Develop Reference

Error using native smiles of Android in text field (Unity3d)

I make application with Unity3d and build it for Android, when I write in input field android native smiles - I got error in line
(invalid utf-16 sequence at 1411555520 (missing surrogate tail)):
r.font.RequestCharactersInTexture(chars, size, style);
chars contains string than contains native android smiles. How I may support native smiles? I use own class for Input Field.

Unfortunately, supporting emojis with Unity is hard. When I implemented this feature, it took about a month to finish it, with a custom text layout engine and string class. So, if this requirement is not particularly important, I would suggest axing this feature.
The reason behind this particular error is that Unity gets characters from the input string one by one, and updates the visual string every character. From the layman point of view, this makes complete sense. However, it doesn't take into account how UTF-16 encoding, which is used in C#, works.
UTF-16 encoding uses 16 bits per a single unicode characters. It is enough for almost all characters that you would normally use. (And, as every developer knows, "almost all" is a red flag that will lay dormant for a long time and then will explode and destroy everything you love.) But it so happens, that Emoji characters are do not fit into 16 bit UTF-16 character, and use a special case — surrogate pair:
Surrogate pair is a pair of UTF-16 characters that represent a single Unicode character. That means that they don't have any meaning on their own individually, and when you try to render a UTF-16 character that is a surrogate head or surrogate tail, you can expect to get an error like this, or something similar.
Essentially, what you need to implement is some kind of buffer, that will accept C# UTF-16 characters one by one, and then pass them to rendering code when it verifies that all surrogate pairs are closed.
Oh, and I almost forgot! Some Emoji characters, like country flags, are represented by two unicode characters. Which means that they can potentially take up to four UTF-16 characters. Aren't text encodings fun?

How can I put utf-16 characters in Android string resource?

I want to use Emojis in my app's strings. All strings reside, of course, in strings.xml
The problem is that not all Emojis are 16 bit friendly. Some Emojis can be represented as "normal" 16 bit hex: '\u26FF' but some are 32 bit hexes (UTF-16), usually represented as: '\x1F600'. I have no problem dealing with those inside the app, in code. But the strings.xml resource file is UTF8 encoded, and does not deal properly with non 16 bit escape chars.
I tried using '\x1F600' - because I saw that '\u26FF' works just fine. But it seems not to devour the 'x' escape char. Nor did it like the regexp notation '\x{1F600}'
So I ended up using a string placeholder '%1$s' and filling in the Emoji in code like this:
// greeting_3 is defined as: "hello there %1$s!"
String s = context.getString(R.string.greeting_3, "😜");
// OR:
String s = context.getString(R.string.greeting_3, new String(Character.toChars(0x1F61C)));
This is not a very elegant solution... is there a proper way to put 32 bit UTF-8 chars in strings.xml ?

But the strings.xml resource file is UTF8
If it's UTF-8 encoded, you can put your emojis directly. But then you risk that your editor or another piece of software destroys them.
If you are putting them in XML, you can try using XML entities: 😀, I'm not sure how well Android supports them though.
You can also use surrogate pairs: convert the emoji to UTF-16 and use standard \u escape. You can for example check out this page, it even tells you how to create a string litaral in Java: http://www.fileformat.info/info/unicode/char/1F600/index.htm
😜 → U+1F600 → "\uD83D\uDE00"

The easiest way it just copying and pasting the emoji, it works from Android Studio 3.0 and newer

Add the resource like follows:
<string name="string_title">This is a emoji example <U+1F642></string>
In Android Studio 3.0 you can copy and paste an emoji:
And here how it looks:

Performance at working with strings android

Could somebody tell me what is better in terms of performance?
Is it better to save 2 strings at string.xml, like 'abc' and 'abc:'
Or should I save only the first one and concatenate ':' when needed at Java coding ???

Very difficult to answer depending on what your strings will represent and what you need to append. Localization is also an issue, for example...
Dog // English
Chien // French
Hund // German
Using string resources allows you to create different resource files depending on the locale of the device and Android will automatically use the right localized string resource file. If all you need to do is append a single character such as : then you'll double every string for every language.
If you choose to only save the basic strings and append the character using code, then the code will be universal and you'll simply need to append the character to whatever localized word - potentially a lot more efficient.

