Python KIvy 旋转矩形在调整大小时移动

Question

我有一个旋转的矩形，当我调整它的大小时它会稍微改变它的位置。 但我不希望它移动...

发生这种位置变化，当我重置中心时，如果我不改变中心，它不会移动，但中心正确对我来说很重要。

我创建了 2 个视频。 目前是这样的：https://youtu.be/TqY3Ji0rnLw 这就是我想要的（我删除了中心重置，但正如我之前所说的我想要中心重置）：https://youtu.be/Jfq777nzu6o

我该如何解决这个问题？

这是我的代码：

from kivy.app import App
from kivy.uix.widget import Widget
from kivy.graphics import Color, Rectangle, PushMatrix, Rotate, PopMatrix
from kivy.clock import Clock
from kivy.core.window import Window



class Canvas:
    def __init__(self, root, pos, size, rotation=0, color=(1, 0, 0, 1)):
        with root.canvas:
            PushMatrix()
            self._color_instruction = Color(rgba=color)
            self._rotation_instruction = Rotate(angle=rotation, origin=(150, 150))
            self._rectangle_instruction = Rectangle(pos=pos, size=size)
            PopMatrix()

    @property
    def center(self):
        pos = self.pos
        size = self.size
        center_x = pos[0] + size[0] / 2
        center_y = pos[1] + size[1] / 2
        return (center_x, center_y)

    @property
    def pos(self):
        return self._rectangle_instruction.pos

    @pos.setter
    def pos(self, value):
        self._rectangle_instruction.pos = value
        self._rotation_instruction.origin = self.center

    @property
    def size(self):
        return self._rectangle_instruction.size

    @size.setter
    def size(self, value):  
        self._rectangle_instruction.size = value
        self._rotation_instruction.origin = self.center

    @property
    def rotation(self):
        return self._rotation_instruction.angle

    @rotation.setter
    def rotation(self, value):
        self._rotation_instruction.angle = value

    @property
    def color(self):
        return self._color_instruction.rgba

    @color.setter
    def color(self, value):
        self._color_instruction.rgba = value


class Root(Widget):
    def __init__(self, **kwargs):
        super(Root, self).__init__(**kwargs)

        self.rectangle = Canvas(self, (100, 100), (100, 100), rotation=45)

        self.keys_pressed = set()

        self._keyboard = Window.request_keyboard(self._on_keyboard_closed, self)
        self._keyboard.bind(on_key_down = self._on_key_down)
        self._keyboard.bind(on_key_up = self._on_key_up)

        Clock.schedule_interval(self.step, 0)

    def step(self, dt):
        x = self.rectangle.pos[0]
        y = self.rectangle.pos[1]
        width = self.rectangle.size[0]
        height = self.rectangle.size[1]
        rotation = self.rectangle.rotation

        step_size = 300 * dt

        if "up" in self.keys_pressed:
            y += step_size
        if "left" in self.keys_pressed:
            x -= step_size
        if "right" in self.keys_pressed:
            x += step_size
        if "down" in self.keys_pressed:
            y -= step_size
        if "y" in self.keys_pressed:
            rotation += step_size
        if "x" in self.keys_pressed:
            rotation -= step_size
        if "w" in self.keys_pressed:
            height = min(height + step_size, 300)
        if "a" in self.keys_pressed:
            width = max(width - step_size, 10)
        if "d" in self.keys_pressed:
            width = min(width + step_size, 300)
        if "s" in self.keys_pressed:
            height = max(height - step_size, 10)

        self.rectangle.pos = (x, y)
        self.rectangle.size = (width, height)
        self.rectangle.rotation = rotation

    def _on_keyboard_closed(self):
        self._keyboard.unbind(_on_key_down = self._on_key_down)
        self._keyboard.ubind(_on_key_up = self._on_key_up)

        self._keyboard = None

    def _on_key_down(self, keyboard, keycode, text, modifiers):
        self.keys_pressed.add(text if text != None else keycode[1])

    def _on_key_up(self, keyboard, keycode):
        if keycode[1] in self.keys_pressed:
            self.keys_pressed.remove(keycode[1])


class TestApp(App):
    def __init__(self, **kwargs):
        super(TestApp, self).__init__(**kwargs)

    def build(self):
        return Root()


def main():
    app = TestApp()
    app.run()


if __name__ == "__main__":
    main()

