Flash CS5: The Missing Manual

Making Drawings Move

As shown earlier in this chapter, you draw lines and shapes on three classes of objects: Shape, Sprite, and MovieClip. In effect, these objects are canvases for the drawings. To make drawings move from one location to another, you move the canvas. You can think of the Shape, Sprite, and MovieClip containers as transparent sheets of film with the drawings inked on top. You place the film on the stage. Then to create motion, you reposition the film on the stage. If you want to move objects together, you can place them on the same piece of film. If you want to move them independently, you have to place them on separate pieces of film.

To make Shapes, Sprites, and MovieClips move, you change those good old friends, the x and y properties. You can make them move in response to mouse clicks or other input from your audience. If you want them to move without prompting, you need to set up the mechanism.

Using ActionScript's TimerEvent to Animate Drawings

One popular animation technique makes use of Flash's TimerEvent. It's sort of like setting one of those kitchen minute timers, and each time it goes "ding!" you move the drawing. ActionScript's Timer class uses two constants: TIMER_COMPLETE and TIMER. In earlier examples (Keeping Time with TimerEvent) you saw TIMER_COMPLETE in action. It triggers an event when the time has completely run out. You use the TIMER constant when you want to trigger repeated events at regular intervals.

Here's how it works: When you create an ...