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COMP126A

Lecture 5: Action ScriptEvents and Properties

Items

Progress with labs Should have finished assignment 1 Hand out Practical 7 and 8

Action Script Events and Properties

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Demonstrations

http://home.scarlet.be/~bbonte/bonteroom.html

Events

Event: Whenever something happens. Eg: User presses a mouse button press, release, releaseOutside, rollOver, ...

Many events occur. A detailed response toeach provides the richness of moderncomputer interfaces (and excellent Flashweb pages)

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Event Handlers

An event handler is some ActionScriptinstructions to provide a response to anevent.

In a button on (release) { . . . . . . . }

A movie clip can also respond to events onClipEvent (mouseUp) { . . . . . . . . }

Commands

Setting properties Built-in properties all start with the “_” character property = expression ;

_x = _x + 5 ;

_xscale = 200.0 ;

Symbols (movie clips) have properties See lab handout for a list of interesting ones

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Getting at properties

In a movie clip event handler we just usethe property name to refer to a property ofthat clip instance: _x

We can also use: this._x ‘this’ means the current movie clip, or

whatever we are coding in at the time The style symbol._x is always a way of

getting at a property

Getting at properties

Symbols can be given ‘instance’ names With instance name ‘StarOne’

we can write StarOne._x The special name _root means the

timeline for our current movie. Objects onthe stage are owned by the timeline

We can write _root.StarOne._x

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Adding Properties to Instances

We can add our own properties (variables)to named instances Eg. StarOne.direction = 1; For example, could be used to record the initial

state of a clip this.startx = this._x;