A collection of tutorials and walkthrough guides are provided with Qt to help new users Qt Creator Manual - The manual contains information on how to achieve training material are available as videos, downloadable code, and PDF files. You can use Qt Creator to create applications for several platforms by using several technologies. The tutorials in this manual explain how to create some basic. Remark: This tutorial series target mainly Qt4. Even if most of these tutorials are Before writing our first GUI app, let's discover Qt Creator.
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Get pass the Hello World state and learn some basic Qt programming idioms. • You can find everything in this guide on . Using Qt on Linux with the Creator. Qt is a complete C++ application development framework, including. – A comprehensive C++ class library. – RAD GUI development tool (Qt Designer). 3 Qt Creator IDE. In the background, Qt Creator runs qmlscene and passes your QML document as the first argument. The qmlscene.
Let's say while playing a song, a progress bar is needed to show how much time remains before the song is over. A media player might have a class that is used to check the progress of the media.
An instance of this class might periodically send a tick signal, with the progress value.
This signal can be connected to a QProgressBar , that can be used to display the progress. The hypothetical class used to check the progress might have a signal that have this signature:. You can see that the signal and the slot have the same kind of parameters, especially the type. If you connect a signal to a slot that does not share the same kind of parameters, when the connection is done at run-time you will get a warning like:.
This is because the signal transmits the information to the slot using the parameters. The first parameter of the signal is passed to the first one of the slot, and the same for second, third, and so forth. You may also provide the name of the variable if you want. It is actually even better.
Remember our button app? Let's try to actually make something with this app, like being able to close it while clicking on the button. We already know that QPushButton provides the clicked signal.
We also have to know that QApplication provides the quit slot, that closes the application. In order to make a click on a button close the app, we have to connect the signal clicked of the button to the quit slot of QApplication instance. We can modify the code from the previous chapter to do this, but before that, you might wonder how to access to the QApplication instance while you are in another class.
Actually, it is pretty simple, since there exists a static function in QApplication , with the following signature, that is used to get it:. Here is a simpler example for information transmission. It only displays a progress bar and a slider created by QSlider inside a window, and while the slider is moved, the value of the progress bar is synced with a very simple connection.
QSlider automatically emits the signal valueChanged with the new value passed as a parameter when the value is changed, and the method setValue of QProgressBar, is used, as we have seen, to set the value of the progress bar.
This section can be skipped for now if you only want to program with Qt. If you want to know how Qt works, it is better to read this. Qt provides a meta-object system.
To use such meta-object capabilities in an application, one can subclass QObject and mark it so that the meta-object compiler moc can interpret and translate it.
Code produced by moc includes signals and slots signatures, methods that are used to retrieve meta-information from those marked classes, properties handling All this information can be accessed using the following method:. QMetaObject class contains all the methods that deal with meta-objects.
When a signal is emitted, the meta-object system is used to compare the signature of the signal, to check the connection, and to find the slot using it's signature. These macros are actually used to convert the provided method signature into a string that matches the one stored in the meta-object. Creating custom slots and signals is really simple.
Slots are like normal methods, but with small decorations around, while signals need little to no implementation at all. In order to implement a slot, we first need to make the class be able to send signals and have slots see the previous chapter. After that, a slot should be declared in the corresponding section, and implemented as a normal method.
Signals should also be declared in the signals section, and there is no need for them to be implemented.
Note that in order to send signals that have parameters, you have to pass them in the signal emission:. We might want to remove our previous connection that makes the application quit while clicking the button. Now, we want that, when clicking on the button, the text is changed.
More precisely, we want that the button can be checked , and that, when checked, it displays "checked", and when unchecked, it restores "Hello World". QPushButton does not implement such a specific slot, so we have to implement it on our own. We also add our custom slot.
Since we are trying to react from the button being checked, and since the corresponding signal is. Most of the time, by convention, we implement private and protected slots by prefixing them with "slot". Here, we are not interested in exposing this slot as a public function, we can make it private.
The new header is then. We need to make the button checkable, and establish the connection, we have to add this code in the constructor:.
Based on the previous example, we want to close the application if the button is clicked checked or unchecked 10 times.
We first need to implement a counter that will count the number of clicks. These modifications implement it:. Even if the signal is declared as a method, there is no need to implement it. The meta-object compiler is used to do this. This is because of the meta-object compiler not being run on a class that should have meta-object.
Radio button is a standard GUI component. It is often used to make a unique choice from a list. In Qt, the QRadioButton is used to create radio buttons. All properties of the QPushButton are also the same in the QRadioButton, and everything that was learned in the second chapter can be reused here.
By default, QRadioButtons are not grouped, so many of them can be checked at the same time. In order to have the "exclusive" behaviour of many radio buttons, we need to use QButtonGroup.
This class can be used like this: We allocate a new button group and attach it to the parent object. Note that the parent object might be the mainwindow, or "this":.
What we want is to create a menu picker. In a window, a list of yummy plates should be displayed with radio buttons, and a push button that is used to select the chosen plate should be displayed. Here is an example about signals and slots. We are going to write an application with two buttons. The first button should display information about Qt.
You can also add icons on the buttons, or resize them. Obviously, the "Quit" button should be more important, so why not make it bigger? Qt documentation is a very valuable piece of information. It is the place to find everything related to Qt. But, Qt documentation is not a tutorial on how to use Qt. It is a collection of all information related to classes, as well as some examples. Click on "Download". The website will ask you a few questions to determine whether you want the Open Source or commercial versions of Qt.
Once downloaded, run the installer program. You will probably need to accept the Windows dialog that requests permission to run the installer. The installer will come up. Hit Next. If you have a Qt online account, enter the information here. If you want to create one, go ahead. Otherwise just select Skip to proceed. Click Next. It will now download information about the available components from a remote server.
Pick the installation folder the default is normally fine unless you need more disk space on another drive. A path with spaces in it or that is very long may cause problems later, so avoid doing that. Let's do a minimal install. If you want more components you can select them.
I expanded Qt 5. The only other item I selected was under Tools, where Qt Creator 4. Next read and accept the license agreement. Then pick the Start menu shortcuts you want. Feel free to play around with the various mechanisms for aligning and arranging these widgets. There are lots of fun springy Spacer tools as well as vertical, horizontal, grid, and form Layouts.
You may also want to play with setting the Size Constraints for some of your widgets like buttons in conjunction with these layouts. Note that again, the header and source les are automatically declared for you: 3. To do so, select the spin box you want to limit, and then scroll to the bottom of the Property Value window the lower righthand corner.
The three methods we will need to include are: initializeGL which will be called to initialize the GL Context resizeGL which will be called when the widget is resized There you can set the minimum and maximum values for each spin box, as well as the number of decimals and the size of each step.
We recommend: Sides: ranging [3, 60] Radius: ranging [1, 5] with 1 decimal place, and each step being 0. To do this, lets add a new class to the project by selecting: File New File or Project Notice how the header le is automatically lled in for you, and click Add.
For clarity, lets rename this object to panelGL: 5. Unfortunately, you will notice that the changeSides int method isnt available from the list of slots, and so you will need to add it by clicking Edit Now, to add some functionality! Using this same method, congure another connection so that: when the Radius spin box has its valueChanged double , the changeRadius double method is called.
Now its nally time to make those buttons do something. While still in the Design editor, select: Filling in Functions Youll notice that every object now has a blue box around it, and youre able to click and drag arrows to indicate interactive relationships.
Well start with an easy one: 5. We will leave the coding of the straightforward methods changeSides int s and changeRadius double r to you without additional instruction, and move on to the more interesting OpenGL methods.