Basic Graphics 03/03/16 & 03/07/16 Imagine! Java: Programming Concepts in Context by Frank M. Carrano, (c) Pearson Education - Prentice Hall, 2010

This Week's Topics Creating a Window  Getting Ready to Draw  A Sample Drawing Panel  Displaying a Panel The Class Graphics  The Coordinate System  Drawing Rectangles  Painting Shapes Imagine! Java: Programming Concepts in Context by Frank M. Carrano, (c) Pearson Education - Prentice Hall, 2010

Objectives After studying this chapter, you should be able to: Write a program that creates a window with graphics Display in a window  Rectangles, Ovals and Arcs Use color in Graphics Imagine! Java: Programming Concepts in Context by Frank M. Carrano, (c) Pearson Education - Prentice Hall, 2010

Creating a Window A rectangular area  Part of a user interface  Called a frame  Contains title bar An empty frame Imagine! Java: Programming Concepts in Context by Frank M. Carrano, (c) Pearson Education - Prentice Hall, 2010

Creating a Window Construct object of class JFrame  From package javax.swing JFrame aWindow = new JFrame(); Specify size aWindow.setSize(400, 600); setTitle() puts a title in the title bar: aWindow.setTitle(“Bronco Window”); Imagine! Java: Programming Concepts in Context by Frank M. Carrano, (c) Pearson Education - Prentice Hall, 2010

Creating a Window Window must be made visible. aWindow.setVisible(true); View sample program, EmptyWindow Imagine! Java: Programming Concepts in Context by Frank M. Carrano, (c) Pearson Education - Prentice Hall, 2010

Creating a Window If the user closes the window with the control button, the window closes. The program keeps running. aWindow.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE);  Exits program when window closes.

Preparing to Draw Cannot draw directly on JFrame object  This is a container  Contains other objects Can create a JPanel object and add it to the JFrame, but it would be blank. The JPanel class is in javax.swing

Preparing to Draw Create a class of panels upon which to draw. DrawingPanel inherits JPanel. Graphics g parameter allows it to draw. Imagine! Java: Programming Concepts in Context by Frank M. Carrano, (c) Pearson Education - Prentice Hall, 2010

Simple Drawing Panel Some basic shapes. Now we create a window and add an instance of class DrawingPanel to the window. Example in WindowWithDrawing Imagine! Java: Programming Concepts in Context by Frank M. Carrano, (c) Pearson Education - Prentice Hall, 2010

Class Graphics Java runtime environment instantiates a Graphics object  The graphics context  Made available to method paintComponent Use methods of that Graphics object to display shapes.

Coordinate System Figure 5-2 The axes and some points on the coordinate system used for graphics

Lines, Shapes, Text Methods:  g.drawline (x1, y1, x2, y2);  g.drawRect(x, y, width, height);  g.drawOval(x, y, width, height); Note pixels on edges of 5 x 4 rectangle Figure 5-3

Lines, Shapes, Text Filled rectangles and squares  Specify position, dimensions g.fillRect(x, y, width, height); Pixels in 5 x 4 rectangle painted by fillRect Imagine! Java: Programming Concepts in Context by Frank M. Carrano, (c) Pearson Education - Prentice Hall, 2010

Lines, Shapes, Text Ovals, Circles  g.drawOval(x, y, width, height); ( for circle, height = width) Imaginary rectangle encloses oval Imagine! Java: Programming Concepts in Context by Frank M. Carrano, (c) Pearson Education - Prentice Hall, 2010

Draw Arc g.drawArc(35, 45, 75, 95, 0, 90); drawArc(int x, int y, int width, int length, int startAngle, int arcAngle) Used to draw an arc inside an imaginary rectangle whose upper left corner is at (x,y). The arc is drawn from the startAngle to startAngle + arcAngle and is measured in degrees. A startAngle of 0º points horizontally to the right (like the unit circle in math). Positive is a counterclockwise rotation starting at 0º.

Class Color In java.awt.Color Create a color by specifying RGB values  Each primary color given by integer 0 – 255 Predefined color constants from Color Imagine! Java: Programming Concepts in Context by Frank M. Carrano, (c) Pearson Education - Prentice Hall, 2010

Change Colors Assume g is a Graphic object. g.setColor(Color.RED); //Makes the “pen” // red.

Example Make a project that uses Graphics to make a smiley face. Make a Frame Put a Jpanel on the Frame Make a Drawing on the panel

Smiley Face Draw a yellow circle Draw two solid arcs for the eyes Draw a smile

Participation Create a Jframe (window) Create a Panel and add it to the JFrame Use the paintComponent to make a Japanese flag.  Draw a solid white rectangle.  Draw a solid red circle centered inside the white rectangle.

import javax.swing.JFrame; public class WindowWithDrawing { public static void main(String[] args) { //set up a JFrame window JFrame bWindow = new JFrame(); bWindow.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); bWindow.setSize(400,300); bWindow.setTitle("Shapes"); //Put a DrawingPanel in the Window //Make the window visible bWindow.setVisible(true); }

import javax.swing.JPanel; import java.awt.Graphics; public class DrawingPanel extends JPanel { //A panel to draw on. public void paintComponent(Graphics pen){ //Statements that draw go here }

Basic Graphics Chapter 2 Imagine! Java: Programming Concepts in Context by Frank M. Carrano