如何改变它在第二个视频中的位置？

Answer 1

这是您的代码的修改版本，它使用kv 和现有的canvas 对象来绘制Rectangle：

from kivy.app import App
from kivy.lang import Builder
from kivy.properties import ListProperty, NumericProperty
from kivy.uix.widget import Widget
from kivy.clock import Clock
from kivy.core.window import Window

class MyCanvas(Widget):
    color = ListProperty([1,0,0,1])
    rotation = NumericProperty(0)

Builder.load_string('''
<MyCanvas>:
    size_hint: None, None
    canvas:
        Color:
            rgba: self.color
        PushMatrix:
        Translate:
            xy: self.x, self.y
        Rotate:
            axis: 0,0,1
            origin: 0,0
            angle: self.rotation
        Scale:
            origin: 0,0
            xyz: self.width, self.height, 1
        Rectangle:  # unit rectangle centered on origin
            pos: -0.5, -0.5
            size: 1, 1
        PopMatrix:
        
''')


class Root(Widget):
    def __init__(self, **kwargs):
        super(Root, self).__init__(**kwargs)

        # self.rectangle = Canvas(self, (100, 100), (100, 100), rotation=45)
        self.rectangle = MyCanvas(pos=(100,100), size=(100,100), rotation=45)
        self.add_widget(self.rectangle)

        self.keys_pressed = set()

        self._keyboard = Window.request_keyboard(self._on_keyboard_closed, self)
        self._keyboard.bind(on_key_down = self._on_key_down)
        self._keyboard.bind(on_key_up = self._on_key_up)

        Clock.schedule_interval(self.step, 0)

    def step(self, dt):
        x = self.rectangle.pos[0]
        y = self.rectangle.pos[1]
        width = self.rectangle.size[0]
        height = self.rectangle.size[1]
        rotation = self.rectangle.rotation

        step_size = 300 * dt

        if "up" in self.keys_pressed:
            y += step_size
        if "left" in self.keys_pressed:
            x -= step_size
        if "right" in self.keys_pressed:
            x += step_size
        if "down" in self.keys_pressed:
            y -= step_size
        if "y" in self.keys_pressed:
            rotation += step_size
        if "x" in self.keys_pressed:
            rotation -= step_size
        if "w" in self.keys_pressed:
            height = min(height + step_size, 300)
        if "a" in self.keys_pressed:
            width = max(width - step_size, 10)
        if "d" in self.keys_pressed:
            width = min(width + step_size, 300)
        if "s" in self.keys_pressed:
            height = max(height - step_size, 10)

        self.rectangle.pos = (x, y)
        self.rectangle.size = (width, height)
        self.rectangle.rotation = rotation

    def _on_keyboard_closed(self):
        self._keyboard.unbind(_on_key_down = self._on_key_down)
        self._keyboard.ubind(_on_key_up = self._on_key_up)

        self._keyboard = None

    def _on_key_down(self, keyboard, keycode, text, modifiers):
        self.keys_pressed.add(text if text != None else keycode[1])

    def _on_key_up(self, keyboard, keycode):
        if keycode[1] in self.keys_pressed:
            self.keys_pressed.remove(keycode[1])


class TestApp(App):
    def __init__(self, **kwargs):
        super(TestApp, self).__init__(**kwargs)

    def build(self):
        return Root()


def main():
    app = TestApp()
    app.run()


if __name__ == "__main__":
    main()

Rectangle 的大小与您的视频显示的不完全一样，但很接近。

您可以通过将kv 更改为：

<MyCanvas>:
    size_hint: None, None
    canvas.before:
        PushMatrix:
        Rotate:
            axis: 0,0,1
            origin: self.pos
            angle: self.rotation
    canvas:
        Color:
            rgba: self.color
        Rectangle:
            pos: self.pos
            size: self.size
    canvas.after:
        PopMatrix:

但这会影响旋转行为，因此旋转是围绕Rectangle 的一个角而不是center。