i created an android project and connect it to firebase and when i build it and give run it runs withouit an error but when i enter data and click the button that adds date to the database its crashing and gives me this error
2022-10-24 10:20:46.955 16722-16722/com.example.testdemo E/AndroidRuntime: FATAL EXCEPTION: main Process: com.example.testdemo, PID: 16722 java.lang.NullPointerException: Attempt to invoke virtual method 'com.google.firebase.database.DatabaseReference com.google.firebase.database.DatabaseReference.child(java.lang.String)' on a null object reference at com.example.testdemo.MainActivity$2.onClick(MainActivity.java:62) at android.view.View.performClick(View.java:7300) at com.google.android.material.button.MaterialButton.performClick(MaterialButton.java:1219) at android.view.View.performClickInternal(View.java:7277) at android.view.View.access$3600(View.java:822) at android.view.View$PerformClick.run(View.java:28033) 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:7565) 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)
