How to center text horizontally in a kivy text input?

问题:

I want to center a single line text in kivt text input. I'm going to use padding

widget.padding = [ (self.textinput.width - width of line) / 2, 20, 0, 0] 

but i can't find width of the line. how can i calculate or reach width of the line?

回答1:

There is an internal TextInput._get_text_width method you can use to calculate proper padding:

from kivy.app import App from kivy.uix.floatlayout import FloatLayout from kivy.lang import Builder  Builder.load_string('''  <MyWidget>:     TextInput:         multiline: False         on_text: root.update_padding(args[0])         padding_x: self.width/2 # initial padding ''')  class MyWidget(FloatLayout):     def update_padding(self, text_input, *args):         text_width = text_input._get_text_width(             text_input.text,             text_input.tab_width,             text_input._label_cached         )         text_input.padding_x = (text_input.width - text_width)/2  class MyApp(App):     def build(self):                 return MyWidget()  if __name__ == '__main__':     MyApp().run() 

回答2:

You could make a textinput behind a button, and make the button visualize as the text input.

When pushing the button, put the focus to the textinput, and update the buttons text.

I have made an example here.

from kivy.uix.textinput import TextInput from kivy.uix.boxlayout import BoxLayout from kivy.uix.floatlayout import FloatLayout from kivy.uix.button import Button from kivy.uix.label import Label from kivy.clock import Clock from kivy.app import App from kivy import require  require('1.9.1')   class MyWidget(BoxLayout):     def __init__(self,**kwargs):         super(MyWidget,self).__init__(**kwargs)          self.orientation = "vertical"          self.cur = False          self.textinput = TextInput(text='',halign="center",multiline=False)         self.textinput.bind(text=self.on_text)          self.button = Button(background_normal="",background_color=[0,0,0.1,1],font_size="40sp")         self.button.bind(on_release=self.button_click)          self.my_float_layout = FloatLayout()          self.my_float_layout.add_widget(self.textinput)         self.my_float_layout.add_widget(self.button)          self.add_widget(Label(text="type text below",font_size="40sp"))         self.add_widget(self.my_float_layout)          Clock.schedule_interval(self.cursor, 0.5)       def cursor(self,dt):          # function to visualize a cursor         if self.textinput.focus:             cur_pos = self.textinput.cursor[0]             if not self.cur:                 self.button.text = self.textinput.text[:cur_pos] + "|" + self.textinput.text[cur_pos:]                 self.cur = True             else:                 self.button.text = self.textinput.text[:cur_pos] + " " + self.textinput.text[cur_pos:]                 self.cur = False         elif self.cur:             self.button.text = self.textinput.text + " "             self.cur = False        def on_text(self, *args):     # function to set the button text         self.button.text = self.textinput.text       def button_click(self,*args): # function to focus the input         self.textinput.focus = True    class MyApp(App):     def build(self):         return MyWidget()   if __name__ == "__main__":     MyApp().run() 

回答3:

The solution above almost worked for me. Sometimes the padding wouldn't be updated correctly. Here is my slight change, setting text_width as a NumericProperty:

In Kivy:

<CenteredTextInput@TextInput>:     multiline: False     on_text: root.update_padding()     padding_x: (self.width - self.text_width) / 2 

In Python:

class CenteredTextInput(TextInput):     '''     A centered TextInput.     '''      text_width = NumericProperty()     '''The text width     '''      def update_padding(self, *args):         '''         Update the padding so the text is centered         '''         self.text_width = self._get_text_width(             self.text,             self.tab_width,             self._label_cached         ) 

文章来源: How to center text horizontally in a kivy text input?