Qt构建静态库后，丢失背景图片

问题现象：静态库项目UI属性设置qrc资源图片，显示成功，同一项目调用测试显示成功。

主程序调用静态库，无法显示背景图片。

原因及解决：

Using Resources in a Library

If you have resources in a library, you need to force initialization of your resources by calling Q_INIT_RESOURCE() with the base name of the .qrc file. For example:

MyClass::MyClass() : BaseClass()
{
    Q_INIT_RESOURCE(resources);

    QFile file(":/myfile.dat");
    ...
}

This ensures that the resources are linked into the final application binary in the case of static linking. You should put the initialization code close to where the resources are used in your library, so that clients of your library will only link in the resources if they use the feature of the library that depends on them.

Note: As the resource initializers generated by rcc are declared in the global namespace, your calls to Q_INIT_RESOURCE() also need to be done outside of any namespace.

If the library includes resources that are not used internally, but instead exposed to clients of the library, the initialization needs to happen in the application code. For example:

int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
    Q_INIT_RESOURCE(graphlib);

    QFile file(":/graph.png");
    ...
    return app.exec();
}

As before, this ensures that the resources are linked into the final application binary in the case of static linking, but also triggers loading of the library in the case of dynamic linking, such as plugins.

Similarly, if you must unload a set of resources explicitly (because a plugin is being unloaded or the resources are not valid any longer), you can force removal of your resources by calling Q_CLEANUP_RESOURCE() with the same base name as above.

Note: The use of Q_INIT_RESOURCE() and Q_CLEANUP_RESOURCE() is not necessary when the resource is built as part of the application.