将“ on_start数据”传递给MyScreen和MyImage需要ScreenManager中的屏幕名称

时间：2019-07-12 06:54:20

标签： python python-3.x kivy

我正在使用Kivy库主要使用Python代码来创建应用。我是Python和Kivy的新手。这里是我的代码片段。

我试图将定义为“ on_start”的图像传递给我的NavButton。 @ikolim帮助我确定了问题所在。您可以在下面看到我的评论。

小部件 

class NavButton(GridLayout):

    def __init__(self, **kwargs):
        super(NavButton, self).__init__(**kwargs)
        self.rows = 1
        frame = FloatLayout(id = "frame")
        grid1 = MyGrid(
            rows = 1,
            cols = 5,
            pos_hint = {"top":1, "left": 1},
            size_hint = [1, .2]                         )
        grid1.set_background(0.95,0.95,0.95,1)

        grid1.add_widget(MyButton(
            source = "img/settings.png",
            size_hint = [0.2,0.2]                       ))
        grid1.add_widget(MyButton(
            source = "img/arrow-left.png"               ))
        city_icon = Image(
            source="img/image1.png",
            id="city_icon",
            size_hint=[0.8, 0.8])

        self.ids.cityicon = city_icon
        grid1.add_widget(city_icon)
        grid1.add_widget(MyButton(
            source = "img/arrow-right.png"              ))
        grid1.add_widget(MyButton(
            source = "img/globe.png",
            size_hint = [0.2,0.2]                       ))
        frame.add_widget(grid1)
        self.add_widget(frame)

屏幕

class Homescreen(Screen):

        def __init__(self, **kwargs):
            super(Homescreen, self).__init__(**kwargs)
            frame = FloatLayout(id = "frame")
            grid1 = NavButton()
            frame.add_widget(grid1)

        ...

屏幕管理器

这是我搞砸的地方！显然，您必须定义主屏幕的名称（即homescreen = Homescreen(name="home_screen")），否则在启动应用程序时它不会更新NavButton的图像。我不知道为什么，但是我只是为将来的编码员强调这一点。

 class MyScreenManager(ScreenManager):

        def __init__(self, **kwargs):
        super(MyScreenManager, self).__init__(**kwargs)
        homescreen = Homescreen()
        self.add_widget(homescreen)
        self.ids.screenmanager =  self

    def change_screen(self, name):
         self.current = name

Builder 

GUI = Builder.load_file("main.kv")

class Main(App):

    def build(self):
        return GUI

    def on_start(self):

        self.mynewimage = "image2"
        homescreen = self.root.get_screen("home_screen")
        homescreen.ids.navbutton.ids.cityicon.source = f"img/{self.mynewimage}.png"


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

再次，@ ikolim感谢您的支持。

1 个答案:

答案 0 :(得分：1)

解决方案2

需要以下增强功能才能解决该问题。

class NavButton（）

  1. 替换self.ids.cityicon = "cityicon" 与self.ids.cityicon = city_icon
  2. 删除self.bind(on_start=self.update_image)和方法update_image()

方法on_start()

  1. 将homescreen = Main.get_running_app().root.get_screen("home_screen")替换为 homescreen = self.root.get_screen("home_screen")
  2. 替换     frame.children[3].children[0].children[0].children[2].source与     homescreen.ids.navbutton.ids.cityicon.source
  3. 删除行（frame = homescreen.children[0]，navbutton = frame.children[3]和print(...)）

代码段-py文件

class NavButton(GridLayout):

    def __init__(self, **kwargs):
        super(NavButton, self).__init__(**kwargs)
        ...
        city_icon = Image(
            source="img/settings.png",
            id="city_icon",
            size_hint=[0.8, 0.8])

        self.ids.cityicon = city_icon
        ...


class Main(App):

    ...

    def on_start(self):
        self.my_city = "it-Rome"
        homescreen = self.root.get_screen("home_screen")
        homescreen.ids.navbutton.ids.cityicon.source = f"img/{self.my_city}.png"
    ...

