[SOLVED] { Qt5.0.2/QtQuick2.0/C++ } What is the right way to make a class outside main.cpp to use QtQuick2ApplicationViewer?

iviv1

I have described the question in detail in stack overflow:

http://stackoverflow.com/questions/16066428/qt5-0-2-qtquick2-0-c-what-is-the-right-way-to-make-a-class-outside-main-cp

The problem:

I want to make a C++ application that uses QML for dialog UI.

I am trying to put my UI code outside main.cpp (in a class called "Dialog"), so that I can later separate it to run in a thread.

I build & run: No errors in compilation, no errors in application output.

However, nothing shows up on the screen. But if written in main.cpp, this chunk of code shows the QML dialog correctly:

@QtQuick2ApplicationViewer viewer;
viewer.setMainQmlFile(QStringLiteral("qml/Kiosk/main.qml"));

viewer.showExpanded();@

==============================================================

I wonder why this is happening, could you please advise - what am I doing wrong?

melghawi

Looking at the code you posted on stack overflow I notice that you are creating an instance of QtQuick2ApplicationViewer on the stack.

@
void Dialog::show()
{
QtQuick2ApplicationViewer viewer;
viewer.setMainQmlFile(QStringLiteral("qml/Kiosk/main.qml"));

viewer.showExpanded();

}
@

This will go out of scope and be destroyed once your function returns.

Try this:

@
void Dialog::show()
{
QtQuick2ApplicationViewer *viewer = new QtQuick2ApplicationViewer;
viewer->setMainQmlFile(QStringLiteral("qml/Kiosk/main.qml"));

viewer->showExpanded();

}
@

You will need to retain the viewer pointer and explicitly call delete in order to avoid memory leaks.

iviv1

Thank you, @moeg687 ! This helped a lot.