如何在 Kivy 的 ScrollView 边缘移动 cursor 时滚动 ScrollView

Question

So basically I'm using draggable function from Kivy Garden, and currently using it with ScrollView, example can be found here.

The problem is that when I'm dragging a widget, I only can move it inside my viewport. Because the ScrollView does not auto scroll when you drag and move it to the edge of the Layout.

So my question is there any way to make the ScrollView auto scroll when my cursor is at the edge of the ScrollView layout without using the mouse's wheel?

Answer 1

You can extend your DraggableItem to force scrolling when the DraggableItem is at the top or bottom of the ScrollView . Here is an idea about how to do this, but it may need more work:

class DraggableItem(KXDraggableBehavior, Button):
    scroll_up_event = ObjectProperty(None, allownone=True)
    scroll_down_event = ObjectProperty(None, allownone=True)

    def on_touch_move(self, touch):
        super(DraggableItem, self).on_touch_move(touch)
        if self.is_being_dragged:
            self.handle_scrolling()

    def handle_scrolling(self):
        global root
        if self.y < root.y:
            # scroll down
            if self.scroll_down_event is None:
                self.scroll_down_event = Clock.schedule_interval(self.do_scroll_down, 0.2)
        elif self.y >= root.y:
            # stop any down scrolling
            if self.scroll_down_event:
                self.scroll_down_event.cancel()
                self.scroll_down_event = None
        if self.top > root.top:
            # scroll up
            if self.scroll_up_event is None:
                self.scroll_up_event = Clock.schedule_interval(self.do_scroll_up, 0.2)
        elif self.top <= root.top:
            # stop any up scrolling
            if self.scroll_up_event:
                self.scroll_up_event.cancel()
                self.scroll_up_event = None

    def do_scroll_up(self, *args):
        global root
        scroll = root.scroll_y + 0.01
        if scroll <= 1:
            root.scroll_y = scroll
        else:
            # cannot scroll up any farther
            self.scroll_up_event.cancel()
            self.scroll_up_event = None

    def do_scroll_down(self, *args):
        global root
        scroll = root.scroll_y - 0.01
        if scroll >= 0:
            root.scroll_y = scroll
        else:
            # cannot scroll down any farther
            self.scroll_down_event.cancel()
            self.scroll_down_event = None