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
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:
- 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)
orgetText(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'sname
will be 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
- 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:
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
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).
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'sname
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:
- example:
- XML file saved at
res/values/strings.xml
:<?xml version="1.0" encoding="utf-8"?> <resources> <plurals name="numberOfSongsAvailable"> <item quantity="one">One 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 jedną 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 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
.
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 or a quote in your string, you must either escape it or enclose the whole string in the other type of enclosing quotes. For example, here are some stings 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> <string name="bad_example_2">XML encodings don't work</string>
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:
- 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: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)));