Why i am getting this error: androidx.constraintlayout.widget.ConstraintLayout cannot be cast to android.widget.TextView?

Question

I'm just starting to working with Android studio and i was following this tutorial on youtube : https://www.youtube.com/watch?v=EOfCEhWq8sg

But for some reason i'm getting this error:

androidx.constraintlayout.widget.ConstraintLayout cannot be cast to android.widget.TextView

I searched for the same error and it looks like someone had the same problem because he was using the ConstraintLayout and the TextView with the same ID. But this is not my case:

<?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:id="@+id/resultsTextView"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <Button
        android:id="@+id/rollButton"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginStart="96dp"
        android:layout_marginLeft="96dp"
        android:layout_marginEnd="96dp"
        android:layout_marginRight="96dp"
        android:layout_marginBottom="24dp"
        android:text="Roll"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent" />

    <SeekBar
        android:id="@+id/seekBar"
        style="@style/Widget.AppCompat.SeekBar.Discrete"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginStart="32dp"
        android:layout_marginLeft="32dp"
        android:layout_marginEnd="32dp"
        android:layout_marginRight="32dp"
        android:layout_marginBottom="24dp"
        android:max="10"
        android:progress="3"
        app:layout_constraintBottom_toTopOf="@+id/rollButton"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent" />

    <TextView
        android:id="@+id/textView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="24dp"
        android:layout_marginLeft="24dp"
        android:layout_marginBottom="16dp"
        android:text="How many?"
        app:layout_constraintBottom_toTopOf="@+id/seekBar"
        app:layout_constraintStart_toStartOf="parent" />

    <View
        android:id="@+id/divider"
        android:layout_width="409dp"
        android:layout_height="1dp"
        android:layout_marginBottom="16dp"
        android:background="?android:attr/listDivider"
        app:layout_constraintBottom_toTopOf="@+id/textView"
        tools:layout_editor_absoluteX="1dp" />

    <TextView
        android:id="@+id/textView2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textSize="144sp"
        app:layout_constraintBottom_toTopOf="@+id/divider"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>

This is the full log :

E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.example.randomizer, PID: 12977
    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.randomizer/com.example.randomizer.MainActivity}: java.lang.ClassCastException: androidx.constraintlayout.widget.ConstraintLayout cannot be cast to android.widget.TextView
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3270)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3409)
        at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:83)
        at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2016)
        at android.os.Handler.dispatchMessage(Handler.java:107)
        at android.os.Looper.loop(Looper.java:214)
        at android.app.ActivityThread.main(ActivityThread.java:7356)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:492)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:930)
     Caused by: java.lang.ClassCastException: androidx.constraintlayout.widget.ConstraintLayout cannot be cast to android.widget.TextView
        at com.example.randomizer.MainActivity.onCreate(MainActivity.kt:15)
        at android.app.Activity.performCreate(Activity.java:7802)
        at android.app.Activity.performCreate(Activity.java:7791)
        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1299)
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3245)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3409) 
        at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:83) 
        at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135) 
        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95) 
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2016) 
        at android.os.Handler.dispatchMessage(Handler.java:107) 
        at android.os.Looper.loop(Looper.java:214) 
        at android.app.ActivityThread.main(ActivityThread.java:7356) 
        at java.lang.reflect.Method.invoke(Native Method) 
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:492) 
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:930) 

I will be glad for anyone who tries to help me

MainActivity.kt:

package com.example.randomizer

import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.widget.Button
import android.widget.SeekBar
import android.widget.TextView
import java.util.*

class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        val rollButton = findViewById<Button>(R.id.rollButton)
        val resultsTextView = findViewById<TextView>(R.id.resultsTextView)
        val seekBar = findViewById<SeekBar>(R.id.seekBar)

        rollButton.setOnClickListener {

            val rand = Random().nextInt(seekBar.progress) + 1
            resultsTextView.text = rand.toString()
        }
    }
}

Answer 1

Here

val resultsTextView = findViewById<TextView>(R.id.resultsTextView)

the resultsTextView is the id of the constraint layout, not the one of the text view. Use R.id.textView2 instead.

Answer 2

Your issue is here:

val resultsTextView = findViewById<TextView>(R.id.resultsTextView)

and in your layout:

<androidx.constraintlayout.widget.ConstraintLayout 
    android:id="@+id/resultsTextView"

You can't cast a ConstraintLayout into a TextView.