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Ereignissteuerung (Events)

Ereignissteuerung (Events). Learning By Doing. Unterprogrammaufruf an fest codierter Stelle. Event kann irgendwo auftreten. ereignisgesteuert. prozedural. Wann immer der Event auftritt, führe möglichst bald aus. TimerEvent (UML-Diagramm) im Delegations-Eventmodell. Learning By Doing.

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Ereignissteuerung (Events)

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  1. Ereignissteuerung (Events) Learning By Doing Unterprogrammaufrufan fest codierter Stelle Event kann irgendwo auftreten ereignisgesteuert prozedural Wann immer der Event auftritt, führe möglichst bald aus ...

  2. TimerEvent (UML-Diagramm)im Delegations-Eventmodell Learning By Doing Garantieerklärung: timeElapsed() existiert! Implementierung derCallbackmethode Zur Registrierung derCallbackmethode Event! Aufruf von timerListener.timeElapsed() Registrierung derCallbackmethode Registrierung: Übergeben einer Referenz der Klasse, welche die Callbackmethode enthält, an den Eventhandler, der die Callbackmethode bei jedem Event aufruft.

  3. DigitalWatch Learning By Doing // DigitalWatch.java import ch.aplu.util.*; import java.awt.Font; public class DigitalWatch implements TimerListener { private int seconds = 0; private boolean isBell = true; private LoResAlarmTimer timer = new LoResAlarmTimer(1000000L); private GPanel panel = new GPanel(); public DigitalWatch() { panel.font(new Font( "Arial", Font.PLAIN, 200)); timer.addTimerListener(this); while (true) { if (isBell) { isBell = false; panel.clear(); panel.text(0.3, 0.4, Integer.toString(seconds)); seconds++; } } } while (true) { if (isBell) { isBell = false; panel.clear(); panel.text(0.3, 0.4, Integer.toString(seconds)); seconds++; } } Implementierung "DigitalWatch implementiert einen TimerListener" Registrierung"Dieser TimerListener wird beim Eventhandler registriert" Callbackmethode Eventloop public boolean timeElapsed() { isBell = true; return true; } public static void main(String[] args) { new DigitalWatch(); } }

  4. MouseEvents Learning By Doing // WbzEx11.java import java.awt.event.*; import java.awt.Color; import ch.aplu.util.*; public class WbzEx11 { class MyMouseAdapter extends MouseAdapter { public void mousePressed(MouseEvent evt) { Color c = new Color((float)Math.random(), (float)Math.random(), (float)Math.random()); Stern stern = new Stern(p, 50, c); stern.moveAt((int)p.toWindowX(evt.getX()), (int)p.toWindowY(evt.getY())); stern.showMe(); } } private GPanel p = new GPanel(0, 500, 0, 500); public WbzEx11() { p.addMouseListener(new MyMouseAdapter()); } public static void main(String[] args) { new WbzEx11(); } } Innere Klasse hat Zugriff Callbackmethode Registrie-rung Mausevents

  5. Anonyme Klassen Learning By Doing // WbzEx11a.java import java.awt.event.*; import java.awt.Color; import ch.aplu.util.*; public class WbzEx11a { private GPanel p = new GPanel(0, 500, 0, 500); public WbzEx11a() { p.addMouseListener(new MouseAdapter() { public void mousePressed(MouseEvent evt) { Color c = new Color((float)Math.random(), (float)Math.random(), (float)Math.random()); Stern stern = new Stern(p, 50, c); stern.moveAt((int)p.toWindowX(evt.getX()), (int)p.toWindowY(evt.getY())); stern.showMe(); } }); } public static void main(String[] args) { new WbzEx11a(); } } Registrierung Anonyme Klasseabgeleitet von MouseAdapter Anonyme Klassen

  6. ButtonEvents Learning By Doing // WbzEx12.java import java.awt.event.*; import javax.swing.*; import ch.aplu.turtle.*; public class WbzEx12 { private class ButtonActionAdapter implements ActionListener { public void actionPerformed(ActionEvent evt) { Object source = evt.getSource(); if (source == runButton) state = States.RUNNING; if (source == stopButton) state = States.STOPPED; if (source == quitButton) state = States.QUITTING; } } private enum States {STOPPED, RUNNING, QUITTING}; private States state = States.STOPPED; private JButton runButton = new JButton("Run"); private JButton stopButton = new JButton("Stop"); private JButton quitButton = new JButton("Quit"); Innere Klasse, implementiertActionListener State switch Zustände (Aufzählungstyp) aktueller Zustand Instanzvariablen Buttonevents

