How To Use Pyqt Signals And Slots
Design multiple windows in designer
To jump, of course, there must be multiple windows, so we design another window in designer. When we click the login button in the main interface, we will jump to this window.
The method is the same. Drag the control, save it as a. ui file after it is designed, and then convert the. ui file to a. py file.
Add signals and slots. On the control where you want to add a signal, add a statement. For example, we add a signal to the login button with the object name as the pushButton to connect to the open slot function, which is used to open a new window. Self.pushButton.clicked.connect(self.open) self: for UI Instantiation object of MainWindow. Sending Python values with signals and slots On the #pyqt channel on Freenode, Khertan asked about sending Python values via Qt's signals and slots mechanism. The following example uses the PyQtPyObject value declaration with an old-style signal-slot connection, and again when the signal is emitted, to communicate a Python dictionary.
They are connected by signals and slots
What are signals, slots?
This is a feature of designer. The user will send a signal to guide the slot function to complete the corresponding action. Too abstract, for example.
The code for the main window looks like this.
The above statement to complete the window jump is as follows.
signal
Slot function
So to complete the jump, we have to go through the following steps:
1. Add signals and slots
On the control where you want to add a signal, add a statement. For example, we add a signal to the login button with the object name as the pushButton to connect to the open() slot function, which is used to open a new window.
- self: for UI_ Instantiation object of MainWindow
- pushbutton: the object name of the login button
- Click: signal means to send the signal to the slot function when the user clicks the login button
- Slot and signal connection functions: connect
- open: slot function, that is, after receiving the signal, the function is called.
- Import: is the name of the new window, tiaozhuan.py .
In addition, when opening a new window, we need to close the original login window. In the same way, add a signal on the login button.
signal
Slot function
It is important to note that the close() method must be called with the real instantiated object when closing the window. It can't be replaced by self.
2. Modify the called window
Two modifications are needed:
class Ui_MainWindow(QMainWindow): change the object to QMainWindow
def __init__(self): ා add initialization function super (UI)_ MainWindow,self).__ init__ () self.setupUi (self)
Add initialization function to class
3. Run the main window
Directly run the main window, you can see the heart of the GUI!
Note: in this case, if you want to run the program, you have to add a file.
Because in the tiaozhuan.py In this window, we introduce three pictures. How to solve this problem, put the resource file in the tiaozhuan.py File in the same directory.
Resource file code link: (put a piece of words, the article is too long to send out... )
https://download.csdn.net/download/leidawangzi/13613277
How to get the resource file? Moving on to the next section, we'll learn how to add pictures to the control.
Bibliography: Python GUI design (PyQt5 from introduction to practice) - tomorrow Technology
Introduction
How To Use Pyqt Signals And Slots Using
Remember old X-Windows call-back system? Generally it isn't type safe and flexible. There are many problems with them. Qt offers a new event handling system: signal-slot connections. Imagine an alarm clock. When alarm is ringing, a signal is being sent (emit). And you're handling it in a slot.
- Every QObject class may have as many signals and slots as you want
- You can emit signals only from within that class, where the signal is located
- You can connect signal with another signal (make chains of signals);
- Every signal and slot can have unlimited count of connections with other.
- ATTENTION! You can't set default value in slot attributes e.g. void mySlot(int i = 0);
Connection
You can connect signal with this template:
QObject::connect (
);
You have to wrap const char * signal and const char * method into SIGNAL() and SLOT() macros.
And you also can disconnect signal-slot:
QObject::disconnect (
);
Deeper
Widgets emit signals when events occur. For example, a button will emit a clicked signal when it is clicked. A developer can choose to connect to a signal by creating a function (a slot) and calling the connect() function to relate the signal to the slot. Qt's signals and slots mechanism does not require classes to have knowledge of each other, which makes it much easier to develop highly reusable classes. Since signals and slots are type-safe, type errors are reported as warnings and do not cause crashes to occur.
For example, if a Quit button's clicked() signal is connected to the application's quit() slot, a user's click on Quit makes the application terminate. In code, this is written as
connect(button, SIGNAL (clicked()), qApp, SLOT (quit()));
Connections can be added or removed at any time during the execution of a Qt application, they can be set up so that they are executed when a signal is emitted or queued for later execution, and they can be made between objects in different threads.
The signals and slots mechanism is implemented in standard C++. The implementation uses the C++ preprocessor and moc, the Meta Object Compiler, included with Qt. Code generation is performed automatically by Qt's build system. Developers never have to edit or even look at the generated code.
In addition to handling signals and slots, the Meta Object Compiler supports Qt's translation mechanism, its property system, and its extended runtime type information. It also makes runtime introspection of C++ programs possible in a way that works on all supported platforms.
To make moc compile the meta object classes don't forget to add the Q_OBJECT macro to your class.