問題描述

假設我在 Kivy 中動態定義了一些小部件(按鈕)并動態分配它們的 ID.在這個用例中我沒有使用 kv 語言.我可以在不跟蹤小部件本身的情況下保留小部件 ID 的引用:然后我想通過它的 ID 訪問小部件.我可以做類似通過 id 獲取小部件"之類的事情嗎?(如果我在 kv 文件中定義了小部件，我可以使用 self.ids.the_widget_id 通過其 id 訪問小部件本身)

Let's say I define on the fly in Kivy a few widgets (buttons) and dynamically assign their id. I'm not using kv language in this use case. I can keep a reference of a widget id without keeping track of the widget itself : then I'd like to access the widget through its id. Can I do something like "get widget by id" ? (If I had defined the widget in a kv file, I could have used self.ids.the_widget_id to access the widget itself through its id)

推薦答案

Kivy 小部件制作樹形結構.任何小部件的子級都可以通過 children 屬性獲得.如果需要，您可以只保留對根窗口的引用，然后使用 walk 方法迭代它的小部件:

Kivy widgets make tree structure. Children of any widget are avaiable through children atribute. If you want, you can keep reference only to root window and then iterate over it's widgets using walk method:

from kivy.app import App
from kivy.uix.boxlayout import BoxLayout
from kivy.uix.button import Button 

class MyWidget(BoxLayout):
    def __init__(self, **kwargs):
        super().__init__(**kwargs)

        button = Button(text="...", id="1")
        button.bind(on_release=self.print_label)

        l1 = BoxLayout(id="2")
        l2 = BoxLayout(id="3")

        self.add_widget(l1)
        l1.add_widget(l2)             
        l2.add_widget(button)

    def print_label(self, *args):
        for widget in self.walk():
            print("{} -> {}".format(widget, widget.id))

class MyApp(App):
    def build(self):
        return MyWidget()

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

walk() 和 walk_reverse() 方法被添加到 Kivy 1.8.1 版本的 kivy.uix.widget.Widget 中.對于舊版本，您需要自己遞歸解析樹:

walk() and walk_reverse() method were added to kivy.uix.widget.Widget in 1.8.1 version of Kivy. For older versions you need to recursively parse tree yourself:

from kivy.app import App
from kivy.uix.boxlayout import BoxLayout
from kivy.uix.button import Button 

class MyWidget(BoxLayout):
    def __init__(self, **kwargs):
        super().__init__(**kwargs)

        button = Button(text="...", id="1")
        button.bind(on_release=self.print_label)

        l1 = BoxLayout(id="2")
        l2 = BoxLayout(id="3")

        self.add_widget(l1)
        l1.add_widget(l2)             
        l2.add_widget(button)

    def print_label(self, *args):
        children = self.children[:]
        while children:
            child = children.pop()
            print("{} -> {}".format(child, child.id))
            children.extend(child.children)

class MyApp(App):
    def build(self):
        return MyWidget()

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

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