Question

我想从ViewHolder的itemView clicklistener设置TextView文本。我尝试在Activity类中创建伴侣对象，并尝试从ViewHolders itemView clicklistener调用它。但是在同伴对象内部，我无法访问布局中的TextView对象

以下是用于设置 recyclerview

的适配器代码

class QnAdapter(val context: Context, val ques: List<QnoList>):
    RecyclerView.Adapter<QnAdapter.ViewHolder>(){
override fun onCreateViewHolder(p0: ViewGroup, p1: Int): ViewHolder{
    val view = LayoutInflater.from(context).inflate(R.layout.recycler_qno, p0, false)
    return ViewHolder(view)
}
override fun getItemCount(): Int {
    return ques.size
}

override fun onBindViewHolder(p0: ViewHolder, p1: Int){
    val question = ques[p1]
    p0.setData(question, p1)

}

inner class ViewHolder(itemView: View): RecyclerView.ViewHolder(itemView){

    var currentQ: QnoList?=null
    var currentQno: Int =0
    init{
        itemView.setOnClickListener{
            Toast.makeText(context,currentQ!!.qno.toString()+" Selected",Toast.LENGTH_SHORT).show()
            var a1 = MCQActivity
            a1.setText(context)
            a1.setTxt()  // here I want to set TextView, present in Layout of activity(not of recyclerview) text from recyclerview event 


        }

    }
    fun setData(ques:QnoList?,p1:Int){
        itemView.rqno.text = ques!!.qno.toString()
        this.currentQ = ques
        this.currentQno = p1+1
    }
}
}

private fun MCQActivity.Companion.setTxt() {

TODO("not implemented") //To change body of created functions use File | Settings | File Templates.
 }

以下是activity类代码

class MCQActivity : AppCompatActivity() {
companion object {

    fun setText(context: Context){
        Toast.makeText(context, "Hi I am called", Toast.LENGTH_SHORT).show()
    }
}
override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setContentView(R.layout.activity_mcq)

    setRecyclerView()

}

open fun setRecyclerView(){
    val layoutmanager = LinearLayoutManager(this)
    layoutmanager.orientation= LinearLayoutManager.HORIZONTAL
    recycler_qno.layoutManager = layoutmanager
    val adapter = QnAdapter(this, mcq.queslst)
    recycler_qno.adapter = adapter
 }
}

Answer 1

当然，您不能通过伴随对象访问TextView。

首先，您应该了解伴随对象的定义。它是该类或任何其他类的所有实例共有的对象。它会类似于Java中的静态字段。它没有为该类创建的任何对象的引用。

那么如何解决您的问题？

由于您已经将上下文传递给QnAdapter，并且我想它是MCQActivity的实例/对象，因此可以将该上下文转换为MCQActivity并为该实例设置文本。请参考此代码

class MCQActivity : AppCompatActivity() {
    fun setText(theTextYouWantToSet: String) {
        findViewById<TextView>(R.id.textView).text = theTextYouWantToSet
    }
}

class QnAdapter(val context: Context, val ques: List<String>) : RecyclerView.Adapter<QnAdapter.ViewHolder>() {
    inner class ViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {
        init {
            itemView.setOnClickListener {
                (context as MCQActivity).setText("I am handsome")
            }
        }
    }
}

Answer 2

companion函数与Java中的静态函数相同。在这种情况下，您应该删除伴随对象，并在setText中将MCQActivity函数公开。

要从ViewHolder访问您的活动，很简单：

 (itemView.context as? MCQActivity)?.setText("I am handsome")

我想从ViewHolder的itemView clicklistener设置TextView文本。我可以调用伴随功能。但无法从中访问TextView对象

2 个答案: