“qt.qpa.plugin：即使已找到，也无法在“”中加载 Qt 平台插件“xcb”。”

Question

我通过 Oracle VM Virtual Box 使用 Ubuntu 20.04，并且遇到了与其他人完全相同的错误。

使用官方 Qt 手册构建 Qt6 源代码后，我尝试运行不同的项目来测试一切是否正常工作。控制台类型的项目可以正常构建和运行。没有错误。不幸的是，当我尝试运行小部件类型应用程序时，它失败并出现众所周知的错误：

t.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.

我的同事在他的 Ubuntu 上可以正常运行 Qt6，他看到我libqxcb.so的 中没有.../qtbase/plugins/platforms，并与我分享了它。

不幸的是，这并没有多大帮助。只是错误消息发生了一些变化：它说找到了插件，但无法使用。

以下命令没有影响：

sudo apt install libxcb-icccm4 libxcb-image0 libxcb-keysyms1 libxcb-render-util0

此外，环境变量还有更详细的输出QT_DEBUG_PLUGINS=1：

QFactoryLoader::QFactoryLoader() checking directory path "/home/curiouspan/qt6-build/qtbase/plugins/platforms" ...
QFactoryLoader::QFactoryLoader() looking at "/home/curiouspan/qt6-build/qtbase/plugins/platforms/libqeglfs.so"
Found metadata in lib /home/curiouspan/qt6-build/qtbase/plugins/platforms/libqeglfs.so, metadata=
{
    "IID": "org.qt-project.Qt.QPA.QPlatformIntegrationFactoryInterface.5.3",
    "MetaData": {
        "Keys": [
            "eglfs"
        ]
    },
    "archreq": 1,
    "className": "QEglFSIntegrationPlugin",
    "debug": true,
    "version": 393728
}


Got keys from plugin meta data QList("eglfs")
QFactoryLoader::QFactoryLoader() looking at "/home/curiouspan/qt6-build/qtbase/plugins/platforms/libqlinuxfb.so"
Found metadata in lib /home/curiouspan/qt6-build/qtbase/plugins/platforms/libqlinuxfb.so, metadata=
{
    "IID": "org.qt-project.Qt.QPA.QPlatformIntegrationFactoryInterface.5.3",
    "MetaData": {
        "Keys": [
            "linuxfb"
        ]
    },
    "archreq": 1,
    "className": "QLinuxFbIntegrationPlugin",
    "debug": true,
    "version": 393728
}


Got keys from plugin meta data QList("linuxfb")
QFactoryLoader::QFactoryLoader() looking at "/home/curiouspan/qt6-build/qtbase/plugins/platforms/libqminimal.so"
Found metadata in lib /home/curiouspan/qt6-build/qtbase/plugins/platforms/libqminimal.so, metadata=
{
    "IID": "org.qt-project.Qt.QPA.QPlatformIntegrationFactoryInterface.5.3",
    "MetaData": {
        "Keys": [
            "minimal"
        ]
    },
    "archreq": 1,
    "className": "QMinimalIntegrationPlugin",
    "debug": true,
    "version": 393728
}


Got keys from plugin meta data QList("minimal")
QFactoryLoader::QFactoryLoader() looking at "/home/curiouspan/qt6-build/qtbase/plugins/platforms/libqminimalegl.so"
Found metadata in lib /home/curiouspan/qt6-build/qtbase/plugins/platforms/libqminimalegl.so, metadata=
{
    "IID": "org.qt-project.Qt.QPA.QPlatformIntegrationFactoryInterface.5.3",
    "MetaData": {
        "Keys": [
            "minimalegl"
        ]
    },
    "archreq": 1,
    "className": "QMinimalEglIntegrationPlugin",
    "debug": true,
    "version": 393728
}


Got keys from plugin meta data QList("minimalegl")
QFactoryLoader::QFactoryLoader() looking at "/home/curiouspan/qt6-build/qtbase/plugins/platforms/libqoffscreen.so"
Found metadata in lib /home/curiouspan/qt6-build/qtbase/plugins/platforms/libqoffscreen.so, metadata=
{
    "IID": "org.qt-project.Qt.QPA.QPlatformIntegrationFactoryInterface.5.3",
    "MetaData": {
        "Keys": [
            "offscreen"
        ]
    },
    "archreq": 1,
    "className": "QOffscreenIntegrationPlugin",
    "debug": true,
    "version": 393728
}


Got keys from plugin meta data QList("offscreen")
QFactoryLoader::QFactoryLoader() looking at "/home/curiouspan/qt6-build/qtbase/plugins/platforms/libqvnc.so"
Found metadata in lib /home/curiouspan/qt6-build/qtbase/plugins/platforms/libqvnc.so, metadata=
{
    "IID": "org.qt-project.Qt.QPA.QPlatformIntegrationFactoryInterface.5.3",
    "MetaData": {
        "Keys": [
            "vnc"
        ]
    },
    "archreq": 1,
    "className": "QVncIntegrationPlugin",
    "debug": true,
    "version": 393728
}


