String resources
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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'snameis 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:
-
<?xmlversion="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 is used as the resource ID.
- example:
- XML file saved at
res/values/strings.xml:<?xmlversion="1.0"encoding="utf-8"?> <resources> <stringname="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'snameis used as the resource ID.- compiled resource datatype:
- Resource pointer to an array of
Strings. - resource reference:
-
In Java:
R.array.string_array_name
In XML:@[package:]array/string_array_name - syntax:
-
<?xmlversion="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 is 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:<?xmlversion="1.0"encoding="utf-8"?> <resources> <string-arrayname="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
valarray:Array<String>=
resources.getStringArray(R.array.planets_array)Java
Resourcesres=
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'snameis used as the resource ID.- resource reference:
-
In Java:
R.plurals.plural_name - syntax:
-
<?xmlversion="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 is 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 zeroWhen the language requires special treatment of the number 0 (as in Arabic). oneWhen 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). twoWhen the language requires special treatment of numbers like two (as with 2 in Welsh, or 102 in Slovenian). fewWhen 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). manyWhen the language requires special treatment of "large" numbers (as with numbers ending 11-99 in Maltese). otherWhen 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:<?xmlversion="1.0"encoding="utf-8"?> <resources> <pluralsname="numberOfSongsAvailable"> <!-- Asadeveloper,youshouldalwayssupply"one"and"other" strings.Yourtranslatorswillknowwhichstringsareactually neededfortheirlanguage.Alwaysinclude%din"one"because translatorswillneedtouse%dforlanguageswhere"one" doesn'tmean1(asexplainedabove). --> <itemquantity="one">%dsongfound.</item> <itemquantity="other">%dsongsfound.</item> </plurals> </resources>
XML file saved at
res/values-pl/strings.xml:<?xmlversion="1.0"encoding="utf-8"?> <resources> <pluralsname="numberOfSongsAvailable"> <itemquantity="one">Znaleziono%dpiosenkę.</item> <itemquantity="few">Znaleziono%dpiosenki.</item> <itemquantity="other">Znaleziono%dpiosenek.</item> </plurals> </resources>
Usage:
Kotlin
valcount=getNumberOfSongsAvailable() valsongsFound=resources.
getQuantityString(R.plurals.numberOfSongsAvailable,count,count)Java
intcount=getNumberOfSongsAvailable(); Resourcesres=
getResources(); StringsongsFound=res.getQuantityString(R.plurals.numberOfSongsAvailable,count,count);When using the
getQuantityString()method, you need to pass thecounttwice if your string includes string formatting with a number. For example, for the string%d songs found, the firstcountparameter selects the appropriate plural string and the secondcountparameter is inserted into the%dplaceholder. 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.
<stringname="welcome_messages">Hello,%1$s!Youhave%2$dnewmessages.</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
vartext=getString(R.string.welcome_messages,username,mailCount)
Java
Stringtext=getString(R.string.welcome_messages,username,mailCount);
Styling with HTML markup
You can add styling to your strings with HTML markup. For example:
<?xmlversion="1.0"encoding="utf-8"?> <resources> <stringname="welcome">Welcometo<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> <stringname="welcome_messages">Hello,%1$s!Youhave<b>%2$dnewmessages</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
valtext:String=getString(R.string.welcome_messages,username,mailCount) valstyledText:Spanned=Html.fromHtml(text,FROM_HTML_MODE_LEGACY)
Java
Stringtext=getString(R.string.welcome_messages,username,mailCount); SpannedstyledText=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
valescapedUsername:String=TextUtils.htmlEncode (username)
valtext:String=getString(R.string.welcome_messages,escapedUsername,mailCount)
valstyledText:Spanned=Html.fromHtml(text,FROM_HTML_MODE_LEGACY)Java
StringescapedUsername=TextUtils.htmlEncode (username);
Stringtext=getString(R.string.welcome_messages,escapedUsername,mailCount);
