我写了一个可执行的示例 - 你可以测试它。当您启动此程序时，您将获得三个 QPushButton() 对象和一个 QLineEdit() 对象。您可以在那里安装或卸载/卸载事件过滤器或关闭应用程序。请安装事件过滤器并输入文本。你会看到我想要的。我希望示例程序能够保护空格键。在当前版本中，用户不能按空格键超过 2 次。这个程序确实有效。
但是我有一个小问题。当我在 QLineEdit() 对象中写入文本，然后突出显示该文本并按删除或返回键时，没有任何反应。我无法删除文本。我也无法复制标记的文本。
下面的代码有什么问题吗？
#!/usr/bin/env python
import sys
from PyQt4.QtCore import QEvent, Qt
from PyQt4.QtGui import QMainWindow, QWidget, QApplication, QVBoxLayout, QLineEdit, QPushButton
class Window(QMainWindow):
def __init__(self, parent=None):
QMainWindow.__init__(self, parent)
self.count_space_pressed = 0
self.current_pos = None
self.init_ui()
self.init_signal_slot_push_button()
def init_ui(self):
centralwidget = QWidget(self)
self.input_line_edit = QLineEdit(self)
self.close_push = QPushButton(self)
self.close_push.setEnabled(False)
self.close_push.setText("Close")
self.push_install = QPushButton(self)
self.push_install.setText("Install eventFilter")
self.push_deinstall = QPushButton(self)
self.push_deinstall.setText("Deinstall eventFilter")
layout = QVBoxLayout(centralwidget)
layout.addWidget(self.input_line_edit)
layout.addWidget(self.push_install)
layout.addWidget(self.push_deinstall)
layout.addWidget(self.close_push)
self.setCentralWidget(centralwidget)
return
def install_filter_event(self, widget_object):
widget_object.installEventFilter(self)
return
def deinstall_filter_event(self, widget_object):
widget_object.removeEventFilter(self)
return
def init_signal_slot_push_button(self):
self.close_push.clicked.connect(self.close)
self.push_install.clicked.connect(lambda: self.install_filter_event(self.input_line_edit))
self.push_deinstall.clicked.connect(lambda: self.deinstall_filter_event(self.input_line_edit))
return
def strip_string(self, content, site=None):
if site == "right":
return content.rstrip()
elif site == "right_left":
return content.strip()
elif site == "left":
return content.lstrip()
def eventFilter(self, received_object, event):
content_line_edit = unicode(received_object.text())
if event.type() == QEvent.KeyPress:
if event.key() == Qt.Key_Space:
'''
Yes, the user did press the Space-Key. We
count how often he pressed the space key.
'''
self.count_space_pressed = self.count_space_pressed + 1
if int(self.count_space_pressed) > 1:
'''
The user did press the space key more than 1 time.
'''
self.close_push.setEnabled(False)
'''
Now we know the user did press the
space key more than 1 time. We take a look,
if variablenamed (sel.current_pos) is None.
That means, no current position is saved.
'''
if self.current_pos is None:
'''
Well no current position is saved,
that why we save the new position anf
then we set the position of the cursor.
'''
self.current_pos = received_object.cursorPosition()
received_object.setCursorPosition(int(self.current_pos))
received_object.clear()
received_object.setText(self.strip_string(content_line_edit, site="right"))
else:
'''
Well the user press the space key again, for
example 3, 4, 5, 6 times we want to keep the
old position of the cursor until he press
no space key.
'''
received_object.setCursorPosition(int(self.current_pos))
'''
We have to remove all spaces in a string
on the right side and set the content on QLineEdit-widget.
'''
received_object.clear()
received_object.setText(self.strip_string(content_line_edit, site="right"))
else: pass
else:
'''
No the user didn't press the space key.
So we set all setting on default.
'''
self.close_push.setEnabled(True)
self.current_pos = None
self.count_space_pressed = 0
received_object.clear()
received_object.setText(self.strip_string(content_line_edit, site="left"))
# Call Base Class Method to Continue Normal Event Processing
return QMainWindow.eventFilter(self, received_object, event)
if __name__ == '__main__':
app = QApplication(sys.argv)
window = Window()
window.show()
app.exec_()
编辑：
import sys, re
from PyQt4 import QtCore, QtGui
class Window(QtGui.QWidget):
def __init__(self):
super(Window, self).__init__()
self.edit = QtGui.QLineEdit(self)
self.edit.textChanged.connect(self.handleTextChanged)
layout = QtGui.QVBoxLayout(self)
layout.addWidget(self.edit)
# First we save the the regular expression pattern
# in a variable named regex.
#@ This means: one whitespace character, followed by
#@ one or more whitespaces chatacters
regex = r"\s\s+"
# Now we comple the pattern.
# After then we save the compiled patter
# as result in a variable named compiled_re.
self.compiled_re = re.compile(regex)
def handleTextChanged(self, text):
# When the text of a widget-object is changed,
# we do something.
# Here I am really not sure.
# Do you want to look if the given text isn't empty?
#@ No, we want to search the string to see if it
#@ contains any runs of multiple spaces
if self.compiled_re.search(text):
# We know that given text is a QString-object.
# So we have to convert the given text
# into a python-string, because we want to work
# with them in python.
text = unicode(text)
# NOTICE: Do replacements before and after cursor pos
# We save the current and correct cursor position
# of a QLineEdit()-object in the variable named pos.
pos = self.edit.cursorPosition()
