PySide——Python圖形化界面入門教程(三)

PySide——Python圖形化界面入門教程(三)

　　　　　　　　　　　　　　 ——使用內建新號和槽

　　　　　　　　　　　　　　——Using Built-In Signals and Slots

上一個教程中，我們學習了如何創建和建立交互widgets，以及將他們布局的兩種不同的方法。今天我們繼續討論Python/Qt應用響應用戶觸發的事件：信號和槽。

當用戶執行一個動作——點擊按鈕，選擇組合框的值，在文本框中打字——這個widget就會發出一個信號。這個信號自己什么都不做，它必須和槽連接起來才行。槽是一個接受信號的執行動作的對象。

 

連接內建PySide/PyQt信號

Qt widgets有許多的內建信號。例如，當QPushButton被點擊的時候，它發出它的clicked信號。clicked信號可以被連接到一個擁有槽功能的函數（只是一個概要，需要更多內容去運行）

@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()裝飾（decorator）在clicked_slot()的定義上方，盡管它不是嚴格需要的，但它提示C++ Qt庫clicked_slot應該被調用。（更多decorators的信息參見http://www.pythoncentral.io/python-decorators-overview/）我們之后會了解到@Slot宏更多的信息。現在，只要知道按鈕被點擊時會發出clicked信號，它會調用它連接的函數，這個函數生動的輸出“Ouch！”。

我們接下來看看QPushButton發出它的三個相關信號，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_()

當你點擊應用的按鈕時，它會輸出

pressed
released
clicked

pressed信號是按鈕被按下時發出，released信號在按鈕釋放時發出，最后，所有動作完成后，clicked信號被發出。

 

完成我們的例子程序

現在，很容易完成上一個教程創建的例子程序了。我們為LayoutExample類添加一個顯示問候信息的槽方法。

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

 我們使用recipient QLineEdit的text()方法來取回用戶輸入的文本，salutation QComboBox的currentIndex()方法獲得用戶的選擇。這里同樣使用Slot()修飾符來表明show_greeting將被作為槽來使用。然后，我們將按鈕的clicked信號與之連接：

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

最后，例子像是這樣：

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()

運行它你會發現點擊按鈕可以產生問候信息了。現在我們知道了如何使用我們創建的槽去連接內建的信號，下一個教程中，我們將學習創建並連接自己的信號。

 

By Ascii0x03

轉載請注明出處：http://www.cnblogs.com/ascii0x03/p/5499507.html