Inner Classes Ancora eventi

2 Design considerations The most important rule to keep in mind about event listeners that they should execute very quickly. Because all drawing and event- listening methods are executed in the same thread, a slow event- listener method can make the program seem unresponsive and slow to repaint itself. You might choose to implement separate classes for different kinds of event listeners. This can be an easy architecture to maintain, but many classes can also mean reduced performance. When designing your program, you might want to implement your event listeners in a class that is not public, but somewhere more hidden. A private implementation is a more secure implementation.

3 Low-Level Events and Semantic Events Events can be divided into two groups: low-level events and semantic events. Low-level events represent window-system occurrences or low-level input. Everything else is a semantic event. Examples of low-level events include mouse and key events both of which result directly from user input. Examples of semantic events include action and item events. Whenever possible, you should listen for semantic events rather than low-level events. That way, you can make your code as robust and portable as possible. For example, listening for action events on buttons, rather than mouse events, means that the button will react appropriately when the user tries to activate the button using a keyboard alternative or a look-and-feel-specific gesture.

4 Listeners/Adapters public class MyClass implements MouseListener {... someObject.addMouseListener(this);... /* Empty method definition. */ public void mousePressed(MouseEvent e) { } /* Empty method definition. */ public void mouseReleased(MouseEvent e) { } /* Empty method definition. */ public void mouseEntered(MouseEvent e) { } /* Empty method definition. */ public void mouseExited(MouseEvent e) { } public void mouseClicked(MouseEvent e) {...//Event listener implementation goes here... } }

5 Listeners/Adapters /* * An example of extending an adapter class instead of * directly implementing a listener interface. */ public class MyClass extends MouseAdapter {... someObject.addMouseListener(this);... public void mouseClicked(MouseEvent e) { //Event listener implementation goes here... } }

6 Inner classes //An example of using an inner class. public class MyClass extends JFrame {... someObject.addMouseListener( new MyAdapter());... class MyAdapter extends MouseAdapter { public void mouseClicked(MouseEvent e){...//Event listener implementation goes here... } }

7 Anonymous Inner classes //An example of using an inner class. public class MyClass extends JFrame {... someObject.addMouseListener( new MouseAdapter () { public void mouseClicked(MouseEvent e){...//Event listener implementation goes here... } ); … }

8 Inner classes An instance of InnerClass can exist only within an instance of EnclosingClass and it has direct access to the instance variables and methods of its enclosing instance.

9 Anonymous Inner classes //An example of using an inner class. public class MyClass extends JFrame {... someObject.addMouseListener( new MouseAdapter() { public void mouseClicked(MouseEvent e){...//Event listener implementation goes here... } } });... }

10 Listeners supported by all Swing components component listener Listens for changes in the component's size, position, or visibility. focus listener Listens for whether the component gained or lost the ability to receive keyboard input. key listener Listens for key presses; key events are fired only by the component that has the current keyboard focus. mouse listener Listens for mouse clicks and mouse movement into or out of the component's drawing area. mouse-motion listener Listens for changes in the cursor's position over the component. mouse-wheel listenermouse-wheel listener (introduced in 1.4) Listens for mouse wheel movement over the component.

11 Altri listeners action caret change document undoable edit item list selection window + Listeners speciali per componenti specifiche (treeNodeExpansion, ecc)

Layouts and Graphics

component - container - layout Un Container contiene [0 o +] Components Il Layout specifica come i Components sono disposti nel Container Un Container è un Component (quindi il contenimento è ricorsivo) Un Component ha una Graphics associata

Layouts Gestione del Layout Vedi anche:

Layouts

class YellowWindow package it.unitn.science.prog2.guiApp; import java.awt.*; import javax.swing.*; public class YellowWindow extends JFrame { private JPanel contentPane; public YellowWindow() { try { jbInit(); } catch(Exception e) { e.printStackTrace(); } } private void jbInit() throws Exception { contentPane=(JPanel)this.getContentPane(); this.setSize(new Dimension(400, 300)); contentPane.setBackground(Color.YELLOW); }

class App package it.unitn.science.prog2.guiApp; import javax.swing.*; import java.awt.*; public class App { JFrame finestra=null; public static void main(String[ ] a){ new App(); } public App() { // aggiungere qui: set look&feel (vedi oltre) this.setupGraphicEnvironment(); }

class App private void setupGraphicEnvironment() { finestra = new YellowWindow(); //new MyWindow // trova le dimensioni dello schermo e della finestra Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize(); Dimension frameSize = finestra.getSize(); // assicurati che la finestra non sia più grande dello schermo if (frameSize.height > screenSize.height) frameSize.height = screenSize.height; if (frameSize.width > screenSize.width) frameSize.width = screenSize.width;

class App // centra la finestra nello schermo finestra.setLocation((screenSize.width - frameSize.width) / 2, (screenSize.height - frameSize.height) / 2); // fai in modo che la chiusura della finestra // termini l'applicazione finestra.setDefaultCloseOperation(JFrame. EXIT_ON_CLOSE ); // rendi la finestra visibile finestra.setVisible(true); }

