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）

1 @Slot()2 defclicked_slot():3 '''This is called when the button is clicked.'''

4 print('Ouch!')5

6

7 #Create the button

8 btn = QPushButton('Sample')9

10 #Connect its clicked signal to our slot

11 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。

1 importsys2 from PySide.QtCore importSlot3 from PySide.QtGui import *

4

5 #... insert the rest of the imports here

6 #Imports must precede all others ...

7

8 #Create a Qt app and a window

9 app =QApplication(sys.argv)10

11 win =QWidget()12 win.setWindowTitle('Test Window')13

14 #Create a button in the window

15 btn = QPushButton('Test', win)16

17 @Slot()18 defon_click():19 '''Tell when the button is clicked.'''

20 print('clicked')21

22 @Slot()23 defon_press():24 '''Tell when the button is pressed.'''

25 print('pressed')26

27 @Slot()28 defon_release():29 '''Tell when the button is released.'''

30 print('released')31

32 #Connect the signals to the slots

33 btn.clicked.connect(on_click)34 btn.pressed.connect(on_press)35 btn.released.connect(on_release)36

37 #Show the window and run the app

38 win.show()39 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()defshow_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：

1 importsys2 from PySide.QtCore importSlot3 from PySide.QtGui import *

4

5 #Every Qt application must have one and only one QApplication object;

6 #it receives the command line arguments passed to the script, as they

7 #can be used to customize the application's appearance and behavior

8 qt_app =QApplication(sys.argv)9

10 classLayoutExample(QWidget):11 '''An example of PySide absolute positioning; the main window12 inherits from QWidget, a convenient widget for an empty window.'''

13

14 def __init__(self):15 #Initialize the object as a QWidget and

16 #set its title and minimum width

17 QWidget.__init__(self)18 self.setWindowTitle('Dynamic Greeter')19 self.setMinimumWidth(400)20

21 #Create the QVBoxLayout that lays out the whole form

22 self.layout =QVBoxLayout()23

24 #Create the form layout that manages the labeled controls

25 self.form_layout =QFormLayout()26

27 self.salutations = ['Ahoy',28 'Good day',29 'Hello',30 'Heyo',31 'Hi',32 'Salutations',33 'Wassup',34 'Yo']35

36 #Create and fill the combo box to choose the salutation

37 self.salutation =QComboBox(self)38 self.salutation.addItems(self.salutations)39 #Add it to the form layout with a label

40 self.form_layout.addRow('&Salutation:', self.salutation)41

42 #Create the entry control to specify a

43 #recipient and set its placeholder text

44 self.recipient =QLineEdit(self)45 self.recipient.setPlaceholderText("e.g. 'world' or 'Matey'")46

47 #Add it to the form layout with a label

48 self.form_layout.addRow('&Recipient:', self.recipient)49

50 #Create and add the label to show the greeting text

51 self.greeting = QLabel('', self)52 self.form_layout.addRow('Greeting:', self.greeting)53

54 #Add the form layout to the main VBox layout

55 self.layout.addLayout(self.form_layout)56

57 #Add stretch to separate the form layout from the button

58 self.layout.addStretch(1)59

60 #Create a horizontal box layout to hold the button

61 self.button_box =QHBoxLayout()62

63 #Add stretch to push the button to the far right

64 self.button_box.addStretch(1)65

66 #Create the build button with its caption

67 self.build_button = QPushButton('&Build Greeting', self)68

69 #Connect the button's clicked signal to show_greeting

70 self.build_button.clicked.connect(self.show_greeting)71

72 #Add it to the button box

73 self.button_box.addWidget(self.build_button)74

75 #Add the button box to the bottom of the main VBox layout

76 self.layout.addLayout(self.button_box)77

78 #Set the VBox layout as the window's main layout

79 self.setLayout(self.layout)80

81 @Slot()82 defshow_greeting(self):83 '''Show the constructed greeting.'''

84 self.greeting.setText('%s, %s!' %

85 (self.salutations[self.salutation.currentIndex()],86 self.recipient.text()))87

88 defrun(self):89 #Show the form

90 self.show()91 #Run the qt application

92 qt_app.exec_()93

94 #Create an instance of the application window and run it

95 app =LayoutExample()96 app.run()

View Code

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，我們將學習創建并連接自己的信號。

By Ascii0x03

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

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