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). 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’snamewill 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"> <!-- 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 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.
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);
谢嘉琪 