BorderLayout In YellowWindow cambio il metodo jbInit: private void jbInit() throws Exception { JPanel f=(JPanel)this.getContentPane(); JButton north, south, east, west, center; north = new JButton("North"); east = new JButton("East"); west = new JButton("West"); center = new JButton("Center"); south = new JButton("South"); f.setLayout(new BorderLayout(2, 2)); f.add(north, BorderLayout.NORTH); f.add(south, BorderLayout.SOUTH); f.add(east, BorderLayout.EAST); f.add(west, BorderLayout.WEST); f.add(center, BorderLayout.CENTER); this.setSize(300,300); }

FlowLayout In YellowWindow cambio il metodo jbInit: private void jbInit() throws Exception { JPanel f=(JPanel)this.getContentPane(); JButton one, two, three, four, five, six; one = new JButton("one"); two = new JButton("two"); three = new JButton("three"); four = new JButton("four"); five = new JButton("five"); six = new JButton("six"); f.setLayout(new FlowLayout()); f.add(one); f.add(six); f.add(five); // attenzione allordine! f.add(two); f.add(three); f.add(four); // aggiungo five per la seconda volta: - la prima viene eliminata ! f.add(five); this.setSize(300,300); }

BorderLayout In YellowWindow cambio il metodo jbInit: private void jbInit() throws Exception { JPanel f=(JPanel)this.getContentPane(); f.setLayout(new GridLayout(3,4)); JButton b[]=new JButton[10]; // VETTORE DI 10 BOTTON for (int k=0; k<10; k++){ b[k]=new JButton(); // Integer.toString(int a) traduce lintero a in una String b[k].setLabel(Integer.toString(k)); f.add(b[k]); } this.setSize(300,300); }

BorderLayout In YellowWindow cambio il metodo jbInit: private void jbInit() throws Exception{ JPanel f=(JPanel)this.getContentPane(); CardLayout cl=new CardLayout(); f.setLayout(cl); JPanel p[ ]=new JPanel[5]; Color c[ ]={Color.red,Color.orange,Color.green,Color.blue,Color.pink}; for (int k=0;k<5; k++){ p[k]=new JPanel(); p[k].setBackground(c[k]); f.add(Integer.toString(k),p[k]); // il primo parametro è una stringa con la quale riferirsi al componente aggiunto } this.setSize(300,300); this.setVisible(true); while (true) { // ciclo infinito try { Thread.sleep(800); // dormi per 500 millisecondi } catch (Exception e) { } cl.next(f); // richiama il prossimo componente }

Posizionamento assoluto: Null Layout It's possible to set the layout manager to null: no layout control. You might do this to position an object on the display at some absolute coordinates. This is almost never the right approach. Components might have different minimum sizes on different platforms, and your interface would not be very portable. import java.awt.*; public class Applicazione { public static void main(String s[]) {Applicazione a=new Applicazione()} Applicazione() { JFrame g= new JFrame ("Finestra controllata da BORDER Layout"); JPanel f=(JPanel)(g.getContentFrame(); f.setSize(200,200); // Dimensione della finestra f.setLocation(50,100); // Posizione della finestra JButton b=new JButton(("Push me"); f.setLayout(null); f.add(b); b.setSize(25,75); // Dimensiono il Bottone b.setLocation(10,100); // Posiziono il bottone nella finestra g.setVisible(true); }

Custom Painting Gestione della Grafica customizzata Vedi anche:

Metodi grafici di Graphics drawLine()Draws a line drawRect()Draws a rectangle fillRect()Draws a filled rectangle drawRoundRect()Draws a rounded-corner rectangle fillRoundRect()Draws a filled, rounded-corner rectangle draw3DRect()Draws a highlighted, 3D rectangle fill3DRect()Draws a filled, highlighted, 3D rectangle drawArc()Draws an arc fillArc()Draws a filled arc drawOval()Draws an oval fillOval()Draws a filled oval drawPolygon()Draws a polygon, connecting endpoints fillPolygon()Draws a filled polygon drawPolyline()Draws a line connecting a polygon's points

