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'sname
is 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:
- 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:
You can use either
getString(int)
orgetText(int)
to retrieve a string.getText(int)
retains 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'sname
is used as the resource ID.- compiled resource datatype:
- Resource pointer to an array of
String
s. - resource reference:
-
In Java:
R.array.string_array_name
In XML:@[package:]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:
- 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:
Kotlin
val array: Array<String> =
resources
.getStringArray
(R.array.planets_array)Java
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 as
getQuantityString()
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
is 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 is
ever 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.
If your message doesn't contain the quantity number, it is probably not a good candidate for a plural. For example, in Lithuanian the singular form is used for both 1 and 101, so "1 book" is translated as "1 knyga", and "101 books" is translated as "101 knyga". Meanwhile "a book" is "knyga" and "many books" is "daug knygų". If an English plural message contains "a book" (singular) and "many books" (plural) without the actual number, it can be translated as "knyga" (a book)/"daug knygų" (many books), but with Lithuanian rules, it will show "knyga" (a single book), when the number happens to be 101.
It's often possible to avoid quantity strings by using quantity-neutral formulations such as "Books: 1". This makes your life and your translators' lives easier, if it's an acceptable style for your application.
On API 24+ you can use the much more powerful ICU MessageFormat
class instead.
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'sname
is 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:
- 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>
Usage:
Kotlin
val count = getNumberOfSongsAvailable() val songsFound = resources.
getQuantityString
(R.plurals.numberOfSongsAvailable, count, count)Java
int count = getNumberOfSongsAvailable(); Resources res =
getResources()
; String songsFound = res.getQuantityString
(R.plurals.numberOfSongsAvailable, count, count);When using the
getQuantityString()
method, you need to pass thecount
twice if your string includes string formatting with a number. For example, for the string%d songs found
, the firstcount
parameter selects the appropriate plural string and the secondcount
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 togetQuantityString
.
Format and style
Here are a few important things you should know about how to properly format and style your string resources.
Handle special characters
When a string contains characters that have special usage in XML, you must escape the characters according to the standard XML/HTML escaping rules. If you need to escape a character that has special meaning in Android you should use a preceding backslash.
By default Android will collapse sequences of whitespace characters into a single space. You can avoid this by enclosing the relevant part of your string in double quotes. In this case all whitespace characters (including new lines) will get preserved within the quoted region. Double quotes will allow you to use regular single unescaped quotes as well.
Character | Escaped form(s) |
---|---|
@ | \@ |
? | \? |
New line | \n |
Tab | \t |
U+XXXX Unicode character | \uXXXX |
Single quote (' ) |
Any of the following:
|
Double quote (" ) |
\"
Note that surrounding the string with single quotes does not work. |
Whitespace collapsing and Android escaping happens after your
resource file gets parsed as XML. This means that
<string>      </string>
(space, punctuation space, Unicode Em space) all collapse to a single space
(" "
), because they are all Unicode spaces after the file is parsed as an XML.
To preserve those spaces as they are, you can either quote them
(<string>"      "</string>
)
or use Android escaping
(<string> \u0032 \u8200 \u8195</string>
).
Note: From XML parser's perspective, there is no difference between
<string>"Test this"</string>
and
<string>"Test this"</string>
whatsoever. Both forms
will not show any quotes but trigger Android whitespace-preserving quoting (that will have no
practical effect in this case).
Formatting strings
If you need to format your strings, then you can do so by putting your format arguments in the string resource, as demonstrated by the following example 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. Then, format the string by calling getString(int, Object...)
. For example:
Kotlin
var text = getString(R.string.welcome_messages, username, mailCount)
Java
String text = 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>
The following HTML elements are supported:
- Bold: <b>
- Italic: <i>, <cite>, <dfn>, <em>
- 25% larger text: <big>
- 20% smaller text: <small>
- Setting font properties: <font face=”font_family“ color=”hex_color”>. Examples of
possible font families include
monospace
,serif
, andsans_serif
. - Setting a monospace font family: <tt>
- Strikethrough: <s>, <strike>, <del>
- Underline: <u>
- Superscript: <sup>
- Subscript: <sub>
- Bullet points: <ul>, <li>
- Line breaks: <br>
- Division: <div>
- CSS style: <span style=”color|background_color|text-decoration”>
- Paragraphs: <p dir=”rtl | ltr” style=”…”>
If you aren't applying formatting, you can set TextView text directly by calling
setText(java.lang.CharSequence)
. In some cases, however, you may
want to create a styled text resource that is also used as a format string. Normally, this
doesn't work because the format(String, Object...)
