Custom Painting

1
Custom Painting

• Gestione
• della
• Grafica customizzata
• Vedi anche
• http//java.sun.com/docs/books/tutorial/uiswing/14
  painting/index.html

2
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

3
Il sistema di coordinate
4
Disegno Grafico
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)
5
Disegno Grafico
class MyPanel extends JPanel int theta 45
int delta 90 public void paintComponent(Graph
ics 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)
6
Animazione
Click!
Click!
Click!
7
Animazione
class MyPanel extends JPanel implements
MouseListener int theta 45 int delta
90 public void paintComponent(Graphics g)
... public void mouseClicked(MouseEvent
e) thetatheta-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!
8
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...)
9
Colore
class MyPanel extends JPanel implements
MouseListener public void paintComponent(Graphi
cs g) super.paintComponent(g) int
rval, gval, bval for (int j 30 j lt
(this.size().height -25) j 30) for
(int i 5 i lt (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.rando
m() 256) g.setColor(new
Color(rval,gval,bval))
g.fillRect(i,j,25,25) g.setColor(Color.bl
ack) g.drawRect(i-1,j-1,25,25)
...
Double buffering dietro le quinte!
10
Animazione
Click!
Resize!
11
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. /...
12
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.
13
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.

14
Fonts
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
fbinew 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) ...