矩形设置为MyPaintWidget的大小，在父小部件上以默认大小绘制。如果MyPaintWidget是根小部件，那么设置self.size将允许它占用整个窗口空间。(请注意，当前结构只会在on-touch-down事件上调整画布的大小。因此，如果调整窗口大小，则需要单击以调整图像大小。)#Change MyPaintApp to the following...

class MyPaintApp(App):

def build(self):

return MyPaintWidget()

您还可以创建一个单独的小部件来保存背景。下面我添加了一个MyBackground小部件，它用于背景，当屏幕大小改变时，它将调整大小。还有其他几种方法可以做到这一点。from random import random

from kivy.app import App

from kivy.uix.button import Button

from kivy.uix.widget import Widget

from kivy.graphics import Color, Line, Rectangle

from kivy.uix.filechooser import FileChooserListView, FileChooserIconView

from kivy.uix.floatlayout import FloatLayout

from kivy.uix.image import Image

class MyBackground(Widget):

def __init__(self, **kwargs):

super(MyBackground, self).__init__(**kwargs)

with self.canvas:

self.bg = Rectangle(source='water.png', pos=self.pos, size=self.size)

self.bind(pos=self.update_bg)

self.bind(size=self.update_bg)

def update_bg(self, *args):

self.bg.pos = self.pos

self.bg.size = self.size

class MyPaintWidget(Widget):

def on_touch_down(self, touch):

color = (random(), random(), random())

with self.canvas:

Color(*color)

d = 30.

touch.ud['line'] = Line(points=(touch.x, touch.y))

def on_touch_move(self, touch):

touch.ud['line'].points += [touch.x, touch.y]

class MyPaintApp(App):

def build(self):

parent = MyBackground()

painter = MyPaintWidget()

parent.add_widget(painter)

return parent

if __name__ == '__main__':

MyPaintApp().run()