Root Control: LoginScreen
To initialize the control:
Note To add super, covered with a new initialization method of the obsolete initialization method
Dispatched property of the event: kivy control properties Property, provides a on_ default event. When the property is changed, we will call this incident.
pressed = ListProperty ([0,0]): based on press ListProperty defines a property attribute, the default value is [0,0]. From that point on, as long as the property has changed, on_presses event will be called.
on_ event will be called in position within the class definition attributes. In addition to the definition of the class of the property, to monitor / observe any change in a property, it must bind to this binding operations property.