and
getString(int, Object...)
methods 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:
- Store your styled text resource as an HTML-escaped string:
<resources> <string name="welcome_messages">Hello, %1$s! You have <b>%2$d new messages</b>.</string> </resources>
In this formatted string, a
<b>
element is added. Notice that the opening bracket is HTML-escaped, using the<
notation. - Then format the string as usual, but also call
fromHtml(String)
to convert the HTML text into styled text:Kotlin
val text: String = getString(R.string.welcome_messages, username, mailCount) val styledText: Spanned = Html.fromHtml(text, FROM_HTML_MODE_LEGACY)
Java
String text = getString(R.string.welcome_messages, username, mailCount); Spanned styledText = Html.fromHtml(text, FROM_HTML_MODE_LEGACY);
Because the fromHtml(String)
method formats 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 are formatting a string that contains 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:
Kotlin
val escapedUsername: String = TextUtils.htmlEncode
(username)
val text: String = getString(R.string.welcome_messages, escapedUsername, mailCount)
val styledText: Spanned = Html.fromHtml(text, FROM_HTML_MODE_LEGACY)
Java
String escapedUsername = TextUtils.htmlEncode
(username);
String text = getString(R.string.welcome_messages, escapedUsername, mailCount);
Spanned 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:
Kotlin
/** * 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 fun apply(content: Array<out CharSequence>, vararg tags: Any): CharSequence { return SpannableStringBuilder().apply { openTags(tags) content.forEach { charSequence -> append(charSequence) } closeTags(tags) } } /** * 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 fun Spannable.openTags(tags: Array<out Any>) { tags.forEach { tag -> 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 fun Spannable.closeTags(tags: Array<out Any>) { tags.forEach { tag -> if (length > 0) { setSpan(tag, 0, length, Spanned.SPAN_EXCLUSIVE_EXCLUSIVE) } else { removeSpan(tag) } } }
Java
/** * 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 applyStyles(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 wrap the helper methods above and demonstrate specific examples of applying
styles defined in the android.text.style
package. You
can create similar methods to do other types of text styling.
Kotlin
/** * Returns a CharSequence that applies boldface to the concatenation * of the specified CharSequence objects. */ fun bold(vararg content: CharSequence): CharSequence = apply(content, StyleSpan(Typeface.BOLD)) /** * Returns a CharSequence that applies italics to the concatenation * of the specified CharSequence objects. */ fun italic(vararg content: CharSequence): CharSequence = apply(content, StyleSpan(Typeface.ITALIC)) /** * Returns a CharSequence that applies a foreground color to the * concatenation of the specified CharSequence objects. */ fun color(color: Int, vararg content: CharSequence): CharSequence = apply(content, ForegroundColorSpan(color))
Java
/** * 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 together to apply various styles to individual words within a phrase:
Kotlin
// Create an italic "hello, " a red "world", // and bold the entire sequence. val text: CharSequence = bold(italic(getString(R.string.hello)), color(Color.RED, getString(R.string.world)))
Java
// Create an italic "hello, " a red "world", // and bold the entire sequence. CharSequence text = bold(italic(getString(R.string.hello)), color(Color.RED, getString(R.string.world)));
The core-ktx Kotlin module also contains extension functions that make working with spans even easier. You can check out the android.text package documentation on GitHub to learn more.
For more information on working with spans, see the following links:
Styling with annotations
You can apply complex or custom styling by using the Annotation
class along with the
<annotation>
tag in your strings.xml resource files. The annotation tag allows
you to mark parts of the string for custom styling by defining custom key-value pairs in the XML
that the framework then converts into Annotation
spans. You can then retrieve these
annotations and use the key and value to apply the styling.
When creating annotations, make sure you add the <annotation>
tag to all translations of the string in every strings.xml file.
