Is there a focus lost event dispatcher for a kivy TextInput?

问题

Problem:

Is there a way to fire an event if a multiline = True TextInput lost its focus?

Background:

I have tried on_touch_up function. But it returns the instances of all my TextInputs, not just the current widget. I tried text_validate_unfocus = False, with the same result.

Code:

import kivy
kivy.require("1.10.1")

from kivy.app import App
from kivy.uix.floatlayout import FloatLayout
from kivy.properties import ObjectProperty, NumericProperty
from kivy.uix.textinput import TextInput
from kivy.uix.bubble import Bubble
from kivy.lang import Builder
from kivy.storage.jsonstore import JsonStore

Builder.load_string('''
#: import Window kivy.core.window.Window
<Button>:
    background_normal: ''
<Label>:
    canvas.before:
        Color:
            rgba: (0,0.59,0.36,1)
        Rectangle:
            pos: self.pos
            size: self.size
<TextInput>:
    hint_text: 'Nuwe nota'
    font_size: self.height / 4.5 if self.focus else self.height / 3
    background_normal: ''
    background_active: ''
    foreground_color: (0,0.61,0.36,1) if self.focus else (0.71,0.75,0.71,1)
    unfocus_on_touch: False
    canvas.after:
        Color:
            rgb: (0,0,0,1)
        Line:
            points: self.pos[0] , self.pos[1], self.pos[0] + self.size[0], self.pos[1]
    size_hint_y: None
    height: Window.height / 6 if self.focus else Window.height / 12
<ChoiceBubble>:
    orientation: 'horizontal'
    size_hint: (None, None)
    size: (160, 120)
    pos_hint: {'top': 0.2, 'right': 0.8}
    arrow_pos: 'top_left'
    BubbleButton:
        text: 'Save'
    BubbleButton:
        text: 'Encrypt..'
    BubbleButton:
        text: 'Delete'
        on_release: root.del_txt_input()
<Notation>:
    canvas:
        Color:
            rgba: (0,0.43,0.37,1)
        Rectangle:
            pos: self.pos
            size: self.size
    Label:
        pos_hint: {'top': 1, 'right': 0.8}
        size_hint: [0.8, None]
        height: Window.height / 15
    Button:
        color: (0,0,0,1)
        pos_hint: {'top': 1, 'right': 0.9}
        size_hint: [0.1, None]
        height: Window.height / 15
        Image:
            source: 'gear_2.png'
            center_y: self.parent.center_y
            center_x: self.parent.center_x
            size: self.parent.width /1.5, self.parent.height/ 1.5
            allow_stretch: True
    Button:
        color: (0,0,0,1)
        pos_hint: {'top': 1, 'right': 1}
        size_hint: [0.1, None]
        height: Window.height / 15
        on_release: root.add_input()
        Image:
            source: 'plus_text12354.png'
            center_y: self.parent.center_y
            center_x: self.parent.center_x
            size: self.parent.width /1.5, self.parent.height/ 1.5
            allow_stretch: True
    ScrollView:
        size_hint_y: None
        size: Window.width, Window.height
        pos_hint: {'top': 0.92, 'right': 1}
        GridLayout:
            id: text_holder
            cols: 1
            pos_hint: {'top': 0.92, 'right': 1}
            padding: 4
            size_hint_x: 1
            size_hint_y: None
            height: self.minimum_height

''')
class ChoiceBubble(Bubble):
    pass
class TextInput(TextInput):
    got_txt = ObjectProperty(None)
    def on_touch_up(self, touch):
        if not self.collide_point(*touch.pos):
            self.text_validate_unfocus = False
            note = Notation()
            note.show_bubble
            self.got_txt=note.que_txt_input(self)
        return super(TextInput, self).on_touch_up(touch)
class Notation(FloatLayout):
    which_txt = ObjectProperty(None)
    new_txt = ObjectProperty(None)
    cnt = NumericProperty(0)
    def __init__(self, **kwargs):
        super().__init__(**kwargs)
        self.the_file=JsonStore('txt_input.json')
        self.cnt = self.the_file.count()
        lst = self.the_file.keys
    def add_input(self):
        txt_hld = self.ids.text_holder
        self.cnt += 1
        self.new_txt = TextInput(id=str(self.cnt))
        self.the_file.put(str(self.cnt), the_id=str(self.cnt), the_input='')
        txt_hld.add_widget(self.new_txt)
    def que_txt_input(self, instance):
        self.which_txt = instance
        print(instance.text, instance)
        return instance
    def del_txt_input(self):
        print(self.which_txt)
    def the_file(self, notestore):
        self.notestore = notestore
    def show_bubble(self):
        self.add_widget(ChoiceBubble())
    def get_store(self):
        the_keys = list(self.the_file.keys)
        print(the_keys)
        return the_keys

class theNoteApp(App):
    title = 'My Notes'
    def build(self):
        return Notation()

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

Desired Result:

Once the focus is lost I want a bubble widget to be added to the top of my root class. This will give the user the option to save, encrypt or delete the TextInput id and text that just lost its focus, to a JSON file.

回答1:

Problems

1. Multiple instances of object, Notation. One from build() method (return Notation()) in App class, and another instance created in on_touch_up() method (note = Notation()) whenever on_touch_up event is fired. Those instances created in on_touch_up() method does not has a visible view i.e. it won't show up in the window.
2. AttributeError: 'ChoiceBubble' object has no attribute 'del_txt_input'
3. Text in ChoiceBubble not visible i.e. the default text color is white on white background.

Solutions

1. Use App.get_running_app().root to get the instantiated root.
2. Replace root.del_txt_input() with app.root.del_txt_input()
3. Add color: 0, 0, 0, 1 to class rule, <Label>:
4. Use on_focus event to display BubbleButton

Snippets - kv

<Label>:
    color: 0, 0, 0, 1
    ...

<ChoiceBubble>:
    ...
    BubbleButton:
        text: 'Delete'
        on_release: app.root.del_txt_input()

Snippets - py file

class TextInput(TextInput):
    got_txt = ObjectProperty(None)

    def on_focus(self, instance, value):
        if not value:   # defocused
            note = App.get_running_app().root
            note.show_bubble()
            self.got_txt = note.que_txt_input(self)

Output

回答2:

The on_focus event will fire when the focus boolean changes.

I have tried on_touch_up function. But it returns the instances of all my TextInputs, not just the current widget.

This is because you didn't write any code that would limit it to the widget you care about, you can do this if you want to.

来源：https://stackoverflow.com/questions/56410573/is-there-a-focus-lost-event-dispatcher-for-a-kivy-textinput