How to use CompleteThis keyboard shortcuts continuely

Hi , I am a new to QT , now I have encountered a problem when use Qt creator.

when I editing a C++ file, I usually use the "CompleteThis" shortcuts to auto complete codes, it is very convenient,

But the function can not use continually, for example ui->txt1->document()->setHtml("aaaaaaa");
txt1 is a QTextEdit*. when I type "." after ui it will change to "->" automatically and the autocomplete code will show:Attachment 7858
but after "txt1" I type "." there is nothing promoted,

What should I do ? Thanks

Did you remember to #include <QTextEdit> or whatever txt1 is?

Thanks wysota, I have include QTextEdit