如何使用/制作kivy语言的自定义小部件，但使用python代码？

Question

我希望能够在kv文件和python代码中使用我的自定义（python编写的）小部件。我不知道如何创建一个小部件，然后在我选择的布局中使用它

class SelectableList(FocusBehavior, CompoundSelectionBehavior, StackLayout):
    previous_nodes=[]
    # this class has a whole bunch of "def's" that I got rid of so that stack would let me post a shorter question

class myScreen(Screen):
    def build(self):
        self.root_boi = StackLayout(size=(1,1))
        stack = SelectableList(touch_multiselect=True,
                               multiselect=True)
        for i in range(0, 6):
            stack.add_widget(Button(size_hint_y=None, height=30, text="Button {0}".format(i)))
        self.root_boi.add_widget(stack)
        return self.root_boi

class TestApp(App):
    def build(self):
        sm = ScreenManager()
        sm.add_widget(myScreen(name='whatever you want it to be...'))
        return myScreen()

TestApp().run()

我不确定我到底做错了什么。我正在尝试将“SelectableList”小部件添加到堆栈布局中。我希望能够将它添加到我选择的任何小部件中，无论是在kv文件中还是在我的python代码中。如果这有道理的话

Answer 1

我怀疑myScreen的build()方法实际上应该是一个__init__()方法（没有返回）。我添加了self.add_widget(self.root_boi)来代替return。类名应该大写（MyScreen），因为kv语言有时会对这一点很挑剔

下面是代码的修改版本，演示如何使用自定义小部件：

from kivy.app import App
from kivy.lang import Builder
from kivy.uix.behaviors import FocusBehavior, CompoundSelectionBehavior
from kivy.uix.button import Button
from kivy.uix.screenmanager import Screen, ScreenManager
from kivy.uix.stacklayout import StackLayout


class SelectableList(FocusBehavior, CompoundSelectionBehavior, StackLayout):
    previous_nodes=[]
    # this class has a whole bunch of "def's" that I got rid of so that stack would let me post a shorter question

class MyScreen(Screen):
    def __init__(self, **kwargs):
        super(MyScreen, self).__init__(**kwargs)
        self.root_boi = StackLayout(size=(1,1))
        stack = SelectableList(touch_multiselect=True,
                               multiselect=True)
        for i in range(0, 6):
            stack.add_widget(Button(size_hint_y=None, height=30, text="Button {0}".format(i)))
        self.root_boi.add_widget(stack)
        self.add_widget(self.root_boi)

class TestApp(App):
    def build(self):
        return Builder.load_string(kv)

kv = '''
# ScreenManager:
#     MyScreen:
#
#    or
#
ScreenManager:
    Screen:
        name: 'whatever'
        StackLayout:
            SelectableList:
                touch_multiselect: True
                multiselect: True
                Button:
                    text: 'Button 0'
                    size_hint_y: None
                    height: 30
                Button:
                    text: 'Button 1'
                    size_hint_y: None
                    height: 30
                Button:
                    text: 'Button 2'
                    size_hint_y: None
                    height: 30
'''
TestApp().run()

MyScreen的__init__()方法必须包含对super{}的调用

上面代码中的kv字符串显示了自定义小部件的两种不同用法。第一个（注释掉）使用MyScreen自定义小部件。第二个（未注释掉）使用SelectableList自定义小部件