Chapter 2.6 – String Resources

November 15, 2016
by Akshay Raj
14 min read

A string resource provides text strings for your application with optional text styling and formatting. There are three types of resources that can provide your application with strings:

String
XML resource that provides a single string.
String Array
XML resource that provides an array of strings.
Quantity Strings (Plurals)
XML resource that carries different strings for pluralization.

All strings are capable of applying some styling markup and formatting arguments. For information about styling and formatting strings, see the section about Formatting and Styling.

String

A single string that can be referenced from the application or from other resource files (such as an XML layout).

Note: A string is a simple resource that is referenced using the value provided in the name attribute (not the name of the XML file). So, you can combine string resources with other simple resources in the one XML file, under one <resources> element.

FILE LOCATION:
res/values/filename.xml
The filename is arbitrary. The <string> element’s name will be used as the resource ID.
COMPILED RESOURCE DATATYPE:
Resource pointer to a String.
RESOURCE REFERENCE:
In Java: R.string.string_name
In XML:@string/string_name
SYNTAX:
<?xml version="1.0" encoding="utf-8"?>
<resources>
    <string
        name="string_name"
        >text_string</string>
</resources>
ELEMENTS:
<resources>
Required. This must be the root node.No attributes.
<string>
A string, which can include styling tags. Beware that you must escape apostrophes and quotation marks. For more information about how to properly style and format your strings see Formatting and Styling, below.

attributes:

name
String. A name for the string. This name will be used as the resource ID.
EXAMPLE:
XML file saved at res/values/strings.xml:

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <string name="hello">Hello!</string>
</resources>

This layout XML applies a string to a View:

<TextView
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:text="@string/hello" />

This application code retrieves a string:

String string = getString(R.string.hello);

You can use either getString(int) or getText(int) to retrieve a string. getText(int) will retain any rich text styling applied to the string.

String Array

An array of strings that can be referenced from the application.

Note: A string array is a simple resource that is referenced using the value provided in the name attribute (not the name of the XML file). As such, you can combine string array resources with other simple resources in the one XML file, under one <resources> element.

FILE LOCATION:
res/values/filename.xml
The filename is arbitrary. The <string-array> element’s name will be used as the resource ID.
COMPILED RESOURCE DATATYPE:
Resource pointer to an array of Strings.
RESOURCE REFERENCE:
In Java: R.array.string_array_name
SYNTAX:
<?xml version="1.0" encoding="utf-8"?>
<resources>
    <string-array
        name="string_array_name">
        <item
            >text_string</item>
    </string-array>
</resources>
ELEMENTS:
<resources>
Required. This must be the root node.No attributes.
<string-array>
Defines an array of strings. Contains one or more <item> elements.

attributes:

name
String. A name for the array. This name will be used as the resource ID to reference the array.
<item>
A string, which can include styling tags. The value can be a reference to another string resource. Must be a child of a <string-array>element. Beware that you must escape apostrophes and quotation marks. See Formatting and Styling, below, for information about to properly style and format your strings.No attributes.
EXAMPLE:
XML file saved at res/values/strings.xml:

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <string-array name="planets_array">
        <item>Mercury</item>
        <item>Venus</item>
        <item>Earth</item>
        <item>Mars</item>
    </string-array>
</resources>

This application code retrieves a string array:

Resources res = getResources(); String[] planets = res.getStringArray(R.array.planets_array);

Quantity Strings (Plurals)

Different languages have different rules for grammatical agreement with quantity. In English, for example, the quantity 1 is a special case. We write “1 book”, but for any other quantity we’d write “n books”. This distinction between singular and plural is very common, but other languages make finer distinctions. The full set supported by Android is zero, one, two, few, many, and other.
The rules for deciding which case to use for a given language and quantity can be very complex, so Android provides you with methods such asgetQuantityString() to select the appropriate resource for you.
Although historically called “quantity strings” (and still called that in API), quantity strings should only be used for plurals. It would be a mistake to use quantity strings to implement something like Gmail’s “Inbox” versus “Inbox (12)” when there are unread messages, for example. It might seem convenient to use quantity strings instead of an if statement, but it’s important to note that some languages (such as Chinese) don’t make these grammatical distinctions at all, so you’ll always get the other string.
The selection of which string to use is made solely based on grammatical necessity. In English, a string for zero will be ignored even if the quantity is 0, because 0 isn’t grammatically different from 2, or any other number except 1 (“zero books”, “one book”, “two books”, and so on). Conversely, in Korean only the other string will ever be used.
Don’t be misled either by the fact that, say, two sounds like it could only apply to the quantity 2: a language may require that 2, 12, 102 (and so on) are all treated like one another but differently to other quantities. Rely on your translator to know what distinctions their language actually insists upon.
It’s often possible to avoid quantity strings by using quantity-neutral formulations such as “Books: 1”. This will make your life and your translators’ lives easier, if it’s a style that’s in keeping with your application.

