Qt QML应用程序在使用库中定义的小部件时崩溃。

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英文:

Qt QML app crashing using gadgets defined in a library

问题

在你提供的代码和描述中，问题似乎出现在你尝试使用QML中的obj.bar.x时，应用程序崩溃，而不是obj.foo.x。根据你提供的信息，这可能是由于Bar类型没有正确注册为Qt元类型而引起的。

为了正确注册Bar类型，你可以在foo项目的代码中添加以下行：

  1. #include <QMetaType>
  2. Q_DECLARE_METATYPE(Bar)

然后，在main.cpp的main函数之前，添加以下行，以确保Bar类型在使用前已注册：

  1. qRegisterMetaType<Bar>();

这应该解决你遇到的问题，因为它会正确注册Bar类型，以便在QML中使用它。如果问题仍然存在，可能需要仔细检查项目的配置和代码，确保没有其他问题导致崩溃。

英文:

Given two CMake subprojects: foo and bar, I want to define Q_GADGET in bar and use it in foo, but the application crashes when accessing a QObject property of type Bar (defined in bar project).

foo CMakeLists, created by QtCreator, I just added SOURCES / HEADER and added bar to target_link_libraries:

  1. cmake_minimum_required(VERSION 3.16)
  3. project(foo VERSION 0.1 LANGUAGES CXX)
  5. set(CMAKE_CXX_STANDARD_REQUIRED ON)
  7. find_package(Qt6 6.5 REQUIRED COMPONENTS Quick)
  9. qt_standard_project_setup(REQUIRES 6.5)
  11. set(SOURCES
  12.     # cmake-format: sort
  13.     main.cpp
  14.     foo.cpp
  15.     fooobjectwithbarproperty.cpp
  16. )
  18. set(HEADER
  19.     # cmake-format: sort
  20.     fooobjectwithbarproperty.h
  21.     foo.h
  22. )
  24. qt_add_executable(appfoo
  25.     main.cpp
  26. )
  28. qt_add_qml_module(appfoo
  29.     URI foo
  30.     VERSION 1.0
  31.     QML_FILES Main.qml
  32.     SOURCES
  33.         ${SOURCES}
  34.         ${HEADER}
  35. )
  37. set_target_properties(appfoo PROPERTIES
  38.     MACOSX_BUNDLE_GUI_IDENTIFIER my.example.com
  39.     MACOSX_BUNDLE_BUNDLE_VERSION ${PROJECT_VERSION}
  40.     MACOSX_BUNDLE_SHORT_VERSION_STRING ${PROJECT_VERSION_MAJOR}.${PROJECT_VERSION_MINOR}
  41.     MACOSX_BUNDLE TRUE
  42.     WIN32_EXECUTABLE TRUE
  43. )
  45. target_link_libraries(appfoo
  46.     PUBLIC Qt6::Quick bar
  47. )
  49. install(TARGETS appfoo
  50.     BUNDLE DESTINATION .
  51.     LIBRARY DESTINATION ${CMAKE_INSTALL_LIBDIR}
  52.     RUNTIME DESTINATION ${CMAKE_INSTALL_BINDIR}
  54. )

bar CMakeLists:

  1. cmake_minimum_required(VERSION 3.14)
  3. project(bar LANGUAGES CXX)
  6. set(CMAKE_AUTOUIC ON)
  7. set(CMAKE_AUTOMOC ON)
  8. set(CMAKE_AUTORCC ON)
  9. set(CMAKE_CXX_STANDARD 17)
  10. set(CMAKE_CXX_STANDARD_REQUIRED ON)
  12. find_package(QT NAMES Qt6 Qt5 REQUIRED COMPONENTS Core)
  13. find_package(Qt${QT_VERSION_MAJOR} REQUIRED COMPONENTS Core)
  15. add_library(bar SHARED
  16.   bar_global.h
  17.   bar.cpp
  18.   bar.h
  19. )
  21. target_link_libraries(bar PRIVATE Qt${QT_VERSION_MAJOR}::Core)
  23. target_compile_definitions(bar PRIVATE BAR_LIBRARY)

top-level CMakeLists:

