java.awt.IllegalComponentStateException: component must be showing on the screen to determine its location

at java.awt.Component.getLocationOnScreen_NoTreeLock(Component.java:2054)

at java.awt.Component.getLocationOnScreen(Component.java:2028)

at sun.lwawt.macosx.CAccessibility$23.call(CAccessibility.java:395)

at sun.lwawt.macosx.CAccessibility$23.call(CAccessibility.java:393)

at sun.lwawt.macosx.LWCToolkit$CallableWrapper.run(LWCToolkit.java:598)

java combobox遇到的bug 翻来覆去的测试 发现原来是mac系统的故障 真恶心 

在windows上准确无误

component must be showing on the screen to determine its location