Question

在旋转图像和移动图像时使用Kivy语言时，我很难理解Kivy在幕后所做的事情。

下面是一个代码，它应该在屏幕上以45度角绘制两张图像，然后每按一次鼠标就可以旋转它，然后将它移到屏幕右侧。

使用Kivy语言中定义的旋转绘制第一个图像，其中第二个图像是我尝试仅在python中重做它（以更好地理解Kivy实际上在做什么），但是我失败了，因为当我增加x时，Python版本首先不会将图像向右移动，但看起来整个坐标系已经为该图像旋转，因为它在屏幕上以45度角移动，其次它不会旋转该图像我点击了。

我缺少什么，以及在Python中（不使用Kivy语言）获取与第一张图像相同的行为需要做什么？

from kivy.app import App
from kivy.lang import Builder
from kivy.uix.image import Image
from kivy.graphics import Rotate
from kivy.uix.widget import Widget
from kivy.properties import NumericProperty
from kivy.graphics.context_instructions import PopMatrix, PushMatrix


Builder.load_string('''
<TestKV>:
    canvas.before:
        PushMatrix
        Rotate:
            angle: self.angle
            axis: (0, 0, 1)
            origin: self.center
    canvas.after:
        PopMatrix
''')

class TestKV(Image):
    angle = NumericProperty(0)

    def __init__(self, x, **kwargs):
        super(TestKV, self).__init__(**kwargs)
        self.x = x
        self.angle = 45

    def on_touch_down(self, touch):
        self.angle += 20
        self.x += 10


class TestPY(Image):
    angle = NumericProperty(0)

    def __init__(self, x, **kwargs):
        super(TestPY, self).__init__(**kwargs)
        self.x = x
        with self.canvas.before:
            PushMatrix()
            rot = Rotate()
            rot.angle = 45
            rot.origin = self.center
            rot.axis = (0, 0, 1)
        with self.canvas.after:
            PopMatrix()

    def on_touch_down(self, touch):
        self.angle += 20
        self.x += 10

class MainWidget(Widget):
    #this is the main widget that contains the game.

    def __init__(self, **kwargs):
        super(MainWidget, self).__init__(**kwargs)
        self.all_sprites = []

        self.k = TestKV(source="myTestImage.bmp", x=10)
        self.add_widget(self.k)

        self.p = TestPY(source="myTestImage.bmp", x=200)
        self.add_widget(self.p)


class TheApp(App):

    def build(self):
        parent = Widget()
        app = MainWidget()
        parent.add_widget(app)

        return parent

if __name__ == '__main__':
    TheApp().run()

Answer 1

您永远不会更改Rotate指令的角度。您的小部件上有angle属性，但它与任何内容都没有关联。请尝试更新Rotate指令：

class TestPY(Image):
    def __init__(self, **kwargs):
        super(TestPY, self).__init__(**kwargs)
        # self.x = x -- not necessary, x is a property and will be handled by super()
        with self.canvas.before:
            PushMatrix()
            self.rot = Rotate()
            self.rot.angle = 45
            self.rot.origin = self.center
            self.rot.axis = (0, 0, 1)
        with self.canvas.after:
            PopMatrix()

    def on_touch_down(self, touch):
        self.x += 10
        self.rot.origin = self.center  # center has changed; update here or bind instead
        self.rot.angle += 20

Kivy和Python之间旋转图像的行为

1 个答案: