如何在RecyclerView元素中更改标题背景色onClick？

Question

我有一个RecyclerView与两个ViewHolder。一个用于标题，另一个用于实际项目。现在我想要改变标题中的背景颜色（它是一个ImageView），具体取决于点击了哪个列表项。我试过，但有：

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

这是我的代码：

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 
    } 
    } 

的头的ImageView实际上是在自己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) 
    } 

如何从访问我的MyItemHolder？

Answer 1

尝试从监听器中访问的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 
    }