Recipe 7.4 Reversing Playback

7.4.1 Problem

You want to play a movie clip's timeline in reverse.

7.4.2 Solution

Use an onEnterFrame( ) event handler with the prevFrame( ) method.

7.4.3 Discussion

You can programmatically reverse the playback of a movie clip's timeline with ActionScript. The onEnterFrame( ) event handler of a movie clip is called repeatedly at the same frequency as the movie's frame rate. Therefore, if you create an onEnterFrame( ) method definition for a movie clip that includes a call to the prevFrame( ) method, the movie clip's timeline will continually move to the previous frame at the movie's frame rate:

myMovieClip.onEnterFrame = function (  ) {
    this.prevFrame(  );
};

If the movie clip's playhead is already on the first frame, prevFrame( ) has no effect. Therefore, to loop the movie clip's timeline while playing in reverse, add a conditional statement that goes to the last frame of the movie clip if it is already on the first frame. The current frame number is determined using the _currentframe property, and the last frame is determined using the _totalframes property:

myMovieClip.onEnterFrame = function (  ) {
  if (this._currentframe > 1) {
    // Play the clip backwards.
    this.prevFrame(  );
  } else {
    // Loop back to the end if we're already at the beginning.
    this.gotoAndStop(this._totalframes);
  }
};