Write a string literal in your code like
mButton.setText("Text to add as String resource");
Then select the string literal like this:
and press ALT+SHIFT+A, a yellow menu will appear in the bottom-right corner,
double click on “Extract Android String” , this menu will appear:
choose a proper name for the String resource and click Ok.
You will get a new strings.xml entry:
<string name="my_string_resource">Text to add as string resource</string>
And your Button’s setText line replaced by:
mButton.setText(R.string.my_string_resource);