Download on Drawing Figures

Any object can be drawn …
Suppose we are creating a Dog class …………..
public class Dog {
private String name = “Fido”;
private String breed = “unknown”;
//dog’s name
// dog’s breed
public Dog (String nm, String brd){
name = nm;
breed = brd;
}
// .... We might have some other methods here
public String toString( ) {
return “ " + name;
}
}
And we wanted the capability of ‘drawing’ a dog……..
we will add the following method to the Dog class..
Remember, we have been using a Graphics2D object to draw
public void
draw(Graphics2D
g2){
shapes,
If one
of our Dog methods
had access to a Graphics2D
x = 10;
object,
then it could ‘draw a dog’ ! SO..
y = 10;
Ellipse2D.Double oval = new Ellipse2D.Double(x,y,100,50);
g2.draw(oval);
//eyes
oval = new Ellipse2D.Double(x+25,y+12,5,5);
g2.draw(oval);
oval = new Ellipse2D.Double(x+12,y+12,5,5);
g2.draw(oval);
//nose
oval = new Ellipse2D.Double(x+16,y+25,10,10);
g2.fill(oval);
// left ear
oval = new Ellipse2D.Double(x+62,y+13,50,75);
g2.fill(oval);
}
Any object can be drawn …
We may want to allow our Dog to be constructed with an initial
drawing position …
public class Dog {
String name = “Fido”;
String breed = “unknown”;
..position is now also specified as instance data
private int x = 10; //x,y drawing position, default 10,10
private int y = 10;
public Dog (String nm, String brd, int xpos, int ypos){
name = nm;
breed = brd;
x = xpos;
y = ypos;
}
Any object can be drawn …
Now any JComponent can easily add a Dog drawing …
import javax.swing.JComponent;
import java.awt.Graphics2D;
import java.awt.Graphics;
import java.awt.Color;
public class DrawPad extends JComponent {
public void paintComponent(Graphics g) {
Graphics2D g2 = (Graphics2D) g;
// create two dog objects
Dog d1 = new Dog("George","Poodle", 10,10);
Dog d2 = new Dog( "Fred","mutt", 150,150);
// call Dog object’s Draw method
d1.draw(g2);
d2.draw(g2);
}
}
Drawing Complex Shapes
• Good practice: Make a class for each graphical shape
class Car
{
. . .
public void draw(Graphics2D g2)
{
// Drawing instructions
. . .
}
}
• Plan complex shapes by making sketches on graph paper
File CarComponent.java
import java.awt.Graphics;
import java.awt.Graphics2D;
import javax.swing.JComponent;:
// This component draws two car shapes.
public class CarComponent extends JComponent
{
public void paintComponent(Graphics g)
{
Graphics2D g2 = (Graphics2D) g;
Car car1 = new Car(0, 0); //car created at position 0,0
int x = getWidth() - Car.WIDTH; //another at lower right
int y = getHeight() - Car.HEIGHT;
Car car2 = new Car(x, y); //create car
car1.draw(g2);
car2.draw(g2);
}
}
//draw both cars
Drawing Cars
• Draw two cars: one in top-left corner of window, and another in
the bottom right
• Compute bottom right position, inside paintComponent
method:
int x = getWidth() - 60;
int y = getHeight() - 30;
Car car2 = new Car(x, y);
• getWidth and getHeight are applied to object that executes
paintComponent (the JComponent object)
• If window is resized paintComponent is called and car position
recomputed
Continued…
File CarViewer.java
import javax.swing.JFrame;
public class CarViewer{
public static void main(String[] args) {
JFrame frame = new JFrame();
final int FRAME_WIDTH = 300; //set up frame
final int FRAME_HEIGHT = 400;
frame.setSize(FRAME_WIDTH, FRAME_HEIGHT);
frame.setTitle("Two cars");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
//create component and add to frame
CarComponent component = new CarComponent();
frame.add(component);
frame.setVisible(true);
}
}
//make frame visible
Drawing Cars
The Car Component Draws 2 Shapes
Plan Complex Shapes on Graph
Paper
Using Graph Paper to
Find Shape Coordinates
draw method details..
public void draw(Graphics2D g2) {
Rectangle2D.Double body = new Rectangle2D.Double(xLeft, yTop + 10, 60, 10);
Ellipse2D.Double frontTire = new Ellipse2D.Double(xLeft + 10, yTop + 20, 10, 10);
Ellipse2D.Double rearTire= new Ellipse2D.Double(xLeft + 40, yTop + 20, 10, 10);
// top of front windshield
Point2D.Double r1 = new Point2D.Double(xLeft + 10, yTop + 10);
Point2D.Double r2 = new Point2D.Double(xLeft + 20, yTop);
// front of roof
Point2D.Double r3 = new Point2D.Double(xLeft + 40, yTop);
// rear of roof
// bottom of rear windshield
Point2D.Double r4 = new Point2D.Double(xLeft + 50, yTop + 10);
Line2D.Double frontWindshield = new Line2D.Double(r1, r2);
Line2D.Double roofTop = new Line2D.Double(r2, r3);
Line2D.Double rearWindshield = new Line2D.Double(r3, r4);
g2.draw(body);
g2.draw(frontTire);
g2.draw(rearTire);
g2.draw(frontWindshield);
g2.draw(roofTop);
g2.draw(rearWindshield);
Reading Text Input
• A graphical application can obtain input by displaying a
JOptionPane
• The showInputDialog method displays a prompt and waits for
user input
• The showInputDialog method returns the string that the user
typed
String input = JOptionPane.showInputDialog("Enter x");
double x = Double.parseDouble(input);
Continued…
Reading Text Input
An Input Dialog Box
ColoredSquareComponent.java
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Rectangle;
import javax.swing.JComponent;
// A component that shows a colored square.
public class ColoredSquareComponent extends JComponent {
private Color fillColor;
public ColoredSquareComponent(Color aColor) {
// param aColor the fill color for the square
fillColor = aColor;
}
public void paintComponent(Graphics g) {
Graphics2D g2 = (Graphics2D) g;
g2.setColor(fillColor);
// now draw a filled square
ColoredSquareComponent.java
// now draw a filled square
final int SQUARE_LENGTH = 100;
Rectangle square = new Rectangle(
(getWidth() - SQUARE_LENGTH) / 2,
(getHeight() - SQUARE_LENGTH) / 2,
SQUARE_LENGTH,
SQUARE_LENGTH);
g2.fill(square);
}
}
ColorViewer.java- allows user to specify color
import java.awt.Color;
import javax.swing.JFrame;
import javax.swing.JOptionPane;
public class ColorViewer {
public static void main(String[] args) {
JFrame frame = new JFrame();
final int FRAME_WIDTH = 300;
final int FRAME_HEIGHT = 400;
frame.setSize(FRAME_WIDTH, FRAME_HEIGHT);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
Continued…
ColorViewer.java- allows user to specify color
//ask user for color, create and draw component
String input;
input = JOptionPane.showInputDialog("red:");
double red = Double.parseDouble(input);
input = JOptionPane.showInputDialog("green:");
double green = Double.parseDouble(input);
input = JOptionPane.showInputDialog("blue:");
double blue = Double.parseDouble(input);
//create color object using user RBG values)
Color fillColor = new Color(
(float) red, (float) green, (float) blue);
ColoredSquareComponent component
= new ColoredSquareComponent(fillColor);
frame.add(component);
frame.setVisible(true);
}
}