Firestore project

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"
    tools:context=".MainActivity">

    <EditText
        android:id="@+id/inputFirstName"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:hint="Enter your first name"
        android:layout_margin="10dp"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <EditText
        android:id="@+id/inputLastName"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_margin="10dp"
        app:layout_constraintStart_toStartOf="parent"
        android:hint="Enter your last name"
        app:layout_constraintTop_toBottomOf="@id/inputFirstName"/>

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_margin="10dp"
        android:layout_marginStart="16dp"
        android:layout_marginLeft="16dp"
        android:layout_marginTop="76dp"
        android:id="@+id/saveButton"
        android:text="Save"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@id/inputLastName" />

</androidx.constraintlayout.widget.ConstraintLayout>

MainActivity.kt

class MainActivity : AppCompatActivity() {

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

        val firstName = inputFirstName.text.toString()
        val secondName = inputLastName.text.toString()
        saveButton.setOnClickListener{
            saveFireStore(firstName, secondName)
        }


    }
    fun saveFireStore(firstname:String, lastname:String){
      val db  = FirebaseFirestore.getInstance()
        val user : MutableMap<String, Any> = HashMap()
        user["firstName"] = firstname
        user["lastName"] = lastname
        db.collection("users")
            .add(user)
            .addOnSuccessListener{
                Toast.makeText(this@MainActivity, "Record Added Successfully", Toast.LENGTH_SHORT).show()
                Log.d(String, firstname + lastname)
            }
            .addOnFailureListener{
                Toast.makeText(this@MainActivity, "Record Failed", Toast.LENGTH_SHORT).show()

            }
    }

    companion object {
        const val String  = "show logs"
    }

}