CSE360 Introduction to Software Engineering Lecture 18: Software Design Patterns: Observer II Javier Gonzalez-Sanchez [email protected] javiergs.engineering.asu.edu Office Hours: By appointment

Javier Gonzalez-Sanchez | CSE360 | Summer 2017 | 2 GoF Patterns Creational Patterns • Abstract Factory • Builder • Factory Method • Prototype • Singleton Structural Patterns • Adapter • Bridge • Composite • Decorator • Façade • Flyweight • Proxy Behavioral Patterns • Chain of Responsibility • Command • Interpreter • Iterator • Mediator • Memento • Observer • State • Strategy • Template Method • Visitor

Javier Gonzalez-Sanchez | CSE360 | Summer 2017 | 3 Observer

Java Implementation java.util.*

Javier Gonzalez-Sanchez | CSE360 | Summer 2017 | 5 Java Subject (Observable) import java.util.Observable; public class ObservableDemo extends Observable { private String weather; public ObservableDemo(String weather) { this.weather = weather; } public String getWeather() { return weather; } public void setWeather(String weather) { this.weather = weather; setChanged(); notifyObservers(); } }

Javier Gonzalez-Sanchez | CSE360 | Summer 2017 | 6 Java Observer (Observer) import java.util.Observable; import java.util.Observer; public class ObserverExample implements Observer { private ObservableDemo weatherUpdate ; @Override public void update(Observable observable, Object arg) { weatherUpdate = (ObservableDemo) observable; System.out.println("Weather Report Live. Its "+weatherUpdate.getWeather()); } public static void main(String[] args) { ObservableDemo observable = new ObservableDemo(null); ObserverExample observer = new ObserverExample(); observable.addObserver(observer); observable.setWeather("Bright and sunny... "); observable.setWeather("Raining Heavily!.. "); } }

Everything you need to know for project 4 about Observer pattern.

Javier Gonzalez-Sanchez | CSE360 | Summer 2017 | 8 Scenario Student Tutor Classroom

Javier Gonzalez-Sanchez | CSE360 | Summer 2017 | 9 Scenario Observer + update() Observable + addObserver() + notifyObservers() + setChanged() Tutor Student Classroom

Javier Gonzalez-Sanchez | CSE360 | Summer 2017 | 10 Classroom public class Classroom { public static void main(String[] args) { Student student = new Student(); Tutor tutor = new Tutor(); tutor.addObserver(student); for (int i=0; i<5;i++) tutor.askQuestion(); } }

Javier Gonzalez-Sanchez | CSE360 | Summer 2017 | 11 Tutor import java.util.Observable; public class Tutor extends Observable { private String [] questions = { "2 + 2", "public or private", "functional or not fuctional", "white or black" }; private String theQuestion; public void askQuestion() { theQuestion = questions[((int)(Math.random()*10))%4]; setChanged(); notifyObservers(); } public String getQuestion() { return theQuestion; } }

Javier Gonzalez-Sanchez | CSE360 | Summer 2017 | 12 Student import java.util.Observable; import java.util.Observer; public class Student implements Observer { public String answerQuestion (String question) { return "I am thinking about \'" + question +"\'"; } @Override public void update(Observable o, Object arg) { String x = ((Tutor)o).getQuestion(); String y = this.answerQuestion(x); System.out.println(y); } }

Javier Gonzalez-Sanchez | CSE360 | Summer 2017 | 13 Output

Javier Gonzalez-Sanchez | CSE360 | Summer 2017 | 14 Scenario JFrame Observable + addObserver() + notifyObservers() + setChanged() Tutor Student Classroom Observer + update() JPanel TutorPanel JPanel

Javier Gonzalez-Sanchez | CSE360 | Summer 2017 | 15 Classroom (version 2) import java.awt.GridLayout; import javax.swing.JFrame; public class Classroom extends JFrame { public Classroom() { Student student = new Student (); Tutor tutor = new Tutor(); tutor.addObserver(student); setLayout(new GridLayout(2,1)); add(student); add(new TutorPanel(tutor)); } public static void main(String[] args) { JFrame window = new Classroom(); window.setSize(500, 500); window.setVisible(true); } }

Javier Gonzalez-Sanchez | CSE360 | Summer 2017 | 16 Tutor (version 2) import java.util.Observable; public class Tutor extends Observable { private String theQuestion; public void askQuestion() { theQuestion = questions[((int)(Math.random()*10))%4]; setChanged(); notifyObservers(); } public void askQuestion(String s) { theQuestion = s; setChanged(); notifyObservers(); } public String getQuestion() { return theQuestion; } }

Javier Gonzalez-Sanchez | CSE360 | Summer 2017 | 17 TutorPanel import javax.swing.*; import javax.awt.*; public class TutorPanel extends JPanel implements ActionListener{ JTextField question = new JTextField(15); JButton ok = new JButton("send"); Tutor tutor; public TutorPanel(Tutor tutor) { this.tutor = tutor; setBackground(Color.white); ImageIcon background = new ImageIcon("src/prof.png"); JLabel label = new JLabel(); label.setIcon(background); add (question); add (ok); ok.addActionListener(this); add(label); } @Override public void actionPerformed(ActionEvent e) { tutor.askQuestion(question.getText()); } }

Javier Gonzalez-Sanchez | CSE360 | Summer 2017 | 18 Student (version 2) import java.util.*; import javax.swing.*; public class Student extends JPanel implements Observer { JLabel label = new JLabel(); public Student () { this.setBackground(Color.lightGray); ImageIcon background = new ImageIcon("src/student.png"); label.setIcon(background); add(label); } public String answerQuestion (String question) { return "I am thinking about \'" + question +"\'"; } @Override public void update(Observable o, Object arg) { String x = ((Tutor)o).getQuestion(); String y = this.answerQuestion(x); label.setText(y); } }

Javier Gonzalez-Sanchez | CSE360 | Summer 2017 | 19 Output

CSE360 – Introduction to Software Engineering Javier G onzalez-Sanchez javiergs@ asu.edu Sum m er 2017 Disclaim er. These slides can only be used as study m aterial for the class C SE360 at ASU. They cannot be distributed or used for another purpose.