MessageDialog issue

Tikani

Hi everyone! I have a problem with launching my Windows Qt 5.7 MinGW-builded project in QtCreator.

There is an import looks like this:

import QtQuick 2.7
import QtQuick.Window 2.2
import QtQuick.Dialogs 1.2
import QtQuick.Controls 2.0

And I have a MessageDialog in my main.qml to implement typical modal MessageBox. After successful project building, when I try to launch my program in QtCreator context, application log shows:

QQmlApplicationEngine failed to load component
qrc:/main.qml:129 ??? ?MessageDialog? ??????????
qrc:/QtQuick/Dialogs/DefaultMessageDialog.qml:41 ?????? ?QtQuick.Controls? ?????? 1.2 ?? ??????????

Okay, let's check DefaultMessageDialog.qml out:

import QtQuick.Controls 1.2

I cannot remove QtQuick.Controls 2.0 from my main.qml because of using Button object on the form.

Honourable experts, what should I do with these two conflicting imports of different versions? Please, help.

p3c0

@Tikani What are the question marks ?
Also can you import QtQuick.Controls 2.0 before import QtQuick.Dialogs 1.2 and see if the same error persists?

CharlieG

Hi @Tikani,

There are Button in QtQuick.Controls 1.4... Maybe you can use this ?

If no, have you try this import import QtQuick.Controls 1.4 as ControlA ?

To finish, try with creating yourte dialog in other QML document, for example MyDialog.qml where you don't import QtQuick.Controls 2.0.

? Offline

Hi! Don't invest too much work in a "nice" solution, we get new Quick Controls 2 dialogs with Qt 5.8, see: New Features in 5.8, Qt 5.8 Release.

Tikani

@p3c0 I don't know what the question marks are since I simply copy-pasted here the contents of application log panel. I guess it is due to lack of debug information (however, it is strange, because I built the project with chosen "Debug" configuration in the bottom-left corner).

main.qml

import QtQuick 2.7
import QtQuick.Window 2.2
import QtQuick.Controls 2.0
import QtQuick.Dialogs 1.2


Window {
    visible: true
    width: 640
    height: 480
    maximumHeight: height
    maximumWidth: width
    minimumHeight: height
    minimumWidth: width
    color: "white"
    title: "Однослойный перцептрон"

    Component.onCompleted: {
        setX(Screen.width/2 - width/2)
        setY(Screen.height/2 - height/2)
        neuro.loadWeights()
    }

    property int xpos
    property int ypos
    property bool hold
    property bool clearCanvas:false

    Canvas {
        id:canvas
        anchors.top: parent.top
        width: 640
        height: 410


        onPaint: {
            var ctx = getContext('2d')

            if(clearCanvas) {
                ctx.fillStyle = "white"
                ctx.fillRect(0,0,width,height)
                clearCanvas=false

            }
            else {
                ctx.lineWidth = 30
                ctx.strokeStyle = 'blue'
                ctx.beginPath()
                ctx.moveTo(xpos,ypos)
                xpos = area.mouseX
                ypos = area.mouseY
                ctx.lineTo(xpos, ypos)
                ctx.stroke()
            }
        }

        MouseArea {
            id:area
            anchors.fill: parent
            acceptedButtons: Qt.LeftButton | Qt.RightButton

            onPressed: {
                if(mouse.buttons & Qt.LeftButton) {
                    hold=true
                    xpos = mouseX
                    ypos = mouseY
                }
            }

            onPositionChanged: {
                if(hold & (mouse.buttons & Qt.LeftButton)) {
                    canvas.requestPaint()
                }

            }

            onReleased: {
                hold = false
            }


        }
    }

    Button {
        id:recognize
        anchors.bottom: parent.bottom
        anchors.horizontalCenter: parent.horizontalCenter
        height: 50
        width: 300
        anchors.bottomMargin: 8
        text:"Распознать"

        onClicked: {
            var image = canvas.getContext('2d').getImageData(0,0,canvas.width,canvas.height)
            var norm_px = []

            for(var i = 0, n=image.data.length; i<n; i+=4) {
                if(image.data[i]===0 && image.data[i+1]===0 && image.data[i+2]===255 && image.data[i+3]===255) {
                    norm_px.push(1)
                }
                else
                {
                    norm_px.push(0)
                }
            }

            neuro.signal = norm_px

            neuro.calculate()

            if  (neuro.exitSignal===1) {
                recognitionState.text="Этот символ - тэта"
            }
            else if (neuro.exitSignal===2) {
                recognitionState.text="Этот символ - пси"
            }
            else
                recognitionState.text="Символ не распознан."

            recognitionState.open()

            canvas.requestPaint()
            clearCanvas=true
        }

    }

    MessageDialog {
        id:recognitionState
        title:"Классификация"
        icon:StandardIcon.Information
    }


}

Here I have changed the imports according to your advice but I get the same error.

main.cpp

#include <QGuiApplication>
#include <QQmlApplicationEngine>

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

    QQmlApplicationEngine engine;

    engine.load(QUrl(QStringLiteral("qrc:/main.qml")));

    return app.exec();
}

I suspect that error occurs when QQmlApplicationEngine looks through main.qml resolving dependencies recursively of given objects and when it reaches MessageDialog then it gets 2 conflicting imports. I've tried to import QtQuick.Controls 1.2 in main.qml but it gives nothing.

Tikani

@CharlieG Unfortunately, namespace tricks didn't help :( I'll try the last variant you suggested.

Tikani

@CharlieG Your last variant hasn't helped too. I will try to craft "homemade" MessageBox by combining Popup and Rectangle. Hope it can be a solution in my case.

CharlieG

@Tikani, I've tested your code and I don't have this problem on Mac OS X (build is correct). But I can't make a full test beacause it's missing neuro.

Tikani

@CharlieG You can download my project from Github and test it. You need ANN project.
P.S. When I built this project under Linux everything was OK too. I get this error on Windows only.