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560 lines
12 KiB
Markdown
560 lines
12 KiB
Markdown
# 控件\(1\)
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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`。
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## QCheckBox
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`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。
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```python
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#!/usr/bin/python3
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# -*- coding: utf-8 -*-
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"""
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ZetCode PyQt5 tutorial
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In this example, a QCheckBox widget
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is used to toggle the title of a window.
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Author: Jan Bodnar
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Website: zetcode.com
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Last edited: August 2017
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"""
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from PyQt5.QtWidgets import QWidget, QCheckBox, QApplication
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from PyQt5.QtCore import Qt
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import sys
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class Example(QWidget):
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def __init__(self):
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super().__init__()
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self.initUI()
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def initUI(self):
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cb = QCheckBox('Show title', self)
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cb.move(20, 20)
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cb.toggle()
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cb.stateChanged.connect(self.changeTitle)
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self.setGeometry(300, 300, 250, 150)
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self.setWindowTitle('QCheckBox')
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self.show()
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def changeTitle(self, state):
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if state == Qt.Checked:
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self.setWindowTitle('QCheckBox')
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else:
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self.setWindowTitle(' ')
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if __name__ == '__main__':
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app = QApplication(sys.argv)
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ex = Example()
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sys.exit(app.exec_())
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```
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这个例子中，有一个能切换窗口标题的单选框。
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```text
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cb = QCheckBox('Show title', self)
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```
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这个是`QCheckBox`的构造器。
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```text
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cb.toggle()
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```
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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。
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```text
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cb.stateChanged.connect(self.changeTitle)
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```
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把`changeTitle()`方法和`stateChanged`信号关联起来。这样，`changeTitle()`就能切换窗口标题了。
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```text
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def changeTitle(self, state):
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if state == Qt.Checked:
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self.setWindowTitle('QCheckBox')
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else:
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self.setWindowTitle('')
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```
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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。
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程序展示：
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## 切换按钮
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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。
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```python
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#!/usr/bin/python3
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# -*- coding: utf-8 -*-
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"""
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ZetCode PyQt5 tutorial
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In this example, we create three toggle buttons.
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They will control the background color of a
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QFrame.
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Author: Jan Bodnar
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Website: zetcode.com
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Last edited: August 2017
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"""
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from PyQt5.QtWidgets import (QWidget, QPushButton,
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QFrame, QApplication)
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from PyQt5.QtGui import QColor
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import sys
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class Example(QWidget):
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def __init__(self):
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super().__init__()
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self.initUI()
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def initUI(self):
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self.col = QColor(0, 0, 0)
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redb = QPushButton('Red', self)
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redb.setCheckable(True)
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redb.move(10, 10)
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redb.clicked[bool].connect(self.setColor)
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greenb = QPushButton('Green', self)
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greenb.setCheckable(True)
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greenb.move(10, 60)
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greenb.clicked[bool].connect(self.setColor)
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blueb = QPushButton('Blue', self)
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blueb.setCheckable(True)
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blueb.move(10, 110)
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blueb.clicked[bool].connect(self.setColor)
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self.square = QFrame(self)
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self.square.setGeometry(150, 20, 100, 100)
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self.square.setStyleSheet("QWidget { background-color: %s }" %
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self.col.name())
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self.setGeometry(300, 300, 280, 170)
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self.setWindowTitle('Toggle button')
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self.show()
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def setColor(self, pressed):
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source = self.sender()
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if pressed:
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val = 255
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else: val = 0
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if source.text() == "Red":
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self.col.setRed(val)
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elif source.text() == "Green":
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self.col.setGreen(val)
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else:
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self.col.setBlue(val)
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self.square.setStyleSheet("QFrame { background-color: %s }" %
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self.col.name())
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if __name__ == '__main__':
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app = QApplication(sys.argv)
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ex = Example()
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sys.exit(app.exec_())
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```
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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）。
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```text
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self.col = QColor(0, 0, 0)
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```
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设置颜色为黑色。
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```text
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redb = QPushButton('Red', self)
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redb.setCheckable(True)
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redb.move(10, 10)
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```
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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。
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```text
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redb.clicked[bool].connect(self.setColor)
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```
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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。
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```text
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source = self.sender()
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```
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获取被点击的按钮。
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```text
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if source.text() == "Red":
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self.col.setRed(val)
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```
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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。
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```text
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self.square.setStyleSheet("QFrame { background-color: %s }" %
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self.col.name())
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```
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使用样式表（就是CSS的SS）改变背景色
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程序展示：
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## 滑块
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`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。
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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）。
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> 先准备四个分别表示静音、小音量、中音量、大音量的图标，文件名分别叫mute.png, min.png, med.png, max.png。
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```python
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#!/usr/bin/python3
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# -*- coding: utf-8 -*-
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"""
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ZetCode PyQt5 tutorial
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This example shows a QSlider widget.
