kivy 按钮按下以转到多个屏幕之一

Question

假设我有一个 kivy 程序，其中第一个屏幕有三个按钮，每个按钮都将您带到不同的屏幕。这些屏幕中的每一个都包含一个按钮，可将您带到最终屏幕（同一屏幕）。最后一个屏幕有一个“返回”按钮。如何使最后一个屏幕上的“后退”按钮带您回到前一个屏幕（上面提到的 3 个屏幕中的第一个）？下面是一个粗略的图表，可以更好地帮助可视化我的问题。

                  Screen 1
Start Screen -->  Screen 2 --> Final Screen
                  Screen 3 

截至目前，最终屏幕上的“返回”按钮会将您带回到“开始”屏幕，但这不是我想要的。

我的python代码：

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

class MyScreenManager(ScreenManager):
    pass

# Branch Screen, takes you to S1, S2, or S3
class BRANCH(Screen):
    pass

class S1(Screen):
    pass

class S2(Screen):
    pass

class S3(Screen):
    pass

class FINAL_SCREEN(Screen):
    pass

class MAINApp(App):
    def build(self):
        return MyScreenManager()

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

我的kivy语言代码：

#:kivy 1.0.9

<MyScreenManager>:
    BRANCH:
    name: 'branch'
    S1:
    name: 'screen1'
    S2:
    name: 'screen2'
    S3:
    name: 'screen3'
    FINAL_SCREEN:
    name: 'final_screen'


<BRANCH>
    FloatLayout:
    Button:
        text: 'Screen-1'
        color: 1.0, 0.6, 0.0, 1
        font_size: 30
        size_hint_x: 0.50
        size_hint_y: 0.25
        pos_hint: {'x': 0.20, 'y': 0.75}
        on_release:
            root.manager.transition.direction = 'left'
            root.manager.current = 'screen1'
    Button:
        text: 'Screen-2'
        color: 1.0, 0.6, 0.0, 1
        font_size: 30
        size_hint_x: 0.50
        size_hint_y: 0.25
        pos_hint: {'x': 0.20, 'y': 0.40}
        on_release:
            root.manager.transition.direction = 'left'
            root.manager.current = 'screen2'
    Button:
        text: 'Screen-3'
        color: 1.0, 0.6, 0.0, 1
        font_size: 30
        size_hint_x: 0.50
        size_hint_y: 0.25
        pos_hint: {'x': 0.20, 'y': 0.05}
        on_release:
            root.manager.transition.direction = 'left'
            root.manager.current = 'screen3'
<S1>
    FloatLayout:
    Label:
        pos_hint: {'x': 0.00, 'y': 0.20}
        font_size: 35
        text: 'this is SCREEN-1'
        color: 1, 1, 1, 1
    Button:
        text: 'Forward'
        color: 1.0, 0.6, 0.0, 1
        font_size: 20
        size_hint_x: 0.20
        size_hint_y: 0.20
        pos_hint: {'x': 0.40, 'y': 0.15}
        on_release:
            root.manager.transition.direction = 'left'
            root.manager.current = 'final_screen'
<S2>
    FloatLayout:
    Label:
        pos_hint: {'x': 0.00, 'y': 0.20}
        font_size: 35
        text: 'me este SCREEN-2'
        color: 1, 1, 1, 1
    Button:
        text: 'Onward'
        color: 1.0, 0.6, 0.0, 1
        font_size: 20
        size_hint_x: 0.20
        size_hint_y: 0.20
        pos_hint: {'x': 0.40, 'y': 0.15}
        on_release:
            root.manager.transition.direction = 'left'
            root.manager.current = 'final_screen'
<S3>
    FloatLayout:
    Label:
        pos_hint: {'x': 0.00, 'y': 0.20}
        font_size: 35
        text: 'something SCREEN-3'
        color: 1, 1, 1, 1
    Button:
        text: 'Lets Go'
        color: 1.0, 0.6, 0.0, 1
        font_size: 20
        size_hint_x: 0.20
        size_hint_y: 0.20
        pos_hint: {'x': 0.40, 'y': 0.15}
        on_release:
            root.manager.transition.direction = 'left'
            root.manager.current = 'final_screen'
<FINAL_SCREEN>
    FloatLayout:
    Label:
        pos_hint: {'x': 0.00, 'y': 0.20}
        font_size: 35
        text: 'Final Screen'
        color: 1, 1, 1, 1
    Button:
        text: 'Back'
        color: 1.0, 0.6, 0.0, 1
        font_size: 20
        size_hint_x: 0.20
        size_hint_y: 0.20
        pos_hint: {'x': 0.40, 'y': 0.15}
        on_release:
            root.manager.transition.direction = 'right'
            root.manager.current = 'branch'

