How and where to start Qt5

[JKSH]

@tomy said:

I went for your link and the system is downloading it. But apparently this one is also Qt creator 5.5!

It is useful to know the difference between Qt and Qt Creator:

• Qt is the library. Qt contains the C++ classes that you can use in your app. The latest version is Qt 5.5.1.
• Qt Creator is the Integrated Development Environment (IDE). Qt Creator lets you manage multiple compilers and multiple versions of Qt. It also lets you write code and compile your app. The latest version is Qt Creator 3.6.0.

If you install Qt, it gives you the Qt library AND the Qt Creator IDE. However, Qt 5.5.1 only comes with Qt Creator 3.5.1.

If you install Qt Creator, you only get the IDE.

Right now, you already have Qt 5.5 and Qt Creator 3.5 in your system. You want to install Qt Creator 3.6, so you don't need to download Qt anymore.

Go to http://www.qt.io/download-open-source/ and click on "Qt Creator". Then, click on "Qt Creator 3.6.0 for Windows (80 MB)".

[JKSH]

After you install Qt Creator 3.6.0, you need to do some setup, because does not know about the previous version that you installed:

1. See Adding Compilers to tell Qt Creator where to find your compiler.
2. See Adding Qt Versions to tell Qt Creator where to find the Qt binaries.
3. Finally, see Adding Kits to tell Qt Creator how to combine your compiler with the Qt binaries.

[eureka]

@JKSH said:

However, Qt 5.5.1 only comes with Qt Creator 3.5.1.

I my Qt 5.5.1 installation (Ubuntu 14.04) when I click on Qt 5.5 Creator > Help
I see ... "Qt Creator 3.6.0
Based on Qt 5.5.1 (GCC 4.8.4, 32 bit)"

just to add to the confusion.

[eureka]

@JKSH said:
Right now, you already have Qt 5.5 and Qt Creator 3.5 in your system.

But surely the version of Qt shown in this link refers to Qt 5.1.0 .. not Qt 5.5?
http://uploads.im/QXBsp.png
/qt5/qt.510.win64_msvc2012_64 ... etc

[JKSH]

@eureka said:

@JKSH said:

However, Qt 5.5.1 only comes with Qt Creator 3.5.1.

I my Qt 5.5.1 installation (Ubuntu 14.04) when I click on Qt 5.5 Creator > Help
I see ... "Qt Creator 3.6.0
Based on Qt 5.5.1 (GCC 4.8.4, 32 bit)"

just to add to the confusion.

Did you use the Online installer? That lets you install multiple versions of Qt, and lets you upgrade Qt Creator to the latest version.

The Offline installer doesn't provide that. It only contains one fixed version of Qt and one fixed version of Qt Creator.

But surely the version of Qt shown in this link refers to Qt 5.1.0 .. not Qt 5.5?
http://uploads.im/QXBsp.png
/qt5/qt.510.win64_msvc2012_64 ... etc

Yes, that image shows an attempt to download Qt 5.1.0 via the Online installer.

But before that, @tomy already installed Qt 5.5.1 + Qt Creator 3.5.1 (using the Offline installer): https://forum.qt.io/topic/63499/how-and-where-to-start-qt5/21

[tomy]

@JKSH said:

After you install Qt Creator 3.6.0, you need to do some setup, because does not know about the previous version that you installed:

1. See Adding Compilers to tell Qt Creator where to find your compiler.
2. See Adding Qt Versions to tell Qt Creator where to find the Qt binaries.
3. Finally, see Adding Kits to tell Qt Creator how to combine your compiler with the Qt binaries.

Since I had the file qt-opensource-windows-x86-mingw492-5.5.1 (size = 997 MB) on my system so first I uninstalled it and tried to install Qt creator though the online method via that small file. And then when you said it's not needed to download/install Qt creator that way because I had it already, so I canceled the process and reinstalled the file above (997 MB) and then went for Qt Creator 3.6.0 for Windows (80 MB). Now I have two Qt creator icons on my desktop named Qt Creator 3.6.0 and Qt Creator (Community).
PS: When I installed the Qt creator (the 997 MB one) I selected all the options:
http://uploads.im/RuZQ9.png

Now the tasks I have done are:
For the #1 (Adding Compilers) whatever I could to do is in the link below:
http://uploads.im/5K23g.png
The Compiler path field and Platform codegen flags field are empty. I don't know the path of what file I should insert into those paths.

