Displaying information within a window.68

Displaying information within a window

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1

Objectives

On completion of this period, you would be
able to know

• Displaying information within a window
• Working with Graphics

2

Recap

In the previous class, you have leant
• create a windowed program

3

Displaying Information Within a Window

• A window is a container for information
• AWT has ability to present high-quality
graphics and text
• Displaying Information Within a Window
comprises of
– Java’s graphics, and font-handling
capabilities
• In this lesson we look at Java’s graphics

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Working with Graphics

• The AWT supports a rich set of graphics
methods
• Graphics call contains these methods
• All graphics are drawn relative to a window
• The origin of each window is at the top-left
corner and is 0,0
• Coordinates are specified in pixels


Working with Graphics contd..

• With Graphics object, we
can draw several regular
shapes like
– Lines
– Rectangles
– Ellipses
– Circles
– Ovals
– Arcs
• Any irregular shapes by
drawing polygons


Drawing Lines

• Lines are drawn by means of the drawLine( )
method
• The syntax is
– void drawLine(int startX, int startY, int endX,
int endY)
• drawLine( ) displays a line in the current drawing
color that
– begins at startX,startY
– ends at endX,endY
• The following applet draws several lines

Drawing Lines contd..
// Draw lines
import java.awt.*;
import java.applet.*; The sample output is shown here
/*
<applet code="Lines" width=300 height=200>
</applet>
*/
public class Lines extends Applet {
public void paint(Graphics g) {
g.drawLine(0, 0, 100, 100);
g.drawLine(0, 100, 100, 0);
g.drawLine(40, 25, 250, 180);
g.drawLine(75, 90, 400, 400);
g.drawLine(20, 150, 400, 40);
g.drawLine(5, 290, 80, 19);
Fig. 68.1 Drawing lines
}
}


Drawing Rectangles

• The drawRect( ) and fillRect( ) methods display an
outlined and filled rectangle,
• The sybtax is
– void drawRect(int top, int left, int width, int height)
– void fillRect(int top, int left, int width, int height)
– The upper-left corner of the rectangle is at top,left. The
dimensions of the rectangle are specified by width and height.
• To draw a rounded rectangle, use drawRoundRect( ) or
fillRoundRect( ), both
• The syntax is
– void drawRoundRect(int top, int left, int width, int height, int
xDiam, int yDiam)
– void fillRoundRect(int top, int left, int width, int height, int xDiam,
int yDiam)


Drawing Rectangles contd..
// Draw rectangles The sample output is shown here
import java.awt.*;
import java.applet.*;
/*
<applet code="Rectangles" width=300
height=200>
</applet>
*/
public class Rectangles extends Applet {
public void paint(Graphics g) { Fig. 68.2 Drawing rectangles
g.drawRect(10, 10, 60, 50);
g.fillRect(100, 10, 60, 50);
g.drawRoundRect(190, 10, 60, 50, 15, 15);
g.fillRoundRect(70, 90, 140, 100, 30, 40);
}
}

Drawing Ellipses and Circles

• To draw an ellipse, use drawOval( ). To fill an
ellipse, use fillOval( )
• These methods are shown here
– void drawOval(int top, int left, int width, int
height)
– void fillOval(int top, int left, int width, int
height)


Drawing Ellipses and Circles contd..

// Draw Ellipses
import java.awt.*; The sample output is shown here
/*
<applet code="Ellipses" width=300
height=200>
</applet>
*/
public class Ellipses extends Applet {
g.drawOval(10, 10, 50, 50); Fig. 68.3 Drawing
g.fillOval(100, 10, 75, 50); ellipses and circles
g.drawOval(190, 10, 90, 30);
g.fillOval(70, 90, 140, 100 );
}
} http://improvejava.blogspot.in/ 12

Drawing Arcs

• Arcs can be drawn with drawArc( ) and fillArc( ),
shown here:
– void drawArc(int top, int left, int width, int
height, int startAngle,int sweepAngle)
– void fillArc(int top, int left, int width, int height,
int startAngle,int sweepAngle)
– The arc is drawn from startAngle through the
angular distance specified by sweepAngle
– Angles are specified in degrees


Drawing Arcs contd..
// Draw Arcs
import java.awt.*;
The sample output is shown here
/*
<applet code="Arcs" width=300
height=200>
</applet>
*/
public class Arcs extends Applet {
g.drawArc(10, 40, 70, 70, 0, 75);
Fig. 68.4 Drawing ARCS
g.fillArc(100, 40, 70, 70, 0, 75);
g.drawArc(10, 100, 70, 80, 0, 175);
g.fillArc(100, 100, 70, 90, 0, 270);
g.drawArc(200, 80, 80, 80, 0, 180);
}
} http://improvejava.blogspot.in/ 14

Drawing Polygons

• It is possible to draw arbitrarily shaped figures
using drawPolygon( ) and fillPolygon( ),
• shown here:
– void drawPolygon(int x[ ], int y[ ], int numPoints)
– void fillPolygon(int x[ ], int y[ ], int numPoints)
• The polygon’s endpoints are specified by the
coordinate pairs contained within the x and y
arrays
• The number of points defined by x and y is
specified by numPoints


Drawing Polygons contd..

// Draw Polygon
import java.awt.*; The sample output is shown here
/*
<applet code="HourGlass" width=230
height=210>
</applet>
*/
public class HourGlass extends Applet {
int xpoints[] = {30, 200, 30, 200, 30};
Fig. 68.5 Drawing polygons
int ypoints[] = {30, 30, 200, 200, 30};
int num = 5;
g.drawPolygon(xpoints, ypoints, num);
}
}

Summary

• In this class we have discussed
– Displaying information within a window
– Working with Graphics


Quiz

1. The origin of each window is at
a) Top-right
b) Top-left
c) Bottom-left
d) Bottom-right


Frequently Asked Questions

1. Write a program to draw the following diagram


Displaying information within a window.68

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