(3) Pyqt5 tutorial -- > signal and slot preliminary test

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The last one talked about how to use QTdesigner Generate ui File and convert it into py file , Finally, the effect of interface code separation is realized

The signal and slot are QT The core mechanism of , It's a high-level interface , Applied to communication between objects , It is QT The core feature of , It's also QT The important difference from other toolkits . It automatically generates the additional code needed for high-level event handling . For example, in tkinter A space in the module There is a callback function that responds to every action they can trigger , This callback function is usually a pointer to a function . however , stay QT Signals and slots in replace these function pointers .

all QObject Class can use the signal slot , Inherited from pyqt Basically, all classes in can use the signal slot mechanism .

At present, it can be understood as ： The signal is the trigger of time , And then connect this signal to the slot （ Take retail as an example , It could be something else ） Connect , for instance ： I click a button to close the window , At this time, the button click event is a signal , The window closing is the processing time after the slot receives the signal . Let's look at the following examples .

There are two ways to simply implement slots . The first is in QTdesigner Design the signal and slot well , The other is to connect with code .

The first one is ：
stay QTdesigner The connection between signal and slot is realized in

There are two objects here ：pushbutton Button and form window , Click from the button to pull a line to form It's specified anywhere that the signal will come from pushbutton Generate and send to form This object . After connecting , The pop-up window is the interface for configuring signals , I'll give it to push The configured signal is the click event , then form Object will run after it is received closed function , This time the window will close .

The following figure shows the relationship between the signal and the slot , And the sender and the receiver

QTdesigner Generated py Code ：
stay QTdesigner The connection in is embodied in self.pushButton.clicked.connect(Form.close) This line of code .

# -*- coding: utf-8 -*-

# Form implementation generated from reading ui file '02.ui'
#
# Created by: PyQt5 UI code generator 5.15.2
#
# WARNING: Any manual changes made to this file will be lost when pyuic5 is
# run again. Do not edit this file unless you know what you are doing.


from PyQt5 import QtCore, QtGui, QtWidgets
class Ui_Form(object):
    def setupUi(self, Form):
        Form.setObjectName("Form")
        Form.resize(748, 523)
        self.pushButton = QtWidgets.QPushButton(Form)
        self.pushButton.setGeometry(QtCore.QRect(90, 160, 75, 23))
        self.pushButton.setObjectName("pushButton")

        self.retranslateUi(Form)
        self.pushButton.clicked.connect(Form.close)
        QtCore.QMetaObject.connectSlotsByName(Form)

    def retranslateUi(self, Form):
        _translate = QtCore.QCoreApplication.translate
        Form.setWindowTitle(_translate("Form", "Form"))
        self.pushButton.setText(_translate("Form", "pushButton"))

Master file code ：

from ui2 import Ui_Form# Import on QTdesigner Well designed  ui.py  file 
import sys
from PyQt5 import QtWidgets


class mydesigner(QtWidgets.QWidget,Ui_Form):
    def __init__(self):
        super(mydesigner,self).__init__()
        self.setupUi(self)
        self.pushButton.clicked.connect(self.signaltest)
    def signaltest(self):
        print("haomingHu")

if __name__ == "__main__":
    app = QtWidgets.QApplication(sys.argv)
    myshow = mydesigner()
    myshow.show()
    sys.exit(app.exec_())

The code implementation connection is also very simple , To be clear, this slot can be an intrinsic member function of an object or a custom function , This custom function can be class or individual .

        self.pushButton.clicked.connect(self.signaltest)
    def signaltest(self):
        print("haomingHu")

Is to customize a print function , When you click pushbutton Button time , You can put the button's click The signal is sent to form, After receiving it, you can execute the bound event .（ The function used is connect function , Bound functions don't need to use (), You just need a function name ）
question： What if you need to transfer parameters ？ This one is a little bit winding , Let's make this clear. Please supplement it or put it in the next article .