Java GUI updates

Question

Hey. I'm having issues where elements of my GUI that I am updating are plain not showing or they're flickering on updates rather than running smoothly. Any help would be greatly appreciated. I've included methods that I feel might be of use below.
     public void mouseDragged(MouseEvent event) {
          if(
                    event.getLocationOnScreen().x < 700 && event.getLocationOnScreen().x > 100 &&
                    event.getLocationOnScreen().y > 100)
               if(oldSource != null)
                    eraseRectangle(oldLocation, oldSource);
               Point newPoint = calculateRectangle(event.getLocationOnScreen(), event.getSource());
               drawRectangle(newPoint, event.getSource());
               oldLocation = newPoint;
               oldSource = event.getSource();
     public void mouseReleased(MouseEvent event) {
          // REMOVE RECTANGLE
          if(oldSource != null)
               eraseRectangle(oldLocation, oldSource);
     public void mousePressed(MouseEvent event) {          
          //DRAW RECTANGLE
          if(
                    event.getLocationOnScreen().x < 700 && event.getLocationOnScreen().x > 100 &&
                    event.getLocationOnScreen().y > 100)
                         Point newPoint = calculateRectangle(event.getLocationOnScreen(), event.getSource());
                         drawRectangle(newPoint, event.getSource());
                         oldLocation = newPoint;
                         oldSource = event.getSource();
                         System.out.println(newPoint.y + "fuck!");
    private void drawRectangle(Point locationOnScreen, Object obj){
         ScreenPanel p = (ScreenPanel) obj;
         Graphics g = p.getGraphics();
         g.setColor(Color.RED);
         g.fillRect(locationOnScreen.x, locationOnScreen.y, 50, 500 - locationOnScreen.y);
         update();
    private void eraseRectangle(Point locationOnScreen, Object obj){
         ScreenPanel p = (ScreenPanel) obj;
         Graphics g = p.getGraphics();
         g.setColor(Color.WHITE);
         g.fillRect(locationOnScreen.x, locationOnScreen.y, 50, 500 - locationOnScreen.y);
         update();
    }I realize I've included a lot of code, sorry! Thanks :)

Answer 1

cmoney wrote:
So are you suggesting I create a Graphics object at the top of my class and set that graphics object in the paintComponent method and then use that around?oh no, no, no.
You instead may wish to have a collection such as an ArrayList of Points where rectangles are to be located. Your Mouse Listeners will then change points or add or delete points as needed. The paintComponent will then iterate through the collection drawing the rectangles based on the locations of the Points.