# Search and Replace: Here the sub()-method
# replaces all occurrences of the RE pattern
# in string with text.
# And then it returns modified string and saves
# it in the variables prefix and suffix.
# BUT I am not sure If I understand this: [:pos]
# and [pos:]. I will try to understnand.
# I think we are talking about slicing, right?
# And I think the slicing works like string[start:end]:
# So text[:pos] means, search and replace all whitesapce
# at the end of the text-string. And the same again, but
# text[pos:] means, search and replace all whitesapce
# at the start of the string-text.
#@ Right, but the wrong way round. text[:pos] means from
#@ the start of the string up to pos (the prefix); and
#@ text[pos:] means from pos up to the end of the string
#@ (the suffix)
prefix = self.compiled_re.sub(' ', text[:pos])
suffix = self.compiled_re.sub(' ', text[pos:])
# NOTICE: Cursor might be between spaces
# Now we take a look if the variable prefix ends
# with a whitespace and we check if suffix starts
# with a whitespace.
# BUT, why we do that?
#@ Imagine that the string is "A |B C" (with the cursor
#@ shown as "|"). If "B" is deleted, we will get "A | C"
#@ with the cursor left between multiple spaces. But
#@ when the string is split into prefix and suffix,
#@ each part will contain only *one* space, so the
#@ regexp won't replace them.
if prefix.endswith(' ') and suffix.startswith(' '):
# Yes its True, so we overwrite the variable named
# suffix and slice it. suffix[1:] means, we starts
# at 1 until open end.
#@ This removes the extra space at the start of the
#@ suffix that was missed by the regexp (see above)
suffix = suffix[1:]
# Now we have to set the text of the QLineEdit()-object,
# so we put the both varialbes named prefix and suffix
# together.
self.edit.setText(prefix + suffix)
# After then, we have to set the cursor position.
# I know that the len()-method returns the length of the
# variable named prefix.
# BUT why we have to do that?
#@ When the text is set, it will clear the cursor. The
#@ prefix and suffix gives the text before and after the
#@ old cursor position. Removing spaces may have shifted
#@ the old position, so the new postion is calculated
#@ from the length of the current prefix
self.edit.setCursorPosition(len(prefix))
if __name__ == '__main__':
app = QtGui.QApplication(sys.argv)
window = Window()
window.setGeometry(500, 150, 300, 100)
window.show()
sys.exit(app.exec_())
编辑2：
两个问题：
第一个问题：在if.条件中，我们检查前缀是否以sapces结尾并且后缀是否以sapces开头，我们将删除后缀开头的额外空格。但为什么我们不删除前缀开头的额外空格呢？ 想象一下：用户输入“前缀和后缀” - 在开头和结尾处有额外的空格。我们是否必须删除前缀开头的额外空格 - 例如：
prefix= prefix[:1]第二个问题： 在 handleTextChanged() 方法的最后，我们必须计算光标的新位置。在当前情况下，我们使用前缀来获取字符串的长度。为什么不是新修改文本中的 len，它是前缀和后缀的一部分？ 示例：旧字符串是“ Prefix and Suffix ”，用户删除了单词“and”。现在我们的字符串看起来像“ Prefix | Suffix ”。后缀“。删除所有空格后，我们得到新的修改后的文本：“前缀后缀”。为什么我们不根据修改后的文本计算新位置？或者我错过了什么？
编辑3：
抱歉，我还是不明白情况。
第一种情况：当用户输入以下字符串：“
A B C |A B C |第二种情况：用户输入“
A B D E F |CBDCA B CD E F如果您真的想要防止多个空格，那么过滤按键是不够的。
例如，用户可以简单地拖放多个空格；或使用鼠标、内置上下文菜单或标准键盘快捷键粘贴它们。
打破空格键计数方法也很容易：例如，只需输入
A B CB一种更可靠的方法是连接到
textChanged这是一个演示：
import sys, re
from PyQt4 import QtCore, QtGui
class Window(QtGui.QWidget):
def __init__(self):
super(Window, self).__init__()
self.edit = QtGui.QLineEdit(self)
self.edit.textChanged.connect(self.handleTextChanged)
layout = QtGui.QVBoxLayout(self)
layout.addWidget(self.edit)
self.regexp = re.compile(r'\s\s+')
def handleTextChanged(self, text):
if self.regexp.search(text):
text = unicode(text)
# do replacements before and after cursor pos
pos = self.edit.cursorPosition()
prefix = self.regexp.sub(' ', text[:pos])
suffix = self.regexp.sub(' ', text[pos:])
# cursor might be between spaces
if prefix.endswith(' ') and suffix.startswith(' '):
suffix = suffix[1:]
self.edit.setText(prefix + suffix)
self.edit.setCursorPosition(len(prefix))
if __name__ == '__main__':
app = QtGui.QApplication(sys.argv)
window = Window()
window.setGeometry(500, 150, 300, 100)
window.show()
sys.exit(app.exec_())
如果您使用的是 python 并且已创建用于删除最后一个字符的按钮，请执行以下操作
self.PB_Back.clicked.connect(self.Keypad_Back)
def Keypad_Back(self):
self.LE_Edit.setText(self.LE_Edit.text()[:-1])
这将一次删除最后一个字符
要一次删除所有字符，请执行以下操作
self.PB_DeleteResult.clicked.connect(self.Keypad_DeleteResult)
def Keypad_DeleteResult(self):
self.LE_Edit.setText("")