Question

因此，当用户按下我的JButton时，它会选择一个随机时间，之后，它会在屏幕上绘制一个椭圆形。但是，根据我现在的情况，它会在按下按钮后立即绘制椭圆。我想让它在随机时间后出现。

  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

问题在于你的逻辑：

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

假设重绘是在设定坐标处绘制椭圆。

您可能应该这样做：

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.
}

您的repaint（）方法需要检查drawOval设置：

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

  // draw other stuff.
}

Answer 2

您可以使用Thread类中的sleep函数使程序等待一段随机时间。像这样：

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

用户按下Jbutton后随机时间之后的Java drawOval

2 个答案: