android - 更改recyclerView android数据绑定(bind)中selectedItem的背景颜色

Question

当我使用android数据绑定(bind)时，如何更改recyclerView适配器中selectedItem的backgroudColor？

这是我的Adapte，并且实现了类CategoyItemClickListener来处理项目点击:

class ProgramCatAdapter(
    val mContext: Context,
    val mData: MutableList<CategoryResponse>,
    val clickListener: CategoyItemClickListener
) : RecyclerView.Adapter<ProgramCatAdapter.CategoryViewHolder>() {



    override fun onCreateViewHolder(
        parent: ViewGroup,
        viewType: Int
    ): CategoryViewHolder {
        return CategoryViewHolder.from(parent)
    }

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

    override fun onBindViewHolder(holder: CategoryViewHolder, position: Int) {
        holder.bind(
            mData[position],
            clickListener,
            position

        )


    }

    fun getItem(position: Int): CategoryResponse = mData[position]

    fun getPosition(item: CategoryResponse): Int = mData.indexOf(item)

    class CategoryViewHolder private constructor(val binding: ProgramCatHorizontalBinding) :
        RecyclerView.ViewHolder(binding.root) {



        fun bind(
            item: CategoryResponse,
            clickListener: CategoyItemClickListener,
            position: Int

        ) {
            itemView.isActivated = isSelected
            binding.item = item
            binding.position = position
            binding.clickListener = clickListener
            binding.executePendingBindings()
        }

        companion object {
            fun from(parent: ViewGroup): CategoryViewHolder {
                val layoutInflater = LayoutInflater.from(parent.context)
                val binding = ProgramCatHorizontalBinding.inflate(layoutInflater, parent, false)
                return CategoryViewHolder(binding)
            }
        }
    }
}

class CategoyItemClickListener(val clickListener: (item: CategoryResponse) -> Unit) {
    fun onClick(item: CategoryResponse) {
        clickListener(item)
    }
}

这段代码用于将适配器绑定(bind)到recyclerView:

 private fun bindCategories(cats: MutableList<CategoryResponse>?) {


        programCatAdapter = ProgramCatAdapter(mContext!!,
            cats!!, CategoyItemClickListener {
                viewModel.setSelectedCat(it)

            })

        binding.catRecycler.layoutManager =
            LinearLayoutManager(activity!!, LinearLayoutManager.HORIZONTAL, false)

        binding.catRecycler.adapter = programCatAdapter
}

如何从 CategoyItemClickListener 访问所选项目的位置并更改该项目的 bgColor？

Answer 1

这里是一个例子:

此视频可能会给您一个概述:https://youtu.be/g8GDLOMt600 (您不会在本视频中找到此问题的解决方案。它只是为您提供有关数据绑定(bind)、RecyclerView 和 ClickListener 的一个很好的概述)

您需要以下文件:YourFragment、fragment_your.xml、list_item

class YourFragment : Fragment(){

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

    // Get a reference to the binding object and inflate the fragment views.
    val binding: FragmentYoutFragmentBinding = DataBindingUtil.inflate(
        inflater, R.layout.fragment_your, container, false
    )

    binding.lifecycleOwner = this

     // Very important! Otherwise the layout of the recycler view wont work
    binding.yourList.layoutManager = LinearLayoutManager(this.context)

    // Adapter for the RecyclerView in order to show all items
    val adapter = YourAdapter(YourListener{youtItemObeject: YourItemObject, view: 
      View ->

      // THIS IS THE SOLUTION
      // change selected item image, if user selects this item in the list
      view.ok_image.setImageResource(R.drawable.ok_green)
    })

  }
}

在list_item.xml中

<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android"
  xmlns:app="http://schemas.android.com/apk/res-auto"
  xmlns:tools="http://schemas.android.com/tools">

<data>

    <variable
        name="your_object"
        type="your_package_name.your_folder.YourObject" />

    <variable
        name="clickListener"
        type="your_package_name.your_folder.YourListener" />
</data>

<androidx.constraintlayout.widget.ConstraintLayout
    android:id="@+id/constraint_layout"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_marginStart="@dimen/item_margin_horizontal"
    android:layout_marginTop="@dimen/item_margin_vertical"
    android:layout_marginEnd="@dimen/item_margin_horizontal"
    android:layout_marginBottom="@dimen/item_margin_vertical"
    android:onClick="@{(thisView) -> clickListener.onClick(your_object, thisView)}">

    <ImageView
        android:id="@+id/ok_image"
        ... />

</androidx.constraintlayout.widget.ConstraintLayout>
</layout>

并将 YourListener 类添加到适配器文件中

class YourAdapter(val clickListener: YourListener) :
ListAdapter<YourObject, YourAdapter.ViewHolder>(YourDiffCallback()) {

override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
    return ViewHolder.from(parent)
}

override fun onBindViewHolder(holder: ViewHolder, position: Int) {
    holder.bind(getItem(position)!!, clickListener)
}

class ViewHolder private constructor(val binding: ListItemYourObjectBinding) :
    RecyclerView.ViewHolder(binding.root) {

    companion object {
        fun from(parent: ViewGroup): ViewHolder {
            val layoutInflater = LayoutInflater.from(parent.context)

            val binding = 
              ListItemYourObjectBinding.inflate(layoutInflater, parent, false)
            return ViewHolder(binding)
        }
    }

    fun bind(item: YourObject, clickListener: YourListener) {
        binding.yourObject = item
        binding.clickListener = clickListener

        // for example
        binding.okImage.setImageRessouce(R.drawable.ok_gray)

        binding.executePendingBindings()
    }
  }
}


/**
* Callback for calculating the diff between two non-null items in a list.
*
* Used by ListAdapter to calculate the minimum number of changes between and old list 
* and a new list that's been passed to `submitList`.
*/
class YourObjectDiffCallback : DiffUtil.ItemCallback<YourObject>() {
  override fun areItemsTheSame(oldItem: YourObject, newItem: YourObject): Boolean {
    return oldItem.yourObjectValue == newItem.yourObjectValue 
  }

  override fun areContentsTheSame(oldItem: YourObject, newItem: YourObject): Boolean {
    return oldItem == newItem
  }
}

/**
* Listener for your list items
*/

class YourListener(val clickListener: (yourObject: YourObject, 
  view: View) -> Unit) {
  fun onClick(yourObject: YourObject, view: View) = 
    clickListener(yourObject, view)
}