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