Develop Reference

URL encoding is getting failed for special character. #Android

I'm working on a solution where need to encode string into utf-8 format, this string nothing but device name that I'm reading using BluetoothAdapter.getDefaultAdapter().name.
For one of sampple I got a string like ABC-＆ and encoding this returned ABC-%EF%BC%86 instead of ABC-%26. It was weird until further debugging which helped to identify that there is difference between & and ＆. Second one is some other character which is failing to encoded as expected.
& and ＆ both are different.
For encoding tried both URLEncoder.encode(input, "utf-8") and Uri.encode(input, "utf-8") but nothing worked.
This is just an example, there might be other character which may look like same as actual character but failed to encode. Now question are:
Why this difference, after all it is reading of some data from device using standard SDK API.
How can fix this be fixed. Find and replace with actual character could be a approach but scope is limited, there might be other unknown character.
Any suggestion around !!

One solution would be to define your allowed character scope. Then either replace or remove the characters that fall outside of this scope.
Given the following regex:
[a-zA-Z0-9 -+&#]
You could then either do:
input.replaceAll("[a-zA-Z0-9 -+&#]", "_");
...or if you don't care about possibly empty results:
input.replaceAll("[a-zA-Z0-9 -+&#]", "");
The first approach would give you a length-consistent representation of the original Bluetooth device name.
Either way, this approach has worked wonders for me and my colleagues. Hope this could be of any help 😊.

What are my options for displaying characters that Android can't?

I discovered today that Android can't display a small handful of Japanese characters that I'm using in my Japanese-English dictionary app.
The problem comes when I attempt to display the character via TextView.setText(). All of the characters below show up as blank when I attempt to display them in a TextView. It doesn't appear to be an issue with encoding, though - I'm storing the characters in a SQLite database and have verified that Android can understand the characters. Casting the characters to (int) retrieves proper Unicode decimal escapes for all but one of the characters:
String component = cursor.getString(cursor.getColumnIndex("component"));
Log.i("CursorAdapterGridComponents", "Character Code: " + (int) component.charAt(0) + "(" + component + ")");
I had to use Character.codePointAt() to get the decimal escape for the one problematic character:
int codePoint = Character.codePointAt(component, 0);
I don't think I'm doing anything wrong, and as String's are by default UTF-16 encoded, there should be nothing preventing them from displaying the characters.
Below are all of the decimal escapes for the seven problematic characters:
⺅ Character Code: 11909(⺅)
⺌ Character Code: 11916(⺌)
⺾ Character Code: 11966(⺾)
⻏ Character Code: 11983(⻏)
⻖ Character Code: 11990(⻖)
⺹ Character Code: 11961(⺹)
𠆢 Character Code: 131490(𠆢)
Plugging the first six values into http://unicode-table.com/en/ revealed their corresponding Unicode numbers, so I have no doubt that they're valid UTF-8 characters.
The seventh character could only be retrieved from a table of UTF-16 characters: http://www.fileformat.info/info/unicode/char/201a2/browsertest.htm. I could not use its 5-character Unicode number in setText() (as in "\u201a2") because, as I discovered earlier today, Android has no support for Unicode strings past 0xFFFF. As a result, the string was evaluated as "\u201a" + "2". That still doesn't explain why the first six characters won't show up.
What are my options at this point? My first instinct is to just make graphics out of the problematic characters, but Android's highly variable DPI environment makes this a challenging proposition. Is using another font in my app an option? Aside from that, I really have no idea how to proceed.

Is using another font in my app an option?
Sure. Find a font that you are licensed to distribute with your app and has these characters. Package the font in your assets/ directory. Create a Typeface object for that font face. Apply that font to necessary widgets using setTypeface() on TextView.
Here is a sample application demonstrating applying a custom font to a TextView.

SQLite upper() alike function for international characters

Actually question was asked several times, but I didn't manage to find answer.
There's set of SQLite table(s) which are read-only - I can't change their structure or redefine collation rules. Tables consisting some international characters (Russian/Chinese, etc).
I would like to get some case-insensitive selection like:
select name from names_table where upper(name) glob "*"+constraint.toUpperCase()+"*"
It works only when name is latin/ASCII charset, for international chars it doesn't work.
SQLite's manual reads:
The upper(X) function returns a copy of input string X in which all
lower-case ASCII characters are converted to their upper-case
equivalent.
So the question is: how to resolve this issue and make international chars in upper/lower case?

