java.lang.IllegalStateException: Could not find method count(View) in a parent or ancestor Context for android:onClick attribute defined on view class

Question

The app keeps crashing whenever I click the count or reset button I think that the app is not recognizing the onclick methods count and reset I tried the same using java but it was working fine using java so the problem must be with kotlin Is there any solution对于这个问题？ 还是我应该遵循任何替代方法？

package com.example.a39kotlinfun

import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.view.View
import android.widget.TextView

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


    var textView = findViewById<TextView>(R.id.textView)

    var count = 0

    fun count(view : View){
        count += 1
        textView.text = count.toString()
    }

    fun reset(view : View){
        count = 0
        textView.text = "0"
    }
}

}

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=".MainActivity">
<TextView
    android:id="@+id/textView"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_marginTop="50dp"
    android:layout_marginBottom="400dp"
    android:text="Hello World!"
    android:textSize="36sp"
    app:layout_constraintBottom_toBottomOf="parent"
    app:layout_constraintLeft_toLeftOf="parent"
    app:layout_constraintRight_toRightOf="parent"
    app:layout_constraintTop_toTopOf="parent" />

<Button
    android:id="@+id/button"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_marginStart="55dp"
    android:layout_marginLeft="55dp"
    android:layout_marginTop="111dp"
    android:layout_marginBottom="247dp"
    android:onClick="count"
    android:text="count"
    app:layout_constraintBottom_toBottomOf="parent"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toBottomOf="@+id/textView" />

<Button
    android:id="@+id/button2"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_marginTop="111dp"
    android:layout_marginEnd="51dp"
    android:layout_marginRight="51dp"
    android:layout_marginBottom="247dp"
    android:onClick="reset"
    android:text="reset"
    app:layout_constraintBottom_toBottomOf="parent"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintTop_toBottomOf="@+id/textView" />

</androidx.constraintlayout.widget.ConstraintLayout>

日志猫：

java.lang.IllegalStateException: Could not find method count(View) in a parent or ancestor Context for android:onClick attribute defined on view class com.google.android.material.button.MaterialButton with id 'button'
    at androidx.appcompat.app.AppCompatViewInflater$DeclaredOnClickListener.resolveMethod(AppCompatViewInflater.java:447)
    at androidx.appcompat.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:405)
    at android.view.View.performClick(View.java:7189)
    at com.google.android.material.button.MaterialButton.performClick(MaterialButton.java:1119)
    at android.view.View.performClickInternal(View.java:7166)
    at android.view.View.access$3500(View.java:819)
    at android.view.View$PerformClick.run(View.java:27682)
    at android.os.Handler.handleCallback(Handler.java:883)
    at android.os.Handler.dispatchMessage(Handler.java:100)
    at android.os.Looper.loop(Looper.java:224)
    at android.app.ActivityThread.main(ActivityThread.java:7592)
    at java.lang.reflect.Method.invoke(Native Method)
    at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:539)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:950)

Answer 1

将count和reset方法移出onCreate方法。

class MainActivity : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
       super.onCreate(savedInstanceState)
       setContentView(R.layout.activity_main)

       var textView = findViewById<TextView>(R.id.textView)
    }

    var count = 0

    fun count(view : View){
        count += 1
        textView.text = count.toString()
    }

    fun reset(view : View){
        count = 0
        textView.text = "0"
    }
}

在任何情况下都应避免设置android:onClick ，最好的解决方案是使用：

val button = findViewById<Button>(R.id.button)
button.setOnClickListener {
    count += 1
    textView.text = count.toString()
}