Question

当我按下工具栏图标时，我试图更改屏幕，但是kivy说str对象是不可调用的。我该如何解决？（我知道，问题出在语法上，请帮忙）

from kivy.lang import Builder
from kivymd.app import MDApp

KV = '''
Screen:    
    MDToolbar:
        id: toolbar
        pos_hint: {"top": 1}
        elevation: 10
        title: "MDNavigationDrawer"
        left_action_items: [["menu", lambda x: nav_drawer.set_state("open")]]

    NavigationLayout:    
        x: toolbar.height    
        ScreenManager:
            id: screen_manager    
            Screen:
                name: "scr 1"                
                  
                MDLabel:
                    text: "Screen 1"
                    halign: "center"    
            Screen:
                name: "scr 2"                    
                MDToolbar:
                    id: toolbar
                    pos_hint: {"top": 1}
                    elevation: 10
                    title: "MDNavigationDrawer"
                    left_action_items: [["arrow-left", lambda x: screen_manager.current("scr 1")]]                    
                MDLabel:
                    text: "Screen 2"
                    halign: "center"    
        MDNavigationDrawer:
            id: nav_drawer
               
            screen_manager: screen_manager
            nav_drawer: nav_drawer
                           
            ScrollView:    
                MDList:            
                    OneLineListItem:
                        text: "Screen 1"
                        on_press:                                self.parent.parent.parent.nav_drawer.set_state("close")                                self.parent.parent.parent.screen_manager.current = "scr 1"            
                    OneLineListItem:
                        text: "Screen 2"
                        on_press:                                self.parent.parent.parent.nav_drawer.set_state("close")                                self.parent.parent.parent.screen_manager.current = "scr 2"               
                    '''       
class TestNavigationDrawer(MDApp):    
    def build(self):
        return Builder.load_string(KV)  
TestNavigationDrawer().run()

TypeError：“ str”对象不可调用

Answer 1

我认为问题是scr 1中的空格，请尝试使用scr1或scr_1

尝试

left_action_items: [["arrow-left", lambda x: root.manager.change_screen("scr1")]]

并在您的main.py中添加此功能

def change_screen(self, screen):
    # the same as in .kv: app.root.current = screen
    self.current = screen

Answer 2

我找到了可行的解决方案。也许它会对某人有所帮助：

/main.py

class App(MDApp):
    kv_file = 'main.kv'


if __name__ == '__main__':
    app = App()
app.run()

/main.kv

<Scr2@Screen>
    name: 'scr2'

    MDBoxLayout:
        orientation: 'vertical'
    
        MDToolbar:
            title: 'MDToolbar'
            left_action_items: [['arrow-left', lambda _: setattr(root.manager, 'current', 'scr1')]]

        MDLabel:
            text: 'Content'
            halign: 'center'

如何从屏幕管理器在kivymd工具栏中回调？

2 个答案: