menuBar() in PyQt5 | 易学教程

问题

I am trying to load a menubar onto my gui, but my class object has no attribute for self.menuBar(). Can someone help me, no tutorials seem to offer any way around.

class EmailBlast(QtWidgets.QWidget):
    def __init__(self):
        super().__init__()
        bar = QtWidgets.menuBar() 
        file_menu = bar.addMenu('File')
        file_edit = bar.addMenu('Edit')

Error message:

File "BasicEmail.py", line 84, in email_config
self.ui = EmailBlast()
File "BasicEmail.py", line 96, in __init__
self.menuBar()
AttributeError: 'EmailBlast' object has no attribute 'menuBar'

What am I missing here.

Updated project:

class MainWindow(QtWidgets.QMainWindow):
def __init__(self):
    super().__init__()
    self.email_blast_widget = EmailBlast()
    self.setCentralWidget(self.email_blast_widget)
    bar = self.menuBar()
    file_file = bar.addMenu('File')         
    file_edit = bar.addMenu('Edit') 

class EmailBlast(QtWidgets.QWidget):
def __init__(self):
    super().__init__()
    self.text_box = QtWidgets.QTextEdit(self)
    self.save_button = QtWidgets.QPushButton('Save')
    self.clear_button = QtWidgets.QPushButton('Clear')        
    self.open_button = QtWidgets.QPushButton('Open')        
    self.init_ui()

回答1:

Exception speaks truth: QWidget class does not have a menuBar attribute, QMainWindow has (as well as toolbars and status bar):

If you have QMainWindow instance somewhere in your code and just want to fill menu items in EmailBlast init, you can get menu bar of mentioned QMainWindow by calling bar = QtWidgets.QMainWindow.menuBar(). Menus consists of an QActions so you probably need to add them too.

If you do not have QMainWindow then consider adding one. QMainWindow must have "Central Widget". In your case it is probably EmailBlast widget. Since EmailBlast will be a part of MainWindow you need to create and show MainWindow instance instead of EmailBlast.

If you have multiple elements (buttons, text edits etc.) in EmailBlast widget then Qt layout system comes into play almost inevitable (quickly glance at pics in docs to grasp a concept).

It can be pretty hard to wrap a head around all this things at once, so once again.

QMainWindow - central part of your app. Has menu bar, toolbars, status bar and central area occupied by central widget.

Central widget - a widget providing main functionality of your app (or it can be a widget holding other widgets like QSplitter). In your case it is probably a EmailBlast widget.

EmailBlast widget provides a piece of (reusable) functionality. To do so it itself consists of various helper widgets (text edits, buttons, check boxes and so on). To place this small widgets in a predictable manner the layout is created. Widgets are placed inside layout and layout is set to EmailBlast widget.

Menu bar consists of zero or more QMenus, which in turn can have QActions. QAction signals (usually triggered) are connecting to slots to provide desired behavior.

Here is a complete example:

import sys
from PyQt5 import QtWidgets


class MainWindow(QtWidgets.QMainWindow):
    def __init__(self, parent=None):
        super().__init__(parent)
        # creating EmailBlast widget and setting it as central
        self.email_blast_widget = EmailBlast(parent=self)
        self.setCentralWidget(self.email_blast_widget)
        # filling up a menu bar
        bar = self.menuBar()
        # File menu
        file_menu = bar.addMenu('File')
        # adding actions to file menu
        open_action = QtWidgets.QAction('Open', self)
        close_action = QtWidgets.QAction('Close', self)
        file_menu.addAction(open_action)
        file_menu.addAction(close_action)
        # Edit menu
        edit_menu = bar.addMenu('Edit')
        # adding actions to edit menu
        undo_action = QtWidgets.QAction('Undo', self)
        redo_action = QtWidgets.QAction('Redo', self)
        edit_menu.addAction(undo_action)
        edit_menu.addAction(redo_action)

        # use `connect` method to bind signals to desired behavior
        close_action.triggered.connect(self.close)


class EmailBlast(QtWidgets.QWidget):
    def __init__(self, parent=None):
        super().__init__(parent)
        # create and set layout to place widgets
        grid_layout = QtWidgets.QGridLayout(self)

        self.text_box = QtWidgets.QTextEdit(self)
        self.save_button = QtWidgets.QPushButton('Save')
        self.clear_button = QtWidgets.QPushButton('Clear')
        self.open_button = QtWidgets.QPushButton('Open')
        # add widgets to layout. Params are:
        # (widget, fromRow, fromColumn, rowSpan=1, columnSpan=1)
        grid_layout.addWidget(self.text_box, 0, 0, 1, 3)
        grid_layout.addWidget(self.save_button, 1, 0)
        grid_layout.addWidget(self.clear_button, 1, 1)
        grid_layout.addWidget(self.open_button, 1, 2)


if __name__ == '__main__':
    app = QtWidgets.QApplication(sys.argv)
    # creating main window
    mw = MainWindow()
    mw.show()
    sys.exit(app.exec_())

This code produces nice little app like that:

来源：https://stackoverflow.com/questions/45680643/menubar-in-pyqt5

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