如何将 function 绑定到 kv 文件中的按钮

Question

Iam trying to print the login credentials in the console,But if the function didn't show error also the credentials are not printing.I wanted to bind the check_data_login function to the 'shoot' button which is defined in kv file the function is defined in py file. im unable to bind it using ID. It is showing the error saying the object doesn't exist. this is my.py file

from kivymd.app import MDApp
from kivy.uix.boxlayout import BoxLayout
from kivy.properties import ObjectProperty




class DemoApp(MDApp):
    def check_data_login(self,obj):
        username = self.username.text
        password = self.password.text

        print(username)
        print(password)


DemoApp().run()

and this is my.kv file

<WhiteLabel@MDLabel>
    size_hint_y:None
    height:self.texture_size[1]
    theme_text_color:"Custom"


<FieldRound@MDTextFieldRound>
    pos_hint:{"center_x":0.5}
    normal_color:0,1,1,0.5
    icon_left_color:1,1,1,1

ScreenManager:
    id: sm
    Screen:
        id:s1
        name:"s1"
        manager:sm
        FitImage:
            source:"bg4.jpg"
        MDToolbar:
            md_bg_color:1,0,156/255,1
            title:"My Demo App"
            pos_hint:{"center_x":0.5,"center_y":0.95}
            elevation:11

        BoxLayout:
            orientation:"vertical"
            size_hint_y:None
            height:self.minimum_height
            pos_hint:{"center_x":0.5,"center_y":0.5}
            padding:"24dp","24dp","24dp","24dp"
            spacing:"12dp"
            size_hint_x:0.85


            canvas:
                Color:
                    rgba: 1,1,1,1
                RoundedRectangle:
                    pos: self.pos
                    size: self.size
                    radius: [10,10,10,10]



            WhiteLabel:
                text:"Welcome to My GUI!!"
                text_color:1,0,156/255,1
                bold:True
                halign:"center"
                font_style:"Caption"
                font_size:25
            Widget:
                size_hint_y:None
                height:"12dp"

            WhiteLabel:
                text:"We just need your details."
                font_style:"H1"
                font_size:20

            WhiteLabel:
                text:"Please enter carefully"
                font_style:"H1"
                font_size:20
            Widget:
                size_hint_y:None
                height:"12dp"
            FieldRound:
                id:'username'
                icon_left:"mail"
                hint_text:"Username"
                normal_color:1,1,1,1
                color_active:1,1,1,1
            FieldRound:
                id:'password'
                icon_left:"key"
                hint_text:"Password"
                normal_color:1,1,1,1
                color_active:1,1,1,1
            Widget:
                size_hint_y:None
                height:"12dp"
            MDFillRoundFlatButton:
                id:'bu'
                text:"Shoot"
                text_color:1,0,156/255,1
                md_bg_color:247/255,171/255,1,1
                pos_hint:{"center_x":0.5}
                on_release:
                    app.check_data_login
                    sm.current = 's2'
        MDFlatButton:
            elevation_normal: 12
            text:"Signup"
            text_color:1,1,1,1
            md_bg_color:1,0,156/255,1
            pos_hint:{"center_x":0.3,"center_y":0.1}
            on_release:
                sm.current = 's2'
        MDFlatButton:
            elevation_normal: 12
            text:"Login"
            text_color:1,1,1,1
            md_bg_color:1,0,156/255,1
            pos_hint:{"center_x":0.7,"center_y":0.1}
            on_release:
                sm.current = 's2'




    Screen:
        id:s2
        name:"s2"
        manager:sm
        BoxLayout:
            Image:
                source:"rajat.jpg"
                opacity:0.5

        MDRaisedButton:
            text:"button"
            pos_hint:{"center_x":0.5,"center_y":0.2}
            on_press:
                sm.current ='s1'

how can i solve this issue

Answer 1

There are few issues both in .py and .kv files. In the kv file the id of FieldRound text fields should not have the quotes. And also in on_release event of shoot button the app.check_data_login missing the () . So the corrected kv file should be as below:

<WhiteLabel@MDLabel>
    size_hint_y:None
    height:self.texture_size[1]
    theme_text_color:"Custom"


<FieldRound@MDTextFieldRound>
    pos_hint:{"center_x":0.5}
    normal_color:0,1,1,0.5
    icon_left_color:1,1,1,1

ScreenManager:
    id: sm
    Screen:
        id:s1
        name:"s1"
        manager:sm
        FitImage:
            source:"bg4.jpg"
        MDToolbar:
            md_bg_color:1,0,156/255,1
            title:"My Demo App"
            pos_hint:{"center_x":0.5,"center_y":0.95}
            elevation:11

        BoxLayout:
            orientation:"vertical"
            size_hint_y:None
            height:self.minimum_height
            pos_hint:{"center_x":0.5,"center_y":0.5}
            padding:"24dp","24dp","24dp","24dp"
            spacing:"12dp"
            size_hint_x:0.85


            canvas:
                Color:
                    rgba: 1,1,1,1
                RoundedRectangle:
                    pos: self.pos
                    size: self.size
                    radius: [10,10,10,10]



            WhiteLabel:
                text:"Welcome to My GUI!!"
                text_color:1,0,156/255,1
                bold:True
                halign:"center"
                font_style:"Caption"
                font_size:25
            Widget:
                size_hint_y:None
                height:"12dp"

            WhiteLabel:
                text:"We just need your details."
                font_style:"H1"
                font_size:20

            WhiteLabel:
                text:"Please enter carefully"
                font_style:"H1"
                font_size:20
            Widget:
                size_hint_y:None
                height:"12dp"
            FieldRound:
                id: username
                icon_left:"mail"
                hint_text:"Username"
                normal_color:1,1,1,1
                color_active:1,1,1,1
            FieldRound:
                id: password
                icon_left:"key"
                hint_text:"Password"
                normal_color:1,1,1,1
                color_active:1,1,1,1
            Widget:
                size_hint_y:None
                height:"12dp"
            MDFillRoundFlatButton:
                id:'bu'
                text:"Shoot"
                text_color:1,0,156/255,1
                md_bg_color:247/255,171/255,1,1
                pos_hint:{"center_x":0.5}
                on_release:
                    app.check_data_login()
                    sm.current = 's2'
        MDFlatButton:
            elevation_normal: 12
            text:"Signup"
            text_color:1,1,1,1
            md_bg_color:1,0,156/255,1
            pos_hint:{"center_x":0.3,"center_y":0.1}
            on_release:
                sm.current = 's2'
        MDFlatButton:
            elevation_normal: 12
            text:"Login"
            text_color:1,1,1,1
            md_bg_color:1,0,156/255,1
            pos_hint:{"center_x":0.7,"center_y":0.1}
            on_release:
                sm.current = 's2'




    Screen:
        id:s2
        name:"s2"
        manager:sm
        BoxLayout:
            Image:
                source:"rajat.jpg"
                opacity:0.5

        MDRaisedButton:
            text:"button"
            pos_hint:{"center_x":0.5,"center_y":0.2}
            on_press:
                sm.current ='s1'

And the corrected py file should be as below with the corrections:

from kivymd.app import MDApp
from kivy.uix.boxlayout import BoxLayout
from kivy.properties import ObjectProperty




class DemoApp(MDApp):
    def check_data_login(self):
        username = self.root.ids.username.text
        password = self.root.ids.password.text

        print(username)
        print(password)


DemoApp().run()