KIVY zindex dynamic change - kivy

Question

I am trying to add 4 boxes in Relativelayout. Able to horizontally move only the box which gets added last in relativelayout. All other box gets strucked up when it is moved closer to its box which got added later. In given sample code below 'Actor 400' freely moves horizontally across the scene. 'Actor 300' able to move freely over 'Actor 200' and 'Actor 100'. But when I try to move Actor 300 above Actor 400, it get strucked and only after mouse moves beyond Actor 400, I am able to move.
Can I change the zindex of the widget dynamically when I touch it.
from kivy.app import App
from kivy.graphics import Line, Color
from kivy.uix.scatter import Scatter
from kivy.uix.relativelayout import RelativeLayout
from kivy.uix.widget import Widget
from kivy.uix.label import Label
from kivy.core.window import Window
from kivy.lang import Builder
KV = '''
<Actor>:
canvas:
Color:
rgba: 0,1,0,.8
Rectangle:
id: _rect_
size: 100, 30
pos: 0, root.height - 30
Line:
points: 50, root.height - 30, 50, 20
width:2
Label:
id: _actr_lbl
text: 'Hello World'
color: 0,0,0,1
size_hint: None, None
size: 100, 30
pos: 0, root.height - 30
'''
Builder.load_string(KV)
class Actor(Scatter):
def __init__(self, **kwargs) :
Name = kwargs.pop('Name', 'Actor-NoName')
super(Actor, self).__init__(**kwargs)
self.Name = Name
self.ids._actr_lbl.text = Name
def on_touch_down(self, touch):
if self.collide_point(*touch.pos):
self.selected = True
self.pos_hint = {'top':1}
self.hint_diff_touch_to_x = self.right - touch.x
return True
return super(Actor, self).on_touch_down(touch)
def on_touch_move(self, touch):
if (self.selected) :
future_right = touch.x + self.hint_diff_touch_to_x
if (future_right <= self.parent.size[0]) and ((future_right - self.width) >= 0) :
self.right = future_right
self.pos_hint = {'top':1}
return True
return super(Actor, self).on_touch_move(touch)
def on_touch_up(self, touch):
if (self.selected) :
self.selected = False
self.hint_diff_touch_to_x = 0
self.iy = 0
return True
return super(Actor, self).on_touch_up(touch)
class MyPaintApp(App):
def build(self):
root = RelativeLayout()
(ix, iy) = (100,100)
clr = Color(0.2, 0.2, 1)
for ix in [100, 200, 300, 400 ] :
root.add_widget(Actor(Name = 'Actor ' + str(ix), pos=(ix,0), size_hint=(None,1)))
return root
if __name__ == '__main__':
Window.clearcolor = (1, 1, 1, 1)
MyPaintApp().run()

Answer 1

When one of your Actor Widgets is selected, you can move it to the top by removing it and re-adding it, like this:
def on_touch_down(self, touch):
if self.collide_point(*touch.pos):
self.selected = True
self.pos_hint = {'top':1}
self.hint_diff_touch_to_x = self.right - touch.x
parent = self.parent
# move this Actor to the front
parent.remove_widget(self)
parent.add_widget(self)
return True
return super(Actor, self).on_touch_down(touch)