[Android] Qt button issues

how to achieve a cpp file defines the button, and then in another cpp file, the button is set to false.
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< img src = "http://forum.csdn.net/PointForum/ui/scripts/csdn/Plugin/003/monkey/16.gif" alt = "" /> signal set , or set to write an interface function
can it
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is not a need to think C language that use extern keyword ?  

xxx-> ui-> button-> setEnable (false)
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you have to pass through the pointer over an object , setting what is not on the list
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is not necessary want to use C language as extern keyword ?