Android 如何从适配器类更改TextView文本？

我需要根据我的

单击listener

功能更改文本。我使用

findViewById

方法获取

textview

，并使用

setText

更改

textview

的文本，但在这里我得到一个错误，它是nullexception。我是Kotlin的新手，没有Java经验。我做了一项研究，我看到了

接口方法

来更改文本，我试过了，但没用。我怎样才能解决它

下面是来自适配器类的我的代码：

var dd = holder.customView.findViewById<TextView>(R.id.toplamSayi)!!
dd.setText(tt)

private class DetailPageAdapterForSepetPage: RecyclerView.Adapter<DetailPageViewHolderForSepetPage>() {

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): DetailPageViewHolderForSepetPage {
        val layoutInflater = LayoutInflater.from(parent?.context)
        val customDetailView = layoutInflater.inflate(R.layout.sepet_sayfasi_list_row_detail, parent,false)
        return DetailPageViewHolderForSepetPage(customDetailView)
    }

    override fun onBindViewHolder(holder: DetailPageViewHolderForSepetPage, position: Int) {
        var urunDb = sepetArr.get(position)

        holder.customView.urun_text.text = urunDb.eklenenUrun
        holder.customView.fiyat_text.text = urunDb.eklenenFiyat
        holder.customView.adet_text.text = "x" + urunDb.eklenenAdet

        var addedCount = urunDb.eklenenAdet.toInt()

        // ekleme butonu fonksiyonu
        holder.customView.imageButton4.setOnClickListener {
            addedCount += 1
            holder.customView.adet_text.text = "x$addedCount"

            // BURADA COUNT U BİR ARTTIRACAGIZ VE ARKADAN DIGER İKİLİ (URUN VE FIYAT) TUTAN ARRAYE DE EKLEME YAPACAGIZ.. YADA CIKARMASINI ASAGIDA..

            var urun = holder.customView.urun_text.text
            var fiyat = holder.customView.fiyat_text.text
            var adet = holder.customView.adet_text.text
            var addedData = SepeteGidenUrunlerModel(
                urunEklenen = urun.toString(),
                fiyatEklenen = fiyat.toString()
            )

            var fiyatStr = fiyat.toString()
            var droped = fiyatStr.dropLast(2)
            var doubleEklenecek = droped.toDouble()

            toplamTutar += doubleEklenecek
            var tt = toplamTutar.toString()

            holder.customView.toplamSayi.setText(tt)
            FirstDetailActivity.sepeteEklenenUrunler.add(addedData)
        }

        // cikarma butonu fonksiyonu
        holder.customView.imageButton5.setOnClickListener {

            if (addedCount > 1) {
                addedCount -= 1
                holder.customView.adet_text.text = "x$addedCount"

                var urun = holder.customView.urun_text.text
                var fiyat = holder.customView.fiyat_text.text

                var cikarilan = SepeteGidenUrunlerModel(
                    urunEklenen = urun.toString(),
                    fiyatEklenen = fiyat.toString()
                )

                FirstDetailActivity.sepeteEklenenUrunler.remove(cikarilan)

            }else if (addedCount == 1) {

                var urun = holder.customView.urun_text.text
                var fiyat = holder.customView.fiyat_text.text
                var adet = holder.customView.adet_text.text
                var cikarilan = SepeteGidenUrunlerModel(
                    urunEklenen = urun.toString(),
                    fiyatEklenen = fiyat.toString()
                )

                FirstDetailActivity.sepeteEklenenUrunler.remove(cikarilan)

                var sepetteData = SepetModel(
                    eklenenUrun = urun.toString(),
                    eklenenFiyat = fiyat.toString(),
                    eklenenAdet = adet.toString()
                )

                sepetArr.removeAt(position)
                notifyDataSetChanged()
            }
        }
    }

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

private class DetailPageViewHolderForSepetPage(val customView: View): RecyclerView.ViewHolder(customView){
}

和XML：

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".SepetSayfasi">


    <androidx.recyclerview.widget.RecyclerView
        android:id="@+id/sepet_recycler_view"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <TextView
        android:id="@+id/toplamText"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="24dp"
        android:layout_marginLeft="24dp"
        android:layout_marginTop="24dp"
        android:text="TextView"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/sepet_recycler_view" />

    <TextView
        android:id="@+id/topalmTutar"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="TextView"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toEndOf="@+id/toplamText"
        app:layout_constraintTop_toTopOf="@+id/toplamText" />

    <TextView
        android:id="@+id/textToplam"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="16dp"
        android:text="TextView"
        app:layout_constraintStart_toStartOf="@+id/toplamText"
        app:layout_constraintTop_toBottomOf="@+id/toplamText" />

    <TextView
        android:id="@+id/toplamSayi"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="TextView"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toEndOf="@+id/textToplam"
        app:layout_constraintTop_toTopOf="@+id/textToplam" />
</androidx.constraintlayout.widget.ConstraintLayout>

您需要将要填充视图的元素列表传递给适配器

您需要在

ViewHolder

中声明

RecyclerView

布局的视图，然后可以在

onBindViewHolder

尝试使用此代码作为适配器的基础，并根据需要完成它

private class DetailPageAdapterForSepetPage(
    private val activity: <the-class-of-your-activity>,
    private val sepetArr: List<the-type-of-your-list>
) : RecyclerView.Adapter<DetailPageViewHolderForSepetPage>() {

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): DetailPageViewHolderForSepetPage {
        val customDetailView = LayoutInflater.from(parent.context).inflate(R.layout.sepet_sayfasi_list_row_detail, parent, false)
        return DetailPageViewHolderForSepetPage(customDetailView)
    }

    override fun onBindViewHolder(holder: DetailPageViewHolderForSepetPage, position: Int) 
    {
        val urunDb = sepetArr[position]

        holder.btn.setOnClickListener {
            activity.updateText("Your text")
        }
        
        // -- Put the rest of your initializazion code here --
    }

    override fun getItemCount(): Int = sepetArr.size

    inner class DetailPageViewHolderForSepetPage(customView: View): RecyclerView.ViewHolder(customView) {
        val btn: Button = customView.findViewById(<your-button-id>)

        // -- Put the other views in your recycler view item here --
    }
}

---

在kotlin中，不需要查找id，您可以像这样直接使用holder.itemView.toplamSayi.setText（tt）您可以发布适配器类代码和XML布局吗？我这样做了，但出现了get错误，即尝试在空对象上调用虚拟方法“void android.widget.TextView.setText（java.lang.CharSequence）”reference@LucaPizzini我现在补充说。我是科特林的新人。如果你看到任何问题，我真的需要建议。separar的类型是什么？我在view holder类中添加了dd行，但它没有解决问题。我也收到了同样的错误。你发布的XML是否参考了

sepet\u sayfasi\u row\u detail

布局？不，我在这里发布了activity\u sepet\u sayfasi.XML，因为我在recycler视图下有文本视图，所以这些文本视图不属于recycler视图确定，你不能访问recycler视图中的

toplamSayi

TextView，仅限

中的布局，如sayfasi\u列表\u行\u详细信息

。这就是为什么它为您提供了

NullPointerException

您可以在父活动中声明一个公共方法来更新按钮，并将父活动作为参数传递给适配器，即在适配器中调用此方法。如果问题符合您的需要，请查看已编辑的问题。

updateText(text: String) {
    // Update the text view
}