KivyMD中MDTextField提示文本、输入文本颜色设置失效求助

问题 #

使用Python 3.9、Kivy 2.1.0、KivyMD 1.1.1编写的代码可正常运行，但无法通过KivyMD文档中的KV关键字设置MDTextField的提示文本、输入文本等颜色。尝试line_color_focus、background_color、disabled_foreground_color、foreground_color、hint_text_color、selection_color等属性均无效，希望根据背景色将提示文本和输入文本设为黑色或白色。

相关代码：

from kivy.lang import Builder
from kivy.metrics import dp
from kivy.properties import StringProperty
from kivymd.uix.list import OneLineIconListItem
from kivymd.app import MDApp
from kivymd.uix.menu import MDDropdownMenu

KV = '''
<IconListItem>
    IconLeftWidget:
        icon: root.icon

MDScreen:
    MDTextField:
        id: waveform
        pos_hint: {'center_x': .3, 'center_y': .6}
        size_hint_x: None
        width: "250dp"
        font_size: '25sp'
        line_color_focus: 0, 0, 0, 1
        required: True
        hint_text: "Wave Form"
        keyboard_mode: "managed"       
        on_focus: if self.focus: {app.open_menu(self, app.menu1), app.set_cust_labels()}

    MDTextField:
        id: freq1
        input_filter: "float"
        input_type: "number"
        pos_hint: {'center_x': .3, 'center_y': .5}
        size_hint_x: None
        width: "250dp"
        font_size: '25sp'
        multiline: False
        line_color_focus: 0, 0, 0, 1
        required: True
        hint_text: "Start Frequency in Hz"
        helper_text: "Enter a number between .01 and 20000"
        helper_text_mode: "persistent"
        on_focus: if self.focus: app.set_cust_labels()


    MDBoxLayout:
        orientation: "horizontal"
        pos_hint: {'center_x': .55, 'center_y': .2}
        MDLabel:
            id: waveform_text
            valign: "center"
            font_size: '25sp'
            theme_text_color: "Primary"

        MDLabel:
            id: freq1_text
            valign: "center"
            font_size: '25sp'
            theme_text_color: "Primary"
'''

class IconListItem(OneLineIconListItem):
    icon = StringProperty()

class Test(MDApp):
    def __init__(self, **kwargs):
        super().__init__(**kwargs)
        self.screen = Builder.load_string(KV)

        self.wf_list_items = ["Sine", "Rectangle", "Sawtooth", "Impulse", "Bemer"]

        menu_items_wf = [
            {
                "viewclass": "IconListItem",
                "icon": "account",
                "height": dp(56),
                "text": f"{self.wf_list_items[i]}",
                "on_release": lambda x=i: self.set_item_waveform(f"{self.wf_list_items[x]}"),
            } for i in range(5)]

        self.menu1 = MDDropdownMenu(
            items=menu_items_wf,
            position="auto",
            width_mult=3,
        )

    def set_item_waveform(self, text__item):
        self.screen.ids.waveform.text = text__item
        self.screen.ids.waveform.focus = False
        self.menu1.dismiss()

    def open_menu(self, textfield, menu):
        textfield.focus = True
        menu.width_mult = textfield.width / dp(55)
        menu.max_height = dp(300)
        menu.caller = textfield
        menu.open()
        textfield.focus = False

    def set_cust_labels(self):
        self.screen.ids.waveform_text.text = self.screen.ids.waveform.text
        self.screen.ids.freq1_text.text = self.screen.ids.freq1.text

    def build(self):
        return self.screen

Test().run()

尝试过以下属性均无法将文本设为黑色：

line_color_focus: 0, 0, 0, 1 <- 代码中无效
background_color: 0, 0, 0, 1
disabled_foreground_color: 0,0,0 1
foreground_color: 0, 0, 0, 1
hint_text_color: 0, 0, 0, 1
selection_color: 0, 0, 0, 1

请问这些颜色设置属性为何不生效？有什么办法可以将文本颜色设为黑色？

解决方案 #

属性不生效原因 #

KivyMD的MDTextField默认继承主题样式，直接设置的颜色属性会被主题的palette和内置文本颜色规则覆盖；另外部分属性（如foreground_color）在对应版本中已被废弃，不再生效。