For the #2 (Adding Qt Versions) I did this: http://uploads.im/mgBTo.png
And for the #3 (Adding Kits) I did this: http://uploads.im/kufsC.png

Then I recreated the project and the Export icons appeared this time :-)
Isn't there any wrong done task in my works please?
And which one of the Qt creator apps should I use for my projects, Qt Creator 3.6.0 or Qt Creator (Community) from now on please?

[JKSH]

@tomy said:

Since I had the file qt-opensource-windows-x86-mingw492-5.5.1 (size = 997 MB) on my system so first I uninstalled it and tried to install Qt creator though the online method via that small file. And then when you said it's not needed to download/install Qt creator that way because I had it already, so I canceled the process and reinstalled the file above (997 MB) and then went for Qt Creator 3.6.0 for Windows (80 MB).

That's fine.

Now I have two Qt creator icons on my desktop named Qt Creator 3.6.0 and Qt Creator (Community).

Yes, that's expected.

The ideal way is to use the online installer. However, since you are experiencing errors, we won't use that. (There is a way to work around that error, but it involves lots of extra work)

PS: When I installed the Qt creator (the 997 MB one) I selected all the options:
http://uploads.im/RuZQ9.png

That's fine.

Now the tasks I have done are:
For the #1 (Adding Compilers) whatever I could to do is in the link below:
http://uploads.im/5K23g.png
The Compiler path field and Platform codegen flags field are empty. I don't know the path of what file I should insert into those paths.

For the #2 (Adding Qt Versions) I did this: http://uploads.im/mgBTo.png
And for the #3 (Adding Kits) I did this: http://uploads.im/kufsC.png

Isn't there any wrong done task in my works please?

Everything looks good! I don't see anything wrong.

And which one of the Qt creator apps should I use for my projects, Qt Creator 3.6.0 or Qt Creator (Community) from now on please?

Use Qt Creator 3.6.0, since it has more features and bugfixes.

(http://code.qt.io/cgit/qt-creator/qt-creator.git/tree/dist/changes-3.6.0.md?h=3.6 shows you all the improvements that Qt Creator 3.6.0 has, compared to Qt Creator 3.5.1)

Then I recreated the project and the Export icons appeared this time :-)

Great! :)

[tomy]

Thank you very much dear JKSH.

After finishing the design part. I went to the Adding Application Logic section of this attempt. And continued until #7 and pressed Ctrl+R to run the application.
I got these from the Application Output window:

*The program has unexpectedly finished.
C:\Users\CS\Documents\build-test1-Desktop-Debug\debug\test1.exe crashed

Starting C:\Users\CS\Documents\build-test1-Desktop-Debug\debug\test1.exe...
QML debugging is enabled. Only use this in a safe environment.
QQmlApplicationEngine failed to load component
qrc:/main.qml:25 Type MainForm unavailable
qrc:/MainForm.ui.qml:73 Syntax error

The program has unexpectedly finished.
C:\Users\CS\Documents\build-test1-Desktop-Debug\debug\test1.exe crashed

Starting C:\Users\CS\Documents\build-test1-Desktop-Debug\debug\test1.exe...
QML debugging is enabled. Only use this in a safe environment.
QQmlApplicationEngine failed to load component
qrc:/main.qml:25 Type MainForm unavailable
qrc:/MainForm.ui.qml:73 Syntax error

The program has unexpectedly finished.
C:\Users\CS\Documents\build-test1-Desktop-Debug\debug\test1.exe crashed

Starting C:\Users\CS\Documents\build-test1-Desktop-Debug\debug\test1.exe...
QML debugging is enabled. Only use this in a safe environment.
QQmlApplicationEngine failed to load component
qrc:/main.qml:25 Type MainForm unavailable
qrc:/MainForm.ui.qml:73 Syntax error

