Qt-Widgets-Application: #include doesn’t work, file cannot found, , ,

Issue

This Content is from Stack Overflow. Question asked by luzylulilu

I’ve been programming with Ot for a week. Everything was fine, but since yesterday I can’t set up a new Qt widgets application or include a file.
Every time I set up a new project it looks like this:
Screenshot Editor

I get the error message that eg QMainWindow cannot be found. I also can’t include other files like string, iostream, … .
I haven’t changed anything and with the same configuration I can open & build old projects or a C++ application without qt.
Does anyone have a solution to fix this problem?



Solution

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