Game Development Reference
In-Depth Information
addChild(buttonBackGroundBitmap);
addChild(buttonTextBitmap);
this.buttonMode = true;
this.useHandCursor = true;
}
public function changeBackGroundColor(typeval:int):void {
if (typeval == SimpleBlitButton.OFF) {
buttonBackGroundBitmap.bitmapData = offBackGroundBD;
}else {
buttonBackGroundBitmap.bitmapData = overBackGroundBD;
}
}
}
}
The class import and variable definition for the SimpleBlitButton class
The button we create is actually a
Sprite
container instance with two
Bitmap
layers. The
bottom layer is the
buttonBackGroundBitmap
. The
bitmapData
property of the
buttonBackGroundBitmap
can be easily swapped between our
offBackGroundBD
and
overBackGroundBD
BitmapData
rectangles on rollover and rollout. The text portion of the button
is the top
Bitmap
layer. It will contain the
buttonTextBitmapData
BitmapData
instance. We
create two constants to define these two basic states for the button:
public static const OFF:int = 1;
public static const OVER:int = 2;
We will create this button text in the constructor of the class. The
buttonTextBitmapData
text is
drawn into a
BitmapData
instance for display. While we could simply use
TextField
directly in the
Sprite
button, we are focusing on games in this topic. Because of this, we want to show an early
use of
Bitmaps
and
BitmapData
for animation. We will focus on this simple blit technique, because
we want to introduce a use of bitting animation early in this section. The more you are familiar
with the various uses of
BitmapData
, the more comfortable you will be as we progress through the
rest of the chapters.
We have one other variable to define in this section. It is used to “bump” the text position back to
the upper left-hand corner of the button if needed. With some fonts you might find that the text on
the button has been truncated to the right. The
positionOffset
variable can be set in the
constructor to help mitigate this issue.
The constructor definition for the SimpleBlitButton class
The constructor function for the
SimpleBlitButton
class accepts in the parameters necessary for
creating the correct size, colors and text for the Button and its two states:
OFF
and
OVER
.
This constructor for the
SimpleBlitButton
accepts these parameters:
x
value screen placement
y
value screen placement
width
of the button