示例-main.py 

from kivy.app import App
from kivy.uix.screenmanager import ScreenManager, Screen
from kivy.uix.gridlayout import GridLayout
from kivy.uix.floatlayout import FloatLayout
from kivy.uix.button import ButtonBehavior
from kivy.uix.label import Label
from kivy.uix.image import Image
from kivy.graphics import Color, Rectangle


class MyButton(ButtonBehavior, Image):
    pass


class ImageButton(ButtonBehavior, Image):
    pass


### Components

class NavButton(GridLayout):

    def __init__(self, **kwargs):
        super(NavButton, self).__init__(**kwargs)
        self.rows = 1
        frame = FloatLayout(id="frame")
        grid1 = MyGrid(
            rows=1,
            cols=5,
            pos_hint={"top": 1, "left": 1},
            size_hint=[1, .2])
        grid1.set_background(0.95, 0.95, 0.95, 1)

        grid1.add_widget(MyButton(
            source="img/settings.png",
            size_hint=[0.2, 0.2]))
        grid1.add_widget(MyButton(
            source="img/arrow-left.png"))
        city_icon = Image(
            source="img/settings.png",
            id="city_icon",
            size_hint=[0.8, 0.8])

        self.ids.cityicon = city_icon

        grid1.add_widget(city_icon)
        grid1.add_widget(MyButton(
            source="img/arrow-right.png"))
        grid1.add_widget(MyButton(
            source="img/globe.png",
            size_hint=[0.2, 0.2]))
        frame.add_widget(grid1)
        self.add_widget(frame)


### Grids

class MyGrid(GridLayout):

    def set_background(self, r, b, g, o):
        self.canvas.before.clear()
        with self.canvas.before:
            Color(r, g, b, o)
            self.rect = Rectangle(pos=self.pos, size=self.size)

        self.bind(pos=self.update_rect,
                  size=self.update_rect)

    def update_rect(self, *args):
        self.rect.pos = self.pos
        self.rect.size = self.size


### Screens

class Homescreen(Screen):

    def __init__(self, **kwargs):
        super(Homescreen, self).__init__(**kwargs)
        frame = FloatLayout(id="frame")
        grid1 = NavButton()
        frame.add_widget(grid1)

        # This grid contains the number of zpots collected

        grid2 = MyGrid(
            cols=1,
            pos_hint={"top": 0.8, "left": 1},
            size_hint=[1, .2], )
        grid2.add_widget(Image(
            source="img/spot.png"))
        grid2.add_widget(Label(
            text="[color=3333ff]20/30[/color]",
            markup=True))
        grid2.set_background(0.95, 0.95, 0.95, 1)
        frame.add_widget(grid2)

        # This grid contains a scrollable list of nearby zpots

        grid3 = MyGrid(
            cols=1,
            pos_hint={"top": 0.6, "left": 1},
            size_hint=[1, .5])
        grid3.set_background(0.95, 0.95, 0.95, 1)
        frame.add_widget(grid3)

        # This grid contains a the map of nearby zpots

        grid4 = MyGrid(
            cols=1,
            pos_hint={"top": 0.1, "left": 1},
            size_hint=[1, .1])
        grid4.set_background(0.95, 0.95, 0.95, 1)
        frame.add_widget(grid4)
        self.ids.navbutton = grid1
        self.add_widget(frame)


class Newscreen(Screen):
    pass


class Settingscreen(Screen):
    pass


### ScreenManager

class MyScreenManager(ScreenManager):

    def __init__(self, **kwargs):
        super(MyScreenManager, self).__init__(**kwargs)
        homescreen = Homescreen(name='home_screen')
        self.add_widget(homescreen)
        self.ids.screenmanager = self

    def change_screen(self, name):
        self.current = name


class TestApp(App):

    def build(self):
        return MyScreenManager()

    def on_start(self):
        self.my_city = "it-Rome"
        homescreen = self.root.get_screen("home_screen")

        print(f"\non_start-Before change: img={homescreen.ids.navbutton.ids.cityicon.source}")
        homescreen.ids.navbutton.ids.cityicon.source = f"img/{self.my_city}.png"
        print(f"\non_start-After change: img={homescreen.ids.navbutton.ids.cityicon.source}")


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

输出

App started

解决方案1 ​​

代码段-py文件

class NavButton(GridLayout):

    def get(self):
        ...
        city_icon = Image(
                source = "img/" + App.get_running_app().my_city,
                size_hint = [0.8,0.8]                       )

...
class Main(App):

    def build(self):
        return GUI

    def on_start(self):
        # get data from DB
        self.my_city = "it-Rome"
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