AWTEventMulticaster.java 文件源码

public void windowGainedFocus(WindowEvent e) {
    if ((a != null) && (a instanceof WindowFocusListener)) {
        ((WindowFocusListener) a).windowGainedFocus(e);
    }
    if ((b != null) && (b instanceof WindowFocusListener)) {
        ((WindowFocusListener) b).windowGainedFocus(e);
    }
}