Full image in Background in a vBox in Flex

I was wrote the following code to set the background image in one vBox.

vBox.setStyle("backgroundImage", "PreviewBackground.png");
vBox.setStyle("backgroundAttachment", "fixed");

Wher开发者_如何学编程e the height and width of vBox was 250 x 350 and the height and width of background image was 400 x 400. The problem is that the background image doesn't show the full image. The image has cropped. How can i show the full image as a background image?

Thanks in advance.

vBox.setStyle("backgroundSize", "100%");

Checkout the backgroundSize style of Container class