Getting error in changing the text of TextView in Kotlin

I'm new to android development(just started a few hours ago) and just to see how things work im trying like when button is clicked the text of TextView should change, but the app crashes when it reaches that line. Can anyone please suggest me what changes should I make.

MainActivity.kt

package com.example.ruthvikapplication

import android.os.Bundle
import android.widget.Button
import android.widget.RatingBar
import android.widget.TextView
import android.widget.Toast
import androidx.appcompat.app.AppCompatActivity

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

        val button1=findViewById<Button>(R.id.button)
        val ratingBar1= findViewById<RatingBar>(R.id.ratingBar)
        val title1= findViewById<TextView>(R.id.title)

        button1.setOnClickListener{
            Toast.makeText(this@MainActivity, "Your rating" ratingBar1.rating.toString(), Toast.LENGTH_SHORT).show()
            title1.text= "Thanks for rating!!" // app crashes here...
        }
    }
}

activity_main.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"
    android:background="#00FFCC"
    tools:context=".MainActivity">

    <TextView
        android:id="@ id/myTitle"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:rotationX="33"
        android:text="Please rate this app!!"
        android:textColor="#FF0000"
        android:textSize="34sp"
        android:textStyle="bold|italic"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <Button
        android:id="@ id/button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Rate"
        app:backgroundTint="#FFC800"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toEndOf="@ id/ratingBar"
        app:layout_constraintTop_toBottomOf="@ id/myTitle" />

    <RatingBar
        android:id="@ id/ratingBar"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginEnd="10dp"
        android:layout_marginRight="10dp"
        android:background="#00FFCC"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toStartOf="@ id/button"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@ id/myTitle"
        tools:ignore="SpeakableTextPresentCheck" />

