android - Android：无法更新 RecyclerView

问题描述

我正在 Kotlin 中开发一个 Android 应用程序，并实现了一个 RecyclerView。

添加到的两个参数parametersList都显示出来了，但是当我按下TEST按钮时，RecyclerView没有更新！我不明白我的错误，你能帮我吗？

这是我的适配器：

class CustomAdapter(private val parameterList: List<Parameter>, private val onClick: ((selectedParameter: Parameter) -> Unit)? = null) : RecyclerView.Adapter<CustomAdapter.ViewHolder>() {

    class ViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {
        fun showItem(parameter: Parameter, onClick: ((selectedParameter: Parameter) -> Unit)? = null) {
            itemView.findViewById<TextView>(R.id.parameterName).text = parameter.parameterName
            itemView.findViewById<TextView>(R.id.parameterValue).text = parameter.parameterValue as CharSequence?

            if(onClick != null) {
                itemView.setOnClickListener {
                    onClick(parameter)
                }
            }
        }
    }

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

    override fun onBindViewHolder(holder: ViewHolder, position: Int) {
        holder.showItem(parameterList[position], onClick)
    }

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

}

我的活动：

class NFCActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_nfc)

        buttonTest.setOnClickListener() {

            parametersList = parametersList + ParameterText("Temperature", "24°C")
            rv_parameters2.adapter?.notifyDataSetChanged()
        }

        rv_parameters2.adapter = CustomAdapter(parametersList) { item ->
            println("------------------OnClick------------------")
        }
        rv_parameters2.layoutManager = LinearLayoutManager(this)

    }


    private var parametersList : List<Parameter> = listOf<Parameter> (
            ParameterText("Temperature", "24°C"),
            ParameterText("Temperature", "24°C")
    )

    companion object {
        fun getStartIntent(context: Context): Intent {
            return Intent(context, NFCActivity::class.java)
        }
    }
}

参数文本.xml：

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:padding="10dp">


    <TextView
        android:id="@+id/parameterName"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:padding="5dp"
        android:text="@string/parameter_name"
        android:textColor="@color/black"
        android:textSize="16sp"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintEnd_toStartOf="@id/parameterValue"
        app:layout_constraintTop_toTopOf="parent" />

    <TextView
        android:id="@+id/parameterValue"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:padding="5dp"
        android:text="@string/parameter_value"
        android:textSize="16sp"
        app:layout_constraintStart_toEndOf="@id/parameterName"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintBottom_toBottomOf="@+id/parameterName"
        app:layout_constraintTop_toTopOf="parent"/>

</androidx.constraintlayout.widget.ConstraintLayout>

活动_nfc.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=".view.ble.NFCActivity">

    <Button
        android:id="@+id/buttonTest"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="TEST"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintEnd_toEndOf="parent" />

    <androidx.recyclerview.widget.RecyclerView
        android:id="@+id/rv_parameters2"
        tools:listitem="@layout/parameter_text"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        app:layout_constraintTop_toBottomOf="@id/buttonTest"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"/>

</androidx.constraintlayout.widget.ConstraintLayout>

编辑 1：（按照 SlothCoding 的回答）

我的新活动：

class NFCActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_nfc)

        buttonTest.setOnClickListener() {

            parametersList = parametersList + ParameterText("Temperature", "24°C")
            rv_parameters2.adapter?.notifyDataSetChanged()
        }

        rv_parameters2.layoutManager = LinearLayoutManager(this, LinearLayoutManager.VERTICAL, false)
        rv_parameters2.adapter = CustomAdapter(parametersList) { item ->
            println("------------------OnClick------------------")
        }
    }

    private var parametersList : List<Parameter> = listOf<Parameter> (
            ParameterText("Temperature", "24°C"),
            ParameterText("Temperature", "24°C")
    )

    companion object {
        fun getStartIntent(context: Context): Intent {
            return Intent(context, NFCActivity::class.java)
        }
    }
}

编辑 2：（按照 Sekiro 的回答）

自定义适配器

class CustomAdapter(private val parameterList: List<Parameter>, private val onClick: ((selectedParameter: Parameter) -> Unit)? = null) : RecyclerView.Adapter<CustomAdapter.ViewHolder>() {

    private var parameterListLocal: List<Parameter> = parameterList

    class ViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {
        fun showItem(parameter: Parameter, onClick: ((selectedParameter: Parameter) -> Unit)? = null) {
            itemView.findViewById<TextView>(R.id.parameterName).text = parameter.parameterName
            itemView.findViewById<TextView>(R.id.parameterValue).text = parameter.parameterValue as CharSequence?

            if(onClick != null) {
                itemView.setOnClickListener {
                    onClick(parameter)
                }
            }
        }
    }

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

    override fun onBindViewHolder(holder: ViewHolder, position: Int) {
        holder.showItem(parameterListLocal[position], onClick)
    }

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

    fun addNewList(newList: List<Parameter>){
        parameterListLocal = newList;
        notifyDataSetChanged();
    }

}

NFC活动

class NFCActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_nfc)

        buttonTest.setOnClickListener() {

            parametersList = parametersList + ParameterText("Temperature", "24°C")
            (rv_parameters2.adapter as CustomAdapter).addNewList(parametersList)
        }

        rv_parameters2.layoutManager = LinearLayoutManager(this, LinearLayoutManager.VERTICAL, false)
        rv_parameters2.adapter = CustomAdapter(parametersList) { item ->
            println("------------------OnClick------------------")
        }
    }

    private var parametersList : List<Parameter> = listOf<Parameter> (
            ParameterText("Temperature", "24°C"),
            ParameterText("Temperature", "24°C")
    )

    companion object {
        fun getStartIntent(context: Context): Intent {
            return Intent(context, NFCActivity::class.java)
        }
    }
}

标签： androidkotlinandroid-recyclerview

问题在于您buttonTest.setOnClickListener()在哪里更新列表，但适配器对数组列表的更新一无所知，而是将新的数组列表传递给适配器并调用notifyDataSetChanged()

尝试以下

自定义适配器

// add this new function

fun addNewList(newList: List<Parameter>){
   parameterList = newList;
   notifyDataSetChanged();
}

addNewList通过触发buttonTest.setOnClickListener

buttonTest.setOnClickListener() {
       parametersList = parametersList + ParameterText("Temperature", "24°C")
       (rv_parameters2.adapter as CustomAdapter).addNewList(parametersList)
}

编辑：

notifyDataSetChanged() is indeed a costly operation and should be replaced with either notifyItemInserted or a better choice would be to use ListAdapter

android - Android：无法更新 RecyclerView

问题描述

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