Question

我找不到在python代码中设置on_press的语法，可以在任何地方更改屏幕。我一直在为Button(text = 'hi', on_press = self.current = 'start_menu之类的东西收到错误。这是代码，它按原样运行。

class LoadMenu(Screen):
    def __init__(self, **kwargs):
        super(LoadMenu, self).__init__(**kwargs)
        Clock.schedule_once(self.update)

    def update(self, dt):
        L = [x for x in range(len(os.listdir('saves')))]
        for x in L:
            x = self.add_widget(Button(text = os.listdir('saves')[x]))

我没有定位按钮，所以它们只是在彼此的顶部，但我可以稍后解决。我需要做的是每个按钮在按下时更改为play屏幕，这对于每个按钮都是相同的，但我还需要每个按钮加载他们引用的Shelve文件。（我知道我'我需要另一个函数）我可以一次on_press触发两个事件，再次如何在python代码中设置它？

Answer 1

考虑以下计划：

from kivy.app import App
from kivy.lang import Builder
from kivy.uix.screenmanager import Screen
from kivy.uix.button import Button
from kivy.clock import Clock
from kivy.properties import StringProperty

dirlist = ['aaa', 'bbb', 'ccc', 'ddd']

class MyButton(Button):
    prop = StringProperty('')
    def on_press(self):
        print "Class-defined on_press handler (I'm {})".format(self.text)

def other_on_press_handler(sender):
    print "other_on_press_handler, from {}".format(sender.text)

def some_func(text):
    print "yeah: " + text

class LoadMenu(Screen):
    def __init__(self, **kwargs):
        super(LoadMenu, self).__init__(**kwargs)
        Clock.schedule_once(self.update)

    def on_press_handler(self, sender):
        print "on_press_handler, from {}".format(sender.text)
        self.parent.current = 'sc2'

    def yet_another_on_press_handler(self, sender):
        print "yet_another_on_press_handler, from {}".format(sender.text)
        self.parent.current = 'sc2'

    def update(self, dt):
        for x in range(len(dirlist)):
            my_b = Button(text = dirlist[x], on_press=self.on_press_handler)
            self.parent.ids.button_container.add_widget(my_b)
            if x > 1:
                my_b.bind(on_press=other_on_press_handler)
            if x == 3:
                my_b.bind(on_press=lambda sender: some_func("Whoa, lambda was here ({})".format(sender.text)))
        for x in range(len(dirlist)):
            my_b = MyButton(text = 'my '+ dirlist[x], prop="{} {}".format(dirlist[x], x))
            self.parent.ids.button_container.add_widget(my_b)
            my_b.bind(on_press=self.yet_another_on_press_handler)

root = Builder.load_string("""
ScreenManager:
    LoadMenu:
        name: 'sc1'
        GridLayout:
            cols: 4
            id: button_container
    Screen:
        name: 'sc2'
        BoxLayout:
            Button:
                text: "Go back"
                on_press: root.current = 'sc1'
""")

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

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

让我们从查看update中的LoadMenu方法开始：在第一个循环中，生成一堆按钮，每个按钮在创建时都会收到on_press回调。循环中的最后两个按钮绑定到另一个回调，最后一个示例显示如何使用lambda表达式生成回调。在第二个for循环中，我们实例化了MyButton的对象，Button的子对象。注意，我们还在类定义中定义了一个on_press处理程序;除了我们可能绑定的其他函数之外，还会调用它。但实际上，这实际上在kivy Events and Properties docs中已经很好地解释了。

使用python逻辑更改屏幕（Kivy Screen manager）

1 个答案: