Java Reference
In-Depth Information
public void mouseReleased(MouseEvent e) {
// Code to handle the mouse button being release...
}
private Point start; // Stores cursor position on press
private Point last; // Stores cursor position on drag
private Element tempElement; // Stores a temporary element
}
private Sketcher theApp; // The application object
}
Directory "Sketcher 4 drawing sketch line and rectangle elements"
You have implemented the three methods that you need to create an element.
The
mousePressed()
method will store the position of the cursor in the
start
member of the
MouseHandler
class, so this point is available to the
mouseDragged()
method that is called repeatedly when
you drag the mouse cursor with the button pressed.
The
mouseDragged()
method creates an element using the current cursor position together with the pos-
ition previously saved in
start
. It stores a reference to the element in the
tempElement
member. The
last
member of the
MouseHandler
class is used to store the cursor position when
mouseDragged()
is called.
Both
start
and
last
are of type
Point
because this is the type that you get for the cursor position, but
remember that
Point
is a subclass of
Point2D
, so you can always cast a
Point
reference to
Point2D
when
necessary.
The
mouseReleased()
method is called when you release the mouse button. This method stores the ele-
ment in the sketch and cleans up where necessary.
An object of type
MouseHandler
is the listener for mouse events for the view object, so you can put this
in place in the
SketcherView
constructor. Add the following code at the end of the existing code:
public SketcherView(Sketcher theApp) {
this.theApp = theApp;
MouseHandler handler = new MouseHandler();
// create the mouse listener
addMouseListener(handler);
// Listen for button events
addMouseMotionListener(handler);
// Listen for motion events
}
Directory "Sketcher 4 drawing sketch line and rectangle elements"
You call the
addMouseListener()
and
addMotionListener()
methods and pass the same listener
object as the argument to both because the
MouseHandler
class deals with both types of event. Both
methods are inherited in the
SketcherView
class from the
Component
class, which also defines an
ad-
dMouseWheelListener()
method for when you want to handle mouse wheel events.
Let's go for the detail of the
MouseHandler
class now, starting with the
mousePressed()
method.
Handling Mouse Button Press Events