  1. cmake_minimum_required(VERSION 3.26.0)
  3. project(
  4.     FooBar
  5.     VERSION 0.0.1
  6.     DESCRIPTION &quot;Demo for Qt issue&quot;
  7.     LANGUAGES CXX)
  9. set(CMAKE_CXX_STANDARD 20)
  11. add_subdirectory(foo)
  12. add_subdirectory(bar)

My QObject, defined in foo, looks like this:

  1. class FooObjectWithBarProperty : public QObject
  2. {
  3.     Q_OBJECT
  4.     Q_PROPERTY(Bar bar READ getBar WRITE setBar NOTIFY barChanged)
  5.     Q_PROPERTY(Foo foo READ getFoo WRITE setFoo NOTIFY fooChanged)
  7. public:
  8.     const Bar getBar() const {
  9.         return _bar;
  10.     }
  12.     void setBar(const Bar&amp; bar) {
  13.         _bar = bar;
  14.         emit barChanged(_bar);
  15.     }
  17.     const Foo getFoo() const {
  18.         return _foo;
  19.     }
  21.     void setFoo(const Foo&amp; foo) {
  22.         _foo = foo;
  23.         emit fooChanged(_foo);
  24.     }
  26. private:
  27.     Bar _bar;
  28.     Foo _foo;
  30. signals:
  31.     void barChanged(const Bar&amp;);
  32.     void fooChanged(const Foo&amp;);
  33. };

Foo is defined in foo, while Bar is defined in Bar, they both look exactly the same:

  1. struct Foo
  2. {
  3.     Q_GADGET
  4.     Q_PROPERTY(double x MEMBER x)
  5.     Q_PROPERTY(double y MEMBER y)
  7. public:
  8.     double x, y;
  9. };

Given the following setup in main.cpp:

  1. QQmlApplicationEngine engine;
  2. engine.rootContext()-&gt;setContextProperty(&quot;obj&quot;, new FooObjectWithBarProperty());

I added a Text item into my Main.qml that looks like this:

  1. Text {
  2.     anchors.centerIn: parent
  3.     text: obj.foo.x
  4. }

This correctly displays 0. If I change the binding too obj.bar.x the app crashes:
Qt QML应用程序在使用库中定义的小部件时崩溃。

Stacktrace here suggest the metatype for Bar is not correctly registered, but I don't know how to correctly register it. I've tried qRegisterMetaType<Bar>, Q_DECLARE_METATYPE(Bar) in both foo or bar, I experimented a bit with QML_FOREIGN, but the docs are very sparse on it. All to no avail.

What is the necessary change here, and why?

Repo for this is available at https://github.com/marcinjakubowski/foo_bar_qt_issue

答案1

得分: 0

由于bar的CMakeLists文件中的这行代码：

  1. find_package(QT NAMES Qt6 Qt5 REQUIRED COMPONENTS Core)

它会寻找Qt6和Qt5，并且由于某些原因选择了Qt5来生成moc（元对象编译器）文件，这也可以从生成的moc_bar.cpp文件中看出：

  1. /****************************************************************************
  2. ** Meta object code from reading C++ file 'bar.h'
  3. **
  4. ** Created by: The Qt Meta Object Compiler version 67 (Qt 5.15.9)

将这行代码中的Qt5移除然后重新构建项目，问题就解决了。

英文:

As it turns out, it's because of this line in bar's CMakeLists:

  1. find_package(QT NAMES Qt6 Qt5 REQUIRED COMPONENTS Core)

It looks for Qt6 and Qt5, and, for some reason, picks Qt5 to generate moc files, as evidenced by the resulting moc_bar.cpp:

  1. /****************************************************************************
  2. ** Meta object code from reading C++ file &#39;bar.h&#39;
  3. **
  4. ** Created by: The Qt Meta Object Compiler version 67 (Qt 5.15.9)

Removing Qt5 from that find_package call and rebuilding the project makes it all work fine.

huangapple
  • 本文由 发表于 2023年5月18日 00:21:03
  • 转载请务必保留本文链接：https://go.coder-hub.com/76274226.html
  • c++
  • cmake
  • qt
  • qt6
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