如何从屏幕管理器在kivymd工具栏中进行回调

Question

当我按下工具栏图标时，我试图更改屏幕，但kivy说str对象是不可调用的。我该怎么解决？(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

我找到了可行的解决方案。也许它会对某人有所帮助：

/主.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'

Answer 2

我认为问题出在scr 1中，请尝试scr1或scr_1而不是

试试这个

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