Android resource strings with placeholders

Android String Placeholders

This article reviews different ways to create dynamic translatable strings in Android.

Quick reminder

In Android, message strings are extracted to XML files, and the system loads the resources corresponding to the current configuration.

Formatting strings

Let’s say we want to display a dynamic string, such as Player Foo — Score: 42.

We may be tempted to implement that quickly with String.format() .

You will get a compile time error message on the definition.

Error

Multiple substitutions specified in non-positional format; did you mean to add the formatted=»false» attribute?

This error message is misleading, because one may believe that using formatted=»false» is the way to go.

Although the error message now disappears, the real solution is to use a positional format.

When translating strings, the word order will change. For instance, Name: John Smith in English becomes Nom : Smith John in French.

Using positional format prevents translation mistakes.

getString()

Did you know that instead of String.format() , you can use an overloaded version of getString() that handles formatting?

Is that stricly equivalent to the previous code? Let’s look at the Android source!

Almost the same, except that we are using the resource configuration locale, whereas we were previously using the default locale.

Locale.getDefault() is usually equal to mConfiguration.locale , so this won’t really be a problem until you start messing with the default locale.

By the way, you probably know that getString() is also available on Context .

What’s the difference? None. It just delegates to Resources .

If someone knows the story behind this weird shortcut method, let me know. For now, I’ll just assume this is a consequence of Drunk Driven Development.

Professional Translation

Your users deserve better than Google translate. XML resource files should be translated by a professional translator.

This translator will know nothing about your app internals. Therefore, it may be really hard to find out what those %1$s cryptic signs mean.

You can use comments to help the translator.

By the way, if you need excellent quality software translation, I know someone that’s been translating software for more than 25 years. Yes, he is my father 🙂 .

Using placeholders

Another interesting approach is to use named placeholders instead of format specifiers.

I won’t discuss which syntax is better for this kind of problem, let’s just pick a simple one: .

I find this much more readable! Now, you’ll need an API to transform that format to the final string.

Implementing this API is fairly straightforward.

This is just an example implementation, I’ll leave a better one to you as an exercice. An interesting point here is that with() returns this , so you can use it as a fluid API.

Conclusion

I shamelessly stole this idea from Eric Burke, and thought it was worth sharing.

Of course, you may already use Java libraries that can do this. If you are aware of a good one that does a decent job, let me know!

Источник

String Resources

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 element.

file location: res/values/filename.xml
The filename is arbitrary. The 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: elements: Required. This must be the root node.

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.

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 :

This layout XML applies a string to a View:

This application code retrieves a string:

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 element.

file location: res/values/filename.xml
The filename is arbitrary. The element’s name 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: elements: Required. This must be the root node.

Defines an array of strings. Contains one or more elements.

name String. A name for the array. This name will be used as the resource ID to reference the array. A string, which can include styling tags. The value can be a reference to another string resource. Must be a child of a 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.

example: XML file saved at res/values/strings.xml :

This application code retrieves a string 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). 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 element.

file location: res/values/filename.xml
The filename is arbitrary. The

element’s name will be used as the resource ID. resource reference: In Java: R.plurals.plural_name syntax: elements: Required. This must be the root node.

A collection of strings, of which, one string is provided depending on the amount of something. Contains one or more elements.

name String. A name for the pair of strings. This name will be used as the resource ID. A plural or singular string. The value can be a reference to another string resource. Must be a child of a

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.

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

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:

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

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:

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:

Styling with HTML markup

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

Supported HTML elements include:

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:

In this formatted string, a 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:

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 » fromHtml(String) , the characters come out the way they were originally written. For example:

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:

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.

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

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Источник

String resources

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 element.

file location: res/values/filename.xml
The filename is arbitrary. The element’s name 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: elements: Required. This must be the root node.

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.

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

This layout XML applies a string to a View:

This application code retrieves a string:

Kotlin

You can use either getString(int) or getText(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 element.

file location: res/values/filename.xml
The filename is arbitrary. The element’s name 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: elements: Required. This must be the root node.

Defines an array of strings. Contains one or more elements.

name String. A name for the array. This name is used as the resource ID to reference the array. A string, which can include styling tags. The value can be a reference to another string resource. Must be a child of a 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.

example: XML file saved at res/values/strings.xml :

This application code retrieves a string array:

Kotlin

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.

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.

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 element.

file location: res/values/filename.xml
The filename is arbitrary. The

element’s name is used as the resource ID. resource reference: In Java: R.plurals.plural_name syntax: elements: Required. This must be the root node.

A collection of strings, of which, one string is provided depending on the amount of something. Contains one or more elements.

name String. A name for the pair of strings. This name is used as the resource ID. A plural or singular string. The value can be a reference to another string resource. Must be a child of a

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.

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).

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example: XML file saved at res/values/strings.xml :

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

Kotlin

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 .

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.

Any of the following:

• \’
• Enclose the entire string in double quotes ( «This’ll work» , for example)

Character	Escaped form(s)
@	\@
?	\?
New line	\n
Tab	\t
U+XXXX Unicode character	\uXXXX
Single quote ( ‘ )
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 (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 ( » » ) or use Android escaping ( \u0032 \u8200 \u8195 ). Note: From XML parser’s perspective, there is no difference between «Test this» and «Test this» 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. 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 Styling with HTML markup You can add styling to your strings with HTML markup. For example: The following HTML elements are supported: Bold: , Italic: , , 25% larger text: 20% smaller text: Setting font properties: . Examples of possible font families include monospace , serif , and sans_serif . Setting a monospace font family: Strikethrough: , , Underline: Superscript: Subscript: Bullet points: , Line breaks: Division: 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: In this formatted string, a 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 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 » fromHtml(String) , the characters come out the way they were originally written. For example: Kotlin 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 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 Here’s an example of how to chain these methods together to apply various styles to individual words within a phrase: Kotlin 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 Applying a custom typeface to the word “text” in all languages Example — adding a custom typeface Load the string resource and find the annotations with the font key. Then create a custom span and replace the existing span. Kotlin 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 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 Retrieve the text from the Bundle as a SpannableString and then parse the annotations attached, as shown in the example above. Kotlin For more information on text styling, see the following links: Content and code samples on this page are subject to the licenses described in the Content License. Java is a registered trademark of Oracle and/or its affiliates. Источник Оцените статью Вам также может понравиться Как деактивировать режим наушников на смартфоне с Android? 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