Java Reference
In-Depth Information
(Optional) GUI and Graphics Case Study Exercise: Expanding the Interface
12.17
(Interactive Drawing Application)
In this exercise, you'll implement a GUI application
that uses the
MyShape
hierarchy from GUI and Graphics Case Study Exercise 10.2 to create an in-
teractive drawing application. You'll create two classes for the GUI and provide a test class that
launches the application. The classes of the
MyShape
hierarchy require no additional changes.
The first class to create is a subclass of
JPanel
called
DrawPanel
, which represents the area on
which the user draws the shapes. Class
DrawPanel
should have the following instance variables:
a) An array
shapes
of type
MyShape
that will store all the shapes the user draws.
b) An integer
shapeCount
that counts the number of shapes in the array.
c) An integer
shapeType
that determines the type of shape to draw.
d) A
MyShape
currentShape
that represents the current shape the user is drawing.
e) A
Color
currentColor
that represents the current drawing color.
f) A boolean
filledShape
that determines whether to draw a filled shape.
g) A
JLabel
statusLabel
that represents the status bar. The status bar will display the co-
ordinates of the current mouse position.
Class
DrawPanel
should also declare the following methods:
a) Overridden method
paintComponent
that draws the shapes in the array. Use instance
variable
shapeCount
to determine how many shapes to draw. Method
paintComponent
should also call
currentShape
's
draw
method, provided that
currentShape
is not
null
.
b) Set methods for the
shapeType
,
currentColor
and
filledShape
.
c) Method
clearLastShape
should clear the last shape drawn by decrementing instance
variable
shapeCount
. Ensure that
shapeCount
is never less than zero.
d) Method
clearDrawing
should remove all the shapes in the current drawing by setting
shapeCount
to zero.
Methods
clearLastShape
and
clearDrawing
should call
repaint
(inherited from
JPanel
) to refresh
the drawing on the
DrawPanel
by indicating that the system should call method
paintComponent
.
Class
DrawPanel
should also provide event handling to enable the user to draw with the
mouse. Create a single inner class that both extends
MouseAdapter
and implements
MouseMotion-
Listener
to handle all mouse events in one class.
In the inner class, override method
mousePressed
so that it assigns
currentShape
a new shape
of the type specified by
shapeType
and initializes both points to the mouse position. Next, override
method
mouseReleased
to finish drawing the current shape and place it in the array. Set the second
point of
currentShape
to the current mouse position and add
currentShape
to the array. Instance
variable
shapeCount
determines the insertion index. Set
currentShape
to
null
and call method
repaint
to update the drawing with the new shape.
Override method
mouseMoved
to set the text of the
statusLabel
so that it displays the mouse
coordinates—this will update the label with the coordinates every time the user moves (but does
not drag) the mouse within the
DrawPanel
. Next, override method
mouseDragged
so that it sets the
second point of the
currentShape
to the current mouse position and calls method
repaint
. This
will allow the user to see the shape while dragging the mouse. Also, update the
JLabel
in
mouse-
Dragged
with the current position of the mouse.
Create a constructor for
DrawPanel
that has a single
JLabel
parameter. In the constructor, ini-
tialize
statusLabel
with the value passed to the parameter. Also initialize array
shapes
with 100
entries,
shapeCount
to 0,
shapeType
to the value that represents a line,
currentShape
to
null
and
currentColor
to
Color.BLACK
. The constructor should then set the background color of the
Draw-
Panel
to
Color.WHITE
and register the
MouseListener
and
MouseMotionListener
so the
JPanel
properly handles mouse events.
Next, create a
JFrame
subclass called
DrawFrame
that provides a GUI that enables the user to
control various aspects of drawing. For the layout of the
DrawFrame
, we recommend a
BorderLay-
