ACTIONSCRIPT 3 Developer’s Guide en

ACTIONSCRIPT 3.0 DEVELOPER’S GUIDE
Display programming
import flash.events.MouseEvent;
import flash.geom.Rectangle;
// Define the initial viewable area of the TextField instance:
// left: 0, top: 0, width: TextField's width, height: 350 pixels.
bigText.scrollRect = new Rectangle(0, 0, bigText.width, 350);
// Cache the TextField as a bitmap to improve performance.
bigText.cacheAsBitmap = true;
// called when the "up" button is clicked
function scrollUp(event:MouseEvent):void
{
// Get access to the current scroll rectangle.
var rect:Rectangle = bigText.scrollRect;
// Decrease the y value of the rectangle by 20, effectively
// shifting the rectangle down by 20 pixels.
rect.y -= 20;
// Reassign the rectangle to the TextField to "apply" the change.
bigText.scrollRect = rect;
}
// called when the "down" button is clicked
function scrollDown(event:MouseEvent):void
{
// Get access to the current scroll rectangle.
var rect:Rectangle = bigText.scrollRect;
// Increase the y value of the rectangle by 20, effectively
// shifting the rectangle up by 20 pixels.
rect.y += 20;
// Reassign the rectangle to the TextField to "apply" the change.
bigText.scrollRect = rect;
}
up.addEventListener(MouseEvent.CLICK, scrollUp);
down.addEventListener(MouseEvent.CLICK, scrollDown);
As this example illustrates, when you work with the scrollRect property of a display object, it’s best to specify that
Flash Player or AIR should cache the display object’s content as a bitmap, using the cacheAsBitmap property. When
you do so, Flash Player and AIR don’t have to re-draw the entire contents of the display object each time it is scrolled,
and can instead use the cached bitmap to render the necessary portion directly to the screen. For details, see “Caching
display objects” on page 182.
Manipulating size and scaling objects
Flash Player 9 and later, Adobe AIR 1.0 and later
You can measure and manipulate the size of a display object in two ways, using either the dimension properties (width
and height) or the scale properties (scaleX and scaleY).
Every display object has a width property and a height property, which are initially set to the size of the object in
pixels. You can read the values of those properties to measure the size of the display object. You can also specify new
values to change the size of the object, as follows:
Last updated 6/6/2012
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