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Author: Jan Bodnar
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Website: zetcode.com
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Last edited: August 2017
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"""
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from PyQt5.QtWidgets import (QWidget, QSlider,
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QLabel, QApplication)
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from PyQt5.QtCore import Qt
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from PyQt5.QtGui import QPixmap
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import sys
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class Example(QWidget):
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def __init__(self):
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super().__init__()
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self.initUI()
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def initUI(self):
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sld = QSlider(Qt.Horizontal, self)
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sld.setFocusPolicy(Qt.NoFocus)
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sld.setGeometry(30, 40, 100, 30)
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sld.valueChanged[int].connect(self.changeValue)
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self.label = QLabel(self)
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self.label.setPixmap(QPixmap('mute.png'))
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self.label.setGeometry(160, 40, 80, 30)
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self.setGeometry(300, 300, 280, 170)
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self.setWindowTitle('QSlider')
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self.show()
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def changeValue(self, value):
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if value == 0:
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self.label.setPixmap(QPixmap('mute.png'))
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elif value > 0 and value <= 30:
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self.label.setPixmap(QPixmap('min.png'))
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elif value > 30 and value < 80:
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self.label.setPixmap(QPixmap('med.png'))
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else:
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self.label.setPixmap(QPixmap('max.png'))
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if __name__ == '__main__':
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app = QApplication(sys.argv)
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ex = Example()
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sys.exit(app.exec_())
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```
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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。
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```text
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sld = QSlider(Qt.Horizontal, self)
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```
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创建一个水平的`QSlider`。
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```text
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self.label = QLabel(self)
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self.label.setPixmap(QPixmap('mute.png'))
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```
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创建一个`QLabel`组件并给它设置一个静音图标。
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```text
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sld.valueChanged[int].connect(self.changeValue)
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```
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把`valueChanged`信号跟`changeValue()`方法关联起来。
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```text
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if value == 0:
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self.label.setPixmap(QPixmap('mute.png'))
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...
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```
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根据音量值的大小更换标签位置的图片。这段代码是：如果音量为0，就把图片换成 mute.png。
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程序展示：
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## 进度条
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进度条是用来展示任务进度的（我也不想这样说话）。它的滚动能让用户了解到任务的进度。`QProgressBar`组件提供了水平和垂直两种进度条，进度条可以设置最大值和最小值，默认情况是0~99。
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```python
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#!/usr/bin/python3
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# -*- coding: utf-8 -*-
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"""
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ZetCode PyQt5 tutorial
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This example shows a QProgressBar widget.
