How to report errors from custom QML components?

Crawl.W

Today, I encounter a error:

Histogram_Plot.qml:95 Cannot assign to non-existent property "onDragChanged"

Which is report by qmlscene.exe when I preview it. But When I wanna run the whole application, I got a white window. My main() use QQmlApplicationEngine, code as following:

QQmlApplicationEngine engine;
//other coding about initializing
engine.load(QUrl(QStringLiteral("qrc:/main.qml")));

How could I locate error like qmlscene.exe reports when run application in the QtCreator.

sierdzio

Is Histogram_Plot.qml a file from your project? Then go to line 95 in that file - this is where the error lies.

Crawl.W

@sierdzio I know it. Just I need locate error when run the application and there are no hint in this mode.

JonB

@Crawl-W
https://doc.qt.io/qt-5/qqmlapplicationengine.html#load-1 says:

If an error occurs, error messages are printed with qWarning.

You could look at accessing those via https://doc.qt.io/qt-5/qtglobal.html#qInstallMessageHandler.

Or, what about https://doc.qt.io/qt-5/qqmlengine.html#warnings.

?

Crawl.W

@JonB said in How to report errors from custom QML components?:

uld look at accessing tho

I tried the following code：

QQmlApplicationEngine engine;
QObject::connect(&engine, &QQmlApplicationEngine::warnings, [](const QList<QQmlError> warnings){qDebug() << warnings;});

But, I got nothing.May there are no QQmlError being reported.
Have you encountered such a problem? Any tricks?

JonB

@Crawl-W
Then you do need to go down the https://doc.qt.io/qt-5/qtglobal.html#qInstallMessageHandler link route I showed you first. All qWarning() etc. messages go via this. You can write your own interceptor code and do whatever you want with the messages.

Crawl.W

@JonB said in How to report errors from custom QML components?:

. messages go via this. You can write your own interceptor code and do whatever you want with the messages.

Still can't catch any exceptions. Direct run does not seem to do the inspection of qml objects, but qmlscene.exe does.

GrecKo

Maybe there's no error, try adding an obvious syntax error in your code and watch the log.

Warning and errors are written to the console output by default.

Crawl.W

@GrecKo Same code with qmlscene.exe will report error and can not preview UI.