注意，两种情况都会导致显示列表无效，因为您需要 Flex 呈现（或删除）方框周围的焦点矩形。

Note that you invalidate the display list in either case because you want Flex to render (or remove) the focus rectangle around the box.

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图5显示了最终的Flex控件的节点元素，包含了焦点矩形。

Figure 5 shows you the final version of the node element Flex control, complete with its rollover focus rectangle.

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在指定边界内使用指定文本和一个可选焦点矩形绘制指定状态的按钮控制项。

Draws a button control in the specified state and bounds, with the specified text, and with an optional focus rectangle.

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