1. Java events

2. Teme
Opšta strategija asinhrone obrade događaja (asynchronous event-handling)
Opcije obrade događaja
Obrada pomoću odvojenih slušača (listeners)
Obrada pomoću implementacije interfejsa
Obrada pomoću imenovane ugnježdene klase
Obrada pomoću anonimne ugnježdene klase
Standardni AWT tipovi slušača
Detalji sa događajima miša
Primjeri

3. Opšta strategija Odredimo tip slušača koji nas zanima
11 standardnih AWT tipova listenera: ActionListener, AdjustmentListener, ComponentListener, ContainerListener, FocusListener, ItemListener, KeyListener, MouseListener, MouseMotionListener, TextListener, WindowListener
Definišemo klasu tog tipa
Implementira inetrfejs (KeyListener, MouseListener, itd.)
Nasljeđuje klasu (KeyAdapter, MouseAdapter, itd.)
Registrujemo objekat naše klase listenera
w.addXxxListener(new MyListenerClass());
Npr. addKeyListener, addMouseListener

4. Obrada pomoću odvojenih slušača (listeners)

5. Obrada pomoću odvojenih slušača (listeners)
Slušač ne mora da poziva nijedan metod prozora za koji je zakačen
import java.applet.Applet;
import java.awt.*;
public class ClickReporter extends Applet {
public void init() {
setBackground(Color.YELLOW);
addMouseListener(new ClickListener()); }

6. Obrada pomoću odvojenih slušača (listeners)
import java.awt.event.*;
public class ClickListener extends MouseAdapter {
public void mousePressed(MouseEvent event) {
System.out.println("Mouse pressed at (" +
event.getX() + "," +
event.getY() + ")."); }

7. Složeniji slučaj Klik na miša crta krug import java.applet.Applet;
import java.awt.*;
public class CircleDrawer1 extends Applet {
public void init() {
setForeground(Color.BLUE);
addMouseListener(new CircleListener()); }

8. Složeniji slučaj import java.applet.Applet; import java.awt.*;
import java.awt.event.*;
public class CircleListener extends MouseAdapter {
private int radius = 25;
public void mousePressed(MouseEvent event) {
Applet app = (Applet)event.getSource();
Graphics g = app.getGraphics();
g.fillOval(event.getX()-radius,
event.getY()-radius,
2*radius, 2*radius); }

9. Obrada pomoću implementacije interfejsa

10. Pregled interfejsa Shape interface Klasa Circle
public interface Shape {
public double getArea(); // No body, just specification }
Klasa Circle
public class Circle implements Shape {
public double getArea() { some real code }
Napomena: Jedna klasa može implementirati više interfejsa
public class MyClass implements Foo, Bar, Baz{ … }

11. Pregled interfejsa Klasa se može tretirati kao interfejs
public interface Shape {
public double getArea(); }
public class Circle implements Shape { … }
public class Rectangle implements Shape { … }
Shape[] shapes =
{ new Circle(…), new Rectangle(…) … };
double sum = 0;
for(Shape s: shapes) {
sum = sum + s.getArea();

12. Source za MouseListener
public interface MouseListener {
public void mouseClicked(MouseEvent e);
public void mousePressed(MouseEvent e);
public void mouseReleased(MouseEvent e);
public void mouseEntered(MouseEvent e);
public void mouseExited(MouseEvent e); }
public abstract class MouseAdapter
implements MouseListener {
public void mouseClicked(MouseEvent e) {}
public void mousePressed(MouseEvent e) {}
public void mouseReleased(MouseEvent e) {}
public void mouseEntered(MouseEvent e) {}
public void mouseExited(MouseEvent e) {}

13. Obrada pomoću implementacije interfejsa
import java.applet.Applet;
import java.awt.*;
import java.awt.event.*;
public class CircleDrawer2 extends Applet
implements MouseListener {
private int radius = 25;
public void init() {
setForeground(Color.BLUE);
addMouseListener(this); }

14. Obrada pomoću implementacije interfejsa (nastavak)
public void mouseEntered(MouseEvent event) {}
public void mouseExited(MouseEvent event) {}
public void mouseReleased(MouseEvent event) {}
public void mouseClicked(MouseEvent event) {}
public void mousePressed(MouseEvent event) {
Graphics g = getGraphics();
g.fillOval(event.getX()-radius,
event.getY()-radius, 2*radius, 2*radius); }

15. Adapateri vs. Interfejsi
Šta ako zabrljamo sa zaglavljem metoda? Npr.
public void mousepressed(MouseEvent e)
public void mousePressed()
Interfaces - Compile time error
Adapters – Nema compile time error, ali se ništa neće desiti kada se klikne na dugme miša
Rješenje za adaptere (i za redefinisaje u Java 5+ anotacija. Kada mislimo da redefinišemo (overriding) metod, dodamo:
u red iznad početka metoda.
Ako taj metod stvarno ne redefiniše naslijeđeni metod, dobijamo compile-time error.

