Update to graphics only working when maximise window

Question

Hi folks, I'm trying to put together a java application but have run into trouble with a JPanel that displays graphics.
The JPanel is inside of a JScrollPane, which is itself inside of a larger panel in the main JFrame. The JPanel inside of the scrollPane displays some graphics depending upon what is stored in an arraylist that it keeps. What I would like is for the image to be updated when the user adds or changes one of the elements in this arraylist (the user does this by pressing buttons).
Presently, I have it so that when for example the user adds to the arraylist, the repaint() method is called after this addition. However, the image is not changed unless the JFrame itself is maximised (then it appears as I want it). Obviously I would rather it updated without this! :-)
I have experimented with the various paint, repaint, and validating methods to no avail, but I'm hoping this is a problem that has cropped up with people before.
Any help will be greatly appreciated

Answer 1

Sure can. The inner most panel is a chart that increases in size when you add to it. Each row of the chart has a description and a bar (kinda like a gantt chart).
taskList is the arraylist.
getBarLocation is a method that returns the x-position of the bar depending on the date of the task
     public void paint(Graphics g)
          // increase height of the chart to accomodate new tasks
          setPreferredSize(new Dimension(4000, 42 + (taskList.size() * 20) ) );
          Graphics2D g2d = (Graphics2D) g;
          g2d.setFont(new Font("Courier", Font.PLAIN, 12));
          drawMonthsString(g2d);
          g2d.drawString(makeDatesString(), 200, 40);
          g2d.drawLine(0, 41, 4000, 41);
          // now we draw the tasks in
          // this variable tracks progress down y-axis (top pixel of the task)
          int y = 42;
          // this iterates over the list of tasks
          Iterator taskIterator = taskList.iterator();
          while(taskIterator.hasNext())
               Task currTask = (Task) taskIterator.next();
               // write task name
               g2d.drawString(currTask.getName(), 20, y+14);
               // draw bar showing task time
               int barStartX = getBarLocation(currTask.getStartDate());
               int barEndX   = getBarLocation(currTask.getEndDate()) + 12; //to cover last date
               g2d.draw(new Rectangle(barStartX, y, (barEndX-barStartX), 19));
               y += 20;
     Hope that helps your understanding.