python - Kivy Recycleview updates from button but not from app build method

Question

A sample Kivy app populates Recycleview upon a button click. However, when I copy the code from the class functions into the App.build to populate the Recycleview upon app loading, it doesn't do it. Is it not referencing the Recycleview correctly? Why is this not working?

I saw some answers here that used "self.ids." to find the Recycleview data, and also "App.get_running_app()." but it didn't work.

(Note: requires Kivy 2.0.0rc4 to compile)

from random import sample, randint
from string import ascii_lowercase


from kivy.app import App
from kivy.lang import Builder
from kivy.uix.boxlayout import BoxLayout


kv = """
<Row@RecycleKVIDsDataViewBehavior+BoxLayout>:
    canvas.before:
        Color:
            rgba: 0.5, 0.5, 0.5, 1
        Rectangle:
            size: self.size
            pos: self.pos
    value: ''
    Label:
        id: name
    Label:
        text: root.value

<Test>:
    canvas:
        Color:
            rgba: 0.3, 0.3, 0.3, 1
        Rectangle:
            size: self.size
            pos: self.pos
    rv: rv
    orientation: 'vertical'
    GridLayout:
        cols: 3
        rows: 2
        size_hint_y: None
        height: dp(108)
        padding: dp(8)
        spacing: dp(16)
        Button:
            text: 'Populate list'
            on_press: root.populate()
        Button:
            text: 'Sort list'
            on_press: root.sort()
        Button:
            text: 'Clear list'
            on_press: root.clear()
        BoxLayout:
            spacing: dp(8)
            Button:
                text: 'Insert new item'
                on_press: root.insert(new_item_input.text)
            TextInput:
                id: new_item_input
                size_hint_x: 0.6
                hint_text: 'value'
                padding: dp(10), dp(10), 0, 0
        BoxLayout:
            spacing: dp(8)
            Button:
                text: 'Update first item'
                on_press: root.update(update_item_input.text)
            TextInput:
                id: update_item_input
                size_hint_x: 0.6
                hint_text: 'new value'
                padding: dp(10), dp(10), 0, 0
        Button:
            text: 'Remove first item'
            on_press: root.remove()

    RecycleView:
        id: rv
        scroll_type: ['bars', 'content']
        scroll_wheel_distance: dp(114)
        bar_width: dp(10)
        viewclass: 'Row'
        RecycleBoxLayout:
            default_size: None, dp(56)
            default_size_hint: 1, None
            size_hint_y: None
            height: self.minimum_height
            orientation: 'vertical'
            spacing: dp(2)
"""

Builder.load_string(kv)


class Test(BoxLayout):

    def populate(self):
        self.rv.data = [
            {'name.text': ''.join(sample(ascii_lowercase, 6)),
             'value': str(randint(0, 2000))}
            for x in range(50)]


    def sort(self):
        self.rv.data = sorted(self.rv.data, key=lambda x: x['name.text'])

    def clear(self):
        self.rv.data = []

    def insert(self, value):
        self.rv.data.insert(0, {
            'name.text': value or 'default value', 'value': 'unknown'})

    def update(self, value):
        if self.rv.data:
            self.rv.data[0]['name.text'] = value or 'default new value'
            self.rv.refresh_from_data()

    def remove(self):
        if self.rv.data:
            self.rv.data.pop(0)


class TestApp(App):
    def build(self):
        t = Test()
        t.rv.data = [
            {'name.text': ''.join(sample(ascii_lowercase, 6)),
             'value': str(randint(0, 2000))}
            for x in range(50)]
        t.rv.refresh_from_data()
        return Test()


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

标签： pythonkivy

Answer 1

一种解决方案是从 Test 类执行 Recycleview 更新。

from random import sample, randint
from string import ascii_lowercase


from kivy.app import App
from kivy.lang import Builder
from kivy.uix.boxlayout import BoxLayout


kv = """
<Row@RecycleKVIDsDataViewBehavior+BoxLayout>:
    canvas.before:
        Color:
            rgba: 0.5, 0.5, 0.5, 1
        Rectangle:
            size: self.size
            pos: self.pos
    value: ''
    Label:
        id: name
    Label:
        text: root.value

<Test>:
    canvas:
        Color:
            rgba: 0.3, 0.3, 0.3, 1
        Rectangle:
            size: self.size
            pos: self.pos
    rv: rv
    orientation: 'vertical'
    GridLayout:
        cols: 3
        rows: 2
        size_hint_y: None
        height: dp(108)
        padding: dp(8)
        spacing: dp(16)
        Button:
            text: 'Populate list'
            on_press: root.populate()
        Button:
            text: 'Sort list'
            on_press: root.sort()
        Button:
            text: 'Clear list'
            on_press: root.clear()
        BoxLayout:
            spacing: dp(8)
            Button:
                text: 'Insert new item'
                on_press: root.insert(new_item_input.text)
            TextInput:
                id: new_item_input
                size_hint_x: 0.6
                hint_text: 'value'
                padding: dp(10), dp(10), 0, 0
        BoxLayout:
            spacing: dp(8)
            Button:
                text: 'Update first item'
                on_press: root.update(update_item_input.text)
            TextInput:
                id: update_item_input
                size_hint_x: 0.6
                hint_text: 'new value'
                padding: dp(10), dp(10), 0, 0
        Button:
            text: 'Remove first item'
            on_press: root.remove()

    RecycleView:
        id: rv
        scroll_type: ['bars', 'content']
        scroll_wheel_distance: dp(114)
        bar_width: dp(10)
        viewclass: 'Row'
        RecycleBoxLayout:
            default_size: None, dp(56)
            default_size_hint: 1, None
            size_hint_y: None
            height: self.minimum_height
            orientation: 'vertical'
            spacing: dp(2)
"""

Builder.load_string(kv)


class Test(BoxLayout):

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

    def populate(self):
        self.rv.data = [
            {'name.text': ''.join(sample(ascii_lowercase, 6)),
             'value': str(randint(0, 2000))}
            for x in range(50)]


    def sort(self):
        self.rv.data = sorted(self.rv.data, key=lambda x: x['name.text'])

    def clear(self):
        self.rv.data = []

    def insert(self, value):
        self.rv.data.insert(0, {
            'name.text': value or 'default value', 'value': 'unknown'})

    def update(self, value):
        if self.rv.data:
            self.rv.data[0]['name.text'] = value or 'default new value'
            self.rv.refresh_from_data()

    def remove(self):
        if self.rv.data:
            self.rv.data.pop(0)


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


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

这似乎是层次结构和 Kivy 设计的问题。没有 RecycleView 的实例被传递给顶部对象 App。