Android: How do I set the textsize for a layout?

To set the global styling for all TextViews, set the android:textViewStyle attribute in a custom theme and apply the theme to your application or individual activities.

Pseudocode:

<style name="MyTheme" parent="android:Theme">  <item name="android:textViewStyle">@style/MyTextView</item></style><style name="MyTextView" parent="android:Widget.TextView">  <item name="android:textSize">14sp</item></style>...<activity android:theme="@style/MyTheme">  ...

Or if you wanted to set the default all around text style but override parts of it for certain things (like the button in this example) you could do something like this:

       <style name="whiteText" parent="@android:style/TextAppearance.Medium">            <item name="android:textStyle">normal</item>            <item name="android:textColor">@android:color/white</item>        </style>        <style name="buttonStyle" parent="@android:style/Widget.Button">            <item name="android:textAppearance">@style/whiteText</item>            <item name="android:textStyle">bold</item>            <item name="android:textColor">@android:color/black</item>            <item name="android:gravity">center</item>            <item name="android:background">@drawable/pinkbutton</item>            <item name="android:cacheColorHint">@android:color/transparent</item>            <item name="android:minHeight">50.0dip</item>        </style>        <style name="DarkTheme" parent="@android:style/Theme.Black.NoTitleBar">            <item name="android:buttonStyle">@style/buttonStyle</item>            <item name="android:textAppearance">@style/whiteText</item>        </style>

Probably your single best place to get started though would be: http://developer.android.com/design/style/index.html