非常感谢任何帮助或建议。

Answer 1

这是在Final 屏幕上使用 StringProperty 的一种解决方案。

我是在进入最终画面时设置的

root.manager.ids.final.previous = root.name

当返回时，我使用它转到此屏幕

root.manager.current = root.previous

这是你的整个应用程序

from kivy.app import App
from kivy.uix.screenmanager import Screen, ScreenManager
from kivy.lang import Builder
from kivy.properties import StringProperty

kv_str = """
MyScreenManager:
    BRANCH:
        name: 'branch'
    S1:
        name: 'screen1'
    S2:
        name: 'screen2'
    S3:
        name: 'screen3'
    FINAL_SCREEN:
        id: final
        name: 'final_screen'


<BRANCH>
    FloatLayout:
    Button:
        text: 'Screen-1'
        color: 1.0, 0.6, 0.0, 1
        font_size: 30
        size_hint_x: 0.50
        size_hint_y: 0.25
        pos_hint: {'x': 0.20, 'y': 0.75}
        on_release:
            root.manager.transition.direction = 'left'
            root.manager.current = 'screen1'
    Button:
        text: 'Screen-2'
        color: 1.0, 0.6, 0.0, 1
        font_size: 30
        size_hint_x: 0.50
        size_hint_y: 0.25
        pos_hint: {'x': 0.20, 'y': 0.40}
        on_release:
            root.manager.transition.direction = 'left'
            root.manager.current = 'screen2'
    Button:
        text: 'Screen-3'
        color: 1.0, 0.6, 0.0, 1
        font_size: 30
        size_hint_x: 0.50
        size_hint_y: 0.25
        pos_hint: {'x': 0.20, 'y': 0.05}
        on_release:
            root.manager.transition.direction = 'left'
            root.manager.current = 'screen3'
<S1>:
    FloatLayout:
        Label:
            pos_hint: {'x': 0.00, 'y': 0.20}
            font_size: 35
            text: 'this is SCREEN-1'
            color: 1, 1, 1, 1
        Button:
            text: 'Forward'
            color: 1.0, 0.6, 0.0, 1
            font_size: 20
            size_hint_x: 0.20
            size_hint_y: 0.20
            pos_hint: {'x': 0.40, 'y': 0.15}
            on_release:
                root.manager.transition.direction = 'left'
                root.manager.current = 'final_screen'
                root.manager.ids.final.previous = root.name
<S2>:
    FloatLayout:
        Label:
            pos_hint: {'x': 0.00, 'y': 0.20}
            font_size: 35
            text: 'me este SCREEN-2'
            color: 1, 1, 1, 1
        Button:
            text: 'Onward'
            color: 1.0, 0.6, 0.0, 1
            font_size: 20
            size_hint_x: 0.20
            size_hint_y: 0.20
            pos_hint: {'x': 0.40, 'y': 0.15}
            on_release:
                root.manager.transition.direction = 'left'
                root.manager.current = 'final_screen'
                root.manager.ids.final.previous = root.name
<S3>:
    FloatLayout:
        Label:
            pos_hint: {'x': 0.00, 'y': 0.20}
            font_size: 35
            text: 'something SCREEN-3'
            color: 1, 1, 1, 1
        Button:
            text: 'Lets Go'
            color: 1.0, 0.6, 0.0, 1
            font_size: 20
            size_hint_x: 0.20
            size_hint_y: 0.20
            pos_hint: {'x': 0.40, 'y': 0.15}
            on_release:
                root.manager.transition.direction = 'left'
                root.manager.current = 'final_screen'
                root.manager.ids.final.previous = root.name
<FINAL_SCREEN>:
    FloatLayout:
        Label:
            pos_hint: {'x': 0.00, 'y': 0.20}
            font_size: 35
            text: 'Final Screen'
            color: 1, 1, 1, 1
        Button:
            text: 'Back'
            color: 1.0, 0.6, 0.0, 1
            font_size: 20
            size_hint_x: 0.20
            size_hint_y: 0.20
            pos_hint: {'x': 0.40, 'y': 0.15}
            on_release:
                root.manager.transition.direction = 'right'
                root.manager.current = root.previous

"""

class MyScreenManager(ScreenManager):
    pass

# Branch Screen, takes you to S1, S2, or S3
class BRANCH(Screen):
    pass

class S1(Screen):
    pass

class S2(Screen):
    pass

class S3(Screen):
    pass

class FINAL_SCREEN(Screen):
    previous = StringProperty()


class MAINApp(App):
    def build(self):
        return Builder.load_string(kv_str)

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

---

我按照 cmets 中的建议尝试了 previous()

<FINAL_SCREEN>:
    FloatLayout:
        Label:
            pos_hint: {'x': 0.00, 'y': 0.20}
            font_size: 35
            text: 'Final Screen'
            color: 1, 1, 1, 1
        Button:
            text: 'Back'
            color: 1.0, 0.6, 0.0, 1
            font_size: 20
            size_hint_x: 0.20
            size_hint_y: 0.20
            pos_hint: {'x': 0.40, 'y': 0.15}
            on_release:
                print(root.manager.previous())
                root.manager.current = root.manager.previous()

奇怪的是，它总是返回 screen3，因此我使用了上面的版本。