  7. ButtonEvents public WbzEx12() { Turtle t = new Turtle(); JPanel jp = t.getPlayground(); jp.add(runButton); jp.add(stopButton); jp.add(quitButton); jp.validate(); ButtonActionAdapter adapter = new ButtonActionAdapter(); runButton.addActionListener(adapter); stopButton.addActionListener(adapter); quitButton.addActionListener(adapter); while (state != States.QUITTING) { switch(state) { case STOPPED: Thread.yield(); break; case RUNNING: t.forward(10).left(10); break; } } System.exit(0); } public static void main(String[] args) { new WbzEx12(); } } Learning By Doing Buttons in der Komponente anzeigen Registrierung Prozessor freiwillig anderen abgeben Event loop Buttonevents

  8. ButtonEvents // WbzEx12a.java import java.awt.event.*; import javax.swing.*; import ch.aplu.turtle.*; public class WbzEx12a { interface State { int QUITTING = 0; int STOPPED = 1; int RUNNING = 2; } private class ButtonActionAdapter implements ActionListener { public void actionPerformed(ActionEvent evt) { Object source = evt.getSource(); if (source == runButton) state = State.RUNNING; if (source == stopButton) state = State.STOPPED; if (source == quitButton) state = State.QUITTING; } } private int state = State.STOPPED; private JButton runButton = new JButton("Run"); private JButton stopButton = new JButton("Stop"); private JButton quitButton = new JButton("Quit"); Learning By Doing Simulation des Enum-Typs Verwendung durch Vorstellendes Interface-Bezeichners state-Variable als "dekorierter" int Buttonevents (J2SE 1.4) Schon viel besser als state = 2

  9. ButtonEvents Learning By Doing Verwendung durch Vorstellendes Interface-Bezeichners public WbzEx12a() { Turtle t = new Turtle(); JPanel jp = t.getPlayground(); jp.add(runButton); jp.add(stopButton); jp.add(quitButton); jp.validate(); ButtonActionAdapter adapter = new ButtonActionAdapter(); runButton.addActionListener(adapter); stopButton.addActionListener(adapter); quitButton.addActionListener(adapter); while (state != State.QUITTING) { switch(state) { case State.STOPPED: Thread.yield(); break; case State.RUNNING: t.forward(10).left(10); break; } } System.exit(0); } public static void main(String[] args) { new WbzEx12a(); } } Buttonevents (J2SE 1.4)

  10. GUI Muster Learning By Doing JPanel als Grafik-Fenster Position und Grösse des JFrames JFrame als umfassendes Fenster Aktion beim Klicken des Close-Buttons Füge das JPanel in das JFrame Zeige das JFrame mit Inhalt paintComponent() wird bei jedemSystem-Trigger aufgerufen Aufruf überschr. Methode aus JPanel Zeichnen mit dem Graphics-Context Linie als Objekt Text als Grafik Neue Linieneigenschaft (Dicke) Zeichne Grafikobjket Hole Graphics2D-Context Indikator für Aufruf von paintComponent // WbzEx13.java import java.awt.*; import javax.swing.*; import ch.aplu.util.*; public class WbzEx13 extends JPanel { private int count = 0; public WbzEx13() { JFrame f = new JFrame("Frame Window"); f.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE); f.getContentPane().add(this); f.setBounds(50, 50, 550, 550); f.setVisible(true); } public void paintComponent(Graphics g) { super.paintComponent(g); g.drawOval(0, 0, 500, 500); g.drawString("WBZ-Kurs \"Java im Unterricht\"", 180, 250); Graphics2D g2D = (Graphics2D)g; g2D.setStroke(new BasicStroke(8)); Line2D.Double line = new Line2D.Double(20, 300, 480, 300); g2D.draw(line); System.out.println(count++); } public static void main(String[] args) { Console.init(); new WbzEx13(); } } GUI-Muster

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