在 Kivy 中使用 DragBehavior

Question

我是 python 和 kivy 的新手，正在与它们斗争。

我想用kivy实现拖放功能（当一个图像被拖到另一个图像并放在它上面时，做一些事情的功能。）。

我想做的是以下三件事；

• 知道用户现在持有的元素的id。
• 知道用户悬停的元素的 ID。
• 知道当用户放下他所拥有的东西时指针下的元素的 ID。

我认为this 对处理它们很有用，所以我写下了下面的python 脚本和.kivy 文件。但是，它并没有按我的预期工作。

有很多问题我不知道如何解决；

• print(self.id) 返回无。
• 即使我只拖动 1 个元素，on_touch_up 也会打印 None 两次。
• 一旦拖放图像，该图像将无法再拖动。

python 文件：

from kivy.app import App
from kivy.uix.image import Image
from kivy.uix.behaviors import DragBehavior
from kivy.properties import BooleanProperty
from kivy.properties import ObjectProperty
from kivy.factory import Factory
from kivy.core.window import Window


class HoverBehavior(object):
    """Hover behavior.
    :Events:
        `on_enter`
            Fired when mouse enter the bbox of the widget.
        `on_leave`
            Fired when the mouse exit the widget
    """

    hovered = BooleanProperty(False)
    border_point = ObjectProperty(None)
    '''Contains the last relevant point received by the Hoverable. This can
    be used in `on_enter` or `on_leave` in order to know where was dispatched the event.
    '''

    def __init__(self, **kwargs):
        self.register_event_type('on_enter')
        self.register_event_type('on_leave')
        Window.bind(mouse_pos=self.on_mouse_pos)
        super(HoverBehavior, self).__init__(**kwargs)

    def on_mouse_pos(self, *args):
        if not self.get_root_window():
            return  # do proceed if I'm not displayed <=> If have no parent
        pos = args[1]
        # Next line to_widget allow to compensate for relative layout
        inside = self.collide_point(*self.to_widget(*pos))
        if self.hovered == inside:
            # We have already done what was needed
            return
        self.border_point = pos
        self.hovered = inside
        if inside:
            self.dispatch('on_enter')
        else:
            self.dispatch('on_leave')

    def on_enter(self):
        pass

    def on_leave(self):
        pass


Factory.register('HoverBehavior', HoverBehavior)


class DraggableImage(DragBehavior, HoverBehavior, Image):
    def __init__(self, **args):
        super(DraggableImage, self).__init__(**args)
        self.source_file = ""
        self.is_on_hover = False

    def on_enter(self):
        self.source_file = self.source
        self.source = "green.png"
        self.is_on_hover = True
        print(self.id)

    def on_leave(self):
        self.source = self.source_file
        self.is_on_hover = False
        print(self.id)

    def on_touch_up(self, touch):
        if self.is_on_hover:
            print(self.id)


class TestApp(App):
    def build(self):
        pass


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

test.kivy：

<DraggableImage>
    drag_rectangle: self.x, self.y, self.width, self.height
    drag_timeout: 10000000
    drag_distance: 0

BoxLayout:
    orientation: "horizontal"
    DraggableImage:
        id: "left_left"
        source: "red.png"
    DraggableImage:
        id: "left_right"
        source: "yellow.png"
    DraggableImage:
        id: "right_left"
        source: "red.png"
    DraggableImage:
        id: "right_right"
        source: "yellow.png"

Answer 1

创建一个名为StringProperty 的名称，例如name。不要使用id，因为在kv中使用了id。
改变你的班级和kv：

from kivy.properties import StringProperty

class DraggableImage(DragBehavior, HoverBehavior, Image):

    name = StringProperty("")

    def __init__(self, **args):
        super(DraggableImage, self).__init__(**args)
        self.source_file = ""
        self.is_on_hover = False

    def on_enter(self):
        self.source_file = self.source
        self.source = "green.png"
        self.is_on_hover = True
        print(self.name)

    def on_leave(self):
        self.source = self.source_file
        self.is_on_hover = False
        print(self.name)

    def on_touch_up(self, touch):
        if self.is_on_hover:
            print(self.name)




KV = """

<DraggableImage>:
    drag_rectangle: self.x, self.y, self.width, self.height
    drag_timeout: 10000000
    drag_distance: 0

BoxLayout:
    orientation: "horizontal"
    DraggableImage:
        name: "left_left"
        source: "red.png"
    DraggableImage:
        name: "left_right"
        source: "yellow.png"
    DraggableImage:
        name: "right_left"
        source: "red.png"
    DraggableImage:
        name: "right_right"
        source: "yellow.png"

"""