Apply Style to MaterialButton programmatically

I'm also facing the same issue. The only workaround I've found so far is to set the tint programmatically like:

button.setBackgroundTintList(ColorStateList.valueOf(Color.RED));

For a TextButton there shouldn't be a background (just the text has a color). For a colored button, you should use the default Filled Button style which is Widget.MaterialComponents.Button.

And when applied as a theme, the button uses different attributes. It's described in section Themed Attribute Mapping here: https://material.io/develop/android/components/material-button/

Filled button
+------------------------+-----------------------------------------+
| Component Attribute    | Default Theme Attribute Value           |
+------------------------+-----------------------------------------+
| android:textAppearance | textAppearanceButton                    |
| android:textColor      | colorOnPrimary                          |
| iconTint               | colorOnPrimary                          |
| rippleColor            | colorOnPrimary at 32% opacity (pressed) |
| iconTint               | colorOnPrimary                          |
| backgroundTint         | colorPrimary                            |
| ...                    | ...                                     |
+------------------------+-----------------------------------------+

In your case, the theme should look something like:

<style name="ButtonRedTheme" parent="Theme.MaterialComponents.Light.NoActionBar">
    <item name="colorPrimary">@color/red</item>
    <item name="colorOnPrimary">@color/white</item>
    <item name="colorOnSurface">@color/black</item>
</style>

You can also change all buttons to a specific style with

<item name="materialButtonStyle">@style/ButtonRedTheme</item>

in your app theme.

Using

MaterialButton(ContextThemeWrapper(context, R.style.ButtonRedStyle), attrs, defStyleAttr)

you are applying a themeoverlay to default style, you are not applying a different style.

It means:

<style name="ButtonRedTheme" parent="...">
    <item name="colorPrimary">@color/...</item>
    <item name="colorOnPrimary">@color/...</item>
    <item name="colorSecondary">@color/...</item>
</style>

If you want to apply a different style you have to:

• Define a custom attribute in attrs.xml

    <attr name="myButtonStyle" format="reference"/>

• Assing a style to this attribute in your app theme:

   <style name="AppTheme" parent="Theme.MaterialComponents.DayNight">
        <item name="myButtonStyle">@style/CustomButtonStyle</item>
   </style>

• Define the custom style:

    <style name="CustomButtonStyle" parent="Widget.MaterialComponents.Button.*">
        <item name="backgroundTint">@color/...</item>
        <item name="rippleColor">@color/grey</item>
        <item name="strokeWidth">1dp</item>
        <item name="strokeColor">@color/black</item>
    </style>

Finally use:

val customButton = MaterialButton(context, null, R.attr.myButtonStyle)

If you want to change your style for CustomView, you've to pass it to constructor by passing it into third param defStyleAttr like this:

class CustomRedButton @JvmOverloads constructor(
    context: Context, 
    attrs: AttributeSet? = null, 
    defStyleAttr: Int = R.style.ButtonRedStyle // Just default style like this
) : MaterialButton(context, attrs, defStyleAttr)

and you can initialize it like this programmatically,

CustomRedButton(this, null, R.style.ButtonRedStyle) // Initialization, ('this' is context)

For more details refer here