Android Resource Configuration override and Large Text Mode

In Android, the resource Configuration dictates what resources and assets are selected. The system populates a default configuration to match your device and settings (screen size, device orientation, language). Sometimes, you need to deviate from these defaults. Since API 17 you can use applyOverrideConfiguration(Configuration) to specify an alternative resource config. The normal place to do so is in the attachBaseContext(Context) method of your Activity.

[code language=”java”]
public class MainActivity extends Activity {
@Override
protected void attachBaseContext(Context newBase) {
super.attachBaseContext(newBase);
final Configuration override = new Configuration();
override.locale = new Locale("nl", "NL");
applyOverrideConfiguration(override);
}
//…
}
[/code]

Here’s what that looks like:

Unfortunately, there’s a catch.

Android has a “Large Text” setting in its accessibility options (and in some cases a different text size setting in the display options). If you use the overrideConfiguration method to set your own resource configurtation, you will wipe out the Large Text preference, hurting your accessibilty support. This problem is easily overlooked, and luckily, easily fixed.

The large fonts setting works by changing the Configuration.fontScale attribute, which is a public float. This works with the scaled density-independent pixels (sp‘s) that you use to define fontSize attributes. All sp dimensions have this fontScale multiplier applied. My Nexus 5 has two font size settings, normal at 1.0 and large at 1.3. The Nexus 5 emulator image has four, and many Samsung devices have seven different font sizes you can choose from.

When you set the override configuration, the new Configuration object has its fontScale set to 1.0f, thereby breaking the large fonts mode. To fix this problem, you simply have to copy the current fontScale value from the base context. This is best done using the copy constructor, which will also account for any other properties that come with the same issue.

[code language=”java”]
public class MainActivity extends Activity {
@Override
protected void attachBaseContext(Context newBase) {
super.attachBaseContext(newBase);
final Configuration override = new Configuration(
// Copy the original configuration so it isn’t lost.
newBase.getResources().getConfiguration()
);
override.locale = new Locale("nl", "NL");
applyOverrideConfiguration(override);
// BTW: You can also access the fontScale value using Settings.System:
// Settings.System.getFloat(getContentResolver(), Settings.System.FONT_SCALE, 1.0f);
}
//…
}
[/code]

The app now works as intended, with accessibility support intact.

Long story short: when you use applyOverrideConfiguration, always test your app in the Large Fonts accessibility setting. Be sure to copy the original Configuration in your new Configuration constructor, or use the System.Settings.FONT_SCALE property to retrieve the font scale separately.