Question

我在片段中有recyclerview。当我单击recyclerview项目时，背景颜色会改变。但是当我参加另一项活动并返回时，按下的项目颜色保持不变。

我给adapter.notifyDataSetChanged()打过电话，但什么都没发生。

这是我的RecyclerView.ViewHolder类

  class GreetingsView(itemView: View) : RecyclerView.ViewHolder(itemView) {

        var imageView: ImageView? = null
        var category: TextView? = null
        var frameLayout: FrameLayout? = null
        var context: Context? = itemView.context
        private var listOfGreetings: List<GreetingModel>? = null

        init {
            imageView = itemView.findViewById(R.id.greetingImage)
            category = itemView.findViewById(R.id.greetingCategory)
            frameLayout = itemView.findViewById(R.id.card_view)
            this.listOfGreetings = listOfGreetings
            itemView.setOnClickListener {
                val position = adapterPosition

                if (position != RecyclerView.NO_POSITION) {
                    frameLayout?.setBackgroundColor(Color.BLACK)
                    val intent = Intent(context, GridGreetingListActivity::class.java)
                    intent.putExtra("position", position)
                    context?.startActivity(intent)

                }else {
                    frameLayout?.setBackgroundColor(Color.WHITE)
                }

            }

        }

    }

这是我的片段


class CategoryFragment : Fragment(), SendItemPositionListener {

    var greetingAdapter: GreetingAdapter? = null
    var listOfGreetings: ArrayList<GreetingModel>? = arrayListOf()

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

        listOfGreetings?.apply {
            add(0, GreetingModel("Greeting 1", R.drawable.img_1))
            add(1,
                GreetingModel("Greeting 2", R.drawable.greeting_1)
            )
            add(2, GreetingModel("Greeting 3", R.drawable.img_3))
            add(3, GreetingModel("Greeting 4", R.drawable.img_4))
            add(4, GreetingModel("Greeting 5", R.drawable.img_5))
            add(5, GreetingModel("Greeting 6", R.drawable.img_6))
            add(6, GreetingModel("Greeting 7", R.drawable.img_7))
            add(7, GreetingModel("Greeting 8", R.drawable.img_8))
        }


        val view = inflater.inflate(R.layout.fragment_category, container, false)

        //Get the recyclerView from the inflated view.
        val recyclerView = view.findViewById<RecyclerView>(R.id.recyclerView)
        val manager = LinearLayoutManager(activity)

        recyclerView.setHasFixedSize(true)
        recyclerView.layoutManager = manager
        greetingAdapter = GreetingAdapter(activity!!, listOfGreetings!!.toList())
        recyclerView.adapter = greetingAdapter

        greetingAdapter!!.notifyDataSetChanged()

        return view

    }

我不确定我在正确的地方打电话给notifyDataSetChanged()。希望你能帮忙！

Answer 1

我找到了解决问题的方法。需要在setOnClickListener的{{1}}上调用itemView，而不是onBindViewHolder上的ViewHolder，并在greetingAdapter?.notifyDataSetChanged()方法上调用onResume()。

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

        holder.category?.text = listOfGreetings?.get(position)?.greetingCategory
        holder.cardView?.setBackgroundColor(Color.TRANSPARENT)

        Glide
            .with(context?.applicationContext!!)
            .load(listOfGreetings?.get(position)?.imageId)
            .apply(
                RequestOptions()
                    .placeholder(R.drawable.loading)
                    .fitCenter()
            )
            .into(holder.imageView!!)

        holder.itemView.setOnClickListener {
            holder.cardView?.setBackgroundColor(Color.RED)

            if (position != RecyclerView.NO_POSITION) {
                val intent = Intent(context, GridGreetingListActivity::class.java)
                intent.putExtra("position", 1)
                context?.startActivity(intent)
            }
        }
    }

    class GreetingsView(itemView: View) : RecyclerView.ViewHolder(itemView) {


        var imageView: ImageView? = null
        var category: TextView? = null
        var cardView: FrameLayout? = itemView.findViewById(R.id.card_view)
        var context: Context? = itemView.context
        private var listOfGreetings: List<GreetingModel>? = null

        init {
            imageView = itemView.findViewById(R.id.greetingImage)
            category = itemView.findViewById(R.id.greetingCategory)
            this.listOfGreetings = listOfGreetings
        }
    }

RecyclerView adapterNotifychanged不起作用

1 个答案: