Kivy 中的 RecycleView 模块

Question

新成员，第一次发帖。我会尽量具体和明确。以下代码取自 kivy 的关于RecycleView module 的网页。我想使用这段代码，但是，我不想使用 KV lang 和 Builder，而是用纯 Python 3 编写代码。我尝试将 RecycleBoxLayout 类添加为小部件是完全失败的，因为结果只是一个黑色的窗口。只有添加“视图类”才有效。显然，这里有一些我不理解或遗漏的东西。我还附上了我重写代码的尝试。

任何帮助将不胜感激。提前谢谢你。

原始代码：

from kivy.app import App
from kivy.lang import Builder
from kivy.uix.recycleview import RecycleView

Builder.load_string('''
<RV>:
    viewclass: 'Label'
    RecycleBoxLayout:
    default_size: None, dp(56)
    default_size_hint: 1, None
    size_hint_y: None
    height: self.minimum_height
    orientation: 'vertical'
''')

class RV(RecycleView):
    def __init__(self, **kwargs):
        super(RV, self).__init__(**kwargs)
        self.data = [{'text': str(x)} for x in range(100)]

class TestApp(App):
    def build(self):
        return RV()


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

我的失败尝试：

from kivy.app import App
from kivy.lang import Builder
from kivy.uix.recycleview import RecycleView
from kivy.uix.label import Label
from kivy.uix.recycleboxlayout import RecycleBoxLayout

class RV(RecycleView):
    def __init__(self, **kwargs):
        super(RV, self).__init__(**kwargs)
        self.data = [{'text': str(x)} for x in range(100)]
        self.viewclass = Label
        layout = RecycleBoxLayout()
        self.add_widget(layout)

class TestApp(App):
    def build(self):
        return RV()


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

Answer 1

我一直在寻找同样的东西，我不喜欢 kv lang，并且还没有确信它比在代码中做所有事情更好。

https://kivy.org/docs/api-kivy.uix.recycleview.html#kivy.uix.recycleview.RecycleView 的示例将按如下方式创建。

from kivy.app import App
from kivy.graphics import Color, Rectangle
from kivy.uix.recycleview import RecycleView
from kivy.uix.recycleview.views import RecycleDataViewBehavior
from kivy.uix.label import Label
from kivy.properties import BooleanProperty
from kivy.uix.recycleboxlayout import RecycleBoxLayout
from kivy.uix.behaviors import FocusBehavior
from kivy.uix.recycleview.layout import LayoutSelectionBehavior

class SelectableRecycleBoxLayout(FocusBehavior, LayoutSelectionBehavior,
                                 RecycleBoxLayout):
    ''' Adds selection and focus behaviour to the view. '''
    def __init__(self, **kw):
        super().__init__(**kw, default_size=(0, 28), default_size_hint=(1, None), size_hint_y=None,
                         touch_multiselect=True, multiselect=True, orientation='vertical')

        self.bind(minimum_height=self._min)

    def _min(self, inst, val):
        self.height = val

class SelectableLabel(RecycleDataViewBehavior, Label):
    ''' Add selection support to the Label '''
    index = None
    selected = BooleanProperty(False)
    selectable = BooleanProperty(True)

    def __init__(self, **kw):
        super().__init__(**kw)
        self.canvas.before.clear()
        with self.canvas.before:
            if self.selected:
                Color(.0, 0.9, .1, .3)
            else:
                Color(0, 0, 0, 1)
            self.rect = Rectangle(size=self.size, pos=self.pos)
        self.bind(size=self._update_rect, pos=self._update_rect)

    def _update_rect(self, inst, value):
        self.rect.pos = inst.pos
        self.rect.size = inst.size

    def refresh_view_attrs(self, rv, index, data):
        ''' Catch and handle the view changes '''
        self.index = index
        return super().refresh_view_attrs(rv, index, data)

    def on_touch_down(self, touch):
        ''' Add selection on touch down '''
        if super(SelectableLabel, self).on_touch_down(touch):
            return True
        if self.collide_point(*touch.pos) and self.selectable:
            return self.parent.select_with_touch(self.index, touch)

    def apply_selection(self, rv, index, is_selected):
        ''' Respond to the selection of items in the view. '''
        self.selected = is_selected
        if is_selected:
            print("selection changed to {0}".format(rv.data[index]))
        else:
            print("selection removed for {0}".format(rv.data[index]))
        self.canvas.before.clear()
        with self.canvas.before:
            if self.selected:
                Color(.0, 0.9, .1, .3)
            else:
                Color(0, 0, 0, 1)
            self.rect = Rectangle(size=self.size, pos=self.pos)


class RV(RecycleView):
    def __init__(self, **kwargs):
        super(RV, self).__init__(**kwargs)
        self.add_widget(SelectableRecycleBoxLayout())
        self.viewclass = 'SelectableLabel'
        self.data = [{'text': str(x)} for x in range(100)]


class TestApp(App):
    def build(self):
        return RV()

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

KV 类中的顺序很重要。不确定 需要 在哪里，但 self.data 需要在添加小部件后进行修改。

Answer 2

我不是 Kivy 方面的专家，但我强烈建议您尽可能使用 kv lang。它只不过是一个简洁的python，它会让你的代码更干净。
如果您阅读了 RecycleBoxLayout 的文档，它的实验性很强，您应该使用有效的方法。

话虽如此，您的代码看起来还不错，但有几个问题。

1) 替换 self.viewclass = Label 和 self.viewclass = 'Label' 和
2) 您尚未在 python 代码中为您的RecycleBoxLayout 指定height、size 和orientation 参数。