How to use a QT QML C++ plugin in another application?

Question

I'm trying to wrap my head around QML plugins and I hope that someone can explain it to me because I seem to be missing something.

So I've gone ahead and created a Qt Quick 2 Extension Plugin. I have a simple source file, I've subclassed the QQmlExtensionPlugin class and registered the new type with qmlRegisterType. I've built this project and it gives me a DLL (I'm on Windows 7, and using QT 5.13). As I understand it, I should now be able to take this DLL and the qmldir file and drop into a new project and I should be able to load the QML from the DLL that is exposed via the qmldir file.

Unfortunately, when I do that, it doesn't work. All the examples I'm seeing online are showing a qml file that does an import of the plugin qml, but every time I try that, the import doesn't work and gives me a "QML module not found" error.

So my question is: How do I actually use the DLL and qmldir files in another project to expose the QML from the DLL to the new project?

GPBeta · Accepted Answer · 2019-08-27 18:15:27Z

6

It seems that you're missing the root QML import path.

The default root import path is %QTDIR%/qml, you can simply copy&paste your plugin modules into this folder so that the QML engine can find and load it.

Or a more common practice, using QQmlEngine::addImportPath()

QQmlEngine engine;
engine.addImportPath(qApp->applicationDirPath() + "/qml");

Note that you should always use Module (Namespace) Imports to import your C++ plugin module:

import My.CppModule 1.0

Using Directory Imports to import a C++ plugin module is a Undefined Behavior currently:

import "My/CppModule" // Might fail

answered Aug 27, 2019 at 18:15

GPBeta

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1 Comment

DMfiend Over a year ago

That's all it took, I copied my DLL and qmldir file to the QML import path location and it all worked. Thanks! Now I'm wondering if I can add a different QML import path location so that I don't have to copy DLLs to the QT application folder.

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