在gui - kivy python中按下鼠标添加小部件

Question

I have problem with adding and showing image to the layout every time I press the screen using mouse.

class Myszka(ClickAndGo, Widget):

    def on_touch_down(self, touch):
        super().build()
        flaga_path = os.path.join(self.img_path, "test.png")
        x, y = touch.pos
        self.flaga = Image(source=flaga_path, size_hint=(None, None), size=(64, 64),
                           pos=(round(x, 1), round(y, 1)))
        self.camlayout.add_widget(self.flaga)
        print(touch.pos)

• Actual results: only touch position is printed, image has not been shown.
• Expected results: Image should have been shown, every time mouse down.

Answer 1

@ikolim

from kivy.app import App
from kivy.uix.floatlayout import FloatLayout


class ClickAndGo(App):
    def build(self):
        self.camlayout = FloatLayout(size=(100,100))
        self.myszka = Myszka()

        self.camlayout.add_widget(self.myszka)

        return self.camlayout

class Myszka(ClickAndGo, Widget):

    def on_touch_down(self, touch):
        super().build()
        # test.png -> any image
        flaga_path = os.path.join(self.img_path, "test.png")
        x, y = touch.pos
        self.flaga = Image(source=flaga_path, size_hint=(None, None), size=(64, 64),
                           pos=(round(x, 1), round(y, 1)))
        self.camlayout.add_widget(self.flaga)
        print(touch.pos)

Answer 2

Problem

I have problem with adding and showing image to the layout every time I press the screen using mouse.

Root Cause

The image is not showing because it is adding to a local attribute, self.camlayout in method on_touch_down() of class Myszka() .

Solution

Replace self.camlayout.add_widget(self.flaga) with App.get_running_app().root.add_widget(self.flaga) ie get an instance of the root ( camlayout ).

Snippets - py

class Myszka(Widget):

    def on_touch_down(self, touch):
        ...
        App.get_running_app().root.add_widget(self.flaga)

Example

The following example illustrates adding Image at the position of the mouse click on a FloatLayout .

main.py

import os
from kivy.app import App
from kivy.uix.floatlayout import FloatLayout
from kivy.uix.image import Image


class Mouse(FloatLayout):

    def on_touch_down(self, touch):
        img_path = "/home/iam/Pictures/AppImages"
        flag_path = os.path.join(img_path, "Android_celebrate.png")
        flag = Image(source=flag_path, size_hint=(None, None), size=(64, 64),
                     pos=(round(touch.pos[0], 1), round(touch.pos[1], 1)))
        self.add_widget(flag)


class TestApp(App):

    def build(self):
        return Mouse()


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

Output