12 KiB
控件1
控件就像是应用这座房子的一块块砖。PyQt5有很多的控件，比如按钮，单选框，滑动条，复选框等等。在本章，我们将介绍一些很有用的控件：QCheckBox，ToggleButton，QSlider，QProgressBar和QCalendarWidget。
QCheckBox
QCheckBox组件有俩状态：开和关。通常跟标签一起使用，用在激活和关闭一些选项的场景。
#!/usr/bin/python3
# -*- coding: utf-8 -*-
"""
ZetCode PyQt5 tutorial
In this example, a QCheckBox widget
is used to toggle the title of a window.
author: Jan Bodnar
website: zetcode.com
last edited: January 2015
"""
import sys
from PyQt5.QtWidgets import QWidget, QCheckBox, QApplication
from PyQt5.QtCore import Qt
class Example(QWidget):
def __init__(self):
super().__init__()
self.initUI()
def initUI(self):
cb = QCheckBox('Show title', self)
cb.move(20, 20)
cb.toggle()
cb.stateChanged.connect(self.changeTitle)
self.setGeometry(300, 300, 250, 150)
self.setWindowTitle('QCheckBox')
self.show()
def changeTitle(self, state):
if state == Qt.Checked:
self.setWindowTitle('QCheckBox')
else:
self.setWindowTitle('')
if __name__ == '__main__':
app = QApplication(sys.argv)
ex = Example()
sys.exit(app.exec_())
这个例子中，有一个能切换窗口标题的单选框。
cb = QCheckBox('Show title', self)
这个是QCheckBox的构造器。
cb.toggle()
要设置窗口标题，我们就要检查单选框的状态。默认情况下，窗口没有标题，单选框未选中。
cb.stateChanged.connect(self.changeTitle)
把changeTitle()方法和stateChanged信号关联起来。这样，changeTitle()就能切换窗口标题了。
def changeTitle(self, state):
if state == Qt.Checked:
self.setWindowTitle('QCheckBox')
else:
self.setWindowTitle('')
控件的状态是由changeTitle()方法控制的，如果空间被选中，我们就给窗口添加一个标题，如果没被选中，就清空标题。
程序展示：
切换按钮
切换按钮就是QPushButton的一种特殊模式。 它只有两种状态：按下和未按下。我们再点击的时候切换两种状态，有很多场景会使用到这个功能。
#!/usr/bin/python3
# -*- coding: utf-8 -*-
"""
ZetCode PyQt5 tutorial
In this example, we create three toggle buttons.
They will control the background colour of a
QFrame.
author: Jan Bodnar
website: zetcode.com
last edited: January 2015
"""
import sys
from PyQt5.QtWidgets import (QWidget, QPushButton,
QFrame, QApplication)
from PyQt5.QtGui import QColor
class Example(QWidget):
def __init__(self):
super().__init__()
self.initUI()
def initUI(self):
self.col = QColor(0, 0, 0)
redb = QPushButton('Red', self)
redb.setCheckable(True)
redb.move(10, 10)
redb.clicked[bool].connect(self.setColor)
redb = QPushButton('Green', self)
redb.setCheckable(True)
redb.move(10, 60)
redb.clicked[bool].connect(self.setColor)
blueb = QPushButton('Blue', self)
blueb.setCheckable(True)
blueb.move(10, 110)
blueb.clicked[bool].connect(self.setColor)
self.square = QFrame(self)
self.square.setGeometry(150, 20, 100, 100)
self.square.setStyleSheet("QWidget { background-color: %s }" %
self.col.name())
self.setGeometry(300, 300, 280, 170)
self.setWindowTitle('Toggle button')
self.show()
def setColor(self, pressed):
source = self.sender()
if pressed:
val = 255
else: val = 0
if source.text() == "Red":
self.col.setRed(val)
elif source.text() == "Green":
self.col.setGreen(val)
else:
self.col.setBlue(val)
self.square.setStyleSheet("QFrame { background-color: %s }" %
self.col.name())
