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