Kivy 访问父方法和兄弟方法

Question

我正在尝试在 Kivy 中创建一个 GUI，显示连接到计算机的 4 个摄像头的 stream（目前仅使用 2 个）。 我的意图是有一个下拉菜单，我可以从中选择正在播放的相机。 播放摄像机的选择也应该对 slider 的值产生影响，这意味着 slider 应该为新选择的播放摄像机设置焦点。

设计非常简单，由一个 BoxLayout 组成，其中包含 2 个 RelativeLayouts，所有其他小部件都位于其中。

当我尝试从下拉菜单访问 Boxlayout 中定义的方法时，我的问题就出现了。

DropDown 菜单是在 python（而不是 in.kv）中实现的，因为我遵循了 Kivy Docu 中的本指南。

这里的 .kv 文件用于设计：

#:import Factory kivy.factory.Factory

<PopupStart@Popup>:
    id : popup_start
    title: "Start Function Pop-up"
    auto_dismiss: False
    size_hint : (.4, .4)

    RelativeLayout:
        size_hint : (.8, .9)
        Button:
            text: 'Close me!'
            size_hint : (.45, .25)
            pos_hint : {'center_x':0.5, 'y':0.1}
            on_release: root.dismiss()
        Label:
            text : "The start function will run the AI Algorithm \n and will be provided soon"
            font_size : 15
            size_hint : (.55, .45)
            pos_hint : {'center_x':0.5, 'top':1}

<PopupCalibrate@Popup>:
    id : popup_calibrate
    title: "Calibrate Function Pop-up"
    auto_dismiss: False
    size_hint : (.4, .4)

    RelativeLayout:
        size_hint : (.8, .9)
        Button:
            text: 'Close me!'
            size_hint : (.45, .25)
            pos_hint : {'center_x':0.5, 'y':0.1}
            on_release: root.dismiss()
        Label:
            text : "The calibrate function will run the Camera Calibration \n and will be provided soon"
            font_size : 13
            size_hint : (.55, .45)
            pos_hint : {'center_x':0.5, 'top':1}






<CameraView>:
    playing_camera : playing_camera
    orientation : "vertical"        #should be omitted (related to BoxLayout) but still works
    Camera:
        id : playing_camera
        play : True
        index : 0

#DA ELIMINARE, MA COSI FUNZIONA
    Button:
        size_hint : (.1,.1)
        on_release : root.parent.select_camera_button()




    Label:
        text : "Camera n.%s" % str(playing_camera.index)
        font_size : "15sp"
        size_hint : (.3,.1)
        pos_hint : {'center_x':0.5, 'top':1}
        bold : True

<ControlsView>:

    focus_value : focus_slider.value

    Button:
        id : btn_start
        text : "Start"
        font_size : 20
        size_hint : (0.7,.1)
        pos_hint :  {'center_x':0.5, 'y':0.05}
        background_normal : ""
        background_color : (0,1,0,.5)
        bold : True
        on_release: Factory.PopupStart().open()
        #Check where the function definition should be placed
                                                        #Also check if "self." is the right expression

    Button:
        id : btn_calibrate
        text : "Calibrate"
        font_size : 18
        size_hint : (0.7,.1)
        pos_hint  :  {'center_x':0.5, 'top':0.75}
        background_normal : ""
        background_color : (0, 0, 1, .5)
        on_release: Factory.PopupCalibrate().open()

#Strange behaviour: If a ")" is present it will interpreted as EOF, hence returning an error

    Label:
        text : "logic.portable"
        font_size : 25
        pos_hint : {'top':1.45}

    Label:
        text : "Gewicht in g"
        pos_hint : {'center_x':0.5, 'top':1.35}
        color : (1,0,0,.5)

    Label:
        text : "Focus"
        font_size : 15
        pos_hint : {'center_x': .5, 'center_y': .27}

