Question

我想将我的方法change_map绑定到我的按钮，并通过on_press函数将屏幕更改为“menu”。

在.kv文件中，它看起来像这样。

        Button:
            id: some_btn
            on_press: root.change_map(); app.root.current = "menu"

我需要以pythonic方式使用它，但我收到错误“AssertionError：None不可调用”。

main.py

class MapScreen(Screen):

    def __init__(self, **kwargs):
        super(MapScreen, self).__init__(**kwargs)

    def change_map(self, map_id):
        global MAP_ID
        MAP_ID = map_id

    def on_enter(self, *args):
        file_system = FileSystemLocal()
        maps_folder = file_system .listdir('data/maps') #Gets all file names in the folder
        for i in range(len(maps_folder)-1):
            if "map" in maps_folder[i] and "~" not in maps_folder[i]: 
                map_number = maps_folder[i].replace("map", "").replace(".txt", "") # If it's a map file, get the map number
                map_button = Button(text=map_number,font_name='data/fonts/Square.ttf', size_hint=(0.2, None)) #Button text is the map number
-->             map_button.bind(on_press=self.change_map(map_number)) #When the button is pressed call change_map to change global var
                self.ids.map_choice.add_widget(map_button) #Add the button(s) to the StackLayout in file.kv

file.kv

<MapScreen>:
    canvas:
        Color:
            rgb: app.rgb(52, 152, 219)
        Rectangle:
            pos: self.pos
            size: self.size
    StackLayout:
        id: map_choice
        orientation: 'lr-tb'
        size_hint: .9, .9
        pos_hint: {'center_x':.5, 'center_y':.5}

Answer 1

map_button.bind(on_press=self.change_map(map_number))

此调用 self.change_map，这是一个返回None的函数，因此在您尝试调用它时会出现错误。

相反，您需要传递 self.change_map以及您的默认参数。一个好方法是使用partial：

from functools import partial
map_button.bind(on_press=partial(self.change_map, map_number))

以pythonic方式使用on_press绑定方法（change_map）

1 个答案: