android - 通过单击Kotlin中的recyclerView来更改activity_main的元素

Question

我需要通过单击RecyclerView中的元素来更改来自activity_main.xml的Button元素的颜色。十六进制颜色值应从选定的项目参数中获取。
仅仅因为我是Kotlin的新手，所以不了解如何执行它。



这是MainActivity:

class MainActivity : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        doAsync {
            val json  = URL("https://api.jsonbin.io/b/5e299cea5eae2c3a26db9cdf/2").readText()
            d("daniel", "json? $json")
//            val dataList: ArrayList<String> = ArrayList()
            uiThread {
                val stations = Gson().fromJson(json, Array<Stations>::class.java).toList()
                ElementsList.apply{
                    layoutManager = LinearLayoutManager(this@MainActivity)
                    adapter = ElementsAdapter(stations)
                }
            }
        }
    }
}

这是ElementsAdapter(recyclerView):

class ElementsAdapter(private val stations: List<Stations>) : RecyclerView.Adapter<ElementsAdapter.ViewHolder>() {

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

        return ViewHolder(view)
    }

    override fun getItemCount() = stations.size

    override fun onBindViewHolder(holder: ViewHolder, position: Int) {
        val stationItem = stations[position]
        val highlightColor = stationItem.properties.color
        val colorFilter = Color.parseColor(highlightColor)
        holder.nameStation.text = stationItem.properties.color
        holder.lineColor.setColorFilter(colorFilter, PorterDuff.Mode.SRC_ATOP)
        holder.view.setOnClickListener{
            val curValue = holder.adapterPosition
            val selectedValue = stations[curValue].name

//              something should be done here to change button's color

        }
    }

    class ViewHolder(val view: View): RecyclerView.ViewHolder(view){
        val nameStation: TextView = itemView.name_station
        val lineColor: ImageView = itemView.line_color
    }

}

Answer 1

请按照以下步骤实现此目的

步骤-1:更改ElementsAdapter的构造函数，以接收Activity实例，如下所示:

class ElementsAdapter(private val context: Context, private val stations: List<Stations>) : RecyclerView.Adapter<ElementsAdapter.ViewHolder>() {

    ....

}

步骤-2:在 MainActivity中创建一个回调函数以更改按钮的颜色

class MainActivity : AppCompatActivity() {

    ....

    fun updateButtonColor(hexColor: String) {

        // update button's color here
    }
}

并在创建适配器期间传递 Activity 实例

adapter = ElementsAdapter(this@MainActivity, stations)

步骤-3:在 onBindViewHolder的 OnClickListener中，使用适当的 调用 Activity 的updateButtonColor十六进制HEX_COLOR

holder.view.setOnClickListener{
    val curValue = holder.adapterPosition
    val selectedValue = stations[curValue].name

    //something should be done here to change button's color

    (context as MainActivity).updateButtonColor(HEX_COLOR)
}