Note: A plurals collection is a simple resource that is referenced using the value provided in the name attribute (not the name of the XML file). As such, you can combine plurals resources with other simple resources in the one XML file, under one <resources> element.

FILE LOCATION:
res/values/filename.xml
The filename is arbitrary. The <plurals> element’s name will be used as the resource ID.
RESOURCE REFERENCE:
In Java: R.plurals.plural_name
SYNTAX:
<?xml version="1.0" encoding="utf-8"?>
<resources>
    <plurals
        name="plural_name">
        <item
            quantity=["zero" | "one" | "two" | "few" | "many" | "other"]
            >text_string</item>
    </plurals>
</resources>
ELEMENTS:
<resources>
Required. This must be the root node.No attributes.
<plurals>
A collection of strings, of which, one string is provided depending on the amount of something. Contains one or more <item> elements.

attributes:

name
String. A name for the pair of strings. This name will be used as the resource ID.
<item>
A plural or singular string. The value can be a reference to another string resource. Must be a child of a <plurals> element. Beware that you must escape apostrophes and quotation marks. See Formatting and Styling, below, for information about to properly style and format your strings.

attributes:

quantity
Keyword. A value indicating when this string should be used. Valid values, with non-exhaustive examples in parentheses:

Value Description
zero When the language requires special treatment of the number 0 (as in Arabic).
one When the language requires special treatment of numbers like one (as with the number 1 in English and most other languages; in Russian, any number ending in 1 but not ending in 11 is in this class).
two When the language requires special treatment of numbers like two (as with 2 in Welsh, or 102 in Slovenian).
few When the language requires special treatment of “small” numbers (as with 2, 3, and 4 in Czech; or numbers ending 2, 3, or 4 but not 12, 13, or 14 in Polish).
many When the language requires special treatment of “large” numbers (as with numbers ending 11-99 in Maltese).
other When the language does not require special treatment of the given quantity (as with all numbers in Chinese, or 42 in English).
EXAMPLE:
XML file saved at res/values/strings.xml:

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <plurals name="numberOfSongsAvailable">
        <!--
             As a developer, you should always supply "one" and "other"
             strings. Your translators will know which strings are actually
             needed for their language. Always include %d in "one" because
             translators will need to use %d for languages where "one"
             doesn't mean 1 (as explained above).
          -->
        <item quantity="one">%d song found.</item>
        <item quantity="other">%d songs found.</item>
    </plurals>
</resources>

XML file saved at res/values-pl/strings.xml:

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <plurals name="numberOfSongsAvailable">
        <item quantity="one">Znaleziono %d piosenkę.</item>
        <item quantity="few">Znaleziono %d piosenki.</item>
        <item quantity="other">Znaleziono %d piosenek.</item>
    </plurals>
</resources>

Java code:

int count = getNumberOfsongsAvailable();
Resources res = getResources(); String songsFound = res.getQuantityString(R.plurals.numberOfSongsAvailable, count, count);

When using the getQuantityString() method, you need to pass the count twice if your string includes string formatting with a number. For example, for the string %d songs found, the first count parameter selects the appropriate plural string and the second count parameter is inserted into the %d placeholder. If your plural strings do not include string formatting, you don’t need to pass the third parameter to getQuantityString.

Formatting and Styling

Here are a few important things you should know about how to properly format and style your string resources.

Escaping apostrophes and quotes

If you have an apostrophe (') in your string, you must either escape it with a backslash (\') or enclose the string in double-quotes (""). For example, here are some strings that do and don’t work:

<string name="good_example">This\'ll work</string>
<string name="good_example_2">"This'll also work"</string>
<string name="bad_example">This doesn't work</string>
    <!-- Causes a compile error -->

If you have a double-quote in your string, you must escape it (\"). Surrounding the string with single-quotes does not work.

<string name="good_example">This is a \"good string\".</string>
<string name="bad_example">This is a "bad string".</string>
    <!-- Quotes are stripped; displays as: This is a bad string. -->
<string name="bad_example_2">'This is another "bad string".'</string>
    <!-- Causes a compile error -->

Formatting strings

If you need to format your strings using String.format(String, Object...), then you can do so by putting your format arguments in the string resource. For example, with the following resource:

<string name="welcome_messages">Hello, %1$s! You have %2$d new messages.</string>

In this example, the format string has two arguments: %1$s is a string and %2$d is a decimal number. You can format the string with arguments from your application like this:

Resources res = getResources(); String text = String.format(res.getString(R.string.welcome_messages), username, mailCount);

Styling with HTML markup

You can add styling to your strings with HTML markup. For example:

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <string name="welcome">Welcome to <b>Android</b>!</string>
</resources>

Supported HTML elements include:

  • <b> for bold text.
  • <i> for italic text.
  • <u> for underline text.

