PySide——Python图形化界面入门教程(四)
——创建自己的信号槽
——Creating Your Own Signals and Slots
翻译自：http://pythoncentral.io/pysidepyqt-tutorial-creating-your-own-signals-and-slots/
你不必局限于Qt widget提供的信号，你可以使用Signal类来创建自己的信号。下面是一个定义的简单例子：
from PySide.QtCore import Signal
tapped = Signal()
然后，当对象需要触发信号的条件满足时，你可以使用信号的emit方法，来发出信号调用关联的槽。
thing.tapped.emit()
这样做有两个优点：第一，允许用户和你定义的对象随意交互；第二，让你的对象使用更加灵活，让自己的代码定义动作行为的影响。
一个简单的PySide信号例子
我们来定义一个简单的PunchingBag类，它只做一件事情，当punch被调用时，发出punched信号：
from PySide.QtCore import QObject, Signal, Slot class PunchingBag(QObject):
''' Represents a punching bag; when you punch it, it
emits a signal that indicates that it was punched. '''
punched = Signal() def __init__(self):
# Initialize the PunchingBag as a QObject
QObject.__init__(self) def punch(self):
''' Punch the bag '''
self.punched.emit()
代码非常的简单：PunchingBag继承自QObject，所以它可以发出信号；它有一个称为punched的信号，不携带任何数据；并且他有一个仅仅发出punched信号的punch方法。
为了让PunchingBag更丰富一些，我们需要将它的punched信号和一个槽连接。槽简单的输出“Bag was punched”。
@Slot()
def say_punched():
''' Give evidence that a bag was punched. '''
print('Bag was punched.') bag = PunchingBag()
# Connect the bag's punched signal to the say_punched slot
bag.punched.connect(say_punched) # Punch the bag 10 times
for i in range(10):
bag.punch()
携带数据的PySide信号
创建信号可以完成一个非常有用的事情——携带数据。例如，你可以创建一个携带整数或者字符串的信号：
updated = Signal(int)
updated = Signal(str)
这个数据类型可以是任何Python的类型名或定义了C++类型的字符串。因为教程不假设有任何C++的知识，故我们只使用Python类型。
例子：一个发送信号的圆
我们用x，y和r定义一个圆，x、y是圆中心的坐标，r是半径。我们想要当圆被改变大小时，发送一个信号resized；当圆被移动时，也发送一个信号moved。虽然我们可以在信号的槽中检测圆的大小和位置，但是使用信号发送这些信息会更加方便。
from PySide.QtCore import QObject, Signal, Slot class Circle(QObject):
''' Represents a circle defined by the x and y
coordinates of its center and its radius r. '''
# Signal emitted when the circle is resized,
# carrying its integer radius
resized = Signal(int)
# Signal emitted when the circle is moved, carrying
# the x and y coordinates of its center.
moved = Signal(int, int) def __init__(self, x, y, r):
# Initialize the Circle as a QObject so it can emit signals
QObject.__init__(self) # "Hide" the values and expose them via properties
self._x = x
self._y = y
self._r = r @property
def x(self):
return self._x @x.setter
def x(self, new_x):
self._x = new_x
# After the center is moved, emit the
# moved signal with the new coordinates
self.moved.emit(new_x, self.y) @property
def y(self):
return self._y
@y.setter
def y(self, new_y):
self._y = new_y
# After the center is moved, emit the moved
# signal with the new coordinates
self.moved.emit(self.x, new_y) @property
def r(self):
return self._r @r.setter
def r(self, new_r):
self._r = new_r
# After the radius is changed, emit the
# resized signal with the new radius
self.resized.emit(new_r)
注意以下几点：
- Circle继承自QObject所以可以发送信号
- 同样的信号可以在不同地方发送
现在我们定义一些连接Circle的信号的槽。还记得我们上次提过的@Slot修饰符（decorator）吗？现在我们来看看如何接收携带了数据的信号。为了接收信号，我们简单的将其定义为与信号一样的结构。
# A slot for the "moved" signal, accepting the x and y coordinates
@Slot(int, int)
def on_moved(x, y):
print('Circle was moved to (%s, %s).' % (x, y)) # A slot for the "resized" signal, accepting the radius
@Slot(int)
def on_resized(r):
print('Circle was resized to radius %s.' % r)
非常的简单直观。更多信息可以参考Python decorators，或者来学习这篇文章Python Decorators Overview。最后我们完成这个Circle，连接信号槽，移动并改变它的大小。
c = Circle(5, 5, 4) # Connect the Circle's signals to our simple slots
c.moved.connect(on_moved)
c.resized.connect(on_resized) # Move the circle one unit to the right
c.x += 1 # Increase the circle's radius by one unit
c.r += 1
当运行脚本的时候，你的结果应该是：
Circle was moved to (6, 5).
Circle was resized to radius 5.
现在我们对信号和槽有了更深入的了解，可以准备使用一些更高级的widgets了。下一个教程开始讨论QListWidget和QListView，两种创建表框（list box）控件的方法。
By Ascii0x03
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