显然，在这个例子中，按钮可以拥有默认状态、鼠标悬停(mouse - over)状态和被按下(pressed)状态。

Obviously, in this example, buttons can have a default state, a mouse-over state, and a pressed state.

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例如，如果您想在鼠标位于按钮之上以及按钮被按下的时候改变按钮上的字体，那么可以使用状态值MOUSE_OVER and PRESSED。

For example, if you want to change fonts on a button when the mouse is over it and the button is pressed, you use a state value of MOUSE_OVER and pressed.

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当鼠标事件触发的时候，鼠标哪个按钮被按下。

The button number that was pressed when the mouse event was fired.

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