ActionScript: The Definitive Guide

Movie-Playback Movie Clip Events

The following events are generated without user intervention as Flash loads and plays movies.

enterFrame

If you’ve ever resorted to empty, looping movie clips to trigger scripts, enterFrame offers a welcome respite. The enterFrame event occurs once for every frame that passes in a movie. For example, if we place the following code on a movie clip, that clip will grow incrementally by 10 pixels per frame:

onClipEvent (enterFrame) {
  _height += 10;
  _width += 10;
}

(Notice that, as we learned earlier, the _height and _width properties are resolved within the scope of the clip to which the enterFrame event handler is attached, so no clip instance name is required before _height and _width.)

Tip

The enterFrame event is generated before each frame is rendered even if the playhead of the clip with the enterFrame handler is stopped. The enterFrame event, hence, is always being triggered.

When displayed in the Flash Player, all Flash movies are constantly running, even when nothing is moving on screen or when a movie’s playhead is stopped on a frame. An individual movie clip’s enterFrame handler will, hence, be executed repeatedly for as long as that clip is on stage, regardless of whether the clip is playing or stopped. If a clip’s playhead is moved by a gotoAndStop( ) function call, the clip’s enterFrame event handler is still triggered with each passing frame. And if every playhead of an entire movie has been halted with a stop( ) function, all enterFrame ...