项目Onclick RecyclerView Kotlin Android

Question

我在Kotlin中有RecyclerView适配器，当用户单击categoryPhoto时，我想打开一个新活动。 我应该如何实施呢？

class CategoryAdapter(private val categoryList: List<Category>, private val context: Context) : RecyclerView.Adapter<CategoryAdapter.MyViewHolder>() {

class MyViewHolder(view: View) : RecyclerView.ViewHolder(view) {

        var categoryName = view.text_view_category_name
        var categoryPhoto = view.image_view_category
        var cardView = view.card_view_category

}

override fun onCreateViewHolder(parent: ViewGroup, viewType: Int) = MyViewHolder(parent.inflate(R.layout.category_list_row))

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

    val category = categoryList[position]

    // Set height of cardview based on screen width
    val displayMetrics = context.resources.displayMetrics
    val finalHeight = displayMetrics.widthPixels / 2
    holder.cardView.layoutParams.height = finalHeight

    holder.categoryName.text = category.oc
    holder.categoryPhoto.loadUrl(category.icon)
}

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

Answer 1

只需将click listener作为参数添加到适配器的构造函数即可。

class CategoryAdapter(
        private val categoryList: List<Category>, 
        private val context: Context,
        private val onClickListener: (View, Category) -> Unit
) : RecyclerView.Adapter<CategoryAdapter.MyViewHolder>() {

    ...

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

        val category = categoryList[position]

        // Set height of cardview based on screen width
        ...

        holder.itemView.setOnClickListener { view ->
            onClickListener.invoke(view, category)
        }      
    }

   ...
}

然后您可以使用以下方法：

fun initList() {
     adapter = CategoryAdapter(
         categoryList = ...,
         context = ...,
         onClickListener = { view, category -> openActivity(view, category) }
}

关闭顶部。 上面代码的一些可选改进

1. 为lambda创建typealias。 使您的代码更具可读性。

    typealias MyCategoryClickListener = (View, Category) -> Unit class CategoryAdapter( private val categoryList: List<Category>, private val context: Context, private val onClickListener: MyCategoryClickListener ) : RecyclerView.Adapter<CategoryAdapter.MyViewHolder>() { 

2. 省略对侦听器的invoke 。 可以像函数一样调用Lambda。

    holder.itemView.setOnClickListener { view -> onClickListener(view, category) } 

3. 创建适配器时用参考替换lambda

     fun initList() { adapter = CategoryAdapter( categoryList = ..., context = ..., onClickListener = this::openActivity) } fun openActivity(view: View, category: Category) { ... } 

Answer 2

您可以在onBindViewHolder（...）中完成此操作

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

    // Set height of cardview based on screen width
    val displayMetrics = context.resources.displayMetrics
    val finalHeight = displayMetrics.widthPixels / 2
    holder.cardView.layoutParams.height = finalHeight

    holder.categoryName.text = category.oc
    holder.categoryPhoto.loadUrl(category.icon)

    holder.categoryPhoto.setOnClickListener { view ->

       // categoryPhoto clicked.
       // start your activity here
    }      
}

Answer 3

像这样

类RecyclerListAdapter：RecyclerView.Adapter {var context：Context？ = null var listData：ArrayList？ =空

步骤1：活动参考..................................... var activityref：MainActivity？= null

    constructor(context: Context?, listData: ArrayList<ItemDetails>?, activityref: MainActivity?) : super() {
        this.context = context
        this.listData = listData
        this.activityref = activityref
    }


    override fun onCreateViewHolder(parent: ViewGroup?, viewType: Int): ViewsHolder {
        val view = LayoutInflater.from(context).inflate(R.layout.row_list, parent, false)

        return ViewsHolder(view)
    }

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

    override fun onBindViewHolder(holder: ViewsHolder?, position: Int) {
        holder?.item=listData?.get(position)
        holder!!.first!!.setText(holder.item?.First)
        holder.second!!.setText(holder.item?.Second)
        holder.third!!.setText(holder.item?.Third)

  Step 2  OnClick on item.....................       
        holder.third!!.setOnClickListener{
            activityref?.OnItemClicked(holder.item!!)
        }

    }


    class ViewsHolder(itemView: View?) : RecyclerView.ViewHolder(itemView) {


        var item:ItemDetails?=null

        var first: TextView? = null;
        var second: TextView? = null;
        var third: TextView? = null;

        init {
            first = itemView?.findViewById(R.id.first)
            second = itemView?.findViewById(R.id.second)
            third = itemView?.findViewById(R.id.third)

        }



    }


}