qt.qpa.plugin error suddenly occurs after I remove Qt backup folder.

Aaron Kim · 12 Jun 2018, 02:47

Recently I struggled with correctly installing Qt again.
In this post, I managed to solve it by copying all the dlls which were correctly installed from the folder which was installed with offline installer (I'll call it "backup folder")
So, there were two folders, one was installed with online installer, and the latter one was done with offline one.
It seems that these two folders have no connection at all. So, I deleted the backup folder and I suddenly got the following error.

qt.qpa.plugin: Could not find the Qt platform plugin "windows" in ""
This application failed to start because no Qt platform plugin could be initialized. Reinstalling the application may fix this problem.

It is quite disconcerting that the original one (online-installed) is affected by the backup one(offline-installed).
What can be the problem?

dheerendra · 6 Dec 2018, 03:00

It is possible that your knowledget something else was working. Can you check the directory <QtInstall>/plugins/platform ? Does this exist ? Does it have windows.dll ?

Aaron Kim · wrote on 6 Dec 2018, 03:00

This post is deleted!

Aaron Kim · wrote on 6 Dec 2018, 03:00

@dheerendra Do you mean qwindows.dll & qwindowsd.dll? Or just windows.dll?
If you mean the latter one, it does not exist.

dheerendra · 6 Dec 2018, 04:56

qwindows.dll & qwindowsd.dll in plugin directory ?

Aaron Kim · wrote on 6 Dec 2018, 04:56

@dheerendra In Qt/5.11.3/mingw53_32/plugins/platforms

dheerendra · 6 Dec 2018, 08:04

Ok.You have qwindows.dll & qwindowsd.dll in Qt/5.11.3/mingw53_32/plugins/platforms. Did you copy these from different installation ?

Aaron Kim · wrote on 6 Dec 2018, 08:04

@dheerendra Maybe that would be the reason. I just installed the new one and it works. Thanks!

dheerendra · wrote on 6 Dec 2018, 08:07

This is what I was suspecting. Since you copied from smoother place(which I knew), it caused the issue. Enjoy the Qt coding.