    Slider:
        id : focus_slider
        value_track : True
        value_track_color : [1, 0, 0, 1]
        range : (20, 100)                                  #Range must be checked with camera Specs!
        value : 20
        step : 1
        pos_hint : {'center_x': .5, 'center_y': .25}
        size_hint_y : None
        height : 50
        on_value : root.focus_value = self.value

    Label:
        text : "Focus at %scm" % str(root.focus_value)
        font_size : 10
        pos_hint : {'center_x': .5, 'center_y': .22}








<InteractiveGUI>:
    cameraview : cameraview
    controlsview : controlsview



    CameraView:
        id : cameraview
        size_hint_x : 4

    ControlsView:
        id : controlsview

和 python 文件：

import kivy
from kivy.properties import ObjectProperty

kivy.require('2.1.0')


from kivy.app import App
from kivy.uix.widget import Widget
from kivy.uix.button import Button
from kivy.uix.boxlayout import BoxLayout
from kivy.uix.gridlayout import GridLayout
from kivy.uix.relativelayout import RelativeLayout
from kivy.uix.label import Label
from kivy.uix.camera import Camera
from kivy.uix.dropdown import DropDown
from kivy.base import runTouchApp
from kivy.uix.slider import Slider
from kivy.uix.screenmanager import ScreenManager


class InteractiveGUI(BoxLayout):
    cameraview = ObjectProperty(None)
    controlsview = ObjectProperty(None)


    def select_camera_button(self):
        if self.cameraview.playing_camera.index == 0:
            self.cameraview.playing_camera.index = 1
        else:
            self.cameraview.playing_camera.index = 0

    def select_camera(self):
        if self.controlsview.mainbutton.text == "Camera 1":
            self.cameraview.playing_camera.index = 0
        elif self.controlsview.mainbutton.text == "Camera 2":
            self.cameraview.playing_camera.index = 1
        else:
            pass


class CameraView(RelativeLayout):
    playing_camera = ObjectProperty(None)
    '''def change_camera(self):
        if (playing_camera.index == 0):
            playing_camera.index = 1
        else:
            playing_camera.index = 0'''

class ControlsView(RelativeLayout):
    playing_camera = ObjectProperty(None)

    def __init__(self, **kwargs):
        super(ControlsView, self).__init__(**kwargs)

        # A dropdown Menu for camera selection needs to be implemented:
        # Define the Dropdown menu here in Python code, because it has a lot of logic behind

        self.camera_sel = DropDown()
        for index in range(1, 5):
            btn = Button(text='Camera %d' % index,
                         size_hint_x=.7,
                         size_hint_y=None,
                         height=25
                         )
            btn.bind(on_release=lambda btn: self.camera_sel.select(btn.text))
            self.camera_sel.add_widget(btn)

        self.mainbutton = Button(text='Select Camera',
                            size_hint_x=.7,
                            size_hint_y=None,
                            height=35,
                            pos_hint={'center_x': .5, 'center_y': .5}
                            )

        self.add_widget(self.mainbutton)
        self.mainbutton.bind(on_release = self.camera_sel.open)
        self.camera_sel.bind(on_select = lambda instance, x: setattr(self.mainbutton, 'text', x))
        self.camera_sel.bind(on_select = self.select_camera())            #CAN'T CALL PARENT INSIDE __init()__

    def select_camera(self):
        print(self.parent)
        return self.parent.select_camera()

错误消息显示：

文件“GUI_DropDown_python.py”，第 78 行，在init
self.camera_sel.bind(on_select = self.select_camera())
文件“GUI_DropDown_python.py”，第 82 行，在 select_camera 返回 self.parent.select_camera() AttributeError: 'NoneType' object 没有属性 'select_camera'

Answer 1

代码行：

self.camera_sel.bind(on_select = self.select_camera())

正在执行self.select_camera()并尝试将其返回绑定到on_select事件。 我怀疑您实际上想要绑定self.select_camera ，而不是它的返回。 尝试将该行代码更改为：

self.camera_sel.bind(on_select = self.select_camera)

注意删除() 。