Resources

What is the res Directory?

The res directory is where you should put things such as images, strings, and layouts. It's included in every Android project, and you can see it in Android Studio here:

Inside of the res directory, are sub folder for the following types of resources. You may have a subset of these directories, depending on the types of resources you're using in your app. Here are some examples

Different Resource Directories

This information can also be found here.

Some Common Resource Types

Name	What's Stored Here
values	XML files that contain simple values, such as string or integers
drawable	A bunch of visual files, including Bitmap file types and shapes. More information is here
layouts	XML layouts for your app

Other Resource Types

Name	What's stored here
animator	XML files for property animations
anim	XML files for tween animations
color	XML files that define state list colors
mipmap	Drawable files for launcher icons
menu	XML files that define application menus
raw	Resource file for arbitrary files saved in their raw form. For example, you could put audio files here. (You might also be interested in the assets folder, depending on how you use that audio)
xml	Arbitrary XML; if you have XML configuration files, this is a good place to put them

Why Resources

You should always keep things like images and layouts separate in the res folder. Keeping resource files and values independent helps you easily maintain them if you need to update, say, all your button images to match a new style. The Android Framework also easily allows for alternative resources that support specific device configurations such as different languages or screen sizes. Providing a customized experience for users from different locations or on different devices becomes increasingly important as more of the world comes online and more devices come on the market. We will see how to provide alternate resources for different configurations and locals later in this course.

Using Resources in XML and Java

You've already seen resources in action. For example, in the MainActivity, you have already seen usage of resources. When we say setContentView(R.layout.activity_main), we are referencing a resource (the activity_main.xml) file to use as the layout of MainActivity. That magical looking R.layout part of the expression above is actually a static class that is generated for us to reference resources in Java code. This is all described in the Android Layouts Primer.

Working with strings.xml

In Java, you can get a String saved in res -> values -> strings.xml by calling the getString method. If you’re in an Activity, you can just call getString, and pass in the String resource ID. The String resource ID can be found in the strings.xml XML. For example, let's look at Sunshine's strings.xml file:

    <string name="today">Today</string>

    <!-- For labelling tomorrow's forecast [CHAR LIMIT=15] -->
    <string name="tomorrow">Tomorrow</string>

    <!-- Date format [CHAR LIMIT=NONE] -->
    <string name="format_full_friendly_date">
        <xliff:g id="month">%1$s</xliff:g>, <xliff:g id="day">%2$s</xliff:g>
    </string>

The id of the String with the value "Today" is today and the id of the String with the value <xliff:g id="month">%1$s</xliff:g>, <xliff:g id="day">%2$s</xliff:g> is format_full_friendly_date
If you wanted to reference the Today string, you would reference it in Java by doing something like this:

String myString = getString(R.string.today);

In XML, you can access a String by using the @string accessor method. For the same String defined above, you could access it like this:

<TextView text=”@string/today” />