Int,
val data: T
)
interface HomeJsonApiService {
@GET("marvel-heroes.asp?h=2")
fun listHeroes(): retrofit2.Call<ResponseData<List<HomeCards>>>
}
class ApiManager {
private var apiService: HomeJsonApiService? = null
init {
createService()
}
val service: HomeJsonApiService get() = apiService!!
private fun createService() {
val loggingInterceptor =
HttpLoggingInterceptor(object : HttpLoggingInterceptor.Logger {
override fun log(message: String) {
Log.i("Retrofit", message)
}
})
loggingInterceptor.level = HttpLoggingInterceptor.Level.BODY
val client = OkHttpClient.Builder()
.readTimeout(30, TimeUnit.SECONDS)
.connectTimeout(30, TimeUnit.SECONDS)
.writeTimeout(30, TimeUnit.SECONDS)
.addInterceptor(loggingInterceptor)
.build()
val retrofit: Retrofit = Retrofit.Builder()
.client(client)
.baseUrl("https://www.mywebsite.com/jsonfolder/JSON/")
.addConverterFactory(GsonConverterFactory.create())
.build()
apiService = retrofit.create(HomeJsonApiService::class.java)
}
companion object {
private var instance: ApiManager? = null
fun getInstance(): ApiManager {
return instance ?: synchronized(this) {
ApiManager().also { instance = it }
}
}
}
}

和适配器:

class HomeCardsAdapter() : RecyclerView.Adapter<HomeCardsAdapter.ViewHolder>() {
private lateinit var itemList: List<HomeCards>
lateinit var context: Context
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
context = parent.context
val view = LayoutInflater.from(context).inflate(R.layout.cards_home, parent, false)
return ViewHolder(view)
}
override fun getItemCount(): Int {
return if (::itemList.isInitialized) itemList.size else 0
}
override fun onBindViewHolder(holder: ViewHolder, position: Int) {
holder.bind()
}
fun updateData(list: List<HomeCards>) {
itemList = list;
notifyDataSetChanged()
}
inner class ViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {
//var binding = ActivityMainBinding(layoutInflater(inf))
fun bind() {
val item = itemList.get(adapterPosition)
ViewHolder(itemView).itemView.findViewById<TextView>(R.id.cardHomeTitle).text = item.name
ViewHolder(itemView).itemView.findViewById<TextView>(R.id.cardHomeTitle).text = item.superheroName
Glide.with(context)
.load(item.photo)
.diskCacheStrategy(DiskCacheStrategy.ALL)
.circleCrop()
.into(ViewHolder(itemView).itemView.findViewById<ImageView>(R.id.cardHomeIcon))
}
}
}
class HomeCards {
@SerializedName("superhero_name")
var superheroName: String = ""
var name: String = ""
var photo: String = ""
}

Answer 1

主要问题是:

var binding = FragmentTabHomeActivityBinding.inflate(layoutInflater)

在onCreate内部但是onCreateView返回另一个视图inflater.inflate(R.layout.cards_home, container, false)

因此，您正在将适配器应用于绑定上的回收器，但是屏幕上的视图从布局中膨胀。改成这样:

private lateinit var binding: FragmentTabHomeActivityBinding
override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?,savedInstanceState: Bundle?): View? {
binding = FragmentTabHomeActivityBinding.inflate(layoutInflater, container, false)
return binding.root
}

并将代码从onCreate移动到onViewCreated，但确保使用lateinit binding

override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
adapter = HomeCardsAdapter()
var rv = binding.rvHomeCards
rv.adapter = adapter
loadData()
}

之后有一个问题在你的适配器:private lateinit var itemList: List<HomeCards>非常具体的List<HomeCards>。notifyDataSetChanged方法不能通过更改或更新数据结构的引用而起作用，而是在修改集合时起作用。改成这样:

private val list = mutableListOf<HomeCards>()

override fun getItemCount(): Int {
return list.size()
}
fun updateData(list: List<HomeCards>) {
this.itemList.clear()
this.itemList.addAll(list)
notifyDataSetChanged()
}

Answer 2

如果onResponse()被调用并提供响应，验证代码更新UI正在主/UI线程上运行。与网络(其他线程)一起工作时常见的问题来源。

activity?.runOnUiThread {
itemList.clear()
itemList.addAll(listData)
adapter.updateData(itemList)
adapter.notifyDataSetChanged()
}