Errore funzione

Ciao a tutti, ricevo un errore in fase di debug:

java.lang.IllegalStateException: Could not find method add(View) in a parent or ancestor Context for android:onClick attribute defined on view class androidx.appcompat.widget.AppCompatButton with id 'add'

Il programma è davvero una stupidata... prende 2 numeri immessi dall'utente, premendo il pulsante add recuperi i valori di edittext e li converte in int.
Successivamente crea un oggetto ris di classe calculate che contiene l' operazione somma. Infine converte il risultato in testo e lo visualizza in un toast...

Activity_mail.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/editText2"
        android:layout_width="143dp"
        android:layout_height="0dp"
        android:layout_marginTop="118dp"
        android:layout_marginEnd="32dp"
        android:ems="10"
        android:inputType="numberDecimal"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <EditText
        android:id="@+id/editText"
        android:layout_width="133dp"
        android:layout_height="0dp"
        android:layout_marginStart="32dp"
        android:layout_marginTop="48dp"
        android:ems="10"
        android:inputType="numberDecimal"
        app:layout_constraintEnd_toStartOf="@+id/editText2"
        app:layout_constraintHorizontal_bias="0.361"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/textView" />

    <TextView
        android:id="@+id/textView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="50dp"
        android:layout_marginBottom="49dp"
        android:text="Numero 1"
        app:layout_constraintBottom_toTopOf="@+id/editText"
        app:layout_constraintEnd_toStartOf="@+id/textView2"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <TextView
        android:id="@+id/textView2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginEnd="80dp"
        android:text="numero 2"
        app:layout_constraintBottom_toTopOf="@+id/editText2"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.491" />

    <androidx.appcompat.widget.AppCompatButton
        android:id="@+id/add"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="76dp"
        android:onClick="add"
        android:text="+"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/editText"
        app:layout_constraintVertical_bias="0.188" />

    <TextView
        android:id="@+id/risultato"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:hint="risultato"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.532" />

</androidx.constraintlayout.widget.ConstraintLayout>

MainActivity

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {
    private EditText num1, num2;
    public Button bAdd;
    private Calculate ris;
    private TextView risultato;

    @Override
    protected void onCreate ( Bundle savedInstanceState ) {
        super.onCreate (savedInstanceState);
        setContentView (R.layout.activity_main);
        risultato = findViewById (R.id.risultato);
        bAdd = findViewById (R.id.add);
    }

    public void add( View view, Calculate ris){
        String n1 = num1.getText ().toString ();
        String n2 = num2.getText ().toString ();
        int numCon1 = Integer.parseInt (n1);
        int numCon2 = Integer.parseInt (n2);
        ris = new Calculate (numCon1, numCon2);
        int tot = ris.somma (numCon1, numCon2);
        String totText = String.valueOf (tot);
        Toast.makeText (getApplicationContext (),totText, Toast.LENGTH_SHORT).show ();

    }

}

Calculate.java

public class Calculate {
    private int numero1;
    private int numero2;

    public Calculate (int numero1, int numero2) {
        this.numero1 = numero1;
        this.numero2 = numero2;
    }

    public Calculate(){
        numero1 = 0;
        numero2 = 0;
    }
    public int getNumero1 () {
        return numero1;
    }

    public void setNumero1 ( int numero1 ) {
        this.numero1 = numero1;
    }

    public int getNumero2 () {
        return numero2;
    }

    public void setNumero2 ( int numero2 ) {
        this.numero2 = numero2;
    }

    public int somma( int numero1, int numero2){
        return numero1 + numero2;
    }
}

Avete idea perchè da errore?
Grazie in aticipo