为什么数据没有加载到回收器视图 MVVM?

Question

我有一个Android应用程序，它从网络请求列表，应该在回收器视图中显示它，但这不会发生。日志中没有错误。我认为问题出在我在视图模型中的函数中。帮助我理解

我的类别客户类：

class CategoryClient {
companion object {
const val KEY = "5de979d34658275ac9dc2375"
}
var category: List<Category>? = null
fun loadCategory(): List<Category>? {
// x-apikey interceptor for restdb API
fun createOkHttpClient(): OkHttpClient? {
val httpClient = OkHttpClient.Builder()
httpClient.addInterceptor(object : Interceptor {
@Throws(IOException::class)
override fun intercept(chain: Interceptor.Chain): okhttp3.Response {
val original = chain.request()
val originalHttpUrl = original.url
val url = originalHttpUrl.newBuilder()
.addQueryParameter("apikey", KEY)
.build()
val requestBuilder = original.newBuilder()
.url(url)
val request = requestBuilder.build()
return chain.proceed(request)
}
})
// logging interceptor
val logging = HttpLoggingInterceptor()
logging.level = HttpLoggingInterceptor.Level.BODY
httpClient.addInterceptor(logging)
return httpClient.build()
}
val retrofit = Retrofit.Builder()
.baseUrl("https://testcategory-d6d7.restdb.io/rest/")
.addConverterFactory(GsonConverterFactory.create())
.client(createOkHttpClient())
.build()
val api = retrofit.create(CategoryApi::class.java)
api.fetchAllCategory().enqueue(object : Callback<List<Category>> {
override fun onFailure(call: Call<List<Category>>, t: Throwable) {
}
override fun onResponse(call: Call<List<Category>>, response: Response<List<Category>>) {
//Log.d(TAG, "onResponse: ${response.body()!![0].name}")
category = response.body()!!
//presenter.setupCategoryList(categoryList = category as ArrayList<Category>)
}
})
return category
}
}

我的类别活动类

val binding: ActivityCategoryBinding =
DataBindingUtil.setContentView(this@CategoryActivity, R.layout.activity_category)
val categoryViewModel =
ViewModelProviders.of(this@CategoryActivity).get(CategoryViewModel::class.java)
binding.categoryViewModel = categoryViewModel
categoryViewModel.getArrayList().observe(this@CategoryActivity, Observer { category ->
mAdapter = CategoryAdapter(this@CategoryActivity, categoryList = category )
recycler_category.layoutManager = LinearLayoutManager(applicationContext, OrientationHelper.VERTICAL, false)
recycler_category.adapter = mAdapter
recycler_category.setHasFixedSize(true)
})

我的回收器视图适配器类

class CategoryAdapter(private val context: Context, private val categoryList: ArrayList<Category>?)
: RecyclerView.Adapter<RecyclerView.ViewHolder>() {
private var mCategoryList: ArrayList<Category> = ArrayList()
private var mSourceList: ArrayList<Category> = ArrayList()
fun setupCategory(categoryList: ArrayList<Category>) {
mSourceList.clear()
mSourceList.addAll(categoryList)
search(query = "")
}
fun search(query: String) {
mCategoryList.clear()
mSourceList.forEach {
if (it.name.contains(query, ignoreCase = true)) {
mCategoryList.add(it)
}
}
notifyDataSetChanged()
}
fun sortByName() {
mCategoryList.sortBy { it.name }
notifyDataSetChanged()
}
fun sortByPrice() {
mCategoryList.sortBy { it.price }
notifyDataSetChanged()
}
fun filter() {
}
override fun onBindViewHolder(holder: RecyclerView.ViewHolder, position: Int) {
if (holder is CategoryViewHolder) {
holder.bind(categoryModel = mCategoryList[position])

}
}
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): RecyclerView.ViewHolder {
val layoutInflater = LayoutInflater.from(parent.context)
val itemView = layoutInflater.inflate(R.layout.cell_category, parent, false)
return CategoryViewHolder(itemView = itemView)
}
override fun getItemCount(): Int {
return mCategoryList.count()
}
class CategoryViewHolder(itemView: View): RecyclerView.ViewHolder(itemView) {
var mCategoryIcon: CircleImageView = itemView.findViewById(R.id.category_icon)
var mCategoryName: TextView = itemView.findViewById(R.id.category_name)
var mCategoryPrice: TextView = itemView.findViewById(R.id.category_price)
private var mCategoryType: TextView = itemView.findViewById(R.id.category_type)
fun bind(categoryModel: Category) {
categoryModel.icon.let { url ->
Picasso.with(itemView.context).load(url)
.into(mCategoryIcon)
}
mCategoryName.text = categoryModel.name
mCategoryPrice.text = categoryModel.price.toString()
mCategoryType.text = categoryModel.category
}
}
}

还有我的视图模型类

class CategoryViewModel : ViewModel() {
var mutableLiveData = MutableLiveData<ArrayList<Category>>()
fun getArrayList(): MutableLiveData<ArrayList<Category>> {
mutableLiveData.value = CategoryClient().loadCategory() as ArrayList<Category>?
return  mutableLiveData
}
}

Answer 1

您的数据不会从asynchronousAPI 调用中更新。更改您的实现，如下所示以获取更新的数据：

class CategoryViewModel : ViewModel() {
fun getArrayList(): MutableLiveData<ArrayList<Category>> {
return CategoryClient().loadCategory()
}
}

还有你的loadCategory

var mutableLiveData = MutableLiveData<ArrayList<Category>>()
fun loadCategory(): MutableLiveData<ArrayList<Category>> {
api.fetchAllCategory().enqueue(object : Callback<List<Category>> {
override fun onFailure(call: Call<List<Category>>, t: Throwable) {
}
override fun onResponse(call: Call<List<Category>>, response: Response<List<Category>>) {
mutableLiveData.postValue(response.body())
}
})
return mutableLiveData
}

并且您的适配器应更正为使用单一来源

class CategoryAdapter(private val context: Context, private val mCategoryList: ArrayList<Category>?)
: RecyclerView.Adapter<RecyclerView.ViewHolder>() {
private var mSourceList: ArrayList<Category> = ArrayList(mCategoryList)
.....
}