问题：1

Question

我一直在尝试使用Accessing id/widget of different class from a kivy file (.kv) using Kivy's clock?中的信息，从Kivy Screen manager reference in kv language建立我的kv语言技能。不幸的是，后一篇文章没有包含完整的工作代码示例，因此我无法理解如何在多屏幕Kivy应用程序的特定屏幕上更改文本元素。

在搜索了大部分时间之后，我找不到任何简单具体的工作示例，说明如何使用kv语言构建多屏幕应用程序，所以我在这里。我似乎无法设置对各个屏幕的正确引用，因此我可以更改它们。

在下面的简单示例代码中，我构建了一个四屏应用程序，可在四个屏幕之间自动切换。我想从这个问题中学习两件事;

将尽可能多地设置屏幕管理器的kv语言代码。即。可以通过kv语言减少或消除第43至47行吗？
实际的python代码（我相信会在应用程序的第56行）将第一个屏幕上的文本更改为＆＃34;嗨我是第五个屏幕＆＃34;在它第二次显示之前。

以下代码。提前致谢。 ......布拉德......

import kivy
kivy.require('1.10.0')
from kivy.app import App
from kivy.lang import Builder
from kivy.clock import Clock
from kivy.uix.screenmanager import ScreenManager, Screen

Builder.load_string("""
<FirstScreen>:
    name: '_first_screen_'
    Label:
        id: first_screen
        text: "Hi I'm The First Screen"
<SecondScreen>:
    name: '_second_screen_'
    Label:
        id: second_screen
        text: "Hi I'm The Second Screen"
<ThirdScreen>:
    name: '_third_screen_'
    Label:
        id: third_screen
        text: "Hi I'm The Third Screen"
<FourthScreen>:
    name: '_fourth_screen_'
    Label:
        id: fourth_screen
        text: "Hi I'm The Fourth Screen"
""")

class FirstScreen(Screen):
    pass

class SecondScreen(Screen):
    pass

class ThirdScreen(Screen):
    pass

class FourthScreen(Screen):
    pass

sm = ScreenManager()
sm.add_widget(FirstScreen())
sm.add_widget(SecondScreen())
sm.add_widget(ThirdScreen())
sm.add_widget(FourthScreen())

class SwitchingScreenApp(App):

    def build(self):
        Clock.schedule_once(self.screen_switch_one, 2)
        Clock.schedule_once(self.screen_switch_two, 4)
        Clock.schedule_once(self.screen_switch_three, 6)
        Clock.schedule_once(self.screen_switch_four, 8)
        # Want to place the code here that changes the first_screen text to "Hi I'm The Fifth Screen"
        Clock.schedule_once(self.screen_switch_one, 10)
        return sm

    def screen_switch_one(a,b):
        sm.current = '_first_screen_'
    def screen_switch_two(a,b):
        sm.current = '_second_screen_'
    def screen_switch_three(a,b):
        sm.current = '_third_screen_'
    def screen_switch_four(a,b):
        sm.current = '_fourth_screen_'

SwitchingScreenApp().run()

Answer 1

首先，我建议将代码拆分为Python和kv文件，因为随着程序的增长，维护UI /小部件和Python代码会更容易。有关详细信息，请参阅示例（app_with_kv.py，switchingscreen.kv，输出）。

问题：1

将尽可能多地设置屏幕管理器的kv语言代码。即。可以通过kv语言减少或消除第43行到第47行吗？

sm = ScreenManager()
sm.add_widget(FirstScreen())
sm.add_widget(SecondScreen())
sm.add_widget(ThirdScreen())
sm.add_widget(FourthScreen())

答案

第1步

将一个MyScreenManager类添加到Python代码中。

class MyScreenManager(ScreenManager):
    pass
...
    def build(self):
        sm = MyScreenManager()

步骤2

在内联或单独的kv文件中添加以下kv规则。这相当于使用语句sm.add_widget（）四次。

<MyScreenManager>:
    FirstScreen:
    SecondScreen:
    ThirdScreen:
    FourthScreen:

