PySide——Python图形化界面入门教程(三)

PySide——Python图形化界面入门教程(三)

　　　　　　　　　　　　　　 ——使用内建新号和槽

　　　　　　　　　　　　　　——Using Built-In Signals and Slots

上一个教程中，我们学习了如何创建和建立交互widgets，以及将他们布局的两种不同的方法。今天我们继续讨论Python/Qt应用响应用户触发的事件：信号和槽。

当用户执行一个动作——点击按钮，选择组合框的值，在文本框中打字——这个widget就会发出一个信号。这个信号自己什么都不做，它必须和槽连接起来才行。槽是一个接受信号的执行动作的对象。

连接内建PySide/PyQt信号

Qt widgets有许多的内建信号。例如，当QPushButton被点击的时候，它发出它的clicked信号。clicked信号可以被连接到一个拥有槽功能的函数（只是一个概要，需要更多内容去运行）

@Slot()
def clicked_slot():
    ''' This is called when the button is clicked. '''
    print('Ouch!')
 
 
# Create the button
btn = QPushButton('Sample')
 
# Connect its clicked signal to our slot
btn.clicked.connect(clicked_slot)

注意@Slot()装饰（decorator）在clicked_slot()的定义上方，尽管它不是严格需要的，但它提示C++ Qt库clicked_slot应该被调用。（更多decorators的信息参见http://www.pythoncentral.io/python-decorators-overview/）我们之后会了解到@Slot宏更多的信息。现在，只要知道按钮被点击时会发出clicked信号，它会调用它连接的函数，这个函数生动的输出“Ouch！”。

我们接下来看看QPushButton发出它的三个相关信号，pressed，released和clicked。

import sys
from PySide.QtCore import Slot
from PySide.QtGui import *
 
# ... insert the rest of the imports here
# Imports must precede all others ...
 
# Create a Qt app and a window
app = QApplication(sys.argv)
 
win = QWidget()
win.setWindowTitle('Test Window')
 
# Create a button in the window
btn = QPushButton('Test', win)
 
@Slot()
def on_click():
    ''' Tell when the button is clicked. '''
    print('clicked')
 
@Slot()
def on_press():
    ''' Tell when the button is pressed. '''
    print('pressed')
 
@Slot()
def on_release():
    ''' Tell when the button is released. '''
    print('released')
 
# Connect the signals to the slots
btn.clicked.connect(on_click)
btn.pressed.connect(on_press)
btn.released.connect(on_release)
 
# Show the window and run the app
win.show()
app.exec_()

当你点击应用的按钮时，它会输出

pressed
released
clicked

pressed信号是按钮被按下时发出，released信号在按钮释放时发出，最后，所有动作完成后，clicked信号被发出。

完成我们的例子程序

现在，很容易完成上一个教程创建的例子程序了。我们为LayoutExample类添加一个显示问候信息的槽方法。

@Slot()
def show_greeting(self):
    self.greeting.setText('%s, %s!' %
                          (self.salutations[self.salutation.currentIndex()],
                          self.recipient.text()))

 我们使用recipient QLineEdit的text()方法来取回用户输入的文本，salutation QComboBox的currentIndex()方法获得用户的选择。这里同样使用Slot()修饰符来表明show_greeting将被作为槽来使用。然后，我们将按钮的clicked信号与之连接：

self.build_button.clicked.connect(self.show_greeting)

最后，例子像是这样：

import sys
from PySide.QtCore import Slot
from PySide.QtGui import *
 
# Every Qt application must have one and only one QApplication object;
# it receives the command line arguments passed to the script, as they
# can be used to customize the application's appearance and behavior
qt_app = QApplication(sys.argv)
 
class LayoutExample(QWidget):
    ''' An example of PySide absolute positioning; the main window
        inherits from QWidget, a convenient widget for an empty window. '''
 
    def __init__(self):
        # Initialize the object as a QWidget and
        # set its title and minimum width
        QWidget.__init__(self)
        self.setWindowTitle('Dynamic Greeter')
        self.setMinimumWidth(400)
 
        # Create the QVBoxLayout that lays out the whole form
        self.layout = QVBoxLayout()
 
        # Create the form layout that manages the labeled controls
        self.form_layout = QFormLayout()
 
        self.salutations = ['Ahoy',
                            'Good day',
                            'Hello',
                            'Heyo',
                            'Hi',
                            'Salutations',
                            'Wassup',
                            'Yo']
 
        # Create and fill the combo box to choose the salutation
        self.salutation = QComboBox(self)
        self.salutation.addItems(self.salutations)
        # Add it to the form layout with a label
        self.form_layout.addRow('&Salutation:', self.salutation)
 
        # Create the entry control to specify a
        # recipient and set its placeholder text
        self.recipient = QLineEdit(self)
        self.recipient.setPlaceholderText("e.g. 'world' or 'Matey'")
 
        # Add it to the form layout with a label
        self.form_layout.addRow('&Recipient:', self.recipient)
 
        # Create and add the label to show the greeting text
        self.greeting = QLabel('', self)
        self.form_layout.addRow('Greeting:', self.greeting)
 
        # Add the form layout to the main VBox layout
        self.layout.addLayout(self.form_layout)
 
        # Add stretch to separate the form layout from the button
        self.layout.addStretch(1)
 
        # Create a horizontal box layout to hold the button
        self.button_box = QHBoxLayout()
 
        # Add stretch to push the button to the far right
        self.button_box.addStretch(1)
 
        # Create the build button with its caption
        self.build_button = QPushButton('&Build Greeting', self)
 
        # Connect the button's clicked signal to show_greeting
        self.build_button.clicked.connect(self.show_greeting)
 
        # Add it to the button box
        self.button_box.addWidget(self.build_button)
 
        # Add the button box to the bottom of the main VBox layout
        self.layout.addLayout(self.button_box)
 
        # Set the VBox layout as the window's main layout
        self.setLayout(self.layout)
 
    @Slot()
    def show_greeting(self):
        ''' Show the constructed greeting. '''
        self.greeting.setText('%s, %s!' %
                              (self.salutations[self.salutation.currentIndex()],
                               self.recipient.text()))
 
    def run(self):
        # Show the form
        self.show()
        # Run the qt application
        qt_app.exec_()
 
# Create an instance of the application window and run it
app = LayoutExample()
app.run()

运行它你会发现点击按钮可以产生问候信息了。现在我们知道了如何使用我们创建的槽去连接内建的信号，下一个教程中，我们将学习创建并连接自己的信号。

By Ascii0x03

转载请注明出处：http://www.cnblogs.com/ascii0x03/p/5499507.html