Why button gets bigger when the background is set in android

For people looking for doing it in the code (Not in XML), you can use this:

button.getBackground().setColorFilter(button.getContext().getResources().getColor(R.color.colorAccent), PorterDuff.Mode.MULTIPLY);

this didn't change the size of the button and works with the old android versions too. Several methods discussed here, but this one worked perfect.

You have to distinguish between the size of the Button, its width and height, the whole area you can click on, and the image used for displaying the button.

The default button on android has a padding applied to its drawable - it seems like it is smaller. It actually has the same size.

If you make your own drawable and apply no padding, the background will draw within the whole bounds of the view, making it seem bigger.

You can always just use the default button but apply your own color by using AppCompat. This supports tinting the background of the default button.

<android.support.v7.widget.AppCompatButton
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    app:backgroundTint="#ffaa00"/> <!-- <--- Your color here  -->

...which will let you use the same appearence.

Use android:backgroundTint attribute in the XML <Button> tag.

Like:

android:backgroundTint="#6567dc"

No need to use <android.support.v7.widget.AppCompatButton> Button.