问题：2

实际的python代码（我相信会在应用程序的第56行），它会在第二次显示之前将第一个屏幕上的文本更改为“我是第五个屏幕”。

答案

除了第一个切换屏幕方法screen_switch_one（）

之外，您必须将以下代码放在3种切换屏幕方法中的任何一种中。

self.ids.first_screen.ids.first_screen_label.text = "Hi I'm The Fifth Screen"

实施例

app_with_kv.py

from kivy.app import App
from kivy.clock import Clock
from kivy.uix.screenmanager import ScreenManager, Screen


class FirstScreen(Screen):
    pass


class SecondScreen(Screen):
    pass


class ThirdScreen(Screen):
    pass


class FourthScreen(Screen):
    pass


class MyScreenManager(ScreenManager):

    def __init__(self, **kwargs):
        super(MyScreenManager, self).__init__(**kwargs)
        Clock.schedule_once(self.screen_switch_one, 2)

    def screen_switch_one(self, dt):
        self.current = '_first_screen_'
        Clock.schedule_once(self.screen_switch_two, 2)

    def screen_switch_two(self, dt):
        self.current = '_second_screen_'
        self.ids.first_screen.ids.first_screen_label.text = "Hi I'm The Fifth Screen"
        Clock.schedule_once(self.screen_switch_three, 2)

    def screen_switch_three(self, dt):
        self.current = '_third_screen_'
        Clock.schedule_once(self.screen_switch_four, 2)

    def screen_switch_four(self, dt):
        self.current = '_fourth_screen_'
        Clock.schedule_once(self.screen_switch_one, 2)


class SwitchingScreenApp(App):

    def build(self):
        return MyScreenManager()


if __name__ == "__main__":
    SwitchingScreenApp().run()

switchingscreen.kv

#:kivy 1.10.0

<MyScreenManager>:
    FirstScreen:
        id: first_screen
    SecondScreen:
    ThirdScreen:
    FourthScreen:

<FirstScreen>:
    name: '_first_screen_'
    Label:
        id: first_screen_label
        text: "Hi I'm The First Screen"

<SecondScreen>:
    name: '_second_screen_'
    Label:
        id: second_screen_label
        text: "Hi I'm The Second Screen"

<ThirdScreen>:
    name: '_third_screen_'
    Label:
        id: third_screen_label
        text: "Hi I'm The Third Screen"

<FourthScreen>:
    name: '_fourth_screen_'
    Label:
        id: fourth_screen_label
        text: "Hi I'm The Fourth Screen"

输出

Answer 2

是的，您可以通过创建root_widget并在app类的构建方法中返回该根小部件并在kv文件中创建屏幕来消除该代码（我希望代码能够更好地解释它）
要更改kv文件中标签的python中的文本，您应该使用kivy properties并访问另一个屏幕的小部件，使用manager.get_screen（＆＃39; screenname＆＃39 ;）。widget命令

这里是main.py文件

    import kivy
    kivy.require('1.10.0')
    from kivy.app import App
    from kivy.lang import Builder
    from kivy.clock import Clock
    from kivy.uix.screenmanager import ScreenManager, Screen
    from kivy.properties import ObjectProperty

    class MenuScreen(Screen):
        pass
    class FirstScreen(Screen):
        #create property in python
        first_screen = ObjectProperty()
        def starttimer(self):
            self.timer = Clock.schedule_once(self.screen_switch_two, 2)
        def screen_switch_two(self, dt):
            self.manager.current = 'second_screen'
    class SecondScreen(Screen):
        def starttimer(self):
            self.timer = Clock.schedule_once(self.screen_switch_three, 4)
        def screen_switch_three(self, dt):
            self.manager.current = 'third_screen'
    class ThirdScreen(Screen):
        def starttimer(self):
            self.timer = Clock.schedule_once(self.screen_switch_four, 6)
        def screen_switch_four(self, dt):
            self.manager.current = 'fourth_screen'
    class FourthScreen(Screen):
        def starttimer(self):
            self.timer = Clock.schedule_once(self.screen_switch_one, 8)
        def screen_switch_one(self, dt):
            #change the text of the label in the first_screen
            self.manager.get_screen('first_screen').first_screen.text = "Hi I'm The Fifth Screen"
            self.manager.current = 'first_screen'