Applying a custom typeface to the word “text” in all languages
Example - adding a custom typeface
-
Add the
<annotation>
tag, and define the key-value pair. In this case, the key is font, and the value is the type of font we want to use: title_emphasis// values/strings.xml <string name="title">Best practices for <annotation font="title_emphasis">text</annotation> on Android</string> // values-es/strings.xml <string name="title"><annotation font="title_emphasis">Texto</annotation> en Android: mejores prácticas</string>
-
Load the string resource and find the annotations with the font key. Then create a custom span and replace the existing span.
Kotlin
// get the text as SpannedString so we can get the spans attached to the text val titleText = getText(R.string.title) as SpannedString // get all the annotation spans from the text val annotations = titleText.getSpans(0, titleText.length, Annotation::class.java) // create a copy of the title text as a SpannableString. // the constructor copies both the text and the spans. so we can add and remove spans val spannableString = SpannableString(titleText) // iterate through all the annotation spans for (annotation in annotations) { // look for the span with the key font if (annotation.key == "font") { val fontName = annotation.value // check the value associated to the annotation key if (fontName == "title_emphasis") { // create the typeface val typeface = getFontCompat(R.font.permanent_marker) // set the span at the same indices as the annotation spannableString.setSpan(CustomTypefaceSpan(typeface), titleText.getSpanStart(annotation), titleText.getSpanEnd(annotation), Spannable.SPAN_EXCLUSIVE_EXCLUSIVE) } } } // now, the spannableString contains both the annotation spans and the CustomTypefaceSpan styledText.text = spannableString
Java
// get the text as SpannedString so we can get the spans attached to the text SpannedString titleText = (SpannedString) getText(R.string.title); // get all the annotation spans from the text Annotation[] annotations = titleText.getSpans(0, titleText.length(), Annotation.class); // create a copy of the title text as a SpannableString. // the constructor copies both the text and the spans. so we can add and remove spans SpannableString spannableString = new SpannableString(titleText); // iterate through all the annotation spans for (Annotation annotation: annotations) { // look for the span with the key font if (annotation.getKey().equals("font")) { String fontName = annotation.getValue(); // check the value associated to the annotation key if (fontName.equals("title_emphasis")) { // create the typeface Typeface typeface = ResourcesCompat.getFont(this, R.font.roboto_mono); // set the span at the same indices as the annotation spannableString.setSpan(new CustomTypefaceSpan(typeface), titleText.getSpanStart(annotation), titleText.getSpanEnd(annotation), Spannable.SPAN_EXCLUSIVE_EXCLUSIVE); } } } // now, the spannableString contains both the annotation spans and the CustomTypefaceSpan styledText.text = spannableString;
If you’re using the same text multiple times, you should construct the SpannableString object once and reuse it as needed to avoid potential performance and memory issues.
For more examples of annotation usage, see Styling internationalized text in Android
Annotation spans and text parceling
Because Annotation
spans are also ParcelableSpans
, the key-value
pairs are parceled and unparceled. As long as the receiver of the parcel knows how to interpret
the annotations, you can use Annotation
spans to apply custom styling to the
parceled text.
To keep your custom styling when you pass the text to an Intent Bundle, you first need to add
Annotation
spans to your text. You can do this in the XML resources via the
<annotation> tag, as shown in the example above, or in code by creating a new
Annotation
and setting it as a span, as shown below:
Kotlin
val spannableString = SpannableString("My spantastic text") val annotation = Annotation("font", "title_emphasis") spannableString.setSpan(annotation, 3, 7, Spannable.SPAN_EXCLUSIVE_EXCLUSIVE) // start Activity with text with spans val intent = Intent(this, MainActivity::class.java) intent.putExtra(TEXT_EXTRA, spannableString) startActivity(intent)
Java
SpannableString spannableString = new SpannableString("My spantastic text"); Annotation annotation = new Annotation("font", "title_emphasis"); spannableString.setSpan(annotation, 3, 7, 33); // start Activity with text with spans Intent intent = new Intent(this, MainActivity.class); intent.putExtra(TEXT_EXTRA, spannableString); this.startActivity(intent);
Retrieve the text from the Bundle
as a SpannableString
and then parse
the annotations attached, as shown in the example above.
Kotlin
// read text with Spans val intentCharSequence = intent.getCharSequenceExtra(TEXT_EXTRA) as SpannableString
Java
// read text with Spans SpannableString intentCharSequence = (SpannableString)intent.getCharSequenceExtra(TEXT_EXTRA);
For more information on text styling, see the following links: