How to programmatically set style attribute in a view

First of all, you don't need to use a layout inflater to create a simple Button. You can just use:

button = new Button(context);

If you want to style the button you have 2 choices: the simplest one is to just specify all the elements in code, like many of the other answers suggest:

button.setTextColor(Color.RED);
button.setTextSize(TypedValue.COMPLEX_UNIT_SP, 18);

The other option is to define the style in XML, and apply it to the button. In the general case, you can use a ContextThemeWrapper for this:

ContextThemeWrapper newContext = new ContextThemeWrapper(baseContext, R.style.MyStyle);
button = new Button(newContext);

To change the text-related attributes on a TextView (or its subclasses like Button) there is a special method:

button.setTextAppearance(R.style.MyTextStyle);

Or, if you need to support devices pre API-23 (Android 6.0)

button.setTextAppearance(context, R.style.MyTextStyle);

This method cannot be used to change all attributes; for example to change padding you need to use a ContextThemeWrapper. But for text color, size, etc. you can use setTextAppearance.

Generally you can't change styles programmatically; you can set the look of a screen, or part of a layout, or individual button in your XML layout using themes or styles. Themes can, however, be applied programmatically.

There is also such a thing as a StateListDrawable which lets you define different drawables for each state the your Button can be in, whether focused, selected, pressed, disabled and so on.

For example, to get your button to change colour when it's pressed, you could define an XML file called res/drawable/my_button.xml directory like this:

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
  <item
    android:state_pressed="true"
    android:drawable="@drawable/btn_pressed" />
  <item
    android:state_pressed="false"
    android:drawable="@drawable/btn_normal" />
</selector>

You can then apply this selector to a Button by setting the property android:background="@drawable/my_button".

Yes, you can use for example in a button

Button b = new Button(this);
b.setBackgroundResource(R.drawable.selector_test);