The program has unexpectedly finished.
C:\Users\CS\Documents\build-test1-Desktop-Debug\debug\test1.exe crashed
Starting C:\Users\CS\Documents\build-test1-Desktop-Debug\debug\test1.exe...
QML debugging is enabled. Only use this in a safe environment.
QQmlApplicationEngine failed to load component
qrc:/main.qml:25 Type MainForm unavailable
qrc:/MainForm.ui.qml:12 Invalid alias reference. Unable to find id "mouseArea3"*

And this is the code for my MainForm.ui.qml file:

import QtQuick 2.5
import QtQuick.Controls 1.4
import QtQuick.Layouts 1.2

Item {
    id: item1
    width: 640
    height: 480
    property alias bottomLeftRect: bottomLeftRect
    property alias topLeftRect: topLeftRect
    property alias icon: icon
    property alias mouseArea3: mouseArea3
    property alias mouseArea2: mouseArea2
    property alias middleRightRect: middleRightRect
    property alias mouseArea1: mouseArea1

    Image {
        id: icon
        x: 10
        y: 20
        source: "qt-logo.PNG"
    }

    Rectangle {
        id: topLeftRect
        width: 46
        height: 55
        color: "#808080"
        radius: 6
        anchors.left: parent.left
        anchors.leftMargin: 10
        anchors.top: icon.bottom
        anchors.topMargin: 20

        MouseArea {
            onClicked: stateGroup.state = ' '
        }
    }

    Rectangle {
        id: middleRightRect
        x: -4
        y: 9
        width: 46
        height: 55
        color: "#808080"
        radius: 6
        anchors.right: parent.right
        anchors.rightMargin: 10
        anchors.horizontalCenter: parent.horizontalCenter
        MouseArea {
             onClicked: stateGroup.state = 'State1'
        }
    }

    Rectangle {
        id: bottomLeftRect
        x: -1
        y: -3
        width: 46
        height: 55
        color: "#808080"
        radius: 6
        anchors.bottom: parent.bottom
        anchors.bottomMargin: 20
        MouseArea {
           onClicked: stateGroup.state = 'State2'
        }
        anchors.left: parent.left
        anchors.leftMargin: 10
    }
    StateGroup {
           id: stateGroup
           states: [
               State {
                   name: "State1"

                   PropertyChanges {
                       target: page.icon
                       x: page.middleRightRect.x
                       y: page.middleRightRect.y
                   }
               },
               State {
                   name: "State2"

                   PropertyChanges {
                       target: page.icon
                       x: page.bottomLeftRect.x
                       y: page.bottomLeftRect.y
                   }
               }
           ]
    }
 }

And this one is the code for my main.qml file:

import QtQuick 2.5
import QtQuick.Controls 1.4
import QtQuick.Dialogs 1.2

ApplicationWindow {
    visible: true
    title: qsTr("Transitions")
    width: 330
    height: 330

    menuBar: MenuBar {
        Menu {
            title: qsTr("File")
            MenuItem {
                text: qsTr("&Open")
                onTriggered: console.log("Open action triggered");
            }
            MenuItem {
                text: qsTr("Exit")
                onTriggered: Qt.quit();
            }
        }
    }

    MainForm {
        anchors.fill: parent
                id: page
    }

    MessageDialog {
        id: messageDialog
        title: qsTr("May I have your attention, please?")

        function show(caption) {
            messageDialog.text = caption;
            messageDialog.open();
        }
    }
}

I tried to do my best according to the instructions given by that program, but I don't know how to solve the issues.
Would you guys please help me?

[JKSH]

@tomy said:

qrc:/MainForm.ui.qml:12 Invalid alias reference. Unable to find id "mouseArea3"

What happens if you delete the line, property alias mouseArea3: mouseArea3 ? (In fact, delete the lines for mouseArea1 and mouseArea2 too)

[tomy]

Just as usual, your advice helped me. Thanks :-)

It ran, but who was the faulty? Was it me? That is, as I said, I did my best when following the instructions (and most of the work is remained still), so why did I get that error?