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Author: Jan Bodnar
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Website: zetcode.com
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Last edited: August 2017
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"""
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from PyQt5.QtWidgets import (QWidget, QProgressBar,
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QPushButton, QApplication)
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from PyQt5.QtCore import QBasicTimer
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import sys
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class Example(QWidget):
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def __init__(self):
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super().__init__()
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self.initUI()
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def initUI(self):
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self.pbar = QProgressBar(self)
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self.pbar.setGeometry(30, 40, 200, 25)
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self.btn = QPushButton('Start', self)
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self.btn.move(40, 80)
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self.btn.clicked.connect(self.doAction)
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self.timer = QBasicTimer()
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self.step = 0
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self.setGeometry(300, 300, 280, 170)
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self.setWindowTitle('QProgressBar')
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self.show()
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def timerEvent(self, e):
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if self.step >= 100:
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self.timer.stop()
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self.btn.setText('Finished')
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return
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self.step = self.step + 1
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self.pbar.setValue(self.step)
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def doAction(self):
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if self.timer.isActive():
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self.timer.stop()
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self.btn.setText('Start')
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else:
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self.timer.start(100, self)
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self.btn.setText('Stop')
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if __name__ == '__main__':
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app = QApplication(sys.argv)
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ex = Example()
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sys.exit(app.exec_())
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```
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我们创建了一个水平的进度条和一个按钮，这个按钮控制进度条的开始和停止。
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```text
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self.pbar = QProgressBar(self)
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```
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新建一个`QProgressBar`构造器。
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```text
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self.timer = QtCore.QBasicTimer()
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```
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用时间控制进度条。
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```text
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self.timer.start(100, self)
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```
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调用`start()`方法加载一个时间事件。这个方法有两个参数：过期时间和事件接收者。
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```text
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def timerEvent(self, e):
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if self.step >= 100:
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self.timer.stop()
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self.btn.setText('Finished')
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return
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self.step = self.step + 1
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self.pbar.setValue(self.step)
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```
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每个`QObject`和又它继承而来的对象都有一个`timerEvent()`事件处理函数。为了触发事件，我们重载了这个方法。
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```text
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def doAction(self):
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if self.timer.isActive():
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self.timer.stop()
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self.btn.setText('Start')
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else:
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self.timer.start(100, self)
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self.btn.setText('Stop')
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```
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里面的`doAction()`方法是用来控制开始和停止的。
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程序展示：
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## 日历
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`QCalendarWidget`提供了基于月份的日历插件，十分简易而且直观。
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```python
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#!/usr/bin/python3
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# -*- coding: utf-8 -*-
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"""
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ZetCode PyQt5 tutorial
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This example shows a QCalendarWidget widget.
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Author: Jan Bodnar
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Website: zetcode.com
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Last edited: August 2017
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"""
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from PyQt5.QtWidgets import (QWidget, QCalendarWidget,
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QLabel, QApplication, QVBoxLayout)
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from PyQt5.QtCore import QDate
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import sys
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class Example(QWidget):
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def __init__(self):
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super().__init__()
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self.initUI()
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def initUI(self):
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vbox = QVBoxLayout(self)
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cal = QCalendarWidget(self)
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cal.setGridVisible(True)
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cal.clicked[QDate].connect(self.showDate)
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vbox.addWidget(cal)
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self.lbl = QLabel(self)
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date = cal.selectedDate()
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self.lbl.setText(date.toString())
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vbox.addWidget(self.lbl)
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self.setLayout(vbox)
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self.setGeometry(300, 300, 350, 300)
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self.setWindowTitle('Calendar')
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self.show()
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def showDate(self, date):
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self.lbl.setText(date.toString())
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if __name__ == '__main__':
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app = QApplication(sys.argv)
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ex = Example()
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sys.exit(app.exec_())
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```
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这个例子有日期组件和标签组件组成，标签显示被选中的日期。
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```text
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cal = QCalendarWidget(self)
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```
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创建一个`QCalendarWidget`。
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```text
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cal.clicked[QDate].connect(self.showDate)
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```
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选择一个日期时，`QDate`的点击信号就触发了，把这个信号和我们自己定义的`showDate()`方法关联起来。
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```text
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def showDate(self, date):
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self.lbl.setText(date.toString())
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```
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使用`selectedDate()`方法获取选中的日期，然后把日期对象转成字符串，在标签里面显示出来。
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程序展示：
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