Send variable value from .cpp to .qml

d4n1

Hello, I am collecting information from a gps (longitude and latitude) without problems. I represent this information in an lcdNumber, but I also want to send it to a .qml file to represent it in a map. After some tests I have not succeeded. Is there any simple way to do this? Do you have information about it?

I am new to using qt and qml.

Best regards

SGaist

Hi and welcome to devnet,

There's a whole chapter dedicated to that in the documentation. It should help you get started.

d4n1

Hi, I try but it doesn't work (QT 5.15.1 and MSVC2019).
The error: module "io.qt.examples.backend" is not installed.
I have tried some solutions that I have found without success. It seems to me that from version 5.15 that example should work.

SGaist

Can you show what your .pro file looks like ?

JoeCFD

one way to do it as follows:
m_qmlAppEngine->rootContext()->setContextProperty( "lcdNumber", new lcdNumber() /* your class instance*/);
define the properties with signal for example longitudeChanged() in lcdNumber and you can use lcdNumber in any qml file

d4n1

Thanks to all, finally including in the .cpp,

    connect(this, SIGNAL(<function_name>(QVariant)), obj, SLOT(<function_name>(QVariant)));

works.

I have put the headers in the .h and defined the operation in the .qml.

Thank you!

jsulm

@d4n1 said in Send variable value from .cpp to .qml:

connect(this, SIGNAL(<function_name>(QVariant)), obj, SLOT(<function_name>(QVariant)));

Just a suggestion: you should switch to Qt5 connect syntax. It has one important advantage: if you do something wrong you will get compiler error during the build instead of a warning during application runtime.