Interference of Sliders in Kivy - slider

Question

I'm learning Kivy and currently try to understand the Slider class. I created two sliders. Slider one is supposed to react to on_touch_move only, while slider two should react to on_touch_up and on_touch_down. If I implement this, like I did in the example below, both sliders interfere, i.e. they react to all three event dispatchers. I tried to understand why that is and how to solve the issue, but I can't. Thank you for helping me out.
The sliders.kv file:
#: kivy 1.9.0
SliderScreen:
<SliderScreen>:
Slider:
min: 0
max: 1
value: 0.75
step: 0.01
on_touch_move: root.test_a()
Slider:
min: 0
max: 1
value: 0.25
step: 0.01
on_touch_up: root.test_b()
on_touch_down: root.test_c()
and main.py:
import kivy
kivy.require('1.9.0')
from kivy.app import App
from kivy.uix.boxlayout import BoxLayout
from kivy.uix.slider import Slider
class SliderScreen(BoxLayout):
def test_a(self):
print("test_a accessed")
def test_b(self):
print("test_b accessed")
def test_c(self):
print("test_c accessed")
class SlidersApp(App):
pass
if __name__ == '__main__':
SlidersApp().run()

Answer 1

on_touch_move, on_touch_up and on_touch_down events are captured by SliderScreen class and then propagated to all its widgets. According to the documentation:
By default, touch events are dispatched to all currently displayed
widgets. This means widgets recieve the touch event whether it occurs
within their physical area or not.
This can be counter intuitive if you have experience with other GUI
toolkits. These typically divide the screen into geometric areas and
only dispatch touch or mouse events to the widget if the coordinate
lies within the widgets area.
This requirement becomes very restrictive when working with touch
input. Swipes, pinches and long presses may well originate from
outside of the widget that wants to know about them and react to them.
In order to provide the maximum flexibility, Kivy dispatches the
events to all the widgets and lets them decide how to react to them.
If you only want to respond to touch events inside the widget, you
simply check:
def on_touch_down(self, touch):
if self.collide_point(*touch.pos):
# The touch has occurred inside the widgets area. Do stuff!
pass
Therefore you should use in your code:
Builder.load_string("""
<SliderScreen>:
Slider:
min: 0
max: 1
value: 0.75
step: 0.01
on_touch_move: if self.collide_point(*args[1].pos): root.test_a()
Slider:
min: 0
max: 1
value: 0.25
step: 0.01
on_touch_up: if self.collide_point(*args[1].pos): root.test_b()
on_touch_down: if self.collide_point(*args[1].pos): root.test_c()
""")
class SliderScreen(BoxLayout):
def test_a(self):
print("test_a accessed")
def test_b(self):
print("test_b accessed")
def test_c(self):
print("test_c accessed")