activity_main.xmlMainActivity.javaExampleDialog.java
<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.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="com.example.application.exampleapplication.MainActivity">

    <TextView
        android:id="@+id/counter_text"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="0"
        android:textSize="60sp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <Button
        android:id="@+id/button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginLeft="8dp"
        android:layout_marginTop="0dp"
        android:layout_marginRight="8dp"
        android:text="open dialog"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toBottomOf="@id/counter_text" />

</android.support.constraint.ConstraintLayout>
package com.example.application.exampleapplication;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity implements ExampleDialog.ExampleDialogListener {
    private TextView counterText;
    private Button button;
    private int counter;

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

        counterText = (TextView) findViewById(R.id.counter_text);
        button = (Button) findViewById(R.id.button);

        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                openDialog();
            }
        });
    }

    public void openDialog() {
        ExampleDialog dialog = new ExampleDialog();
        dialog.show(getSupportFragmentManager(), "example dialog");
    }

    @Override
    public void onYesClicked() {
        counter++;
        counterText.setText("" + counter);
    }
}
package com.example.application.exampleapplication;

import android.app.Dialog;
import android.content.Context;
import android.content.DialogInterface;
import android.os.Bundle;
import android.support.v7.app.AlertDialog;
import android.support.v7.app.AppCompatDialogFragment;


public class ExampleDialog extends AppCompatDialogFragment {
    private ExampleDialogListener listener;

    @Override
    public Dialog onCreateDialog(Bundle savedInstanceState) {
        AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
        builder.setTitle("Attention!")
                .setMessage("Do you want to increase the counter by 1?")
                .setNegativeButton("cancel", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialogInterface, int i) {

                    }
                })
                .setPositiveButton("yes", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialogInterface, int i) {
                        listener.onYesClicked();
                    }
                });
        return builder.create();
    }

    public interface ExampleDialogListener {
        void onYesClicked();
    }

    @Override
    public void onAttach(Context context) {
        super.onAttach(context);

        try {
            listener = (ExampleDialogListener) context;
        } catch (ClassCastException e) {
            throw new ClassCastException(context.toString()
                    + "must implement ExampleDialogListener");
        }
    }
}