QQmlApplicationEngine failed to load component

HenrikZ

The QtQuick program runs without problems on the desktop, but when I compile for an embedded linux system and afterwards try to run the program on the MCU i get the error, but the error first occurs when the program is executed in the embedded linux. There is not issues or messages during compilation. In the command prompt I get the following error.

QQmlApplicationEngine failed to load component
<Unknown File>: Module "GPIO_InputTest2" contains no type named "Main"

This could indicate that the "Main.qml" were not correctly included - The CMakeLists.txt looks like this:

cmake_minimum_required(VERSION 3.16)

project(GPIO_InputTest2 VERSION 0.1 LANGUAGES CXX)

set(CMAKE_CXX_STANDARD_REQUIRED ON)

find_package(Qt6 REQUIRED COMPONENTS Quick)

qt_standard_project_setup(REQUIRES 6.5)

qt_add_executable(appGPIO_InputTest2
    main.cpp
    VirtualInputReader.cpp
    VirtualInputReader.h
)

qt_add_qml_module(appGPIO_InputTest2
    URI GPIO_InputTest2
    VERSION 1.0
    QML_FILES
        "Main.qml"
    SOURCES
        VirtualInputReader.h
        VirtualInputReader.cpp
    RESOURCE_PREFIX /
)

# Qt for iOS sets MACOSX_BUNDLE_GUI_IDENTIFIER automatically since Qt 6.1.
# If you are developing for iOS or macOS you should consider setting an
# explicit, fixed bundle identifier manually though.
set_target_properties(appGPIO_InputTest2 PROPERTIES
#    MACOSX_BUNDLE_GUI_IDENTIFIER com.example.appGPIO_InputTest2
    MACOSX_BUNDLE_BUNDLE_VERSION ${PROJECT_VERSION}
    MACOSX_BUNDLE_SHORT_VERSION_STRING ${PROJECT_VERSION_MAJOR}.${PROJECT_VERSION_MINOR}
    MACOSX_BUNDLE TRUE
    WIN32_EXECUTABLE TRUE
)

target_link_libraries(appGPIO_InputTest2
    PRIVATE Qt6::Quick
)

include(GNUInstallDirs)
install(TARGETS appGPIO_InputTest2
    BUNDLE DESTINATION .
    LIBRARY DESTINATION ${CMAKE_INSTALL_LIBDIR}
    RUNTIME DESTINATION ${CMAKE_INSTALL_BINDIR}
)

Both main.cpp and Main.qml are added.

Any suggestions where the problem is?

HenrikZ

Issue solved

It turned out to be a single line missing in main.cpp

engine.addImportPath(":/");

Exactly why this line is needed, when the program is running on an embedded linux and not on the desktop, I am not sure, but I guess that ":/" tells the program to find the Main.qml in the same root folder as program is running from.

JoeCFD

Wayland or X11 on your embedded Linux system?

HenrikZ

Hi @JoeCFD

Wayland for the embedded linux system.

I have made other small test applications that works without problems, but this one, where I'm testing inputs does not work, and I cannot see the difference from the other the applications I have made and this one.

HenrikZ

Issue solved

It turned out to be a single line missing in main.cpp

engine.addImportPath(":/");

Exactly why this line is needed, when the program is running on an embedded linux and not on the desktop, I am not sure, but I guess that ":/" tells the program to find the Main.qml in the same root folder as program is running from.