I asked this because my purpose is learning Qt and I need to write and run many many programs in Qt (as I have experienced it in C++ using the MS VS compiler) and I should learn them so that I be able to handle the errors for my programs.

And there should be some way to get used to dealing with those codes. I have learnt using functions, pointers, references, exceptions, classes, templates and ... from C++ but the Qt codes don't seem to be much like C++!

[Charby]

@tomy For what it worth, I have learnt QML without the editor, as I thing it help to have a better understanding of it. Furthermore the QML together with its declarative paradigm is so simple that I still never use the UI designer...Regarding your problem, it was clearly the property aliases pointing to not existing anymore elements...

[tomy]

@Charby said:

Regarding your problem, it was clearly the property aliases pointing to not existing anymore elements...

But those mouseAreas still exist in the design mode!
And why didn't the instruction tell me that they are redundant and I should remove them please!?

[tomy]

I went for doing the Adding Animation to the View part. There were problems. The more time I spend on these tutorials the more I be sure that they are not well designed (of course to me).

I appreciate all the helps of you nice guys and also even the designers of the Documentations. I think they are not a good point to start for beginners. I'm sorry for saying that but it's what I experienced through these days reading them and working on applications.

I think I had better use a book.

[JKSH]

@tomy said:

Just as usual, your advice helped me. Thanks :-)

You're welcome :)

It ran, but who was the faulty? Was it me? That is, as I said, I did my best when following the instructions (and most of the work is remained still), so why did I get that error?

It wasn't you.

Unfortunately, it looks like there is a bug in the Qt Quick Designer... it should not have left mouseArea1, mouseArea2, and mouseArea3 in MainForm.ui.qml...

the Qt codes don't seem to be much like C++!

That's because you were using QML, not C++. See http://doc.qt.io/qt-5/qmlapplications.html. QML is a new language, invented by Nokia, for creating mobile phone applications.

Back in https://forum.qt.io/topic/63499/how-and-where-to-start-qt5/13 I recommended that you start with http://doc.qt.io/qt-5/gettingstartedqt.html -- this uses C++ (although it also has a C++ widgets designer).

I'm sorry for saying that but it's what I experienced through these days reading them and working on applications.

I think I had better use a book.

No need to apologize. You genuinely had a bad experience from that tutorial, and personally I also think it's more complex than necessary.

In fact, even http://doc.qt.io/qt-5/gettingstartedqt.html is a bit more complex than necessary.

The best C++ Qt tutorial I've seen is https://doc.qt.io/archives/4.3/tutorial-t1.html -- it starts out very simple and gradually adds more features. It doesn't use a Designer, everything is pure C++ code. They even have a line-by-line walkthrough, where they explain what every bit of code does. It's a shame they removed this tutorial from recent versions of Qt.

Would you still be willing to give https://doc.qt.io/archives/4.3/tutorial-t1.html a chance? It was back in Qt 4.3, but it is still perfectly valid for Qt 5.5. If you're willing, here's what you should do:

1. In Qt Creator, go to File -> New File or Project... -> Projects -> Application -> Qt Widgets Application (not Qt Quick Controls Application)
2. Remove all the code from main.cpp. Replace it with the tutorial's code.
3. At the bottom of the tutorial, ignore the instructions about using qmake. Instead, just press "Ctrl+R" like you did with the 1st tutorial.
4. Try to do the "Exercises" part at the bottom of the tutorial.
5. Continue to do Chapters 2, 3, 4, 5, 6 and 7. (Chapter 8 onwards isn't as useful)

[tomy]

@JKSH said:

No need to apologize. You genuinely had a bad experience from that tutorial, and personally I also think it's more complex than necessary.

I do agree with you. I don't know why the designers of the documentations have arranged them that way. To me, they can very easily confuse any beginner.

In fact, even http://doc.qt.io/qt-5/gettingstartedqt.html is a bit more complex than necessary.

