kivy - 让微调器记住它的选择

Question

我希望有人能告诉我如何让微调器在加载应用时记住它的值。

我正在考虑使用 from kivy.storage.jsonstore import JsonStore 来存储和检索用户在数据库中选择的值，这很容易。

但是经过几个小时的搜索，我找不到任何关于使微调器在加载时说出该值的文档。

例如，我的微调器中有很多项目（大约 60 个），滚动浏览需要一段时间，正如我所说，我可以记住最后选择的项目，但我不知道如何将其设为默认值。

    Spinner:
    id: stationSpinner
    text:'Select a Station'
    values: ('Reset Saved Station','Appledore','Axminster','Bampton','Barnstaple','Bere Alston','Bideford','Bovey Tracey','Braunton','Bridgwater','Brixham','Buckfastleigh','Budleigh Salterton','Burnham on Sea','Camels Head','Castle Cary','Chagford','Chard','Cheddar','Chulmleigh','Colyton','Combe Martin','Crediton','Crewkerne','Crownhill','Cullompton','Dartmouth','Dawlish','Danes Castle','Middlemoor','Exmouth','Frome','Glastonbury','Greenbank','Hartland','Hatherleigh','Holsworthy','Honiton','Ilfracombe','Ilminster','Ivybridge','Kingsbridge','Kingston','Lundy Island','Lynton','Martock','Minehead','Modbury','Moretonhampstead','Nether Stowey','Newton Abbot','North Tawton','Okehampton','Ottery St Mary','Paignton','Plympton','Plymstock','Porlock','Princetown','Salcombe','Seaton','Shepton Mallet','Sidmouth','Somerton','South Molton','Street','Taunton','Tavistock','Teignmouth','Tiverton','Topsham','Torquay','Torrington','Totnes','USAR','Wellington','Wells','Williton','Wincanton','Witheridge','Wiveliscombe','Woolacombe','Yelverton','Yeovil')
    size_hint: None, None
    size: (150, 44)
    pos_hint: {'center_x':0.5, 'y': 0.35}
    on_text: app.show_selected_value()

所以第一次加载应用时，它会显示“选择电台”。第二次加载它显示最后选择的电台。显然我已经把reset选项放进去清除db文件。

我尝试过使用

SvdStn = store.get('Stations')['Saved']
self.root.station.text = SvdStn

但它不起作用，我猜它相当简单，但由于我找不到任何关于它的文档，我无法理解它......我会继续寻找，也许会从不同的方向，也许在微调器旁边选择最后一个按钮时按钮变为可见，但如果 db 为空，则将 visible 属性设置为 false。

编辑：这是我的代码py file and logo on onedrive

欢迎任何想法

谢谢

雷夫

这是代码的相关部分：

import kivy
from kivy.app import App
from kivy.lang import Builder
from kivy.uix.floatlayout import FloatLayout
from kivy.properties import ObjectProperty
from kivy.storage.jsonstore import JsonStore
from os.path import join

kv = '''
<IncidentScreen>:
    canvas.before:
        Color:
            rgba: 1, 1, 1, 1
        Rectangle:
            pos: self.pos
            size: self.size

    station: stationSpinner
    Image:
        source:'DSFRSLogo.png'
        allow_stretch:True
        pos_hint: {'root.x':0.5, 'y':.2}

    Spinner:
        id: stationSpinner
        text:'Select a Station'
        values: ('Reset Saved Station','Appledore','Axminster','Bampton','Barnstaple','Bere Alston','Bideford','Bovey Tracey','Braunton','Bridgwater','Brixham','Buckfastleigh','Budleigh Salterton','Burnham on Sea','Camels Head','Castle Cary','Chagford','Chard','Cheddar','Chulmleigh','Colyton','Combe Martin','Crediton','Crewkerne','Crownhill','Cullompton','Dartmouth','Dawlish','Danes Castle','Middlemoor','Exmouth','Frome','Glastonbury','Greenbank','Hartland','Hatherleigh','Holsworthy','Honiton','Ilfracombe','Ilminster','Ivybridge','Kingsbridge','Kingston','Lundy Island','Lynton','Martock','Minehead','Modbury','Moretonhampstead','Nether Stowey','Newton Abbot','North Tawton','Okehampton','Ottery St Mary','Paignton','Plympton','Plymstock','Porlock','Princetown','Salcombe','Seaton','Shepton Mallet','Sidmouth','Somerton','South Molton','Street','Taunton','Tavistock','Teignmouth','Tiverton','Topsham','Torquay','Torrington','Totnes','USAR','Wellington','Wells','Williton','Wincanton','Witheridge','Wiveliscombe','Woolacombe','Yelverton','Yeovil')
        size_hint: None, None
        size: (150, 44)
        pos_hint: {'center_x':0.5, 'y': 0.35}
        on_text: app.show_selected_value()

'''
class IncidentScreen(FloatLayout):
    station = ObjectProperty(None)
    results = ObjectProperty(None)
    data_dir = App().user_data_dir
    store = JsonStore(join(data_dir, 'storage.json'))
    try:
        store.get('stations')['saved']
    except KeyError:
        SvdStn = ""
    else:
        SvdStn = store.get('stations')['saved']
        print(SvdStn)
        self.root.station.text = SvdStn

class DSFRSapp(App):

    def build(self):            
        Builder.load_string(kv)
        fl = IncidentScreen()
        return fl

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

Answer 1

您提到的微调器方法工作正常，但您似乎误解了self 和App() 的使用。 self 引用类的当前实例，并作为参数提供给类方法，因此您不能在类方法之外使用它。您已尝试直接在 kivy 属性下使用它，但在这种情况下，它不包含值。您还尝试使用App()，但这会尝试创建 App 对象的实例。我会将加载和保存留在应用程序类中，并允许微调器使用其构造函数的额外参数进行初始化，如下所示：

class IncidentScreen(FloatLayout):
    station = ObjectProperty(None)
    results = ObjectProperty(None)

    def __init__(self, station, **kwargs):
        super(IncidentScreen, self).__init__(**kwargs)
        self.station.text = station

class DSFRSapp(App):

    def build(self):            
        Builder.load_string(kv)
        data_dir = self.user_data_dir
        store = JsonStore(join(data_dir, 'storage.json'))
        SvdStn = ""

        try:
            store.get('stations')['saved']
            SvdStn = store.get('stations')['saved']
        except KeyError:
            pass

        fl = IncidentScreen(SvdStn)
        return fl

您必须对show_selected_value 方法执行类似的操作。我必须禁用它才能运行代码，因为它会在 gui 显示时立即调用。总的来说，我建议你仔细看看 python 如何处理类。以后会省很多力气。如果你用谷歌搜索，有很多教程。