Solve the problem of qt.qpa.plugin: Could not load the Qt platform plugin "xcb" in Qt under Ubuntu 18.04

Problem Description

After installing Qt5.15.0, an error pops up when running a test case:

qt.qpa.plugin: Could not load the Qt platform plugin "xcb" in "" even though it was found.
This application failed to start because no Qt platform plugin could be initialized. Reinstalling the application may fix this problem.

Available platform plugins are: eglfs, linuxfb, minimal, minimalegl, offscreen, vnc, xcb.

Aborted (core dumped)

According to the problem description, the Qt platform plug-in "xcb" can be found but cannot be loaded. Although it is said that reinstalling may solve the problem, if this is possible, try to use it as the last option.

Positioning Problem

Modify the configuration file ~/.bashrc:

$ vim ~/.bashrc

Adding the following statement at the end will list detailed error messages when qtcreator is started.

export QT_DEBUG_PLUGINS=1

as follows:

Save and exit editing to make the configuration file effective:

$ source ~/.bashrc

When starting qtcreator, the following detailed error message will pop up:

At the bottom of the printed error message, the real cause of the error was found:

That is the problem of Qt dynamic link library. When loading libqxcb.so library, you also need to load libxcb-xinerama library.
Switch to the directory where the error libxcb.so is located:

#Replace with your own error directory$ cd /home/brainiac/Qt/Tools/QtCreator/lib/Qt/plugins/platforms/

Run ldd libqxcb.so to view the associated content:

$ ldd libqxcb.so 

It was found that the libxcb-xinerama.so.0 library does not exist.

Workaround

Install the libxcb-xinerama library:

#If there are other dependent libraries that have not been installed, install them as well.
$ sudo apt-get install libxcb-xinerama0

After the installation is complete, check the associated content again and find that the problem has been fixed:

$ ldd libqxcb.so 

Run the qt program again and it will run normally.

postscript

I can happily code again.

Summarize

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