Exactly. I'd like to suggest the designers to have a look at the one you named "the best C++ tutorial" and rearrange their valuable contents that way to be as much useful as they can be.

The best C++ Qt tutorial I've seen is https://doc.qt.io/archives/4.3/tutorial-t1.html -- it starts out very simple and gradually adds more features. It doesn't use a Designer, everything is pure C++ code.

Yes, it really is. Thanks so much for introducing it to me. :-)
I'm in chapter 6 now and the codes are really straightforward and easy to follow. And since they are in C++, dealing with them for me is very easy and just as usual with my previous coding on MS VS while using C++.

They even have a line-by-line walkthrough, where they explain what every bit of code does. It's a shame they removed this tutorial from recent versions of Qt.

Yes. I read them and also have done all of the exercises until now. :-)

Would you still be willing to give https://doc.qt.io/archives/4.3/tutorial-t1.html a chance? It was back in Qt 4.3, but it is still perfectly valid for Qt 5.5. If you're willing, here's what you should do:

1. In Qt Creator, go to File -> New File or Project... -> Projects -> Application -> Qt Widgets Application (not Qt Quick Controls Application)
2. Remove all the code from main.cpp. Replace it with the tutorial's code.

As I said, I looked and have read this tut so far. I think I should thank you so much that you cared about me and gave me another change to work on Qt while being connected with this website. :-) You are a really nice person. :-)

3. At the bottom of the tutorial, ignore the instructions about using qmake. Instead, just press "Ctrl+R" like you did with the 1st tutorial.

But why please?
I ran cmd.exe by the start menu (of my Windows machine) then gave the path of Qt creator 3.6.0 (instead of Qt creator community) to that command prompt and then for each chapter of the tut I typed the following commands each one followed by hitting the enter key:
qmake -project
qmake
But I don't know what happened afterwards!
I read some about it but it isn't clear for me still. Let me please ask some questions on qmake!

1- Why should (not) I use qmake?
2- What is its use for?
3- When and how can I use it and get its benefits?

4. Try to do the "Exercises" part at the bottom of the tutorial.
5. Continue to do Chapters 2, 3, 4, 5, 6 and 7. (Chapter 8 onwards isn't as useful)

OK but what after chapter 7 please? Those codes are very exciting!
I also found this. Do you recommend that I go about reading it then?

[JKSH]

@tomy said:

I'd like to suggest the designers to have a look at the one you named "the best C++ tutorial" and rearrange their valuable contents that way to be as much useful as they can be.

You can submit suggestions to https://bugreports.qt.io/ (log in with the same account as you use for this forum). If you do, please post a link here so that others can follow it.

I'm in chapter 6 now and the codes are really straightforward and easy to follow.
...
I read them and also have done all of the exercises until now. :-)

Wow, you're fast. Well done!

I ran cmd.exe by the start menu (of my Windows machine) then gave the path of Qt creator 3.6.0 (instead of Qt creator community) to that command prompt and then for each chapter of the tut I typed the following commands each one followed by hitting the enter key:
qmake -project

This command asks qmake to produce a *.pro file.

qmake

This command asks qmake to read the *.pro file, and use it to produce a Makefile.

After this, you can use nmake (from Visual Studio) or mingw32-make (from MinGW) to use the Makefile to compile your program.

But I don't know what happened afterwards!
...
1- Why should (not) I use qmake?

See my answer for #3 below.

2- What is its use for?

See my answers above ("This command asks qmake to...")

3- When and how can I use it and get its benefits?

Qt Creator already gives you the benefits automatically:

• When you created a new project, Qt Creator already produced a *.pro file for you (see the top-left corner of your window when you are editing your code). So, you don't need to call qmake -project yourself.
• When you press Ctrl+R, Qt Creator calls qmake for you. first, and then runs nmake/mingw32-make for you. So, you don't need to call qmake yourself.

If you want to see this in action, create a new Qt Widgets Application project and press Ctrl+R. Then, click "Window" -> "Output Panes -> "Compile Output". Read what's there -- this is like a "command prompt".

