PyQt5系列教程(七)控件

软硬件环境

• Windows 10
• Python 3.4.2
• PyQt 5.5.1
• PyCharm 5.0.4

前言

控件是PyQt应用程序的基石。PyQt5自带很多不同的控件，包括像button、check box、slider等等。在本节中我们将学习几个非常有用的控件:QCheckBox、ToggleButton、QSlider、QProgressBar和QCalendarWidget。

QCheckBox

一个QCheckBox会有2种状态:选中和为选中。它有一个选择框和一个label组成，它常常被用来表示应用的某些特性是可启用或不启用的。

# -*- coding: utf-8 -*-
__author__ = 'djstava@gmail.com'

"""
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_())

程序执行效果如下

在这个例子中，我们创建了一个选择框，它状态的变化会引起窗口标题的变化。

cb = QCheckBox('Show title', self)

这条语句是QCheckBox的构造函数，它的label是”Show title”。

cb.toggle()

设置默认是选中状态

cb.stateChanged.connect(self.changeTitle)

将自定义的槽函数changeTitle和信号stateChanged绑定起来，槽函数changeTitle会改变窗口的标题

def changeTitle(self, state):

if state == Qt.Checked:
    self.setWindowTitle('QCheckBox')
else:
    self.setWindowTitle('')

选中状态下，窗口标题设置为”QCheckBox”,否则设置为空

Toggle button

Toggle button是一种特殊的QPushButton(按钮),它也有2种状态，按下和未按下，我们通过点击它来区分2种不同的状态。实际很多情况下都会用到它。

# -*- coding: utf-8 -*-
__author__ = 'djstava@gmail.com'

"""
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_())

代码执行效果如下所示

本例中我们创建了3个toggle button和一个QWidget，将QWidget的背景色设置成了黑色，左边的3个toggle button会改变右边QWidget的颜色。

redb = QPushButton('Red', self)
redb.setCheckable(True)

为了创建toggle button,我们首先创建一个QPushButton，然后调用方法setCheckable()。后面的信号和槽的绑定，相信大家都很熟悉了，这里就不说了。

QSlider

QSlider是一个滑动条，允许你在某一范围内拖动。有时候这种方式比输入数字或者使用spin box更加自然。

# -*- coding: utf-8 -*-
__author__ = 'djstava@gmail.com'

"""
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_())

代码运行效果如下所示，我这没有加入图片，所以看不到右侧图片的变化。我这里只解释下QSlider的使用，信号和曹函数跟之前都是一样的。

sld = QSlider(Qt.Horizontal, self)
sld.setFocusPolicy(Qt.NoFocus)
sld.setGeometry(30, 40, 100, 30)
sld.valueChanged[int].connect(self.changeValue)

QSlider构造函数中传入Qt.Horizontal，创建的是一个横向的slider

QProgressBar

ProgressBar一般用来表示任务的进度，也有横向和众向之分。你可以设置进度条的最小值和最大值，默认是0和99。

# -*- coding: utf-8 -*-
__author__ = 'djstava@gmail.com'

"""
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_())

代码运行效果如下所示

这里使用一个计时器来启动进度条

self.timer = QtCore.QBasicTimer()

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)

每个QObject及其子类都有个timerEvent()事件处理器，需要我们重新实现，它的第一个参数是超时时间

QCalendarWidget

QCalendarWidget是一个以月份为基础的日历控件，用来供用户选择日期

# -*- coding: utf-8 -*-
__author__ = 'djstava@gmail.com'

"""
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_())

代码运行效果如下所示

参考文献

http://zetcode.com/gui/pyqt5/widgets/