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Drawing Lines, Rectangles and Ovals

This section presents Graphics methods for drawing lines, rectangles and ovals. The methods and their parameters are summarized in Fig. 12.17. For each drawing method that requires a width and height parameter, the width and height must be nonnegative values. Otherwise, the shape will not display.

Figure 12.17. Graphics methods that draw lines, rectangles and ovals.

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Method

Description

public void drawLine( int x1, int y1, int x2, int y2 )

 

Draws a line between the point (x1, y1) and the point (x2, y2).

public void drawRect( int x, int y, int width, int height)

 

Draws a rectangle of the specified width and height. The top-left corner of the rectangle has the coordinates (x, y). Only the outline of the rectangle is drawn using the Graphics object's colorthe body of the rectangle is not filled with this color.

public void fillRect( int x, int y, int width, int height )

 

Draws a filled rectangle with the specified width and height. The top-left corner of the rectangle has the coordinate (x, y). The rectangle is filled with the Graphics object's color.

public void clearRect( int x, int y, int width, int height )

 

Draws a filled rectangle with the specified width and height in the current background color. The top-left corner of the rectangle has the coordinate (x, y). This method is useful if the programmer wants to remove a portion of an image.

public void drawRoundRect( int x, int y, int width, int height, int arcWidth, int arcHeight )

 

Draws a rectangle with rounded corners in the current color with the specified width and height. The arcWidth and arcHeight determine the rounding of the corners (see Fig. 12.20). Only the outline of the shape is drawn.

public void fillRoundRect( int x, int y, int width, int height, int arcWidth, int arcHeight )

 

Draws a filled rectangle with rounded corners in the current color with the specified width and height. The arcWidth and arcHeight determine the rounding of the corners (see Fig. 12.20).

public void draw3DRect( int x, int y, int width, int height, boolean b )

 

Draws a three-dimensional rectangle in the current color with the specified width and height. The top-left corner of the rectangle has the coordinates (x, y). The rectangle appears raised when b is true and lowered when b is false. Only the outline of the shape is drawn.

public void fill3DRect( int x, int y, int width, int height, boolean b )

 

Draws a filled three-dimensional rectangle in the current color with the specified width and height. The top-left corner of the rectangle has the coordinates (x, y). The rectangle appears raised when b is true and lowered when b is false.

public void drawOval( int x, int y, int width, int height )

 

Draws an oval in the current color with the specified width and height. The bounding rectangle's top-left corner is at the coordinates (v, y). The oval touches all four sides of the bounding rectangle at the center of each side (see Fig. 12.21). Only the outline of the shape is drawn.

public void fillOval( int x, int y, int width, int height )

 

Draws a filled oval in the current color with the specified width and height. The bounding rectangle's top-left corner is at the coordinates (x, y). The oval touches all four sides of the bounding rectangle at the center of each side (see Fig. 12.21).

The application of Fig. 12.18Fig. 12.19 demonstrates drawing a variety of lines, rectangles, three-dimensional rectangles, rounded rectangles and ovals.

Figure 12.18. Drawing lines, rectangles and ovals.

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 1 // Fig. 12.18: LinesRectsOvalsJPanel.java
 2 // Drawing lines, rectangles and ovals.
 3 import java.awt.Color;
 4 import java.awt.Graphics;
 5 import javax.swing.JPanel;
 6
 7 public class LinesRectsOvalsJPanel extends JPanel
 8 {
 9 // display various lines, rectangles and ovals
10 public void paintComponent( Graphics g )
11 {
12 super.paintComponent( g ); // call superclass's paint method
13
14 this.setBackground( Color.WHITE );
15
16 g.setColor( Color.RED );
17 g.drawLine( 5, 30, 380, 30 );
18
19 g.setColor( Color.BLUE );
20 g.drawRect( 5, 40, 90, 55 ); 
21 g.fillRect( 100, 40, 90, 55 );
22
23 g.setColor( Color.CYAN );
24 g.fillRoundRect( 195, 40, 90, 55, 50, 50 );
25 g.drawRoundRect( 290, 40, 90, 55, 20, 20 );
26
27 g.setColor( Color.YELLOW );
28 g.draw3DRect( 5, 100, 90, 55, true ); 
29 g.fill3DRect( 100, 100, 90, 55, false );
30
31 g.setColor( Color.MAGENTA );
32 g.drawOval( 195, 100, 90, 55 );
33 g.fillOval( 290, 100, 90, 55 );
34 } // end method paintComponent
35 } // end class LinesRectsOvalsJPanel

Figure 12.19. Creating JFrame to display lines, rectangles and ovals.