</androidx.constraintlayout.widget.ConstraintLayout>

The console


09/25 21:43:43: Launching 'app' on Pixel 5 API 30.
Install successfully finished in 4 s 826 ms.
$ adb shell am start -n "com.example.ruthvikapplication/com.example.ruthvikapplication.MainActivity" -a android.intent.action.MAIN -c android.intent.category.LAUNCHER
Connected to process 6745 on device 'Pixel_5_API_30 [emulator-5554]'.
Capturing and displaying logcat messages from application. This behavior can be disabled in the "Logcat output" section of the "Debugger" settings page.
D/NetworkSecurityConfig: No Network Security Config specified, using platform default
D/NetworkSecurityConfig: No Network Security Config specified, using platform default
D/libEGL: loaded /vendor/lib/egl/libEGL_emulation.so
D/libEGL: loaded /vendor/lib/egl/libGLESv1_CM_emulation.so
D/libEGL: loaded /vendor/lib/egl/libGLESv2_emulation.so
W/System: A resource failed to call close. 
W/hvikapplicatio: Accessing hidden method Landroid/view/View;->computeFitSystemWindows(Landroid/graphics/Rect;Landroid/graphics/Rect;)Z (greylist, reflection, allowed)
W/hvikapplicatio: Accessing hidden method Landroid/view/ViewGroup;->makeOptionalFitsSystemWindows()V (greylist, reflection, allowed)
D/HostConnection: HostConnection::get() New Host Connection established 0xee45b910, tid 6768
D/HostConnection: HostComposition ext ANDROID_EMU_CHECKSUM_HELPER_v1 ANDROID_EMU_native_sync_v2 ANDROID_EMU_native_sync_v3 ANDROID_EMU_native_sync_v4 ANDROID_EMU_dma_v1 ANDROID_EMU_direct_mem ANDROID_EMU_host_composition_v1 ANDROID_EMU_host_composition_v2 ANDROID_EMU_vulkan ANDROID_EMU_deferred_vulkan_commands ANDROID_EMU_vulkan_null_optional_strings ANDROID_EMU_vulkan_create_resources_with_requirements ANDROID_EMU_YUV_Cache ANDROID_EMU_async_unmap_buffer ANDROID_EMU_vulkan_ignored_handles ANDROID_EMU_has_shared_slots_host_memory_allocator ANDROID_EMU_vulkan_free_memory_sync ANDROID_EMU_vulkan_shader_float16_int8 ANDROID_EMU_vulkan_async_queue_submit ANDROID_EMU_sync_buffer_data GL_OES_vertex_array_object GL_KHR_texture_compression_astc_ldr ANDROID_EMU_host_side_tracing ANDROID_EMU_async_frame_commands ANDROID_EMU_gles_max_version_2 
W/OpenGLRenderer: Failed to choose config with EGL_SWAP_BEHAVIOR_PRESERVED, retrying without...
D/EGL_emulation: eglCreateContext: 0xee460760: maj 2 min 0 rcv 2
D/EGL_emulation: eglMakeCurrent: 0xee460760: ver 2 0 (tinfo 0xee7b43f0) (first time)
I/Gralloc4: mapper 4.x is not supported
D/HostConnection: createUnique: call
D/HostConnection: HostConnection::get() New Host Connection established 0xee461330, tid 6768
D/goldfish-address-space: allocate: Ask for block of size 0x100
D/goldfish-address-space: allocate: ioctl allocate returned offset 0x34dffc000 size 0x2000
D/HostConnection: HostComposition ext ANDROID_EMU_CHECKSUM_HELPER_v1 ANDROID_EMU_native_sync_v2 ANDROID_EMU_native_sync_v3 ANDROID_EMU_native_sync_v4 ANDROID_EMU_dma_v1 ANDROID_EMU_direct_mem ANDROID_EMU_host_composition_v1 ANDROID_EMU_host_composition_v2 ANDROID_EMU_vulkan ANDROID_EMU_deferred_vulkan_commands ANDROID_EMU_vulkan_null_optional_strings ANDROID_EMU_vulkan_create_resources_with_requirements ANDROID_EMU_YUV_Cache ANDROID_EMU_async_unmap_buffer ANDROID_EMU_vulkan_ignored_handles ANDROID_EMU_has_shared_slots_host_memory_allocator ANDROID_EMU_vulkan_free_memory_sync ANDROID_EMU_vulkan_shader_float16_int8 ANDROID_EMU_vulkan_async_queue_submit ANDROID_EMU_sync_buffer_data GL_OES_vertex_array_object GL_KHR_texture_compression_astc_ldr ANDROID_EMU_host_side_tracing ANDROID_EMU_async_frame_commands ANDROID_EMU_gles_max_version_2 
I/Choreographer: Skipped 45 frames!  The application may be doing too much work on its main thread.
I/OpenGLRenderer: Davey! duration=792ms; Flags=0, IntendedVsync=1872865754256, Vsync=1873615754226, OldestInputEvent=9223372036854775807, NewestInputEvent=0, HandleInputStart=1873628675300, AnimationStart=1873628792800, PerformTraversalsStart=1873630847400, DrawStart=1873631928700, SyncQueued=1873632253400, SyncStart=1873637319300, IssueDrawCommandsStart=1873637409900, SwapBuffers=1873651804500, FrameCompleted=1873663434900, DequeueBufferDuration=2445200, QueueBufferDuration=5067700, GpuCompleted=9223372034707292159, 
D/CompatibilityChangeReporter: Compat change id reported: 147798919; UID 10121; state: ENABLED
D/AndroidRuntime: Shutting down VM
E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.example.ruthvikapplication, PID: 6745
    java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setText(java.lang.CharSequence)' on a null object reference
        at com.example.ruthvikapplication.MainActivity.onCreate$lambda-0(MainActivity.kt:21)
        at com.example.ruthvikapplication.MainActivity.$r8$lambda$dEE9GmU9yeAvvuQdJ131D5Xmycc(Unknown Source:0)
        at com.example.ruthvikapplication.MainActivity$$ExternalSyntheticLambda0.onClick(Unknown Source:6)
        at android.view.View.performClick(View.java:7448)
        at com.google.android.material.button.MaterialButton.performClick(MaterialButton.java:1119)
        at android.view.View.performClickInternal(View.java:7425)
        at android.view.View.access$3600(View.java:810)
        at android.view.View$PerformClick.run(View.java:28305)
        at android.os.Handler.handleCallback(Handler.java:938)
        at android.os.Handler.dispatchMessage(Handler.java:99)
        at android.os.Looper.loop(Looper.java:223)
        at android.app.ActivityThread.main(ActivityThread.java:7656)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:592)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:947)
I/Process: Sending signal. PID: 6745 SIG: 9

CodePudding user response：

I think the ID of TextView in XML is myTitle which is different from what you are using in Kotlin file i.e. title

Try log.d("TextView", title1.toString());

to check confirm