ActionScript: The Definitive Guide

Event Handlers Applied

We’ll conclude our exploration of ActionScript events and event handlers with a few real-world examples. These are simple applications, but they give us a sense of how flexible event-based programming can be. The last two examples are available for download from the online Code Depot.

Example 10.7 makes a clip shrink and grow.

Example 10-7. Oscillating the Size of a Movie Clip

onClipEvent (load) {
  var shrinking = false;
  var maxHeight = 300;
  var minHeight = 30;
}

onClipEvent (enterFrame) {
  if (_height < maxHeight && shrinking == false) {
    _height += 10;
    _width  += 10;
  } else {
    shrinking = true;
  }

  if (shrinking == true) {
    if (_height > minHeight) {
      _height -= 10;
      _width  -= 10;
    } else {
      shrinking = false;
      _height += 10;     // Increment here so we don't
      _width  += 10;     // miss a cycle
    }
  }
}

Example 10.8 simulates a custom mouse pointer by hiding the normal system pointer and making a clip follow the mouse location around the screen. In the example, the mouseDown and mouseUp handlers resize the custom pointer slightly to indicate mouseclicks.

Example 10-8. A Custom Mouse Pointer

onClipEvent (load) {
  Mouse.hide( );
}

onClipEvent (mouseMove) {
  _x = _root._xmouse;
  _ y = _root._ymouse;
  updateAfterEvent( );
}

onClipEvent (mouseDown) {
  _width  *= .5;
  _height *= .5;
  updateAfterEvent( );
}

onClipEvent (mouseUp) {
  _width  *= 2;
  _height *= 2;
  updateAfterEvent( );
}

Finally, simply to prove the power of the ActionScript movie clip event handlers, Example 10.9 turns a movie clip into ...