16. @Override primjer public class CircleDrawer1 extends Applet {
public void init() {
setForeground(Color.BLUE);
addMouseListener(new CircleListener()); }
public class CircleListener extends MouseAdapter {
private int radius = 25;
public void mousePressed(MouseEvent event) {
Applet app = (Applet)event.getSource();
Graphics g = app.getGraphics();
g.fillOval(event.getX()-radius,event.getY()- radius, 2*radius, 2*radius);

17. Obrada pomoću imenovane ugnježdene klase

18. Obrada pomoću imenovane ugnježdene klase
import java.applet.Applet;
import java.awt.*;
import java.awt.event.*;
public class CircleDrawer3 extends Applet {
public void init() {
setForeground(Color.BLUE);
addMouseListener(new CircleListener()); }

19. Obrada pomoću imenovane ugnježdene klase (nastavak)
private class CircleListener
extends MouseAdapter {
private int radius = 25;
public void mousePressed(MouseEvent event) {
Graphics g = getGraphics();
g.fillOval(event.getX()-radius,
event.getY()-radius,
2*radius, 2*radius); }
Ovo je nastavak klase sa prethodnog slajda

20. Obrada pomoću anonimne ugnježdene klase

21. Obrada pomoću anonimne ugnježdene klase
public class CircleDrawer4 extends Applet {
public void init() {
setForeground(Color.BLUE);
addMouseListener (new MouseAdapter() {
private int radius = 25;
public void mousePressed(MouseEvent event) {
Graphics g = getGraphics();
g.fillOval(event.getX()-radius,
event.getY()-radius,2*radius, 2*radius); }
});

22. Pregled načina obrade

23. Za i protiv Obrada pomoću odvojenih slušača (listeners)
Za: mogu naslijediti adapter klasu i ignorisati nepotrebne metode
Za: lakše je održavati odvojene klase
Protiv: potreban je dodatni korak za poziv metoda iz glavnog prozora
Obrada pomoću implementacije interfejsa
Za: nema dodatnih koraka za pozivanje metoda
Protiv: moraju se implementirati nepotrebni metodi

24. Za i protiv (nastavak) Obrada pomoću imenovane ugnježdene klase
Za: mogu naslijediti adapter klasu i ignorisati nepotrebne metode
Za: nema dodatnih koraka za pozivanje metoda
Protiv: teške za razumijevanje
Obrada pomoću anonimne ugnježdene klase
Za: isto kao imenovane ugnježdene klase ali su još kraće
Protiv: još teže za razumijevanje

25. Pregled event listenera

26. Standardni AWT event listeneri

27. ActionListener • AdjustmentListener • ComponentListener
Obrada dugmadi i još nekih akcija
actionPerformed(ActionEvent event)
• AdjustmentListener
Primjena na skrolovanje
adjustmentValueChanged(AdjustmentEvent event)
• ComponentListener
Obrada pomjeranja/sakrivanja/promjene veličine GUI objekata
componentResized(ComponentEvent event)
componentMoved (ComponentEvent event)
componentShown(ComponentEvent event)
componentHidden(ComponentEvent event)

28. ContainerListener FocusListener
Okida se kada prozor dodaje/uklanja GUI kontrole
componentAdded(ContainerEvent event)
componentRemoved(ContainerEvent event)
FocusListener
Detektuje kada kontrola dobija/gubi fokus sa tastature
focusGained(FocusEvent event)
focusLost(FocusEvent event)

29. ItemListener KeyListener Obrada selekcija u listama, check-box, itd.
itemStateChanged(ItemEvent event)
KeyListener
Detektuje događaje tastature
keyPressed(KeyEvent event) – bilo koji taster je pritisnut
keyReleased(KeyEvent event) – otpušten
keyTyped(KeyEvent event) – taster za karakter koji se može štampati

30. MouseListener MouseMotionListener Osnovni događaji miša
mouseEntered(MouseEvent event)
mouseExited(MouseEvent event)
mousePressed(MouseEvent event)
mouseReleased(MouseEventevent)
mouseClicked(MouseEvent event)
Otpuštanje bez povlačenja. Do not use this for mousePressed!
Primjenjuju se ako nema pomjeranja miša
MouseMotionListener
Obrada pokreta miša
mouseMoved(MouseEvent event)
mouseDragged(MouseEventevent)

31. U paketu javax.swing.event, a ne u java.awt.event
MouseInputListener
Kombinuje MouseListener i MouseMotionListener
U paketu javax.swing.event, a ne u java.awt.event
Morate pozivati oba: addMouseListener i addMouseMotionListener, pa nema uštede
TextListener
Koristi se sa textfields i text areas
textValueChanged(TextEvent event)
WindowListener
Obrada događaja prozora (high-level window events)
windowOpened, windowClosing, windowClosed,windowIconified, windowDeiconified, windowActivated, windowDeactivated
windowClosing je posebno upotrebljiv

32. Primjeri

33. Klasa SimplePaint import java.applet.Applet; import java.awt.Color;
import java.awt.Graphics;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.event.MouseMotionAdapter;
public class SimplePaint extends Applet{
protected int lastX,lastY;
public int getLastX() {
return lastX; }
public void setLastX(int lastX) {
this.lastX = lastX;
public int getLastY() {
return lastY;
public void setLastY(int lastY) {
this.lastY = lastY;

34. Klasa SimplePaint @Override public void init(){
setBackground(Color.WHITE);
setForeground(Color.BLUE);
addMouseListener(new PositionRecorder());
addMouseMotionListener(new LineDrawer()); }
private class PositionRecorder extends MouseAdapter {
public void mousePressed(MouseEvent event) {
setLastX(event.getX());
setLastY(event.getY());
// da postavimo pocetnu poziciju nase krive
private class LineDrawer extends MouseMotionAdapter {
public void mouseDragged(MouseEvent event) {
int x = event.getX();
int y = event.getY();
Graphics g = getGraphics();
g.drawLine(lastX, lastY, x, y);