ActionScript for Flash MX: The Definitive Guide, Second Edition

MovieClip.onKeyDown () Event Handler

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ActionScript Language Reference

that clip is on stage, regardless of whether the clip is playing or stopped. If a clip’s play-

head is moved by a gotoAndStop() function call, the clip’s onEnterFrame() 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 onEnterFrame() event handlers on all clips will still

execute.

The onEnterFrame() event normally is used to update the state of a movie clip repeatedly

over time. But an onEnterFrame() event handler need not apply directly to the clip that

bears it—onEnterFrame() can be used on a movie’s main timeline or on a single-frame,

empty clip to execute code repeatedly. This technique, called a clip event loop (or, more

loosely, a process) is demonstrated in “Timeline and Clip Event Loops” in Chapter 8. The

setInterval() function is also a useful tool for repeatedly executing code.

To stop a callback from handling the onEnterFrame() event, use the delete operator to

remove the handler, as in:

// Make sure to omit the () operator after the function name!

delete theClip_mc.onEnterFrame;

Note that the code in an onEnterFrame() event handler is executed before any code that

appears on the timeline of the clip containing ...