Question

我想构建一个屏幕，在该屏幕上按下按钮时，标签的大小和位置会发生变化：

Button : Changes
x++   -> x co-ordinate of label increments by 0.1 in pos_hint property
x--   -> x co-ordinate of label decrements by 0.1 in pos_hint property

到目前为止，我已经尝试过了，

from kivy.app import App
from kivy.uix.widget import Widget
from kivy.uix.label import Label
from kivy.uix.scatter import Scatter
from kivy.uix.floatlayout import FloatLayout
from kivy.properties import ObjectProperty



class Screen(Widget):
    lbl = ObjectProperty(None)

    def __init__(self, **kwargs):
        super(Screen, self).__init__(**kwargs)
        self.count_x = 0.1

    def print_pos_change(self,instance,value):
        print(instance,"Moved to", value)

    def callback(self,arg):
        if arg == "x++":
            self.count_x+=0.1
            self.lbl.pos_hint["x"] = self.count_x
        elif arg == "x--":
            self.count_x-=0.1
            self.lbl.pos_hint["x"] = self.count_x

class WidgetEx(App):
    kv_directory = "kv-files"

    def build(self):
        return Screen()


if __name__ == "__main__":
    WidgetEx().run()

这是kv文件，

<Screen>
    lbl:lbl
    FloatLayout:
        size:root.width,root.height
        Label:
            id:lbl
            text:"Hello"
            size_hint:0.5,0.5
            on_pos:root.print_pos_change(self,self.pos)
            canvas:
                Color:
                    rgba: 0, 0, 1, 1
                Rectangle:
                    pos:self.pos
                    size:self.size
        GridLayout:
            cols:2
            size_hint:1,0.1
            Button:
                text:"x++"
                on_press:root.callback("x++")
            Button:
                text:"x--"
                on_press:root.callback("x--")

现在的问题是位置不变，更改期间也不会调用print_pos_change。

我知道我可以直接使用self.lbl.x和self.lbl.y，但是我想使用self.lbl.pos_hint进行更改。我该怎么办？？

这是UI的ss， Image of UI

在方法do_layout()的结尾处，我已将floatlayout用于callback，但是按钮现在也随标签一起移动了？我该如何解决？

为什么size_hint正常工作而pos_hint不起作用？它背后有逻辑吗？

我想增加pos_hint["x"]属性以使每次按下x++按钮增加0.1。

Answer 1

有很多方法可以做到这一点。
尝试在pos提示右侧和顶部使用数字属性。

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

KV = """

MyWidget:
    FloatLayout:
        size:root.width,root.height
        Label:
            text:"Hello"
            size_hint:0.5,0.5
            pos_hint: {"top":root.pos_hint_top, "right":root.pos_hint_right}
            canvas.before:
                Color:
                    rgba: 0, 0, 1, 1
                Rectangle:
                    pos:self.pos
                    size:self.size
        GridLayout:
            cols:2
            size_hint:1,0.1
            Button:
                text:"x++"
                on_press:root.callback("x++")
            Button:
                text:"x--"
                on_press:root.callback("x--")

"""

class MyWidget(Widget):
    pos_hint_right = NumericProperty(0.5)
    pos_hint_top = NumericProperty(0.5)

    def callback(self,arg):
        if arg == "x++":
            self.pos_hint_right += 0.1
        elif arg == "x--":
            self.pos_hint_right -= 0.1

class WidgetEx(App):
    def build(self):
        return Builder.load_string(KV)


if __name__ == "__main__":
    WidgetEx().run()

通过编程方式更改pos_hint时，为什么kivy不更新小部件的位置？

1 个答案: