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
Component
Graphics
posiziona
Container
Layout
Layouts
Gestione
del
Layout
Vedi anche:
http://java.sun.com/docs/books/tutorial/uiswing/layout/index.html
Layouts
Layouts
Layouts
Layouts
http://java.sun.com/docs/books/tutorial/uiswing/layout/spring.html
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 all’ordine!
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 l’intero 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:
http://java.sun.com/docs/books/tutorial/uiswing/14painting/index.html
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
import
import
public
java.awt.*;
javax.swing.*;
java.awt.event.*;
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!
Click!
Click!
class MyPanel extends JPanel implements MouseListener{
int theta = 45; int delta = 90;
public void paintComponent(Graphics g) {
...
Animazione
}
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);}
}
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;
Colore
for (int j
for (int
rval =
gval =
bval =
= 30; j < (this.size().height
i = 5; i < (this.size().width
(int)Math.floor(Math.random()
(int)Math.floor(Math.random()
(int)Math.floor(Math.random()
-25); j += 30)
-25); i+= 30) {
* 256);
* 256);
* 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);
}
}
...
}
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.
•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",
Fonts
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);
}
...
}