MVC in Android develpment (Java) - but who is the Controller?

I'm new at MVC pattern and Android development.

What I did is a simple app which let the user to tap on a button called "Increment" to increment a number's value and another button, called "Reset", which allows to reset that number to 0 if number % 5 == 0.

What I did is:

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">

    <Button
        android:id="@+id/buttonAzzera"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/button_azzera"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.885"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.499" />

    <Button
        android:id="@+id/buttonIncrementa"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/button_incrementa"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.148"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.499" />

    <TextView
        android:id="@+id/textView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="0"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toStartOf="@+id/buttonAzzera"
        app:layout_constraintStart_toEndOf="@+id/buttonIncrementa"
        app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>

MainActivity.java

package com.example.provamvc;

import androidx.appcompat.app.AppCompatActivity;

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

public class MainActivity extends AppCompatActivity {

    Button buttonReset;
    Button buttonIncrement;
    TextView numberLabel;
    Model model = new Model();

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        buttonReset = findViewById(R.id.buttonAzzera);
        buttonIncrement = findViewById(R.id.buttonIncrementa);
        numberLabel = findViewById(R.id.textView);

        buttonIncrement.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                model.incrementNumber();
                numberLabel.setText(String.valueOf(model.getNumber()));
                if (model.isNumberResettable())
                    buttonReset.setEnabled(true);
                else
                    buttonReset.setEnabled(false);
            }
        });


        buttonReset.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                model.resetNumber();
                numberLabel.setText("0");
                buttonReset.setEnabled(false);
            }
        });

    }
}

and finally Model.java

package com.example.provamvc;

public class Model {

    private int number;

    public Model() {
        number = 0;
    }

    public int getNumber() {
        return number;
    }

    public boolean isNumberResettable() {
        return number % 5 == 0;
    }

    public void incrementNumber() {
        number++;
    }

    public void resetNumber() {
        if (isNumberResettable()) {
            number = 0;
        }
    }
}

This works fine.

• My question is: does MainActivity.java represent the Controller (of the whole application) and does the activity_main.xml represent the View? Or should I create another class which will be a Controller?
• Is this tiny application designed well or it violates the MVC Design Pattern and the principle of "high coesion and low low coupling"?
• Should I use Observer-Observable pattern too for better respecting the MVC pattern?