Il sistema di coordinate

import java.awt.*; import javax.swing.*; import java.awt.event.*; public class TestPattern { public static void main(String[] args) { new TestPattern(); } public TestPattern() { startGraphics(); } public void startGraphics();{ JFrame f = new JFrame("TestPattern"); f.setSize(300,300); f.setContentPane(new MyPanel()); f.setVisible(true); } Disegno Grafico

class MyPanel extends JPanel { int theta = 45; int delta = 90; public void paintComponent(Graphics g) { super.paintComponent(g); int width = getSize().width; int height = getSize().height; int hWidth = width / 2; int hHeight = height / 2; int x = (width - hWidth)/2; int y = (height - hHeight)/2; g.setColor(Color.black); g.fillRect(0, 0, size().width, size().height); int[] polyx = {0, width / 2, width, width / 2}; int[] polyy = {height / 2, 0, height / 2, height}; Polygon poly = new Polygon(polyx, polyy, 4); g.setColor(Color.yellow) g.fillPolygon(poly); g.setColor(Color.red); g.fillRect(x, y, hWidth, hHeight); g.setColor(Color.green); g.fillOval(x, y, hWidth, hHeight); g.setColor(Color.blue); g.fillArc(x, y, hWidth, hHeight, theta, delta); g.setColor(Color.white); g.drawLine(x, y, x + hWidth, x + hHeight); } Disegno Grafico

Animazione Click!

class MyPanel extends JPanel implements MouseListener{ int theta = 45; int delta = 90; public void paintComponent(Graphics g) {... } public void mouseClicked(MouseEvent e) { theta=theta-90; this.repaint(); } public void mouseEntered(MouseEvent e) {} public void mouseExited(MouseEvent e) {} public void mousePressed(MouseEvent e) {} public void mouseReleased(MouseEvent e) {} } MyPanel() {this.addMouseListener(this);} } Animazione Double buffering dietro le quinte!

Repainting NON SI CHIAMA MAI ESPLICITAMENTE LA paintComponent(Graphics g)! [ nè la paint(Graphics g) ] Si chiama sempre, solo la repaint() NON SI IMPLEMENTA MAI LA REPAINT! La repaint viene chiamata anche dal sistema quando lo ritiene opportuno (resize, unhide...)

class MyPanel extends JPanel implements MouseListener{ public void paintComponent(Graphics g) { super.paintComponent(g); int rval, gval, bval; for (int j = 30; j < (this.size().height -25); j += 30) for (int i = 5; i < (this.size().width -25); i+= 30) { rval = (int)Math.floor(Math.random() * 256); gval = (int)Math.floor(Math.random() * 256); bval = (int)Math.floor(Math.random() * 256); g.setColor(new Color(rval,gval,bval)); g.fillRect(i,j,25,25); g.setColor(Color.black); g.drawRect(i-1,j-1,25,25); }... } Colore Double buffering dietro le quinte!

Animazione Click! Resize!

Insets protected void paintComponent(Graphics g) {... Insets insets = getInsets(); int currentWidth = getWidth() - insets.left - insets.right; int currentHeight = getHeight() - insets.top - insets.bottom;... /* First painting occurs at (x,y), where x is at least insets.left, and y is at least insets.top. */... }

Come avviene il painting 1. background (if opaque) 2. custom painting (if any) 3. border (if any) 4. children (if any) paintComponent The main method for painting. By default, it first paints the background if the component is opaque. Then it performs any custom painting. paintBorder Tells the component's border (if any) to paint. Do not invoke or override this method. paintChildren Tells any components contained by this component to paint themselves. Do not invoke or override this method.

Regole When implementing custom painting code for a component, keep these rules in mind: Your custom painting code should be in a method with the signature protected void paintComponent(Graphics). To gain access to the power of the 2D graphics API, you can cast the Graphics parameter into a Graphics2D object.2D graphics API You can use a border to paint the outside edges of your component. Except when painting the background of the component, you should avoid painting over the border area of the component. You can determine this area using the getInsets method. Your component must honor the opaque property. If your component is opaque, it must paint its complete area using an opaque color or colors. If its opaque property is false, then you have the option of not painting over the entire component.

class MyPanel extends JPanel { public void paintComponent(Graphics g) { super.paintComponent(g); Font f = new Font("TimesRoman", Font.PLAIN, 18); FontMetrics fm = getFontMetrics(f); g.setFont(f); String s = "This is a plain font"; int xstart = (getSize().width – fm.stringWidth(s))/2; g.drawString(s, xstart, 25); Font fb = new Font("TimesRoman", Font.BOLD, 18); Font fi = new Font("TimesRoman", Font.ITALIC, 18); Font fbi=new Font("TimesRoman",Font.BOLD +Font.ITALIC, 18); g.setFont(fb); g.drawString("This is a bold font", 10, 50); g.setFont(fi); g.drawString("This is an italic font", 10, 75); g.setFont(fbi); g.drawString("This is a bold italic font", 10, 100); }... } Fonts