Both from storage perspective and performance you should save only "abc";
getting extra data from disk takes far longer as some quick in-memory actions.
storing the same data twice is bad practice in general

If you have to concatenate multiple strings you should use StringBuilder - http://docs.oracle.com/javase/1.5.0/docs/api/java/lang/StringBuilder.html
It's much faster then using '+' or '.concat()'

Android: converting between Strings, SpannedStrings and Spannablestrings

I have a string resource called "foo". It may be a simple string... or it may contain HTML. This may change over time: I should be able to box it up as at least a SpannableString immediately upon reading whether it's HTML or not (but how??)
I want to get that raw CharSequence and first be able to display it as-is (the exact characters, not Android's "interpretation" of it). Right now I can't do that... toString() decides to rip out the parts it doesn't think I want to see.
I'd then like to be able to create a SpannableString from this and other Strings or SpannableStrings via concatenation using some method (none of the normal ones work). I'd like to then use that SpannableString to display the HTML-formatted text in a TextView.
This shouldn't be difficult, but clearly I'm not doing it right (there's very little info out there about this that I've found so far). Surely there is a way to accurately interconvert between between Strings, SpannedStrings and even Spannablestrings, without losing the markups along the way?
Note that I've already played with the somewhat broken Linkify, but I want better control over the process (no dangling unformatted "/"s, proper hrefs, etc.) I can get this all to work IF I stay in HTML at all steps, though I can't concatenate anything.
Edit 1: I've learned I can use the following to always ensure I get my raw string (instead of whatever Android decides it thinks the CharSequence really is). Nice... now, how to coax this into a SpannableString?
<string name="foo"><![CDATA[
<b>Some bold</b>
]]>
</string>
Edit 2: Not sure why this didn't work earlier, but... if foo1 and foo2 are strings marked up as above (as CDATA), then one can apparently do this:
String foo1 = (String)getResources().getText(R.string.foo1);
String foo2 = (String)getResources().getText(R.string.foo2);
SpannedString bar = new SpannedString(Html.fromHtml(foo1+foo2));
Curious: is there a more straightforward solution than this? Is this CDATA business actually necessary? It seems convoluted (but not as convoluted as never quite knowing what the resource type will be... String, Spannable, etc.)

I had the same problem. There are two solutions according to Google API Guides.
First is to escape < mark with < in the string resource. Unfortunately, String conversion removes the tag in the background.
Second is to use Format Strings instead of XML/HTML tags. It seems simpler, faster, and evades hidden conversion problems. getString(resource, ...) works like a printf(string, ...) here.
Both work and require some code to replace given part of the string anyway (handle tags or format strings). Enjoy! =)

It appears there isn't a more straightforward way to accomplish this.

Problem with special characters

How can I change the font on android to allow to show special characters like "'" or "à"?
Actually the strings that contains these characters are stored in the sqlite database.

When you load the text into your TextView, will this work for you?
textView.setText(new String(textFromDatabase, "UTF-8"));
This uses the String constructor to set the charset name. You can change "UTF-8" to a different Character encoding -- Also, look at the javadoc for String.
String(byte[] bytes, String charsetName) -
Constructs a new String by decoding the specified array of bytes using the specified charset.

The Droid font supports the "'", "à" and many others characters. I use them all the time (pt language).
Actually, I'm quite sure they support all the Basic Latin, Latin 1 supplement and the first extended latin range. They also support many others like hebrew etc., although I'm not sure if that changed between SDK versions.
You can also download the Unicode Map app in the Market to check which characters are available in your particular device. I also store unicode text in sqlite all the time, and still I don't have any problems.
One thing to consider: check that the encoding you are setting match the encoding of your source. It may be a text or a URL... an example:
BufferedReader b = new BufferedReader(new InputStreamReader(url.openStream(), MY_ENCODING));
Are you sure it's not a problem somewhere?

You should use '' instead of ' to store it into Sqlite database.
For example if you want to store 5 o'clock into database then you have to write this as 5 O''clock. Take a look here, for more information about it.

By default Android SQLite uses UTF-8.
I had this problem because when I populated the database on the first launch I used a txt file with another charset.