Kivy: 添加一條折線

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Quick Start

By copy the codes from the document, you are supposed being able to show the line on the screen and adjust the alpha, width, etc of the line.

ListProperty([(500, 500),
                          [300, 300, 500, 300],
                          [500, 400, 600, 400]])

As you can see above, you can envelope the points by () or [], you can line the points one by one or line them all together if you wish (The examples show down below).

ListProperty([(500, 500),
                          [300, 300], [500, 300],
                          [500, 400], [600, 400]])
```python
or
```python
ListProperty([500, 500, 300, 300, 500, 300, 500, 400, 600, 400])

The minimal codes you’ve to keep is:

from kivy.app import App
from kivy.uix.floatlayout import FloatLayout
from kivy.lang import Builder
Builder.load_string('''
<LinePlayground>:
    # assign a list variate as point so it could be easliy handled in later
    point: [0,0, 200, 100]
    canvas:
        Color:
            rgba: .4, .4, 1, 1
        Line:
            # recall the variate 'point' above
            points: self.point
'''
)
class LinePlayground(FloatLayout):
    pass
class TestLineApp(App):
    def build(self):
        return LinePlayground()
if __name__ == '__main__':
    TestLineApp().run()

updating the line

If you are not satisfied with drawing a line and want to create an animation, than like do some thing cool.

updating….

from kivy.app import App
from kivy.properties import  ListProperty
from kivy.uix.floatlayout import FloatLayout
from kivy.uix.widget import Widget
from kivy.lang import Builder
from kivy.clock import Clock
from kivy.properties import ObjectProperty
## Remove unnecessary codes from this class
class LinePlayground(FloatLayout):
    pass
class Main_app(Widget):
    # assign a numeric variate
    i = 0
    # connect the class in kv file: line -> line_ground -> LinePlayground
    line = ObjectProperty(None)
    def update(self, dt):
        self.i +=1
        # update the point
        self.line.point = [[0,0,], [self.i,self.i]]
        print(self.line.point)
        print(self.line)
        print("1")
class TestLineApp(App):
    def build(self):
        Main = Main_app()
        # update the result with 60 fps (1/60)
        Clock.schedule_interval(Main.update,1/60)
        return Main
if __name__ == '__main__':
    TestLineApp().run()

testline.kv file:

<LinePlayground>:
    # assign a list variate as point so it could be easliy handled in later
    point: [0,0, 200, 100]
    canvas:
        Color:
            rgba: .4, .4, 1, 1
        Line:
            # recall the variate 'point' above
            points: self.point
<Main_app>:
    # assign the id which could be recall later
    line: line_ground
    LinePlayground:
        id: line_ground
        point: [0,10, 100,200]

Enjoy~

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