qt.qpa.plugin:Could not load the Qt platform plugin “xcb“

Prompt information: 

QObject::moveToThread: Current thread (0x563e8bd48ed0) is not the object's thread (0x563e8ced9cf0).
Cannot move to target thread (0x563e8bd48ed0)

qt.qpa.plugin: Could not load the Qt platform plugin "xcb" in "/home/zxq/anaconda3/envs/open3d/lib/python3.9/site-packages/cv2/qt/plugins" 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: xcb, eglfs, linuxfb, minimal, minimalegl, offscreen, vnc, wayland-egl, wayland, wayland-xcomposite-egl, wayland-xcomposite-glx, webgl.

The error message mentions ""/home/zxq/anaconda3/envs/open3d/lib/python3.9/site-packages/cv2/qt/plugins"

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 Solution 1 : First, follow the suggestion of the prompt message "Reinstalling the application may fix this problem." Uninstall the original opencv, which can generally be solved.

pip uninstall opencv-python opencv-contrib-python

// 安装新的opencv 下面这两个都行，最新版本不行。
pip install opencv-python==3.4.3.18 opencv-contrib-python==3.4.3.18
pip install opencv-python==4.0.0.21 opencv-contrib-python==4.0.0.21

Solution 2 : Delete the libqxcb.so file in the above directory

Solution 3 : Another solution tried, uninstall python3.9, install python3.7