Decoding Resource Directory Names

Our app has a bunch of resource directories. Some have simple names, like drawable/ and layout/. Others have suffixes, like drawable-v24/ and mipmap-hdpi/.

The initial segment of the directory name — or the whole name for those that lack suffixes — usually indicates the type of the resource. There are many resource types in Android, and we will explore a few of them in this chapter. The exception is the values/ directory, which can contain a variety of smaller resource types, not just one “values” type.

The suffixes represent “resource sets”, and they indicate that this directory contains resources of a particular type that should only be used in certain scenarios. We call these scenarios “configurations”; the suffixes indicate what configurations those resources are used for.

For example:

• drawable/ has resources that are good for any configuration, but drawable-v24/ has resources that are only going to be used on API Level 24 and higher devices (i.e., Android 7.0 and higher)
• mipmap-anydpi-v26/ has resources that are good for any screen density, but they will only be used on API Level 26 and higher devices
• mipmap-mdpi/ has resources that are designed around “medium density” screens, where the density is around 160dpi (dpi = dots per inch)

We will explore these rules more later in the book, as they get fairly complex fairly quickly.