QML Camera problem

[Lucijan]

Hello,

I have problems trying to use the QML QtMultimedia Camera but the program just crashes and displays a Messagebox:

bq. This application has requested the Runtime to terminate it in an unusual way.
Please contact the application's support team for more information.

The Application Output window displays the message:

bq. QWidget: Cannot create a QWidget without QApplication
Invalid parameter passed to C runtime function.
Invalid parameter passed to C runtime function.
D:\Qt\Programs\build-untitled5-Desktop_Qt_5_1_0_MinGW_32bit-Release\release\untitled5.exe exited with code 3

Here's the program:

@import QtQuick 2.0
import QtMultimedia 5.0

Rectangle {
width: 360
height: 360
color: "lightgrey"

Camera {
    id: bla
}

}
@

I can't seem to find anything on this problem. The webcam works fine. The platform is Win7 x64 and Qt 5.1 with MinGW.

[sierdzio]

First problem are problably some missing dependencies, search for it: I've seen it happen to many people before with MinGW. I don't know the solution myself, I'm mostly on Linux.

For the second one, please post relevant parts of your code, especially where your main() function is.

[Lucijan]

Dependencies? I didn't think this could happen if the program is run from QtCreator. I know it can happen if I try to run the program outside of QtCreator, but this is not what I'm doing.

As for the code, I didn't change anything from what Qt generates for a Qt Quick 2 program.

[sierdzio]

Something is clearly wrong. I won't help you by using my magic wand, though. You either need to check it yourself, or post more info...

[mranger90]

This is a coincidence. I just ran into this one myself. Make sure that in your driver main.cpp the app is a QApplication, NOT a QGuiApplication. Oddly, a QGuiApplication will work in Linux, but not under Win7. I think it probably has to do with what kind of widget gets generated for the underlying camera interface, i.e. DirectShow in Windows.

[Lucijan]

main.cpp

@#include <QtGui/QGuiApplication>
#include "qtquick2applicationviewer.h"

int main(int argc, char *argv[])
{
QGuiApplication app(argc, argv);

QtQuick2ApplicationViewer viewer;
viewer.setMainQmlFile(QStringLiteral("qml/untitled5/main.qml"));
viewer.showExpanded();

return app.exec();

}
@

.pro

@# Add more folders to ship with the application, here
folder_01.source = qml/untitled5
folder_01.target = qml
DEPLOYMENTFOLDERS = folder_01

Additional import path used to resolve QML modules in Creator's code model

QML_IMPORT_PATH =

If your application uses the Qt Mobility libraries, uncomment the following

lines and add the respective components to the MOBILITY variable.

CONFIG += mobility

MOBILITY +=

The .cpp file which was generated for your project. Feel free to hack it.

SOURCES += main.cpp

Installation path

target.path =

Please do not modify the following two lines. Required for deployment.

include(qtquick2applicationviewer/qtquick2applicationviewer.pri)
qtcAddDeployment()

OTHER_FILES +=
android/AndroidManifest.xml
android/res/layout/splash.xml
android/res/values/libs.xml
android/res/values/strings.xml
android/res/values-de/strings.xml
android/res/values-el/strings.xml
android/res/values-es/strings.xml
android/res/values-et/strings.xml
android/res/values-fa/strings.xml
android/res/values-fr/strings.xml
android/res/values-id/strings.xml
android/res/values-it/strings.xml
android/res/values-ja/strings.xml
android/res/values-ms/strings.xml
android/res/values-nb/strings.xml
android/res/values-nl/strings.xml
android/res/values-pl/strings.xml
android/res/values-pt-rBR/strings.xml
android/res/values-ro/strings.xml
android/res/values-rs/strings.xml
android/res/values-ru/strings.xml
android/res/values-zh-rCN/strings.xml
android/res/values-zh-rTW/strings.xml
android/src/org/kde/necessitas/ministro/IMinistro.aidl
android/src/org/kde/necessitas/ministro/IMinistroCallback.aidl
android/src/org/qtproject/qt5/android/bindings/QtActivity.java
android/src/org/qtproject/qt5/android/bindings/QtApplication.java
android/version.xml
@

In addition to switching from QGuiApplication to QApplication, it's also necessary to add QT += widgets to the .pro file.