When I run my Tic Tac Toe App in Android Studio, the App crashes in my emulator.In the emulator, it says "Tic Tac Toe keeps stopping".[Screenshot of App crashing in emulator]: https://i.stack.imgur.com/XL7Tk.png
This is my MainActivity.kt file https://github.com/vishwajeet30/Tic_Tac_Toe/blob/master/app/src/main/java/com/example/tictactoe/MainActivity.kt
This is my activity_main.xml file https://github.com/vishwajeet30/Tic_Tac_Toe/blob/master/app/src/main/res/layout/activity_main.xml
And Android Studio shows this Error in Logcat ->
Process: com.example.tictactoe, PID: 28975java.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:8160) at android.view.View.performClickInternal(View.java:8137) at android.view.View.access$3700(View.java:888) at android.view.View$PerformClick.run(View.java:30236) at android.os.Handler.handleCallback(Handler.java:938) at android.os.Handler.dispatchMessage(Handler.java:99) at android.os.Looper.loop(Looper.java:246) at android.app.ActivityThread.main(ActivityThread.java:8595) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:602) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1130) Caused by: java.lang.reflect.InvocationTargetException at java.lang.reflect.Method.invoke(Native Method) at androidx.appcompat.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:409) at android.view.View.performClick(View.java:8160) at android.view.View.performClickInternal(View.java:8137) at android.view.View.access$3700(View.java:888) at android.view.View$PerformClick.run(View.java:30236) at android.os.Handler.handleCallback(Handler.java:938) at android.os.Handler.dispatchMessage(Handler.java:99) at android.os.Looper.loop(Looper.java:246) at android.app.ActivityThread.main(ActivityThread.java:8595) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:602) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1130) Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String java.lang.Object.toString()' on a null object reference at com.example.tictactoe.MainActivity.dropIn(MainActivity.kt:35) at java.lang.reflect.Method.invoke(Native Method) at androidx.appcompat.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:409) at android.view.View.performClick(View.java:8160) at android.view.View.performClickInternal(View.java:8137) at android.view.View.access$3700(View.java:888) at android.view.View$PerformClick.run(View.java:30236) at android.os.Handler.handleCallback(Handler.java:938) at android.os.Handler.dispatchMessage(Handler.java:99) at android.os.Looper.loop(Looper.java:246) at android.app.ActivityThread.main(ActivityThread.java:8595) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:602) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1130)