Got keys from plugin meta data QList("vnc")
QFactoryLoader::QFactoryLoader() looking at "/home/curiouspan/qt6-build/qtbase/plugins/platforms/libqxcb.so"
Found metadata in lib /home/curiouspan/qt6-build/qtbase/plugins/platforms/libqxcb.so, metadata=
{
    "IID": "org.qt-project.Qt.QPA.QPlatformIntegrationFactoryInterface.5.3",
    "MetaData": {
        "Keys": [
            "xcb"
        ]
    },
    "archreq": 0,
    "className": "QXcbIntegrationPlugin",
    "debug": false,
    "version": 393728
}


Got keys from plugin meta data QList("xcb")
QFactoryLoader::QFactoryLoader() checking directory path "/home/curiouspan/QtTestProjects/build-WidgetTestApp-Own_Desktop-Debug/platforms" ...
Cannot load library /home/curiouspan/qt6-build/qtbase/plugins/platforms/libqxcb.so: (libQt6XcbQpa.so.6: cannot open shared object file: No such file or directory)
QLibraryPrivate::loadPlugin failed on "/home/curiouspan/qt6-build/qtbase/plugins/platforms/libqxcb.so" : "Cannot load library /home/curiouspan/qt6-build/qtbase/plugins/platforms/libqxcb.so: (libQt6XcbQpa.so.6: cannot open shared object file: No such file or directory)"
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.

它显示该libQt6XcbQpa.so.6文件丢失。

运行ldd /home/curiouspan/qt6-build/qtbase/plugins/platforms/libqxcb.so显示依赖关系后，我得到以下输出：

linux-vdso.so.1 (0x00007fffc8770000)
    libQt6XcbQpa.so.6 => not found
    libQt6Gui.so.6 => /home/curiouspan/qt6-build/qtbase/plugins/platforms/../../lib/libQt6Gui.so.6 (0x00007f0873306000)
    libQt6Core.so.6 => /home/curiouspan/qt6-build/qtbase/plugins/platforms/../../lib/libQt6Core.so.6 (0x00007f087295d000)
    libstdc++.so.6 => /lib/x86_64-linux-gnu/libstdc++.so.6 (0x00007f087277c000)
    libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007f087258a000)
    libEGL.so.1 => /lib/x86_64-linux-gnu/libEGL.so.1 (0x00007f0872573000)
    libX11.so.6 => /lib/x86_64-linux-gnu/libX11.so.6 (0x00007f0872436000)
    libdl.so.2 => /lib/x86_64-linux-gnu/libdl.so.2 (0x00007f0872430000)
    libQt6DBus.so.6 => /home/curiouspan/qt6-build/qtbase/plugins/platforms/../../lib/libQt6DBus.so.6 (0x00007f0872262000)
    libGLX.so.0 => /lib/x86_64-linux-gnu/libGLX.so.0 (0x00007f087222e000)
    libOpenGL.so.0 => /lib/x86_64-linux-gnu/libOpenGL.so.0 (0x00007f0872202000)

所以这个文件确实丢失了。潜在的问题是什么？如何解决？

Answer 1

对于 Qt 6.5.0 版本，缺少的库是libxcb-cursor.so.0，通过以下方法解决

sudo apt install libxcb-cursor0

这样，QtCreator 中的示例小部件和 GUI 项目就可以正确运行使用 Qt 6.5.0 构建的了。Qt 6.4.0 以前不需要 libxcb-cursor.so.0。

我用这个 shell 代码识别了丢失的库

for l in /path/to/Qt/6.5.0/gcc_64/lib/*.so; do
  echo $l; objdump -p $l | grep NEEDED | sed "s/^/\t"/;
 done | grep xcb | awk '{print $2}' \
| while read lib; do echo $lib; dlocate $lib; done

这会扫描所有安装的 Qt 库，提取与 xcb 相关的所需依赖库，然后打印哪个 debian 软件包提供了每个 libxcb* 库。在我的系统上，它报告了除 libxcb-cursor.so.0 之外的每个 libxcb*.so 库的 debian 包

Answer 2

我通过在控制台中运行此命令解决了这个问题

sudo apt install libxcb-xinerama0

原始链接在这里

Answer 3

对我有帮助的最简单的方法之一是在控制台中输入：

export QT_QPA_PLATFORM=offscreen

您可以在这里阅读更多内容。我希望它能帮助你！

Answer 4

如果你在Centos，这解决了我的问题：

sudo yum install xcb-util*

Answer 5

我通过安装 PyQt5 依赖项解决了这个问题

sudo apt-get install '^libxcb.*-dev' libx11-xcb-dev libglu1-mesa-dev libxrender-dev libxi-dev libxkbcommon-dev libxkbcommon-x11-dev