OK but what after chapter 7 please? Those codes are very exciting!

It's great to see your enthusiasm :)

If you want to continue Chapters 7 - 14, you can. I think it is still valuable experience for learning Qt's C++ API style. However, these chapters use the Graphics View Framework (see http://doc.qt.io/qt-5/graphicsview.html for info).

I think you will not likely use the Graphics View Framework in a real project. For a desktop project, Qt Widgets are great. However, for Android/iOS projects, you should learn Qt Quick/QML.

I also found this. Do you recommend that I go about reading it then?

The updated version of this manual is at http://doc.qt.io/qt-5/qtdesigner-manual.html . This manual tells you about the Qt Widgets Designer. I don't think it's useful to read it from start to finish.

Instead, I suggest the following:

1. Do http://doc.qt.io/qtcreator/creator-writing-program.html. This is a very simple tutorial that teaches you how to use the Designer.
2. Do http://doc.qt.io/qt-5/gettingstartedqt.html. I think you should be ready to follow this tutorial without problems.
3. (Simple Exercise) Re-implement MyWidget from https://doc.qt.io/archives/4.3/tutorial-t5.html using the Qt Designer, instead of typing pure C++ code.
4. (Advanced Exercise) Re-implement LCDRange AND MyWidget from https://doc.qt.io/archives/4.3/tutorial-t6.html using Qt Designer, instead of typing pure C++ code.
   • Hint 1: You will need to create 2 separate classes in Qt Designer. Go to File -> New File or Project... -> Files and Classes -> Qt -> Qt Designer Form Class
   • Hint 2: You will need to Promote a widget. See http://doc.qt.io/qt-5/designer-using-custom-widgets.html
5. Think about your experiences so far. Which do you like better: Writing pure C++ code, or using Qt Designer? Can you see any advantages in the method that you don't like?

[tomy]

This is the link of the thread I posed the problem of the documentations on the bugreports.
https://bugreports.qt.io/browse/QTBUG-50944
I did it and hope they make some changes. :-)

Thanks for the explanations on qmake.
If I think that you know my purposes on learning Qt, in what step(s) of my road-map do you think I will need to use qmake?

Do http://doc.qt.io/qtcreator/creator-writing-program.html. This is a very simple tutorial that teaches you how to use the Designer.

I did those instructions just like what have been said. The project was good. I had no real difficulty. Although my problem is usually with the functions that are used in the source codes, but I understood all of them in this project well.
Thanks for introducing it.

Do http://doc.qt.io/qt-5/gettingstartedqt.html. I think you should be ready to follow this tutorial without problems.

This one also a good one. The outcome (of my experience) was like the previous project. But some point: I haven't learnt to use qmake still (unfortunately)! And I couldn't do the part Building and Running from the Command Line :-( The instructions are not simple and clear apparently.
If you teach me (of course if it's possible) how to use it for that project, I'll learn it for the rest.

(Simple Exercise) Re-implement MyWidget from https://doc.qt.io/archives/4.3/tutorial-t5.html using the Qt Designer, instead of typing pure C++ code.

Yes, I did it. It was just dealing with the Widgets and Properties on the Design mode. For the Signal and Slot for Lcd and Slider, I used the Edit Signals/Slots (f4) button on the toolbar and didn't wrote any code for it! I don't know it was the method you wanted I use or not.

(Advanced Exercise) Re-implement LCDRange AND MyWidget from https://doc.qt.io/archives/4.3/tutorial-t6.html using Qt Designer, instead of typing pure C++ code.
Hint 1: You will need to create 2 separate classes in Qt Designer. Go to File -> New File or Project... -> Files and Classes -> Qt -> Qt Designer Form Class
Hint 2: You will need to Promote a widget. See http://doc.qt.io/qt-5/designer-using-custom-widgets.html

I tried several ways to build a class below the other one. I also tried to understand the link and do what is needed. Since I hadn't learnt a lesson on solving exercises like this before, I couldn't rely on my guesses too much. Although I found many traces but was not able finally. The solution was somewhat vague for me. Sorry anyway.

