為什么 kivy 沒有畫線

Question

我試圖制作 Galaxy 項目。 我在兩者之間犯了一個錯誤！

這個我是通過freecodecamp.org kivy 全程嘗試的。

我是 kivy 的初學者。

查看canvas是否有問題。

我無法在 kivy window 上看到我畫的線。

這是我的文件：

主程序

from kivy.app import App
from kivy.uix.widget import Widget
from kivy.graphics import *
from kivy.lang import Builder
from kivy.properties import NumericProperty

Builder.load_file('galaxy.kv')
class MainWidget(Widget):
    perspective_point_x = NumericProperty(0)
    perspective_point_y = NumericProperty(0)

    V_NB_LINES = 7
    V_NB_SPACING = .1
    vertical_lines = []

    def __init__(self, **kwargs):
        super(MainWidget, self).__init__(**kwargs)
        self.init_vertical_lines()

    def on_parent(self, widget, parent):
        pass

    def on_size(self, *args):
        self.update_vertical_lines()

    def on_perspective_point_x(self, widget, value):
        pass

    def on_perspective_point_y(self, widget, value):
        pass

    def init_vertical_lines(self):
        with self.canvas:
            Color(1, 1, 1)
            for i in range(0, self.V_NB_LINES):
                self.vertical_lines.append(Line())

    def update_vertical_lines(self):
        central_line_x = int(self.width/2)
        spacing = int(self.V_NB_SPACING * self.width)
        offset = -int(self.V_NB_LINES/2)
        for i in range(0, self.V_NB_LINES):
            line_x = central_line_x + offset*spacing
            self.vertical_lines[i].points = [line_x, 0, line_x, self.height]
            offset += 1

class GalaxyApp(App):
    pass

GalaxyApp().run()

星系.kv

<MainWidget>
    perspective_point_x: self.width  / 2
    perspective_point_y: self.height * 0.75

Answer 1

您在 GalaxyApp 中缺少構建 function

from kivy.app import App
from kivy.uix.widget import Widget
from kivy.graphics import *
from kivy.lang import Builder
from kivy.properties import NumericProperty

Builder.load_file('galaxy.kv')

class MainWidget(Widget):
    perspective_point_x = NumericProperty(0)
    perspective_point_y = NumericProperty(0)

    V_NB_LINES = 7
    V_NB_SPACING = .1
    vertical_lines = []

    def __init__(self, **kwargs):
        super(MainWidget, self).__init__(**kwargs)
        self.init_vertical_lines()

    def on_parent(self, widget, parent):
        pass

    def on_size(self, *args):
        self.update_vertical_lines()

    def on_perspective_point_x(self, widget, value):
        pass

    def on_perspective_point_y(self, widget, value):
        pass

    def init_vertical_lines(self):
        with self.canvas:
            Color(1, 1, 1)
            for i in range(0, self.V_NB_LINES):
                self.vertical_lines.append(Line())

    def update_vertical_lines(self):
        central_line_x = int(self.width/2)
        spacing = int(self.V_NB_SPACING * self.width)
        offset = -int(self.V_NB_LINES/2)
        for i in range(0, self.V_NB_LINES):
            line_x = central_line_x + offset*spacing
            with self.canvas:
                self.vertical_lines[i].points = [line_x, 0, line_x, self.height]
            offset += 1

class GalaxyApp(App):
    def build(self):
        return MainWidget()

GalaxyApp().run()