'KotlinNullPointerException for android::onClick

I`m just started learning Kotlin, and i have a problem with one of the buttons.

In MainActivity i have a button, that shows a popup with EditText and Button. In that popup user enters a city, and variable CITY changes according to user input after pressing a button.

In function cityChange im trying to replace my variable CITY with a text that user enters in EditText named editText. But when user taps on button, my program crashes with a NullPointerException. Can someone explain, or show how to fix that problem?

Exception log

FATAL EXCEPTION: main
    Process: com.example.weatherapp, PID: 16567
    java.lang.IllegalStateException: Could not execute method for android:onClick
        at androidx.appcompat.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:414)
        at android.view.View.performClick(View.java:7192)
        at android.view.View.performClickInternal(View.java:7166)
        at android.view.View.access$3500(View.java:824)
        at android.view.View$PerformClick.run(View.java:27592)
        at android.os.Handler.handleCallback(Handler.java:888)
        at android.os.Handler.dispatchMessage(Handler.java:100)
        at android.os.Looper.loop(Looper.java:213)
        at android.app.ActivityThread.main(ActivityThread.java:8178)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:513)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1101)
     Caused by: java.lang.reflect.InvocationTargetException
        at java.lang.reflect.Method.invoke(Native Method)
        at androidx.appcompat.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:409)
        at android.view.View.performClick(View.java:7192) 
        at android.view.View.performClickInternal(View.java:7166) 
        at android.view.View.access$3500(View.java:824) 
        at android.view.View$PerformClick.run(View.java:27592) 
        at android.os.Handler.handleCallback(Handler.java:888) 
        at android.os.Handler.dispatchMessage(Handler.java:100) 
        at android.os.Looper.loop(Looper.java:213) 
        at android.app.ActivityThread.main(ActivityThread.java:8178) 
        at java.lang.reflect.Method.invoke(Native Method) 
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:513) 
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1101) 
     Caused by: kotlin.KotlinNullPointerException
        at com.example.weatherapp.MainActivity.cityChange(MainActivity.kt:48)
        at java.lang.reflect.Method.invoke(Native Method) 
        at androidx.appcompat.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:409) 
        at android.view.View.performClick(View.java:7192) 
        at android.view.View.performClickInternal(View.java:7166) 
        at android.view.View.access$3500(View.java:824) 
        at android.view.View$PerformClick.run(View.java:27592) 
        at android.os.Handler.handleCallback(Handler.java:888) 
        at android.os.Handler.dispatchMessage(Handler.java:100) 
        at android.os.Looper.loop(Looper.java:213) 
        at android.app.ActivityThread.main(ActivityThread.java:8178) 
        at java.lang.reflect.Method.invoke(Native Method) 
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:513) 
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1101) 
I/Process: Sending signal. PID: 16567 SIG: 9

MainActivity.kt

class MainActivity : AppCompatActivity() {

    var CITY: String = "kyiv, ua"
    val API: String = "7c45088f48678b739d4d8409a2d9d03e"
    private var btn: Button? = null




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

        val menuActivity = findViewById<Button>(R.id.activityButton)
        menuActivity.setOnClickListener(){
            val Intent = Intent(this, MenuActivity::class.java)
            startActivity(Intent)
        }

        var dialog = CustomDialogFragment()
        val clkBtn = findViewById<Button>(R.id.cityChange)

        clkBtn.setOnClickListener {
            dialog.show(supportFragmentManager, "customDialog")
        }

    }

    fun cityChange(view: View){
        btn = findViewById(R.id.changingButton)

        btn!!.setOnClickListener{
            CITY = editText.text.toString()
        }
    }

change_city.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="350dp"
    android:layout_height="200dp"
    android:background="@color/colorPrimaryDark"
    android:padding="5dp"
    android:layout_gravity="center">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="vertical">

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="City Change"
            android:textStyle="bold"
            android:textColor="@color/white"
            android:layout_gravity="center_horizontal"
            android:layout_marginTop="5dp"/>
    </LinearLayout>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginTop="15dp"
        android:orientation="horizontal">

        <EditText
            android:id="@+id/editText"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:ems="10"
            android:gravity="center"
            android:inputType="textPersonName"
            android:text="" />
    </LinearLayout>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="225dp"
        android:orientation="vertical">

        <Button
            android:onClick="cityChange"
            android:id="@+id/changingButton"
            android:layout_width="match_parent"
            android:layout_height="62dp"
            android:layout_gravity="bottom"
            android:background="@color/bluelight"
            android:text="Submit" />
    </LinearLayout>

</LinearLayout>

android kotlin

Solution 1:^[1]

Just simply do this

// Variable declaration 
 private var btn: Button? = null

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

        val menuActivity = findViewById<Button>(R.id.activityButton)
        menuActivity.setOnClickListener(){
            val Intent = Intent(this, MenuActivity::class.java)
            startActivity(Intent)
        }

        var dialog = CustomDialogFragment()
        btn= findViewById<Button>(R.id.changingButton)

        clkBtn.setOnClickListener {
            dialog.show(supportFragmentManager, "customDialog")
        }

    }

Or Else You have to Change

This

  val clkBtn = findViewById<Button>(R.id.cityChange)

 val clkBtn = findViewById<Button>(R.id.changingButton)

Hope this will helpful to you.

Solution 2:^[2]

wrong ID

from this

 val clkBtn = findViewById<Button>(R.id.cityChange)

 val clkBtn = findViewById<Button>(R.id.changingButton)

in your XML the button id is "changingButton" not "cityChange"

and don't use onClick and setOnClickListener together, just choose one

Sources

This article follows the attribution requirements of Stack Overflow and is licensed under CC BY-SA 3.0.

Source: Stack Overflow

Solution	Source
Solution 1	Bhavin Solanki
Solution 2	Jalalkun

'KotlinNullPointerException for android::onClick

Solution 1:[1]

Solution 2:[2]

Sources

Related Questions

Solution 1:^[1]

Solution 2:^[2]