Recycleview Pull to refresh example

examples/widgets/recycleview/pull_to_refresh.py

@@ -0,0 +1,91 @@
+"""Detecting and acting upon "Pull down actions" in a RecycleView
+- When using overscroll or being at the to, a "pull down to refresh" message appears
+- if the user pulls down far enough, then a refresh is triggered, which adds new elements at the top of the list.
+
+"""
+from threading import Thread
+from time import sleep
+from datetime import datetime
+
+from kivy.app import App
+from kivy.lang import Builder
+from kivy.properties import ListProperty, BooleanProperty
+from kivy.metrics import dp
+
+
+KV = r'''
+FloatLayout:
+    Label:
+        opacity: 1 if app.refreshing or rv.scroll_y > 1 else 0
+        size_hint_y: None
+        pos_hint: {'top': 1}
+        text: 'Refreshing…' if app.refreshing else 'Pull down to refresh'
+
+    RecycleView:
+        id: rv
+        data: app.data
+        viewclass: 'Row'
+        do_scroll_y: True
+        do_scroll_x: False
+        on_scroll_y: app.check_pull_refresh(self, grid)
+
+        RecycleGridLayout:
+            id: grid
+            cols: 1
+            size_hint_y: None
+            height: self.minimum_height
+            default_size: 0, 36
+            default_size_hint: 1, None
+
+
+<Row@Label>:
+    _id: 0
+    text: ''
+    canvas:
+        Line:
+            rectangle: self.pos + self.size
+            width: 0.6
+'''
+
+
+class Application(App):
+    data = ListProperty([])
+    refreshing = BooleanProperty()
+
+    def build(self):
+        self.refresh_data()
+        return Builder.load_string(KV)
+
+    def check_pull_refresh(self, view, grid):
+        """Check the amount of overscroll to decide if we want to trigger the
+        refresh or not.
+        """
+        max_pixel = dp(200)
+        to_relative = max_pixel / (grid.height - view.height)
+        if view.scroll_y <= 1.0 + to_relative or self.refreshing:
+            return
+
+        self.refresh_data()
+
+    def refresh_data(self):
+        # using a Thread to do a potentially long operation without blocking
+        # the UI.
+        Thread(target=self._refresh_data).start()
+
+    def _refresh_data(self):
+        self.refreshing = True
+        sleep(2)
+        update_time = datetime.now().strftime("%H:%M:%S")
+
+        self.prepend_data([
+            {'_id': i, 'text': '[{}] hello {}'.format(update_time, i)}
+            for i in range(len(self.data) + 10, len(self.data), -1)
+        ])
+        self.refreshing = False
+
+    def prepend_data(self, data):
+        self.data = data + self.data
+
+
+if __name__ == "__main__":
+    Application().run()