Extending the GUI - Beginning Java - page 1112

if(buttonState == MouseEvent.BUTTON1 && mode == NORMAL) {
g2D = (Graphics2D)getGraphics(); // Get graphics
context
g2D.setXORMode(getBackground()); // Set XOR mode
}
}
Directory "Sketcher 10 moving and rotating elements"
It's only necessary to verify that the sketching mode is NORMAL and button 1 is down before you set
XOR mode. You may wonder why it is not necessary to use the equals() method to compare mode with
NORMAL . You should use equals() to compare arbitrary strings but here, mode is not arbitrary. It can only
be a reference to one of the String objects you defined in the SketcherConstants class. This allows
you to compare the String references for equality.
You have to test for the setting of mode in the mouseDragged() method, and execute different code de-
pending on its value. You have three possibilities: NORMAL , where you do as you did before; MOVE , where
you execute a move operation; and ROTATE , where you execute a rotate operation, which you implement
later. Here's the new version of mouseDragged() to accommodate moving elements:
public void mouseDragged(MouseEvent e) {
last = e.getPoint(); // Save cursor
position
if(theApp.getWindow().getElementType() == TEXT && mode ==
NORMAL) return;
// Select operation based on sketching mode
switch(mode){
case NORMAL:
// Creating an element
if(buttonState == MouseEvent.BUTTON1) {
if(tempElement == null) { // Is there an
element?
tempElement = Element.createElement( // No, so create
one
theApp.getWindow().getElementType(),
theApp.getWindow().getElementColor(),
start, last);
} else {
tempElement.draw(g2D); // Yes - draw to
erase it
tempElement.modify(start, last); // Now modify it
}
tempElement.draw(g2D); // and draw it
}
break;