如何在RecyclerView元素中更改標題背景色onClick？

Question

我有一個RecyclerView與兩個ViewHolder。一個用於標題，另一個用於實際項目。現在我想要改變標題中的背景顏色（它是一個ImageView），具體取決於點擊了哪個列表項。我試過，但有：

java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ImageView.setBackgroundColor(int)' on a null object reference 

這是我的代碼：

case class MyItemHolder(view: View, items: Array[Entry]) extends RecyclerView.ViewHolder(view) with MyHolder with View.OnClickListener{ 
    view.setOnClickListener(this) 
    lazy val currentItem = items(getAdapterPosition - 1) 
    val textView: TextView = view.findViewById(R.id.textView).asInstanceOf[TextView] 
    val imageView: ImageView = view.findViewById(R.id.imageView).asInstanceOf[ImageView] 
    def bind(e: Entry): Unit = textView.setText(e.name) 

    override def onClick(view: View): Unit = { 
     Toast.makeText(getApplicationContext, s"You clicked ${currentItem.name}!", Toast.LENGTH_SHORT).show() 
     imageView.setBackgroundColor(Color.parseColor(currentItem.color)) // crashed with NPE 
    } 
    } 

的頭的ImageView實際上是在自己ViewHolder：

case class MyHeaderHolder(view: View) extends RecyclerView.ViewHolder(view) with MyHolder { 
    val imageView: ImageView = view.findViewById(R.id.imageView).asInstanceOf[ImageView] 
    val image = ContextCompat.getDrawable(getApplicationContext, R.drawable.title) 
    def bind(): Unit = imageView.setImageDrawable(image) 
    } 

如何從訪問我的MyItemHolder？

Answer 1

嘗試從監聽器中訪問的ImageView：

override def onClick(view: View): Unit = { 
      Toast.makeText(getApplicationContext, s"You clicked ${currentItem.name}!", Toast.LENGTH_SHORT).show() 
      val imageView: ImageView = view.findViewById(R.id.imageView).asInstanceOf[ImageView] 
      imageView.setBackgroundColor(Color.parseColor(currentItem.color)) // crashed with NPE 
    }