    root_widget = Builder.load_string("""
    #here the screens will be created
    ScreenManager:
        MenuScreen:
        FirstScreen:
        SecondScreen:
        ThirdScreen:
        FourthScreen:
    #the menu screen is created that the method on_enter in the first screen is called and the loop through the screens can begin
    <MenuScreen>:
        Button:
            text: 'start'
            on_press: app.root.current = 'first_screen'
    <FirstScreen>:
        #link/bind the property in the kv file 
        first_screen: first_screen
        name: 'first_screen'
        on_enter: root.starttimer()
        Label:
            id: first_screen
            text: "Hi I'm The First Screen"
    <SecondScreen>:
        name: 'second_screen'
        on_enter: root.starttimer()
        Label:
            id: second_screen
            text: "Hi I'm The Second Screen"
    <ThirdScreen>:
        name: 'third_screen'
        on_enter: root.starttimer()
        Label:
            id: third_screen
            text: "Hi I'm The Third Screen"
    <FourthScreen>:
        name: 'fourth_screen'
        on_enter: root.starttimer()
        Label:
            id: fourth_screen
            text: "Hi I'm The Fourth Screen"
    """)

    class SwitchingScreenApp(App):

        def build(self):
            return root_widget

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

为了更好地构造代码，我将把kv和python代码分成2个文件：

<强> main.py

import kivy
kivy.require('1.10.0')
from kivy.app import App
from kivy.lang import Builder
from kivy.clock import Clock
from kivy.uix.screenmanager import ScreenManager, Screen
from kivy.properties import ObjectProperty

class MenuScreen(Screen):
    pass
class FirstScreen(Screen):
    first_screen = ObjectProperty()
    def starttimer(self):
        self.timer = Clock.schedule_once(self.screen_switch_two, 2)
    def screen_switch_two(self, dt):
        self.manager.current = 'second_screen'
class SecondScreen(Screen):
    def starttimer(self):
        self.timer = Clock.schedule_once(self.screen_switch_three, 4)
    def screen_switch_three(self, dt):
        self.manager.current = 'third_screen'
class ThirdScreen(Screen):
    def starttimer(self):
        self.timer = Clock.schedule_once(self.screen_switch_four, 6)
    def screen_switch_four(self, dt):
        self.manager.current = 'fourth_screen'
class FourthScreen(Screen):
    def starttimer(self):
        self.timer = Clock.schedule_once(self.screen_switch_one, 8)
    def screen_switch_one(self, dt):
        self.manager.get_screen('first_screen').first_screen.text = "Hi I'm The Fifth Screen"
        self.manager.current = 'first_screen'

class SwitchingScreenApp(App):

    def build(self):
        return Builder.load_file('screen.kv')

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

和screen.kv文件

ScreenManager:
    MenuScreen:
    FirstScreen:
    SecondScreen:
    ThirdScreen:
    FourthScreen:
<MenuScreen>:
    Button:
        text: 'start'
        on_press: app.root.current = 'first_screen'
<FirstScreen>:
    first_screen: first_screen
    name: 'first_screen'
    on_enter: root.starttimer()
    Label:
        id: first_screen
        text: "Hi I'm The First Screen"
<SecondScreen>:
    name: 'second_screen'
    on_enter: root.starttimer()
    Label:
        id: second_screen
        text: "Hi I'm The Second Screen"
<ThirdScreen>:
    name: 'third_screen'
    on_enter: root.starttimer()
    Label:
        id: third_screen
        text: "Hi I'm The Third Screen"
<FourthScreen>:
    name: 'fourth_screen'
    on_enter: root.starttimer()
    Label:
        id: fourth_screen
        text: "Hi I'm The Fourth Screen"

