Qt signals and slots in different classes. Ask Question Asked 8 years, 5 months ago. Active 4 years, 7 months ago. Viewed 21k times 5. I have a class X with a slot. Slots are assigned and overloaded using the decorator QtCore.Slot. Again, to define a signature just pass the types like the QtCore.Signal class. Unlike the Signal class, to overload a function, you don't pass every variation as tuple or list. Instead, you have to define a. (Qt) Signals and Slots. Slots Description The moc that connects objects Why Inter-object communication Exmaple Simple example of signals and slots look at. The connection mechanism uses a vector indexed by signals. But all the slots waste space in the vector and there are usually more slots than signals in an object. So from Qt 4.6, a new internal signal index which only includes the signal index is used. While developing with Qt, you only need to know about the absolute method index.
- Qt Connect Signal Slot Another Class
- Qt Signal Slot Thread
- Qt Signal Slot Different Classic
- Qt Signal Slot Parameter
- Qt Signals And Slots Tutorial
- Qt Connect Signal Slot
- Qt Signal Slot Performance
Qt5 alpha has been released. One of the features which I have been working on is a new syntax for signals and slot.This blog entry will present it.
Here is how you would connect a signal to a slot:
What really happens behind the scenes is that the SIGNAL and SLOT macros will convert their argument to a string. Then QObject::connect() will compare those strings with the introspection data collected by the moc tool.
What's the problem with this syntax?
While working fine in general, we can identify some issues:
- No compile time check: All the checks are done at run-time by parsing the strings. That means if you do a typo in the name of the signal or the slot, it will compile but the connection will not be made, and you will only notice a warning in the standard output.
- Since it operates on the strings, the type names of the slot must match exactly the ones of the signal. And they also need to be the same in the header and in the connect statement. This means it won't work nicely if you want to use
typedefor namespaces
In the upcoming Qt5, an alternative syntax exist. The former syntax will still work. But you can now also use this new way of connecting your signals to your slots:
Which one is the more beautiful is a matter of taste. One can quickly get used to the new syntax.
So apart from the aesthetic point of view, let us go over some of the things that it brings us:
Compile-time checking
You will get a compiler error if you misspelled the signal or slot name, or if the arguments of your slot do not match those from the signal.
This might save you some time while you are doing some re-factoring and change the name or arguments of signals or slots.
An effort has been made, using static_assert to get nice compile errors if the arguments do not match or of you miss a Q_OBJECT
Arguments automatic type conversion
Qt Connect Signal Slot Another Class
Not only you can now use typedef or namespaces properly, but you can also connect signalsto slots that take arguments of different types if an implicit conversion is possible
In the following example, we connect a signal that has a QString as a parameter to a slot that takes a QVariant. It works because QVariant has an implicit constructor that takes a QString Stolovi za texas holdem poker prodaja real money.
Connecting to any function
As you might have seen in the previous example, the slot was just declared as publicand not as slot. Qt will indeed call directly the function pointer of the slot, andwill not need moc introspection anymore. (It still needs it for the signal)
But what we can also do is connecting to any function or functor:
This can become very powerful when you associate that with boost or tr1::bind.
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C++11 lambda expressions
Qt Signal Slot Thread
Everything documented here works with the plain old C++98. But if you use compiler that supportsC++11, I really recommend you to use some of the language's new features.Lambda expressions are supportedby at least MSVC 2010, GCC 4.5, clang 3.1. For the last two, you need to pass -std=c++0x asa flag.
You can then write code like:
This allows you to write asynchronous code very easily.
Update: Also have a look what other C++11 features Qt5 offers.
It is time to try it out. Check out the alpha and start playing. Don't hesistate to report bugs.
I'm writing a simple port communication program. On the GUI side of the application I have a panel with 12 buttons that send signals to the parallel port interface. The communication with the port is done and working. What I need now is an automatic switching between buttons. The goal is to start kind of screensaver that will periodically activate the buttons and send signals to the port. In practice it would look like this: a timer is started for 2 minutes and if any event occurs it is restarted. Otherwise if timer reaches timeout() the qt signal is emitted, the switching begins and the buttons are automatically click()'ed with the interval of 5 seconds.
My questions are:
- How to enable a starting timer that will be reseted if any key/mouse event occurs?
- How to define a transition between the buttons with a sleep interval?
1 answers
Используйте QTimerдля части синхронизации.
Для «экранной заставки» -like один, создать таймер одного выстрела, подключить его к пользовательскому слоту ваших, и установить его интервал до двух минут.
В этом пользовательском слоте, начать второй таймер, без единого выстрела, соединенный со вторым слотом пользовательского
Qt Signal Slot Different Classic
И делать все , что вы хотите с точки зрения передачи сигналов к порту в autoClick.
Qt Signal Slot Parameter
Для отмены либо таймера, просто вызовите их stop()метод / слот.
Qt Signals And Slots Tutorial
Qt Connect Signal Slot
Для реализации «хранитель экрана» поведения, создать функцию, которая:
Qt Signal Slot Performance
- Вызовы ,
autoTimer->stop()чтобы отключить авто щелчков - Вызывает
activeTimerr->start(2*60*1000)перезапустить , что один
И называть эту функцию всякий раз , когда это необходимо. Вы можете сделать это из уже существующих слотов для кнопок, или переописать обработчик событий , как QWidget«S mouseMoveEvent, keyPressedEventи тому подобные. (Обязательно прочитайте документацию для обработчиков, некоторые требуют специальной подготовки.)