Think about your experiences so far. Which do you like better: Writing pure C++ code, or using Qt Designer? Can you see any advantages in the method that you don't like?

I like to answer to these when I solve the advanced exercise. To be honest, I don't fear the hard exercises but what I need is to be familiar with an instance of some exercise then solve the harder one :-)

Thanks so much for your time. I'm really uncomfortable if I'm bothering you by those many questions and problems.

[JKSH]

@tomy said:

This is the link of the thread I posed the problem of the documentations on the bugreports.
https://bugreports.qt.io/browse/QTBUG-50944
I did it and hope they make some changes. :-)

Thanks for submitting!

in what step(s) of my road-map do you think I will need to use qmake?

I don't think you need to learn how to run qmake from the command line.

I haven't learnt to use qmake still (unfortunately)! And I couldn't do the part Building and Running from the Command Line :-( The instructions are not simple and clear apparently.
If you teach me (of course if it's possible) how to use it for that project, I'll learn it for the rest.

You already ran qmake. You did it when you pressed Ctrl+R in your project.

(Simple Exercise) Re-implement MyWidget from https://doc.qt.io/archives/4.3/tutorial-t5.html using the Qt Designer, instead of typing pure C++ code.

Yes, I did it. It was just dealing with the Widgets and Properties on the Design mode. For the Signal and Slot for Lcd and Slider, I used the Edit Signals/Slots (f4) button on the toolbar and didn't wrote any code for it! I don't know it was the method you wanted I use or not.

Yes, that's what I meant.

I tried several ways to build a class below the other one. I also tried to understand the link and do what is needed. Since I hadn't learnt a lesson on solving exercises like this before, I couldn't rely on my guesses too much. Although I found many traces but was not able finally. The solution was somewhat vague for me. Sorry anyway.

1. Create a LCDRange Qt Designer Form Class (lcdrange.ui).
2. Fully implement LCDRange like you did in the Simple Exercise.
3. Create a MyWidget Qt Designer Form Class (mywidget.ui).
4. Open MyWidget in Qt Designer. Drag a blank QWidget onto the MyWidget.
5. Right-click the blank QWidget and select "Promote to..."
6. Under "New Promoted Class", add
   • Base class name: "QWidget"
   • Promoted class name: "LCDRange"
   • Header file: "lcdrange.h"
   • Global include: YES
7. Click "Add"
8. Select "Promoted Classes" -> "LCDRange" and click "Promote".
9. In main.cpp, create a MyWidget object and show() it.
10. Press Ctrl+R to build and run your project. Does your LCDRange appear?
11. Open MyWidget in Qt Designer again.
12. Add 8 more blank QWidgets and promote them to LCDRanges. Put them in a grid layout.
13. Press Ctrl+R to build and run your project. Do all 9 LCDRanges appear?

I like to answer to these when I solve the advanced exercise. To be honest, I don't fear the hard exercises but what I need is to be familiar with an instance of some exercise then solve the harder one :-)

That's a good way to learn

Thanks so much for your time. I'm really uncomfortable if I'm bothering you by those many questions and problems.

No, you are not bothering me. I'm happy to teach you because you work hard. :)

[tomy]

Select "Promoted Classes" -> "LCDRange" and click "Promote".

OK until here.

In main.cpp, create a MyWidget object and show() it.

But there is no main.cpp there.
There are only mywidget.cpp and lcdrange.cpp C++ files there!
I tried to add the code snippet below into the mywidget.cpp and then run it but all of the run and build related buttons are grayed out!
I think it happend because we haven't created a complete Qt Widget Application project yet.

int main(int argc, char *argv[])
 {
     QApplication app(argc, argv);
     MyWidget widget;
     widget.show();
     return app.exec();
 }

[JKSH]

@tomy said:

I think it happend because we haven't created a complete Qt Widget Application project yet.

Yes, that's the reason. You should create a Qt Widgets Application project, and then add the Qt Designer Form Classes to that project.