ADVANCED GUIS AND GRAPHICS - Java Programming: From Problem Analysis to Program Design - page 857

The program FreeDrawApplet uses small circles to draw lines. Because there is no GUI
component we can use, we created the class ColorCircle . This class has two
private members x and y of the type int . The point ( x , y ) specifies the center of the
circle, and the radius of the circle is fixed at 10 pixels. In addition to the methods to set
the values of x and y , the class ColorCircle has only two other methods: paint
and isSelected . The paint method draws a filled circle of radius 10 at the point ( x , y ).
The method isSelected returns true if and only if ( iXcoord , iYcoord ) lies inside a
20-by-20 square with the point ( x , y ) as the center. We use this method to check
whether the mouse is at, say, ( iXcoord , iYcoord ) on the circle with the center ( x , y ).
Note that because ColorCircle is not a GUI component, it can generate any event.
Therefore, any time a mouseDragged event is generated, we must check whether the
mouse is on any of the circles. We do so using the following for loop:
for ( int i = 0; i < NUM_CIRCLES; i++)
if (myGraph[i].selected(iX, iY))
{

myGraph[i].setX(iX);
myGraph[i].setY(iY);
break ;

}

Note that if a mouseDragged event occurs on a ColorCircle object, the preceding for
loop sets the current mouse position as the new center of the ColorCircle object. This,
in effect, moves the ColorCircle object. By continually moving a ColorCircle object,
we create a line.

PROGRAMMING EXAMPLE: Java Kiosk
In this programming example, we design a program that simulates a fast food kiosk.
The program displays a menu similar to one you might find in a fast food restaurant.
The user makes a selection and then presses a JButton to mark the end of the
selection process. The program then calculates and displays the bill. A sample output
is shown in Figure 12-25.

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