How to change the font in a
First, the default is not Arial. The default is Droid Sans.
Second, to change to a different built-in font, use
android:typeface in layout XML or
setTypeface() in Java.
Third, there is no Helvetica font in Android. The built-in choices are Droid Sans (
sans), Droid Sans Mono (
monospace), and Droid Serif (
serif). While you can bundle your own fonts with your application and use them via
setTypeface(), bear in mind that font files are big and, in some cases, require licensing agreements (e.g., Helvetica, a Linotype font).
The Android design language relies on traditional typographic tools such as scale, space, rhythm, and alignment with an underlying grid. Successful deployment of these tools is essential to help users quickly understand a screen of information. To support such use of typography, Ice Cream Sandwich introduced a new type family named Roboto, created specifically for the requirements of UI and high-resolution screens.
The current TextView framework offers Roboto in thin, light, regular and bold weights, along with an italic style for each weight. The framework also offers the Roboto Condensed variant in regular and bold weights, along with an italic style for each weight.
After ICS, android includes Roboto fonts style, Read more Roboto