if __name__ == '__main__':
app = QApplication(sys.argv)
ex = Example()
sys.exit(app.exec_())
我们创建了一个切换按钮和一个QWidget，并把QWidget的背景设置为黑色。点击不同的切换按钮，背景色会在红、绿、蓝之间切换（而且能看到颜色合成的效果，而不是单纯的颜色覆盖）。
self.col = QColor(0, 0, 0)
设置颜色为黑色。
redb = QPushButton('Red', self)
redb.setCheckable(True)
redb.move(10, 10)
创建一个QPushButton，然后调用它的setCheckable()的方法就把这个按钮编程了切换按钮。
redb.clicked[bool].connect(self.setColor)
把点击信号和我们定义好的函数关联起来，这里是把点击事件转换成布尔值。
source = self.sender()
获取被点击的按钮。
if source.text() == "Red":
self.col.setRed(val)
如果是标签为“red”的按钮被点击，就把颜色更改为预设好的对应颜色。
self.square.setStyleSheet("QFrame { background-color: %s }" %
self.col.name())
使用样式表（就是CSS的SS）改变背景色
程序展示：
QSlider
QSlider是个有一个小滑块的组件，这个小滑块能拖着前后滑动，这个经常用于修改一些具有范围的数值，比文本框或者点击增加减少的文本框（spin box）方便多了。
本例用一个滑块和一个标签展示。标签为一个图片，滑块控制标签（的值）。
#!/usr/bin/python3
# -*- coding: utf-8 -*-
"""
ZetCode PyQt5 tutorial
This example shows a QSlider widget.
author: Jan Bodnar
website: zetcode.com
last edited: January 2015
"""
import sys
from PyQt5.QtWidgets import (QWidget, QSlider,
QLabel, QApplication)
from PyQt5.QtCore import Qt
from PyQt5.QtGui import QPixmap
class Example(QWidget):
def __init__(self):
super().__init__()
self.initUI()
def initUI(self):
sld = QSlider(Qt.Horizontal, self)
sld.setFocusPolicy(Qt.NoFocus)
sld.setGeometry(30, 40, 100, 30)
sld.valueChanged[int].connect(self.changeValue)
self.label = QLabel(self)
self.label.setPixmap(QPixmap('mute.png'))
self.label.setGeometry(160, 40, 80, 30)
self.setGeometry(300, 300, 280, 170)
self.setWindowTitle('QSlider')
self.show()
def changeValue(self, value):
if value == 0:
self.label.setPixmap(QPixmap('mute.png'))
elif value > 0 and value <= 30:
self.label.setPixmap(QPixmap('min.png'))
elif value > 30 and value < 80:
self.label.setPixmap(QPixmap('med.png'))
else:
self.label.setPixmap(QPixmap('max.png'))
if __name__ == '__main__':
app = QApplication(sys.argv)
ex = Example()
sys.exit(app.exec_())
这里是模拟的音量控制器。拖动滑块，能改变标签位置的图片。
sld = QSlider(Qt.Horizontal, self)
Here we create a horizontal QSlider.
self.label = QLabel(self)
self.label.setPixmap(QPixmap('mute.png'))
We create a QLabel widget and set an initial mute image to it.
sld.valueChanged[int].connect(self.changeValue)
We connect the valueChanged signal to the user defined changeValue() method.
if value == 0:
self.label.setPixmap(QPixmap('mute.png'))
...
Based on the value of the slider, we set an image to the label. In the above code, we set the mute.png image to the label if the slider is equal to zero.
QSlider widget Figure: QSlider widget
QProgressBar
A progress bar is a widget that is used when we process lengthy tasks. It is animated so that the user knows that the task is progressing. The QProgressBar widget provides a horizontal or a vertical progress bar in PyQt5 toolkit. The programmer can set the minimum and maximum value for the progress bar. The default values are 0 and 99.