SpannedstyledText=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 */ privatefunapply(content:Array<outCharSequence>,varargtags:Any):CharSequence{ returnSpannableStringBuilder().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. */ privatefunSpannable.openTags(tags:Array<outAny>){ 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. */ privatefunSpannable.closeTags(tags:Array<outAny>){ 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 * */ privatestaticCharSequenceapplyStyles(CharSequence[]content,Object[]tags){ SpannableStringBuildertext=newSpannableStringBuilder(); openTags(text,tags); for(CharSequenceitem:content){ text.append(item); } closeTags(text,tags); returntext; } /** * 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. */ privatestaticvoidopenTags(Spannabletext,Object[]tags){ for(Objecttag: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. */ privatestaticvoidcloseTags(Spannabletext,Object[]tags){ intlen=text.length(); for(Objecttag: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. */ funbold(varargcontent:CharSequence):CharSequence=apply(content,StyleSpan(Typeface.BOLD)) /** * Returns a CharSequence that applies italics to the concatenation * of the specified CharSequence objects. */ funitalic(varargcontent:CharSequence):CharSequence=apply(content,StyleSpan(Typeface.ITALIC)) /** * Returns a CharSequence that applies a foreground color to the * concatenation of the specified CharSequence objects. */ funcolor(color:Int,varargcontent:CharSequence):CharSequence= apply(content,ForegroundColorSpan(color))
Java
/** * Returns a CharSequence that applies boldface to the concatenation * of the specified CharSequence objects. */ publicstaticCharSequencebold(CharSequence...content){ returnapply(content,newStyleSpan(Typeface.BOLD)); } /** * Returns a CharSequence that applies italics to the concatenation * of the specified CharSequence objects. */ publicstaticCharSequenceitalic(CharSequence...content){ returnapply(content,newStyleSpan(Typeface.ITALIC)); } /** * Returns a CharSequence that applies a foreground color to the * concatenation of the specified CharSequence objects. */ publicstaticCharSequencecolor(intcolor,CharSequence...content){ returnapply(content,newForegroundColorSpan(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. valtext: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. CharSequencetext=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 <stringname="title">Bestpracticesfor<annotationfont="title_emphasis">text</annotation>onAndroid</string> //values-es/strings.xml <stringname="title"><annotationfont="title_emphasis">Texto</annotation>enAndroid:mejoresprácticas</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 valtitleText=getText(R.string.title)asSpannedString // get all the annotation spans from the text valannotations=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 valspannableString=SpannableString(titleText) // iterate through all the annotation spans for(annotationinannotations){ // look for the span with the key font if(annotation.key=="font"){ valfontName=annotation.value // check the value associated to the annotation key if(fontName=="title_emphasis"){ // create the typeface valtypeface=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 SpannedStringtitleText=(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 SpannableStringspannableString=newSpannableString(titleText); // iterate through all the annotation spans for(Annotationannotation:annotations){ // look for the span with the key font if(annotation.getKey().equals("font")){ StringfontName=annotation.getValue(); // check the value associated to the annotation key if(fontName.equals("title_emphasis")){ // create the typeface Typefacetypeface=ResourcesCompat.getFont(this,R.font.roboto_mono); // set the span at the same indices as the annotation spannableString.setSpan(newCustomTypefaceSpan(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
valspannableString=SpannableString("My spantastic text") valannotation=Annotation("font","title_emphasis") spannableString.setSpan(annotation,3,7,Spannable.SPAN_EXCLUSIVE_EXCLUSIVE) // start Activity with text with spans valintent=Intent(this,MainActivity::class.java) intent.putExtra(TEXT_EXTRA,spannableString) startActivity(intent)
Java
SpannableStringspannableString=newSpannableString("My spantastic text"); Annotationannotation=newAnnotation("font","title_emphasis"); spannableString.setSpan(annotation,3,7,33); // start Activity with text with spans Intentintent=newIntent(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 valintentCharSequence=intent.getCharSequenceExtra(TEXT_EXTRA)asSpannableString
Java
// read text with Spans SpannableStringintentCharSequence=(SpannableString)intent.getCharSequenceExtra(TEXT_EXTRA);
For more information on text styling, see the following links: