我正在为kivy写一个自定义小部件(请参阅this问题),但我发现由于某些未知原因,有时bind
方法实际上并没有绑定回调。
在我的课堂上,我有这段代码:
def __init__(self, **kwargs):
super(SpinBox, self).__init__(**kwargs)
self._value_label = Label(text=str(self.value))
self.inc_button = TimedButton(text='+')
self.dec_button = TimedButton(text='-')
def inc(inst):
if float(self.value) + float(self.step) <= self.max_value:
self.value += self.step
def dec(inst):
if float(self.value) - float(self.step) >= self.min_value:
self.value -= self.step
self.inc_button.bind(on_press=inc)
self.inc_button.bind(on_time_slice=inc)
self.dec_button.bind(on_press=dec)
self.dec_button.bind(on_time_slice=dec)
# ...
其中
TimedButton
是另一个自定义类。这是一个Button
子类,它在on_touch_down
上启动计时器,如果经过一定时间后仍未收到on_touch_up
,它将认为按下是长按,并开始使用以下命令调度on_time_slice
事件Clock.schedule_interval
每几毫秒。因此,尝试使用这样的自定义类:
class MyApp(App):
def build(self):
return SpinBox()
MyApp().run()
value
完全不增加。如果我做:
class MyApp(App):
def build(self):
s = SpinBox()
def inc(inst):
s.value += 1
s.inc_button.bind(on_time_slice=inc)
return s
MyApp().run()
在每个
on_time_slice
事件中,该值都会递增。我不明白为什么MyApp
类内的绑定有效,而SpinBox.__init__
方法中的绑定却无效。我究竟做错了什么?
最佳答案
我找到了解决方法。我没有绑定on_touch_down
和on_touch_up
,而是尝试绑定state
属性,在on_state
中实现了TimedButton
方法,它可以工作。我仍然不理解为什么以前的实现在单独使用而不在SpinBox
中使用时会起作用,除非直接在App
类内部绑定函数。
无论如何,由于看起来TimedButton
类与它有关,因此这是旧实现的代码:
class TimedButton(Button):
"""A simple ``Button`` subclass that produces an event at regular intervals
when pressed.
This class, when long-pressed, emits an ``on_time_slice`` event every
``time_slice`` milliseconds.
:param long_press_interval: Defines the minimum time required to consider
the press a long-press.
:type long_press_interval: int
:param time_slice: The number of milliseconds of each slice.
:type time_slice: int
"""
def __init__(self, long_press_interval=550, time_slice=225, **kwargs):
super(TimedButton, self).__init__(**kwargs)
self.long_press_interval = long_press_interval
self.time_slice = time_slice
self._touch_start = None
self._touch_uid = None
self._long_press_callback = None
self._slice_callback = None
self.register_event_type('on_time_slice')
self.register_event_type('on_long_press')
def on_touch_down(self, touch):
start_time = time.time()
self._touch_start = start_time
self._touch_uid = touch.uid
def callback(dt):
self._check_long_press(dt)
Clock.schedule_once(callback, self.long_press_interval / 1000.0)
self._long_press_callback = callback
super(TimedButton, self).on_touch_down(touch)
def _check_long_press(self, dt):
delta = dt * 1000
if delta > self.long_press_interval and self._touch_uid is not None:
self.dispatch('on_long_press')
self._long_press_callback = None
def slice_callback(dt):
self.dispatch('on_time_slice')
Clock.schedule_interval(slice_callback, self.time_slice / 1000.0)
self._slice_callback = slice_callback
def on_touch_up(self, touch):
end_time = time.time()
delta = (end_time - (self._touch_start or 0)) * 1000
Clock.unschedule(self._slice_callback)
if (self._long_press_callback is not None and
delta > self.long_press_interval):
self.dispatch('on_long_press')
self._touch_start = self._touch_uid = None
self._long_press_callback = self._slice_callback = None
super(TimedButton, self).on_touch_up(touch)
def on_long_press(self):
pass
def on_time_slice(self):
pass
这是使用
state
的新代码,效果很好:class TimedButton(Button):
"""A simple ``Button`` subclass that produces an event at regular intervals
when pressed.
This class, when long-pressed, emits an ``on_time_slice`` event every
``time_slice`` milliseconds.
:param long_press_interval: Defines the minimum time required to consider
the press a long-press.
:type long_press_interval: int
:param time_slice: The number of milliseconds of each slice.
:type time_slice: int
"""
def __init__(self, long_press_interval=550, time_slice=225, **kwargs):
super(TimedButton, self).__init__(**kwargs)
self.long_press_interval = long_press_interval
self.time_slice = time_slice
self._touch_start = None
self._long_press_callback = None
self._slice_callback = None
self.register_event_type('on_time_slice')
self.register_event_type('on_long_press')
def on_state(self, instance, value):
if value == 'down':
start_time = time.time()
self._touch_start = start_time
def callback(dt):
self._check_long_press(dt)
Clock.schedule_once(callback, self.long_press_interval / 1000.0)
self._long_press_callback = callback
else:
end_time = time.time()
delta = (end_time - (self._touch_start or 0)) * 1000
Clock.unschedule(self._slice_callback)
if (self._long_press_callback is not None and
delta > self.long_press_interval):
self.dispatch('on_long_press')
self._touch_start = None
self._long_press_callback = self._slice_callback = None
def _check_long_press(self, dt):
delta = dt * 1000
if delta > self.long_press_interval and self.state == 'down':
self.dispatch('on_long_press')
self._long_press_callback = None
def slice_callback(dt):
self.dispatch('on_time_slice')
return self.state == 'down'
Clock.schedule_interval(slice_callback, self.time_slice / 1000.0)
self._slice_callback = slice_callback
def on_long_press(self):
pass
def on_time_slice(self):
pass
关于python - 随机绑定(bind)工作,我们在Stack Overflow上找到一个类似的问题:https://stackoverflow.com/questions/14074979/