android - 使用MVVM和翻新不会获取任何数据

Question

我正在尝试在我的应用程序上使用MVVM来获取一些数据，并使用Retrofit将其显示在RecyclerView上，但是未显示任何内容，正在记录数据，当我直接从我的 Activity 中调用改造实例时，正在显示数据在我的RecyclerView上，不确定做错了什么。

这是我的适配器的外观

    class CategoryAdapter (val context: Context):RecyclerView.Adapter<CategoryAdapter.CategoryView>(){

    var category : List<Category> = listOf()

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): CategoryAdapter.CategoryView {
        val view = LayoutInflater.from(parent.context).inflate(R.layout.category_item, parent, false)
        return CategoryView(view)
    }

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


    override fun onBindViewHolder(holder:CategoryView, position: Int) {
        val category = category[position]

        holder.categoryName.text = category.name

    }


    class CategoryView(itemView: View, var category: Category? = null) : RecyclerView.ViewHolder(itemView){
        val categoryName: TextView = itemView.findViewById(R.id.category_title)

    }

}

我的ViewModel

fun loadCategories(id:Int): MutableLiveData<List<Category>>? {
    var categoryList: MutableLiveData<List<Category>>? = null

    RetrofitClient.makeRetrofitApi2().getCategoryProducts(id)
            .enqueue(object : Callback<List<Category>> {
                override fun onResponse(call: Call<List<Category>>, response: Response<List<Category>>) {
                    categoryList?.value = response.body()
                }

                override fun onFailure(call: Call<List<Category>>, t: Throwable) {

                }
            })

    return categoryList
    }

我在 Activity 中如何称呼它

private fun productRecyclerView(){

    recyclerView = findViewById(R.id.foodRv)
    categoryAdapter = CategoryAdapter(this)
    recyclerView.layoutManager = LinearLayoutManager(this)
    recyclerView.adapter = categoryAdapter


    userViewModel = ViewModelProviders.of(this).get(UserViewModel::class.java)
    userViewModel!!.loadCategories(intent.getIntExtra("VENDOR_ID", 0))?.observe(this, Observer { categories ->

        categoryAdapter = CategoryAdapter(this)
        categoryAdapter!!.setCategories(categories)
        foodRv!!.adapter = categoryAdapter

    })
}

一切都已初始化。

Answer 1

您再次在Adapter内初始化了Observer并将其设置为foodRv。那是故意的吗？

如果您需要recyclerView来显示类别，则可以执行以下操作:

categoryAdapter!!.setCategories(categories)
categoryAdapter!!.notifyDataSetChanged()