#!/usr/bin/python3
-- coding: utf-8 --
""" ZetCode PyQt5 tutorial
This example shows a QProgressBar widget.
author: Jan Bodnar website: zetcode.com last edited: January 2015 """
import sys from PyQt5.QtWidgets import (QWidget, QProgressBar, QPushButton, QApplication) from PyQt5.QtCore import QBasicTimer
class Example(QWidget):
def __init__(self):
super().__init__()
self.initUI()
def initUI(self):
self.pbar = QProgressBar(self)
self.pbar.setGeometry(30, 40, 200, 25)
self.btn = QPushButton('Start', self)
self.btn.move(40, 80)
self.btn.clicked.connect(self.doAction)
self.timer = QBasicTimer()
self.step = 0
self.setGeometry(300, 300, 280, 170)
self.setWindowTitle('QProgressBar')
self.show()
def timerEvent(self, e):
if self.step >= 100:
self.timer.stop()
self.btn.setText('Finished')
return
self.step = self.step + 1
self.pbar.setValue(self.step)
def doAction(self):
if self.timer.isActive():
self.timer.stop()
self.btn.setText('Start')
else:
self.timer.start(100, self)
self.btn.setText('Stop')
if name == 'main':
app = QApplication(sys.argv)
ex = Example()
sys.exit(app.exec_())
In our example we have a horizontal progress bar and a push button. The push button starts and stops the progress bar.
self.pbar = QProgressBar(self) This is a QProgressBar constructor.
self.timer = QtCore.QBasicTimer() To activate the progress bar, we use a timer object.
self.timer.start(100, self) To launch a timer event, we call its start() method. This method has two parameters: the timeout and the object which will receive the events.
def timerEvent(self, e):
if self.step >= 100:
self.timer.stop()
self.btn.setText('Finished')
return
self.step = self.step + 1
self.pbar.setValue(self.step)
Each QObject and its descendants have a timerEvent() event handler. In order to react to timer events, we reimplement the event handler.
def doAction(self):
if self.timer.isActive():
self.timer.stop()
self.btn.setText('Start')
else:
self.timer.start(100, self)
self.btn.setText('Stop')
Inside the doAction() method, we start and stop the timer.
QProgressBar Figure: QProgressBar
QCalendarWidget
A QCalendarWidget provides a monthly based calendar widget. It allows a user to select a date in a simple and intuitive way.
#!/usr/bin/python3
-- coding: utf-8 --
""" ZetCode PyQt5 tutorial
This example shows a QCalendarWidget widget.
author: Jan Bodnar website: zetcode.com last edited: January 2015 """
import sys from PyQt5.QtWidgets import (QWidget, QCalendarWidget, QLabel, QApplication) from PyQt5.QtCore import QDate
class Example(QWidget):
def __init__(self):
super().__init__()
self.initUI()
def initUI(self):
cal = QCalendarWidget(self)
cal.setGridVisible(True)
cal.move(20, 20)
cal.clicked[QDate].connect(self.showDate)
self.lbl = QLabel(self)
date = cal.selectedDate()
self.lbl.setText(date.toString())
self.lbl.move(130, 260)
self.setGeometry(300, 300, 350, 300)
self.setWindowTitle('Calendar')
self.show()
def showDate(self, date):
self.lbl.setText(date.toString())
if name == 'main':
app = QApplication(sys.argv)
ex = Example()
sys.exit(app.exec_())
The example has a calendar widget and a label widget. The currently selected date is displayed in the label widget.
cal = QCalendarWidget(self) The QCalendarWidget is created.
cal.clicked[QDate].connect(self.showDate) If we select a date from the widget, a clicked[QDate] signal is emitted. We connect this signal to the user defined showDate() method.
def showDate(self, date):
self.lbl.setText(date.toString())
We retrieve the selected date by calling the selectedDate() method. Then we transform the date object into string and set it to the label widget.