Swing and threads - An Introduction to Graphical User Interfaces with Java Swing - page 248

the other one. It is important to copy the drawing and not to use an assignment of
references such as drawing1 = drawing2 .Inthat case the two drawings would be
identified; only one drawing would exist with two references to it. See Section B.1
for a more detailed explanation.

File: its/GraphicsUpdate/GoodUpdateFrame.java

1. package its.GraphicsUpdate;
2.
3. import javax.swing.JFrame;
4. import its.SimpleFrame.SimpleFrame;
5.
6.
7. public class GoodUpdateFrame extends SimpleFrame{
8.
9.

private UpdatePanel uppane;

10.

private Drawing drawing1, drawing2;

11.
12.

public GoodUpdateFrame(){

13.

drawing1 = new Drawing();

14. drawing2 = new Drawing();

15. uppane = new UpdatePanel(drawing1);

16. getContentPane().add(uppane);

17. pack();

18. }

19.
20.

public void goodDemo(){

21. uppane.repaint();

22.

drawing2.flipLines();

23.

uppane.setDrawing(drawing2);

24.

uppane.repaint();

25.

drawing1.copy(drawing2);

26.

drawing1.flipLines();

27.

uppane.setDrawing(drawing1);

28.

uppane.repaint ();

29.

}

30.
31. public static void main(String[] args){

32.

GoodUpdateFrame goodFrame = new GoodUpdateFrame();

33.

goodFrame.showIt("Good Update"); // The drawing contains

34.

goodFrame.goodDemo();

35.

}

36.
37.
38. }