Button 的边缘周围仍然有一条浅灰色线，而它的边缘具有相同的背景颜色

Question

I set a Gradient for a Button with Color Red and edge Color of Red too,
The Button is placed inside a Linear Layout with Red color too

The problem is the edge of the Button still has a light grey line around it
Why?
Since the edge is Red there should be no edge seen

As is seen in the image, when edge is green still a grey thing is seen

Answer 1

It's the default shadow of button in material design guidelines. To remove it put this attribute in your <Button element:

    android:stateListAnimator="@null"

Or, programmatically, you can do it in this way:

if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.LOLLIPOP) { //Check if it's supported
    yourButton.setStateListAnimator(null);
}

Answer 2

You can try to add this code to your button's xml

style="?android:attr/borderlessButtonStyle"