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Run the program
Before continuing, I suggest that you run the program named AppBackground01 to familiarize yourself with the screen output.
The mxml file
An XML listing for the Flex 3 application named AppBackground01 is shown in Listing 2.
<?xml version="1.0" encoding="utf-8"?><mx:Application xmlns:mx="http://www.adobe.com/2006/mxml"backgroundColor="#FF0000"
backgroundGradientColors="[#00FF00, #0000FF]"
backgroundAlpha="1.0"></mx:Application> Background color, color gradient, and transparency
The output for this application is similar to that shown in Figure 2 except that in this case, the color, color gradient, and transparency for thebackground is being controlled through the use of the following attributes:
The code in Listing 2 uses the backgroundColor attribute of the Application element to set the background color of the Flash window to purered using the hexadecimal notation #FF0000.
A few words about color
For those who may not be familiar with this concept, the overall background color is controlled by a mixture of different contributions of the red, green,and blue primary colors. For example, pure red plus pure blue produces a color commonly known as magenta . Pure green plus pure blue produces cyan . Pure red plus pure green produces yellow . Pure red plus pure green plus pure blue produces white . The absence of all three colors produces black.
Three eight-bit bytes
The values for red, green, and blue respectively are specified by the values of three eight-bit bytes. The value of each byte can range from 0 to 255decimal (00 to FF in hexadecimal) . A value of 0 (00 in hexadecimal) means that the primary color is not included in the mixture and a value of 255 (FF in hexadecimal) means that the primary color is included full strength in the mixture.
Using this scheme, it is possible to generate more than sixteen million different colors.
The order of the red, green, and blue contributions to the overall color in hexadecimal notation is RRGGBB, where the letter pairs stand for red, green, andblue respectively.
A color gradient
The Flex 3 application shown in Listing 2 sets the backgroundGradientColors attribute of the Application element to range from pure green (#00FF00) at the top of the Flash window to pure blue (#0000FF) at the bottom. As mentioned earlier, the application sets the backgroundColor to pure red using the hexadecimal notation #FF0000.
As you will see later, the Application element of a Flex 4 application doesn't have an attribute named backgroundGradientColors , so we will have to find another way to create a color gradient in the Flash window for a Flex 4 application.
Alpha
The appearance of the resulting mix of colors can be controlled by changing the value of the backgroundAlpha attribute of the Application element. This attribute can take on values ranging between 0.0 and 1.0. (In other programming systems, alpha is often allowed to vary between 0 and 255 decimal, or between 00 and FF hexadecimal.)
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