Is there a better code than waiting for JOGL display method to finish something?

Question

I gotta tell you I didn't come up with a good title for the question, but I'll explain my situation.

I'm making a simple game in Java using OpenGL (JOGL). There is a key listener waiting for the left key to be pressed, and his happens when you press on the left key:

case KeyEvent.VK_LEFT:
     if (inControl) {
        inControl = false;
        alpha = 0;
        moving = true;
      }

As you can see, inControl decides if the player is able to make a move. Now by setting moving to false, I'm "sending a signal" to the display method, which contains the following code segment:

public void display(GLAutoDrawable drawable) {
   .
   .
   .
   if (moving) {
       .
       .
       .
       // Set color's alpha to alpha
       // Draw contents
       .
       .
       .
       if (alpha < 1.0f)
          alpha += 0.01f;

       if (alpha >= 1.0f) {
           inControl = true;
           moving = false;
       }
   }
   .
   .
   .
}

This means once I click left, somethings will gradually increase opacity until alpha >= 1.0f. The player must wait then, and this is done by putting inControl = true at the end of display method.

Although this works, I'm not a fan at all of this approach. Shouldn't the display method be exclusive to only displaying graphics, and not manipulate data?