a simple program using ActiveX controll developed with activeqt need to force close

I had write a simple program using ActiveX controll. The ActiveX controll is just an activeqt example of Qt 5.1.1, named 'hierarchy'. The program works well. However, when try to click close button to close the program, I found it still work background. So I need to kill it used task manager. Besides, I try to use microsoft 'media player' controll instead of 'hierarchy', it can be closed normally. What is the problem?