User Guide

196 Chapter 6: Creating Interaction with ActionScript
if (zapped) {
bug_mc._y += 25;
}
};
The bug’s instance name is bug_mc, and the outlet’s instance name is zapper_mc. In the script,
the bug is referred to as
this because the script is attached to the bug and the reserved word this
refers to the object that contains it.
There are event handlers with several different events:
onRelease, onPress, and enterFrame.
The event handlers are defined on Frame 1 after the SWF file loads. The actions in the
onEnterFrame() event handler executes every time the playhead enters a frame. Even in a one-
frame SWF file, the playhead still enters that frame repeatedly and the script executes repeatedly.
Two variables,
initx and inity, are defined to store the initial x and y positions of the bug_mc
movie clip instance. A function is defined and assigned to the
onRelease event handler of the
reset_btn instance. This function is called each time the mouse button is pressed and released
on the
reset_btn button. The function places the ladybug back in its starting position on the
Stage, resets its rotation and alpha values, and resets the
zapped variable to false.
A conditional
if statement uses the hitTest() method to check whether the bug instance is
touching the outlet instance (
this._parent.zapper_mc). There are two possible outcomes of
the evaluation,
true or false:
• If the hitTest() method returns true, the stopDrag() method is called, the zapper_mc
variable is set to
true, the alpha and rotation properties are changed, and the zapped instance
is told to play.
• If the hitTest() method returns false, none of the code within the curly braces ({})
immediately following the
if statement runs.
The actions in the
onPress() statement execute when the mouse button is pressed over the
bug_mc instance. The actions in the onRelease() statement execute when the mouse button is
released over the
bug_mc instance.
The
startDrag() action lets you drag the ladybug. Because the script is attached to the bug_mc
instance, the keyword
this indicates that it is the bug instance that is draggable:
bug_mc.onPress = function() {
this.startDrag();
};
The stopDrag() action stops the drag action:
bug_mc.onRelease = function() {
this.stopDrag();
};
To watch the SWF file play, see this section in Using ActionScript Help in Flash.