Android apps are global, they get downloaded all around the world. And this means not only supporting multiple languages via xml files. Its about plurals, date formats, currencies up to things like right-to-left This topic tries to give an introduction into this large topic for new developers.

1. Droidcon Croatia
Danny Preussler
GROUPON
@PreusslerBerlin
All around the World
i18n and l10n in android
http://gizmodo.com/5397215/giz-explains-android-and-how-it-will-take-over-the-world

2. 45 17Millions
downloads
Millions
active users
+

3. #droidconzg #PreusslerBerlin
Definitions
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Internationalization (i18n) is the process of developing products in such a way
that they can be localized for languages and cultures easily.
Localization (l10n), is the process of adapting applications and text to enable
their usability in a particular cultural or linguistic market.
(docs.angularjs.org)
The better internationalized an application is, the easier it is to localize it for
a particular language and character encoding scheme.
(docs.oracle.com)
The main concern (i18n) is that application can be adapted to various
languages and regions without engineering changes.
(Apple Guidelines)

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Try not to kill your user...
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„A Cellphone's Missing Dot Kills Two People, Puts Three More in Jail“
http://gizmodo.com/382026/a-cellphones-missing-dot-kills-two-people-puts-
three-more-in-jail

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Locales
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• Never hardcode text in code or layouts!
(android studio even helps extracting to strings.xml)
• If needed for layouts use the tools namespace
also good for testing long texts:
• Never hardcode text in images
<TextView
android:id="@+id/deal“
android:text="@string/deal_title“
tools:text="deal of killing 2 zombie for one“/>

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Locales
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• How Locale’s work:

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Locales
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• How Locale’s work with Android N:

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Locales
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• How Locale’s work with Android N:

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Strings
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Don’t concatenate strings!
• Order might change in other language for grammar
• Dangerous in Right-to-Left
TextView textView = ...
textView.setText(" ‫לחץ‬‫כאן‬ " + ">");
a) ‫לחץ‬‫כאן‬ >
b) > ‫לחץ‬‫כאן‬
c) < ‫לחץ‬‫כאן‬

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Strings
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Don’t concatenate strings!
• Order might change in other language for grammar
• Dangerous in Right-to-Left
TextView textView = ...
textView.setText(" ‫לחץ‬‫כאן‬ " + ">");
a) ‫לחץ‬‫כאן‬ >
b) > ‫לחץ‬‫כאן‬
c) < ‫לחץ‬‫כאן‬

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Strings
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Don’t concatenate strings!
• Use Formatter.format
• Yes even for numbers!
• Or better: Use Phrase from Square
Phrase.from(
"Hi {first_name}, you are {age} years old.")
.put("first_name", firstName)
.put("age", age)
.format();
format(locale, "Choose a %d-digit PIN", 4)

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Strings
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• Plurals
<?xml version="1.0" encoding="utf-8"?>
<resources>
<plurals
name="tutorials">
<item quantity="zero">no Tutorial </item>
<item quantity="one">one Tutorial </item>
<item quantity="other">%d Tutorials</item>
</plurals>
</resources>
getResources().getQuantityString(
R.plurals.tutorials, number);

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Locales
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• Don’t reuse your strings too often.
Same names for different things might be different names on other
languages
• Provide context to translator
• Be aware: texts have different length in different languages,
English tends to be short, Finnish or German tend to be very long
• Different line-heights, careful with custom fonts or cropping views in height

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Locales
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• Test with Pseudo Localization
buildTypes {
debug {
pseudoLocalesEnabled true
}
}

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Locales
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• Careful with default locales:
assertEquals(
“billy”, “BILLY”.toLowerCase());
assertEquals(
“bılly”,
“BILLY”.toLowerCase(
new Locale(“tr”,“TR”)));
-> FALSE for turkish!!!

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Numbers
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https://en.wikipedia.org/wiki/File:Clock-in-cairo-with-eastern-arabic-numerals.jpg

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Numbers
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The decimal mark: Dot vs. Comma
1.00$
vs
1,00€
With delimiters:
4,294,967,295.00
vs
4 294 967.295,000
In 1958, disputes between European and American delegates over the correct
representation of the decimal mark nearly stalled the development of the ALGOL
computer programming language. (wikipedia)

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Numbers
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The decimal mark: Dot vs. Comma
https://en.wikipedia.org/wiki/Decimal_mark

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Numbers
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NumberFormat.getNumberInstance(Locale)
NumberFormat.getIntegerInstance(Locale)
Same for Percentages, don’t just concatenate!
Example: Turkey has sign before the number!
NumberFormat.getPercentInstance(Locale)

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Currencies
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Currencies
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• WHICH symbols, if ANY
• WHERE to put the symbol (front or back)?
• How many digits after comma/dot?
0-3 are common
• Represent currencies in the Currency class ;-)
NumberFormat.getCurrencyInstance(Locale);

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Currencies
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• Never ever use floating point numbers (float or double)
for Money!
Floats are broken by design (for representing money)
IEEE 754:
it is impossible to represent 0.1 (or any other negative
power of ten)
System.out.println(1.03 - .42);
>>> 0.6100000000000001
(Bloch, J., Effective Java, 2nd ed)
• Use BigDecimal and the String(!) constructor
• Check Martin Fowlers Money pattern class

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Dates
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Dates
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• 12 hours vs 24 hours
• Timezones
• Daylight Time DST

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Dates
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• Careful with calculations and comparison (be aware of DST jumps)
public static Date getYesterday(Date from) {
Calendar c = getCalendarFor(from);
c.add(Calendar.DAY_OF_THE_MONTH, -1);
return c.getTime();
}
public static Date getYesterday(Date from) {
return new Date(from.getTime() - (24*60*60*1000));
}

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Dates
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DateFormat
Careful with custom formats, try to use the standard java one else “pm” might
show up to “nachmittag”
DateFormat.getDateInstance(DateFormat.LONG)
DateFormat.getDateTimeInstance(
DateFormat.SHORT, DateFormat.SHORT);

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Dates
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android.text.format.DateUtils
• Has nice methods like:
isToday()
formatDateRange()
getRelativeTimeSpanString() “5 minutes ago”
• Check out joda-time-android
https://github.com/dlew/joda-time-android
(don’t use normal Java joda-time!
because of GetResourceAsStream performance issue on Android)

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Units
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Units
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• Km vs miles
• Celcius vs Fahrenheit
• Liters vs Galons

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Units
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Regional differences:
• Structure and Length of telephone numbers
• Elements of Address informations
• ZIP code validation

31. #droidconzg #PreusslerBerlin
Dubai Airport #1 by emi emi, CC by 2.0; flickr.com/photos/emi_b/4793218993Right-to-Left

32. #droidconzg #PreusslerBerlin
The signs are in greek by Karl Baron,
flickr.com/photos/kalleboo/6624480775
Dubai Airport #1 by emi emi, CC by 2.0;
flickr.com/photos/emi_b/4793218993

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Right-to-Left

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Right To Left
• Replace left/right with start/end
• Manifest flag:
android:supportsRtl="true"
• Check your images and correct in xml drawable:
android:autoMirrored=“true/false“
• Set margins to both sides
35

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Cultural context
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Cultural context
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• Careful with iconography
©wikipedia

38. #droidconzg #PreusslerBerlin
Thank you
Happy localizing!