Given the following code :
class Game() {
private Shell shell;
public Game(Display display,int level)
{
shell.addPaintListener(new ExmaplePaintListener());
shell.setText("Basic shapes");
shell.setSize(900,900);
shell.setLocation(45, 45);
shell.open();
while (!shell.isDisposed()) {
if (!display.readAndDispatch()) {
display.sleep();
}
}
}
}
The listener :
private class ExmaplePaintListener implements PaintListener {
public void paintControl(PaintEvent e) {
drawMaze(e);
placeTreasuresInMaze2(e);
e.gc.dispose();
}
}
and the method that draw the maze
private void drawMaze(PaintEvent e) {
// this method creates a new maze and draw it using GUI Java
}
My problem is that after the window of the maze is created , if I use the mouse to change the dimensions of the window , then the method drawMaze creates a new maze in the current window . This is obviously a bug , so where is my mistake ? maybe something with the Constructor of the Game class ?
Regards Ron
In general, the paint event happen after resize events. So if you resize using either the mouse or even programmatically, then the drawMaze() function will be called. I think you should not create the maze in drawMaze(), or at least make a lazy initialization. That's because a maze will be created each time the window is painted, which occurs every time you resize the window, you move the window, you hide some part of the window, you change focus, etc... That's a lot of mazes :D.
ReplyDeleteEDIT:
The paint event suggest you that the display has changed, and that the change is likely to affect the portion of the screen you are painting on. So few things:
During a paint event you want to do only one thing: painting. So don't call garbage collection. In general calling the Gc is not a good idea, and moreover in a Listener it will just crush the performance.
The event will not change the state of your Maze. So you should represent your maze using a state. One part is fixed, like the walls, the other side is variable, like the agent position inside the maze. Each time you modify the state, you ask a repaint.
If you skip a paint event, the screen will be blank.
For example if your maze is too big to fit on the screen, you use the paint event to paint only one part, etc..