Sometimes you may want to create a styled text resource that is also used as a format string. Normally, this won’t work because the String.format(String, Object...) method will strip all the style information from the string. The work-around to this is to write the HTML tags with escaped entities, which are then recovered with fromHtml(String), after the formatting takes place. For example:

  1. Store your styled text resource as an HTML-escaped string: 
    <resources>
  <string name="welcome_messages">Hello, %1$s! You have &lt;b>%2$d new messages&lt;/b>.</string>
</resources>

    In this formatted string, a <b> element is added. Notice that the opening bracket is HTML-escaped, using the &lt; notation.

  2. Then format the string as usual, but also call fromHtml(String) to convert the HTML text into styled text: 
    Resources res = getResources(); String text = String.format(res.getString(R.string.welcome_messages), username, mailCount); CharSequence styledText = Html.fromHtml(text);

Because the fromHtml(String) method will format all HTML entities, be sure to escape any possible HTML characters in the strings you use with the formatted text, using htmlEncode(String). For instance, if you’ll be passing a string argument to String.format() that may contain characters such as “<” or “&”, then they must be escaped before formatting, so that when the formatted string is passed through fromHtml(String), the characters come out the way they were originally written. For example:

String escapedUsername = TextUtil.htmlEncode(username); Resources res = getResources(); String text = String.format(res.getString(R.string.welcome_messages), escapedUsername, mailCount); CharSequence styledText = Html.fromHtml(text);

Styling with Spannables

A Spannable is a text object that you can style with typeface properties such as color and font weight. You use SpannableStringBuilder to build your text and then apply styles defined in the android.text.style package to the text.
You can use the following helper methods to set up much of the work of creating spannable text:

/**
 * Returns a CharSequence that concatenates the specified array of CharSequence
 * objects and then applies a list of zero or more tags to the entire range.
 *
 * @param content an array of character sequences to apply a style to
 * @param tags the styled span objects to apply to the content
 *        such as android.text.style.StyleSpan
 *
 */
private static CharSequence apply(CharSequence[] content, Object... tags) {
    SpannableStringBuilder text = new SpannableStringBuilder();
    openTags(text, tags);
    for (CharSequence item : content) {
        text.append(item);
    }
    closeTags(text, tags);
    return text;
}
/**
 * Iterates over an array of tags and applies them to the beginning of the specified
 * Spannable object so that future text appended to the text will have the styling
 * applied to it. Do not call this method directly.
 */
private static void openTags(Spannable text, Object[] tags) {
    for (Object tag : tags) {
        text.setSpan(tag, 0, 0, Spannable.SPAN_MARK_MARK);
    }
}
/**
 * "Closes" the specified tags on a Spannable by updating the spans to be
 * endpoint-exclusive so that future text appended to the end will not take
 * on the same styling. Do not call this method directly.
 */
private static void closeTags(Spannable text, Object[] tags) {
    int len = text.length();
    for (Object tag : tags) {
        if (len > 0) {
            text.setSpan(tag, 0, len, Spanned.SPAN_EXCLUSIVE_EXCLUSIVE);
        } else {
            text.removeSpan(tag);
        }
    }
}

The following bold, italic, and color methods show you how to call the helper methods to apply styles defined in the android.text.style package. You can create similar methods to do other types of text styling.

/**
 * Returns a CharSequence that applies boldface to the concatenation
 * of the specified CharSequence objects.
 */
public static CharSequence bold(CharSequence... content) {
    return apply(content, new StyleSpan(Typeface.BOLD));
}
/**
 * Returns a CharSequence that applies italics to the concatenation
 * of the specified CharSequence objects.
 */
public static CharSequence italic(CharSequence... content) {
    return apply(content, new StyleSpan(Typeface.ITALIC));
}
/**
 * Returns a CharSequence that applies a foreground color to the
 * concatenation of the specified CharSequence objects.
 */
public static CharSequence color(int color, CharSequence... content) {
    return apply(content, new ForegroundColorSpan(color));
}

Here’s an example of how to chain these methods to create a character sequence with different types of styling applied to individual words:

// Create an italic "hello, " a red "world",
// and bold the entire sequence.
CharSequence text = bold(italic(res.getString(R.string.hello)),
    color(Color.RED, res.getString(R.string.world)));

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Akshay Raj

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