Android button border stay deafault after adding drawable file

I'm working on a project in android studio and I'm trying to change the border to my button. My default button when I just add it to my grid look like this:

After adding new XML file (called box_solid_border.XML) in the drawable file that looks like this:

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape="rectangle" >

    <stroke
        android:width="4dp"
        android:color="#000000" />

</shape>

the result is that it's creating the next shape that I can see:

and that exactly what I want to add to my button.

when I come back to my XML at the main file and add to my button the next line:

as you can see in line 226 I'm adding the background that I just created for this button to the button. and near the line, there is the exact border that I want. but in the application, the button still stays the same as the default one with no border added to him. Like this:

Does someone know the reason that the drawable file doesn't affect the button? If I'm doing the same thing for a textView or something else its works perfectly fine, just the button looks like not affected by the drawable extension to him.

Thank you!

You need to add this attribute to your button:

app:backgroundTint="@null"

If it has both attributes android:background and app:backgroundTint(if you are using the default theme for your application, it has a default value), the color specified by app:backgroundTint will be cover on the shape of drawable.