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RecycleView

New in version 1.10.0.

The RecycleView provides a flexible model for viewing selected sections of large data sets. It aims to prevent the performance degradation that can occur when generating large numbers of widgets in order to display many data items.

Warning

This module is highly experimental, its API may change in the future and the documentation is not complete at this time.

The view is generatad by processing the data, essentially a list of dicts, and uses these dicts to generate instances of the viewclass as required. Its design is based on the MVC (Model-view-controller) pattern.

  • Model: The model is formed by data you pass in via a list of dicts.
  • View: The View is split across layout and views and implemented by...
  • Controller: The controller is implemented by RecycleViewBehavior.

These are abstract classes and cannot be used directly. The default concrete implementation is the RecycleDataModel for the model, the RecycleLayout and ... for view, and the RecycleView for the controller.

When a RecycleView is instantiated, it automatically creates the views and data classes. However, one must manually create the layout classes and add them to the RecycleView.

A layout manager is automatically created as a layout_manager when added as the child of the RecycleView. Similarly when removed. A requirement is that the layout manager must be contained as a child somewhere within the RecycleView’s widget tree so the view port can be found.

A minimal example might look something like this:

from kivy.app import App
from kivy.lang import Builder
from kivy.uix.recycleview import RecycleView


Builder.load_string('''
<RV>:
    viewclass: 'Label'
    RecycleBoxLayout:
        default_size: None, dp(56)
        default_size_hint: 1, None
        size_hint_y: None
        height: self.minimum_height
        orientation: 'vertical'
''')

class RV(RecycleView):
    def __init__(self, **kwargs):
        super(RV, self).__init__(**kwargs)
        self.data = [{'text': str(x)} for x in range(100)]


class TestApp(App):
    def build(self):
        return RV()

if __name__ == '__main__':
    TestApp().run()

In order to support selection in the view, you can add the required behaviours as follows:

from kivy.app import App
from kivy.lang import Builder
from kivy.uix.recycleview import RecycleView
from kivy.uix.recycleview.views import RecycleDataViewBehavior
from kivy.uix.label import Label
from kivy.properties import BooleanProperty
from kivy.uix.recycleboxlayout import RecycleBoxLayout
from kivy.uix.behaviors import FocusBehavior
from kivy.uix.recycleview.layout import LayoutSelectionBehavior

Builder.load_string('''
<SelectableLabel>:
    # Draw a background to indicate selection
    canvas.before:
        Color:
            rgba: (.0, 0.9, .1, .3) if self.selected else (0, 0, 0, 1)
        Rectangle:
            pos: self.pos
            size: self.size
<RV>:
    viewclass: 'SelectableLabel'
    SelectableRecycleBoxLayout:
        default_size: None, dp(56)
        default_size_hint: 1, None
        size_hint_y: None
        height: self.minimum_height
        orientation: 'vertical'
        multiselect: True
        touch_multiselect: True
''')


class SelectableRecycleBoxLayout(FocusBehavior, LayoutSelectionBehavior,
                                 RecycleBoxLayout):
    ''' Adds selection and focus behaviour to the view. '''


class SelectableLabel(RecycleDataViewBehavior, Label):
    ''' Add selection support to the Label '''
    index = None
    selected = BooleanProperty(False)
    selectable = BooleanProperty(True)

    def refresh_view_attrs(self, rv, index, data):
        ''' Catch and handle the view changes '''
        self.index = index
        return super(SelectableLabel, self).refresh_view_attrs(
            rv, index, data)

    def on_touch_down(self, touch):
        ''' Add selection on touch down '''
        if super(SelectableLabel, self).on_touch_down(touch):
            return True
        if self.collide_point(*touch.pos) and self.selectable:
            return self.parent.select_with_touch(self.index, touch)

    def apply_selection(self, rv, index, is_selected):
        ''' Respond to the selection of items in the view. '''
        self.selected = is_selected
        if is_selected:
            print("selection changed to {0}".format(rv.data[index]))
        else:
            print("selection removed for {0}".format(rv.data[index]))


class RV(RecycleView):
    def __init__(self, **kwargs):
        super(RV, self).__init__(**kwargs)
        self.data = [{'text': str(x)} for x in range(100)]


class TestApp(App):
    def build(self):
        return RV()

if __name__ == '__main__':
    TestApp().run()

Please see the examples/widgets/recycleview/basic_data.py file for a more complete example.

TODO:
  • Method to clear cached class instances.
  • Test when views cannot be found (e.g. viewclass is None).
  • Fix selection goto.

Warning

When views are re-used they may not trigger if the data remains the same.

class kivy.uix.recycleview.RecycleViewBehavior(**kwargs)[source]

Bases: builtins.object

RecycleViewBehavior provides a behavioral model upon which the RecycleView is built. Together, they offer an extensible and flexible way to produce views with limited windows over large data sets.

See the module documentation for more information.

data_model

The Data model responsible for maintaining the data set.

data_model is an AliasProperty that gets and sets the current data model.

layout_manager

The Layout manager responsible for positioning views within the RecycleView.

layout_manager is an AliasProperty that gets and sets the layout_manger.

refresh_from_data(*largs, **kwargs)[source]

This should be called when data changes. Data changes typically indicate that everything should be recomputed since the source data changed.

This method is automatically bound to the on_data_changed method of the RecycleDataModelBehavior class and therefore responds to and accepts the keyword arguments of that event.

It can be called manually to trigger an update.

refresh_from_layout(*largs, **kwargs)[source]

This should be called when the layout changes or needs to change. It is typically called when a layout parameter has changed and therefore the layout needs to be recomputed.

refresh_from_viewport(*largs)[source]

This should be called when the viewport changes and the displayed data must be updated. Neither the data nor the layout will be recomputed.

view_adapter

The adapter responsible for providing views that represent items in a data set.

view_adapter is an AliasProperty that gets and sets the current view adapter.

class kivy.uix.recycleview.RecycleView(**kwargs)[source]

Bases: kivy.uix.recycleview.RecycleViewBehavior, kivy.uix.scrollview.ScrollView

RecycleView is a flexible view for providing a limited window into a large data set.

See the module documentation for more information.

data

The data used by the current view adapter. This is a list of dicts whose keys map to the corresponding property names of the viewclass.

data is an AliasProperty that gets and sets the data used to generate the views.

key_viewclass

key_viewclass is an AliasProperty that gets and sets the key viewclass for the current layout_manager.

viewclass

The viewclass used by the current layout_manager.

viewclass is an AliasProperty that gets and sets the class used to generate the individual items presented in the view.