Kivy-更改按钮颜色

Question

I've recently started using kivy to design GUI for my python app. In the app one of the actions is sending requests to server using provided API. After a couple of tests I've noticed one annoying thing that happens only when I want to make a request - the button doesn't change color on press (I'm talking about default action). However, it is changing when simple print() is used.

How I can fix it? Any idea?

This is the code of my test app:

class TestApp(App):
    def build(self):
        parent = Widget()
        btn = Button(text='Add')
        btn.bind(on_press=self.add)
        parent.add_widget(btn)
        return parent

    def add(self, obj):
        print("Adding")
        request = Request(url, urlencode(post_fields).encode())
        urlopen(request)

Answer 1

That happened most likely because the UI froze. The self.add is called, but right after that the UI waits until the request is done, which for you might result in that.

Try to do it like this:

import threading

class TestApp(App):
    def build(self):
        parent = Widget()
        btn = Button(text='Add')
        btn.bind(on_press=self.add)
        parent.add_widget(btn)
        return parent

    def add(self, obj):
        print("Adding")
        #self.printer()  # freezing
        threading.Thread(target=self.printer).start()

    def printer(self, *args):
        while True:
            print 'blob'
TestApp().run()

Also, instead of on_press use rather on_release . Prevents accidental events if I remember correctly (checks for collision touch↔button area).