自定义颜色的有效方法 #

要修改输入文本、提示文本颜色，需先将theme_text_color设为"Custom"，再指定对应的颜色属性，这样可以绕过主题样式的优先级限制。

修改后的完整代码如下：

from kivy.lang import Builder
from kivy.metrics import dp
from kivy.properties import StringProperty
from kivymd.uix.list import OneLineIconListItem
from kivymd.app import MDApp
from kivymd.uix.menu import MDDropdownMenu

KV = '''
<IconListItem>
    IconLeftWidget:
        icon: root.icon

MDScreen:
    MDTextField:
        id: waveform
        pos_hint: {'center_x': .3, 'center_y': .6}
        size_hint_x: None
        width: "250dp"
        font_size: '25sp'
        line_color_focus: 0, 0, 0, 1
        required: True
        hint_text: "Wave Form"
        keyboard_mode: "managed"
        # 开启自定义文本颜色模式
        theme_text_color: "Custom"
        # 设置输入文本颜色为黑色
        text_color: 0, 0, 0, 1
        # 设置提示文本颜色为黑色
        hint_text_color: 0, 0, 0, 1
        on_focus: if self.focus: {app.open_menu(self, app.menu1), app.set_cust_labels()}

    MDTextField:
        id: freq1
        input_filter: "float"
        input_type: "number"
        pos_hint: {'center_x': .3, 'center_y': .5}
        size_hint_x: None
        width: "250dp"
        font_size: '25sp'
        multiline: False
        line_color_focus: 0, 0, 0, 1
        required: True
        hint_text: "Start Frequency in Hz"
        helper_text: "Enter a number between .01 and 20000"
        helper_text_mode: "persistent"
        # 开启自定义文本颜色模式
        theme_text_color: "Custom"
        # 设置输入文本颜色为黑色
        text_color: 0, 0, 0, 1
        # 设置提示文本颜色为黑色
        hint_text_color: 0, 0, 0, 1
        on_focus: if self.focus: app.set_cust_labels()


    MDBoxLayout:
        orientation: "horizontal"
        pos_hint: {'center_x': .55, 'center_y': .2}
        MDLabel:
            id: waveform_text
            valign: "center"
            font_size: '25sp'
            theme_text_color: "Primary"

        MDLabel:
            id: freq1_text
            valign: "center"
            font_size: '25sp'
            theme_text_color: "Primary"
'''

class IconListItem(OneLineIconListItem):
    icon = StringProperty()

class Test(MDApp):
    def __init__(self, **kwargs):
        super().__init__(**kwargs)
        self.screen = Builder.load_string(KV)

        self.wf_list_items = ["Sine", "Rectangle", "Sawtooth", "Impulse", "Bemer"]

        menu_items_wf = [
            {
                "viewclass": "IconListItem",
                "icon": "account",
                "height": dp(56),
                "text": f"{self.wf_list_items[i]}",
                "on_release": lambda x=i: self.set_item_waveform(f"{self.wf_list_items[x]}"),
            } for i in range(5)]

        self.menu1 = MDDropdownMenu(
            items=menu_items_wf,
            position="auto",
            width_mult=3,
        )

    def set_item_waveform(self, text__item):
        self.screen.ids.waveform.text = text__item
        self.screen.ids.waveform.focus = False
        self.menu1.dismiss()

    def open_menu(self, textfield, menu):
        textfield.focus = True
        menu.width_mult = textfield.width / dp(55)
        menu.max_height = dp(300)
        menu.caller = textfield
        menu.open()
        textfield.focus = False

    def set_cust_labels(self):
        self.screen.ids.waveform_text.text = self.screen.ids.waveform.text
        self.screen.ids.freq1_text.text = self.screen.ids.freq1.text

    def build(self):
        return self.screen

Test().run()

额外说明 #

• 若需要修改辅助文本（helper_text）颜色，可添加helper_text_color: 0, 0, 0, 1属性；
• 如需根据背景色动态切换文本颜色，可在Python代码中监听背景色变化事件，实时修改text_color和hint_text_color的值。

内容的提问来源于stack exchange，提问作者RAHRAH