(Qt 5.4.1) This application failed to start because it could not find or load the Qt platform plugin "xcb"

Question

I reinstalled my ubuntu 14.04 and Qt 5.4.1 and Qtcreator.

Qt 5.4.1 was built from source with "-opensource -nomake-test -nomake-example" configure options.

When I open an old project in QtCreator and build it everything's OK.

But when I run this project it shows:

This application failed to start because it could not find or load the Qt platform plugin "xcb".

Available platform plugins are: linuxfb, minimal, offscreen, xcb.

Reinstalling the application may fix this problem. Aborted (core dumped)

So I googled this problem and tried everything. I installed every packages (libxcb series) but nothing can help!

Somebody help me please...

I tried your methods.

When I run ldd command in platform directory, It shows:

You can see that nothing is missing. And actually I have made a softlink in the platform directory called libqxcb.so. There was no libqxcb.so in my platform directory before.

And when I run ldd command to my executable. it shows:

And you can see the error when I execute this file.

Answer 1

For a similar issue, in my case I solved with:

export QT_PLUGIN_PATH=<qt base path>/plugins

Answer 2

Try to go to the platforms folder of the Qt installation your program is using and run ldd libqxcb.so in a command prompt. Then check in the output if there are any missing dependencies. If the libqxcb.so is missing one of its dependencies this produces the output you mentioned.

You can also use the ldd command on your executable to check if there are any dependencies that can not be found.

Here is an example of what missing dependencies look like in the ldd output:

PS: the accepted answer of this question might also help you (creating a qt.conf file).