用户按下Jbutton的随机时间后的Java drawOval

Question

So when the user presses my JButton, it picks a random time, and after that time, it will draw a oval to the screen. However, with what I have now, it draws the oval right after the button is pressed. I want it to appear after a random time.

  public void actionPerformed(ActionEvent e) 
  {
  if (e.getSource() == startButton)
  {
      popUpTime = random.nextInt(5000);
      timer = new Timer(popUpTime, this);

      x = random.nextInt(400) + 70;
          y = random.nextInt(400) + 100;

          points[current++] = new Point(x, y);

      timer.start();
      start();

      repaint();
  }


   }

Answer 1

The problem is your logic:

if event is start button, then setup oval and timer and call repaint();

assumedly repaint is drawing your oval at the set coordinates.

You probably should do something like this:

if (e.getSource() == startButton)  {
  drawOval = false;  // flag to repaint method to NOT display oval
  // setup timer 
  repaint();  // oval will not be drawn
else {
  // assuming timer has fired (which is a bit weak)
  x = ....;
  y = ...;
  drawOval = true;
  repaint();  // oval will be drawn.
}

Your repaint() method will need to check the drawOval setting:

public void repaint() {
  if (drawOval) {
    // draw it
  } else {
    // may need to clear oval
  }

  // draw other stuff.
}

Answer 2

You could use the sleep function from the Thread class to make the program wait for a random time. Something like this:

try{
Thread.sleep(PopUpTime);
}
catch(Exception e)
{}
// and then compute new points and repaint