[Button] How MaterialButton set color gradient?

[magic0908]

like this

MaterialButton set horizontal or vertical direction color gradient?
I hope use custom attr label
<declare-styleable name=""> <attr name="horizontal_color_start"/> <attr name="horizontal_color_end"/> ... </declare-styleable>

and then activity_main.xml

<com.google.android.material.button.MaterialButton app:horizontal_color_start="@color/colorPrimary" app:horizontal_color_end="@color/colorAccent" ... />

[pekingme]

Duplicate of #1167