我希望代码可以帮到你。

Answer 3

from kivy.app import App
from kivy.lang import Builder
from kivy.uix.screenmanager import ScreenManager, Screen
from kivy.uix.boxlayout import BoxLayout

class screenone(Screen):
    pass
class screentwo(Screen):
    pass



class mainApp(App):
    def build(self):
        screen_manager=ScreenManager()
        screen_manager.add_widget(screenone(name='screen_one'))
        screen_manager.add_widget(screentwo(name='screen_two'))
        return screen_manager


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



<main.kv>

<screenone>:
    BoxLayout:
        Button:
            text:"go to next screen"
            on_press:root.manager.current='screen_two'
<screentwo>:
    BoxLayout:
        Button:
            text:"go back to first screen"
            on_press:root.manager.current='screen_one'

Answer 4

与我所有帖子中的情况一样，我希望发布完整的工作代码，以便它立即有用。根据YOSHI的回答，我重新设计了他的kv语言代码，以便尽可能多地设置屏幕管理员并遵循原始代码。这回答了问题1。

但是我仍然想知道允许我将屏幕1上的文字更改为＆＃34;嗨我是第五屏幕的代码＆＃34;之前它在第二次显示在下面代码的第55行。这将有助于我了解如何更好地导航绑定以更新各个屏幕上的元素。

对此有任何帮助（使用完整的代码）将不胜感激。更新了下面的工作代码; .... brad ....

import kivy
kivy.require('1.10.0')
from kivy.app import App
from kivy.lang import Builder
from kivy.clock import Clock
from kivy.uix.screenmanager import Screen

class FirstScreen(Screen):
    pass

class SecondScreen(Screen):
    pass

class ThirdScreen(Screen):
    pass

class FourthScreen(Screen):
    pass

root_widget = Builder.load_string("""
ScreenManager:
    FirstScreen:
    SecondScreen:
    ThirdScreen:
    FourthScreen:
<FirstScreen>:
    first_screen: first_screen
    name: '_first_screen_'
    Label:
        id: first_screen
        text: "Hi I'm The First Screen"
<SecondScreen>:
    name: '_second_screen_'
    Label:
        id: second_screen
        text: "Hi I'm The Second Screen"
<ThirdScreen>:
    name: '_third_screen_'
    Label:
        id: third_screen
        text: "Hi I'm The Third Screen"
<FourthScreen>:
    name: '_fourth_screen_'
    Label:
        id: fourth_screen
        text: "Hi I'm The Fourth Screen"
""")

class SwitchingScreenApp(App):
    def build(self):
        Clock.schedule_once(self.screen_switch_one, 2)
        Clock.schedule_once(self.screen_switch_two, 4)
        Clock.schedule_once(self.screen_switch_three, 6)
        Clock.schedule_once(self.screen_switch_four, 8)
        # Want to place the code here that changes the first_screen text to "Hi I'm The Fifth Screen"
        Clock.schedule_once(self.screen_switch_one, 10)
        return root_widget

    def screen_switch_one(a, b):
        root_widget.current = '_first_screen_'

    def screen_switch_two(a, b):
        root_widget.current = '_second_screen_'

    def screen_switch_three(a, b):
        root_widget.current = '_third_screen_'

    def screen_switch_four(a, b):
        root_widget.current = '_fourth_screen_'

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

Answer 5

您只需在第55行添加此行。

root_widget.get_screen('_first_screen_').first_screen.text = "Hi I'm The Fifth Screen"

