Qt could not find the platform plugin cocoa

Question

I'm experimenting a little bit with Qt. I have successfully written a small app which works fine on my Windows 8.1 Laptop. Now I installed XCode and Qt and copied the project folder to my MacBook. The application compiles fine on my Mac but when I wan't to run it via Qt Creator I'm getting the following errors:

[qt.qpa.plugin] Could not find the Qt platform plugin "cocoa" in "" This application failed to start because no Qt platform plugin could be initialized. Reinstall application may fix this problem. 

I have read that the tool macdeployqt is needed when I want to deploy the app to other PCs. But shouldn't my application run without macdeployqt when I execute it directly with the Qt Creator?

I'm using MacOS X 10.14 with Qt 5.11.3. Xcode 10 and the MacOSX SDK 10.13 is installed and setted up correctly (at least it compiles with this SDK and without any error).

Does anyone has an idea?

Answer 1

If you are on Mac, go to the Terminal and paste the following:

pip3 install opencv-python-headless 

The Qt platform plugin requires this library to be installed.

Thanks!

Answer 2

Try setting QT_QPA_PLATFORM_PLUGIN_PATH to the plugin directory of where you installed qt.

E.g. if QT is installed in /Users/ABC/qt, then export QT_QPA_PLATFORM_PLUGIN_PATH=/Users/ABC/qt/plugins likely fixes your problem (did it for me on my brew installed qt).