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 1 // Fig. 12.19: LinesRectsOvals.java
 2 // Drawing lines, rectangles and ovals.
 3 import java.awt.Color;
 4 import javax.swing.JFrame;
 5
 6 public class LinesRectsOvals
 7 {
 8 // execute application
 9 public static void main( String args[] )
10 {
11 // create frame for LinesRectsOvalsJPanel
12 JFrame frame =
13 new JFrame( "Drawing lines, rectangles and ovals" );
14 frame.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );
15
16 LinesRectsOvalsJPanel linesRectsOvalsJPanel =
17 new LinesRectsOvalsJPanel();
18 linesRectsOvalsJPanel.setBackground( Color.WHITE );
19 frame.add( linesRectsOvalsJPanel ); // add panel to frame
20 frame.setSize( 400, 210 ); // set frame size
21 frame.setVisible( true ); // display frame
22 } // end main
23 } // end class LinesRectsOvals
 

In Fig. 12.18, line 17 draws a red line, line 20 draws an empty blue rectangle and line 21 draws a filled blue rectangle. Methods fillRoundRect (line 24) and drawRoundRect (line 25) draw rectangles with rounded corners. Their first two arguments specify the coordinates of the upper-left corner of the bounding rectanglethe area in which the rounded rectangle will be drawn. Note that the upper-left corner coordinates are not the edge of the rounded rectangle, but the coordinates where the edge would be if the rectangle had square corners. The third and fourth arguments specify the width and height of the rectangle. The last two arguments determine the horizontal and vertical diameters of the arc (i.e., the arc width and arc height) used to represent the corners.

Figure 12.20 labels the arc width, arc height, width and height of a rounded rectangle. Using the same value for the arc width and arc height produces a quarter circle at each corner. When the arc width, arc height, width and height have the same values, the result is a circle. If the values for width and height are the same and the values of arcWidth and arcHeight are 0, the result is a square.

Figure 12.20. Arc width and arc height for rounded rectangles.

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Methods draw3DRect (line 28) and fill3DRect (line 29) take the same arguments. The first two arguments specify the top-left corner of the rectangle. The next two arguments specify the width and height of the rectangle, respectively. The last argument determines whether the rectangle is raised (true) or lowered (false). The three-dimensional effect of draw3DRect appears as two edges of the rectangle in the original color and two edges in a slightly darker color. The three-dimensional effect of fill3DRect appears as two edges of the rectangle in the original drawing color and the fill and other two edges in a slightly darker color. Raised rectangles have the original drawing color edges at the top and left of the rectangle. Lowered rectangles have the original drawing color edges at the bottom and right of the rectangle. The three-dimensional effect is difficult to see in some colors.

Methods drawOval and fillOval (lines 3233) take the same four arguments. The first two arguments specify the top-left coordinate of the bounding rectangle that contains the oval. The last two arguments specify the width and height of the bounding rectangle, respectively. Figure 12.21 shows an oval bounded by a rectangle. Note that the oval touches the center of all four sides of the bounding rectangle. (The bounding rectangle is not displayed on the screen.)

Figure 12.21. Oval bounded by a rectangle.


Introduction to Computers, the Internet and the World Wide Web

Introduction to Java Applications

Introduction to Classes and Objects

Control Statements: Part I

Control Statements: Part 2

Methods: A Deeper Look

Arrays

Classes and Objects: A Deeper Look

Object-Oriented Programming: Inheritance

Object-Oriented Programming: Polymorphism

GUI Components: Part 1

Graphics and Java 2D™

Exception Handling

Files and Streams

Recursion

Searching and Sorting

Data Structures

Generics

Collections

Introduction to Java Applets

Multimedia: Applets and Applications

GUI Components: Part 2

Multithreading

Networking

Accessing Databases with JDBC

Servlets

JavaServer Pages (JSP)

Formatted Output

Strings, Characters and Regular Expressions

Appendix A. Operator Precedence Chart

Appendix B. ASCII Character Set

Appendix C. Keywords and Reserved Words

Appendix D. Primitive Types

Appendix E. (On CD) Number Systems

Appendix F. (On CD) Unicode®

Appendix G. Using the Java API Documentation

Appendix H. (On CD) Creating Documentation with javadoc

Appendix I. (On CD) Bit Manipulation

Appendix J. (On CD) ATM Case Study Code

Appendix K. (On CD) Labeled break and continue Statements

Appendix L. (On CD) UML 2: Additional Diagram Types

Appendix M. (On CD) Design Patterns

Appendix N. Using the Debugger

Inside Back Cover

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Java(c) How to Program
Java How to Program (6th Edition) (How to Program (Deitel))
ISBN: 0131483986
EAN: 2147483647
Year: 2003
Pages: 615
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