首先你必须绑定标签（更多信息here），然后你可以使用上面的代码访问标签文本

所以这是完整的代码：

<强> main.py

import kivy
kivy.require('1.10.0')
from kivy.app import App
from kivy.lang import Builder
from kivy.clock import Clock
from kivy.uix.screenmanager import Screen

class FirstScreen(Screen):
    pass

class SecondScreen(Screen):
    pass

class ThirdScreen(Screen):
    pass

class FourthScreen(Screen):
    pass

root_widget = Builder.load_string("""
ScreenManager:
    FirstScreen:
    SecondScreen:
    ThirdScreen:
    FourthScreen:
<FirstScreen>:
    first_screen: first_screen
    name: '_first_screen_'
    Label:
        id: first_screen
        text: "Hi I'm The First Screen"
<SecondScreen>:
    name: '_second_screen_'
    Label:
        id: second_screen
        text: "Hi I'm The Second Screen"
<ThirdScreen>:
    name: '_third_screen_'
    Label:
        id: third_screen
        text: "Hi I'm The Third Screen"
<FourthScreen>:
    name: '_fourth_screen_'
    Label:
        id: fourth_screen
        text: "Hi I'm The Fourth Screen"
""")

class SwitchingScreenApp(App):
    def build(self):
        Clock.schedule_once(self.screen_switch_one, 2)
        Clock.schedule_once(self.screen_switch_two, 4)
        Clock.schedule_once(self.screen_switch_three, 6)
        Clock.schedule_once(self.screen_switch_four, 8)
        root_widget.get_screen('_first_screen_').first_screen.text = "Hi I'm The Fifth Screen"
        Clock.schedule_once(self.screen_switch_one, 10)
        return root_widget

    def screen_switch_one(a, b):
        root_widget.current = '_first_screen_'

    def screen_switch_two(a, b):
        root_widget.current = '_second_screen_'

    def screen_switch_three(a, b):
        root_widget.current = '_third_screen_'

    def screen_switch_four(a, b):
        root_widget.current = '_fourth_screen_'

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

我希望代码可以帮到你。

Answer 6

为了保持每个帖子的简单和完整的工作代码的信条，我根据Yoshi在他的第二个代码帖子中提供的信息确定了代码。因此，最初发布的问题的最终和工作代码如下;

import kivy
kivy.require('1.10.0')
from kivy.app import App
from kivy.lang import Builder
from kivy.clock import Clock
from kivy.uix.screenmanager import Screen

class FirstScreen(Screen):
    pass

class SecondScreen(Screen):
    pass

class ThirdScreen(Screen):
    pass

class FourthScreen(Screen):
    pass

root_widget = Builder.load_string("""
ScreenManager:
    FirstScreen:
    SecondScreen:
    ThirdScreen:
    FourthScreen:
<FirstScreen>:
    first_screen: first_screen
    name: '_first_screen_'
    Label:
        id: first_screen
        text: "Hi I'm The First Screen"
<SecondScreen>:
    name: '_second_screen_'
    Label:
        id: second_screen
        text: "Hi I'm The Second Screen"
<ThirdScreen>:
    name: '_third_screen_'
    Label:
        id: third_screen
        text: "Hi I'm The Third Screen"
<FourthScreen>:
    name: '_fourth_screen_'
    Label:
        id: fourth_screen
        text: "Hi I'm The Fourth Screen"
""")

class SwitchingScreenApp(App):
    def build(self):
        Clock.schedule_once(self.screen_switch_one, 2)
        Clock.schedule_once(self.screen_switch_two, 4)
        Clock.schedule_once(self.screen_switch_three, 6)
        Clock.schedule_once(self.screen_switch_four, 8)
        Clock.schedule_once(self.text_replace_screen_one, 9)
        Clock.schedule_once(self.screen_switch_one, 10)
        return root_widget

    def text_replace_screen_one(a,b):
        root_widget.get_screen('_first_screen_').first_screen.text = "Hi I'm The Fifth Screen"

    def screen_switch_one(a, b):
        root_widget.current = '_first_screen_'

    def screen_switch_two(a, b):
        root_widget.current = '_second_screen_'

    def screen_switch_three(a, b):
        root_widget.current = '_third_screen_'

    def screen_switch_four(a, b):
        root_widget.current = '_fourth_screen_'

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

Kivy的完整代码示例以KV语言编写的工作屏幕管理器参考

6 个答案:

问题：1

答案

第1步

步骤2

问题：2

答案

实施例

app_with_kv.py

switchingscreen.kv

输出