This is known problem in sqlite. You can redefine built-in functions via Android NDK. This is not a simple way. Look at this question
Notice that indexes of your tables will not work (for UDF) and query can be very slow.
Instead of it you can store your data (which you look for) in other column in ascii format.
For example:
"insert into names_table (name, name_ind) values ('"+name+"',"+"'"+toAsciiEquivalent(name)+"')"
name name_ind
----------------
Имя imya
Name name
ыыы yyy
and search string by column name_ind
select name from names_table where name_ind glob "*"+toAsciiEquivalent(constraint)+"*"
This solution requires more space for data, but it is simple and fast.

Instead of providing full Unicode case support by default, SQLite provides the ability to link against external Unicode comparison and conversion routines. The application can overload the built-in NOCASE collating sequence (using sqlite3_create_collation()) and the built-in like(), upper(), and lower() functions (using sqlite3_create_function()). The SQLite source code includes an "ICU" extension that does these overloads. Or, developers can write their own overloads based on their own Unicode-aware comparison routines already contained within their project.
Reference: http://www.sqlite.org/faq.html

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.

How to remove accent characters from an InputStream

I am trying to parse a Rss2.0 feed on Android using a Pull parser.
XmlPullParser parser = Xml.newPullParser();
parser.setInput(url.open(), null);
The prolog of the feed XML says the encoding is "utf-8". When I open the remote stream and pass this to my Pull Parser, I get invalid token, document not well formed exceptions.
When I save the XML file and open it in the browser(FireFox) the browser reports presence of Unicode 0x12 character(grave accent?) in the file and fails to render the XML.
What is the best way to handle such cases assuming that I do not have any control over the XML being returned?
Thanks.

Where did you find that 0x12 is the grave accent? UTF-8 has the character range 0x00-0x7F encoded the same as ASCII, and ASCII code point 0x12 is a control character, DC2, or CTRL+R.
It sounds like an encoding problem of some sort. The simplest way to resolve that is to look at the file you've saved in a hex editor. There are some things to check:
the byte order mark (BOM) at the beginning might confuse some XML parsers
even though the XML declaration says the encoding is in UTF-8, it may not actually have that encoding, and the file will be decoded incorrectly.
not all unicode characters are legal in XML, which is why firefox refuses to render it. In particular, the XML spec says that that 0x9, 0xA and 0xD are the only valid characters less than 0x20, so 0x12 will definitely cause compliant parsers to grumble.
If you can upload the file to pastebin or similar, I can help find the cause and suggest a resolution.
EDIT: Ok, you can't upload. That's understandable.
The XML you're getting is corrupted somehow, and the ideal course of action is to contact the party responsible for producing it, to see if the problem can be resolved.
One thing to check before doing that though - are you sure you are getting the data undisturbed? Some forms of communication (SMS) allow only 7-bit characters. This would turn 0x92 (ASCII forward tick/apostrophe - grave accent?) into 0x12. Seems like quite a coincidence, particularly if these appear in the file where you would expect an accent.
Otherwise, you will have to try to make best do with what you have:
although not strictly necessary, be defensive and pass "UTF-8" as the second paramter to setInput, on the parser.
similarly, force the parser to use another character encoding by passing a different encoding as the second parameter. Encodings to try in addtion to "UTF-8" are "iso-8859-1" and "UTF-16". A full list of supported encodings for java is given on the Sun site - you could try all of these. (I couldn't find a definitive list of supported encodings for Android.)
As a last resort, you can strip out invalid characters, e.g. remove all characters below 0x20 that are not whitespace (0x9,0xA and 0xD are all whitepsace.) If removing them is difficult, you can replace them instead.
For example
class ReplacingInputStream extends FilterInputStream
{
public int read() throws IOException
{
int read = super.read();
if (read!=-1 && read<0x20 && !(read==0x9 || read==0xA || read==0xB))
read = 0x20;
return read;
}
}
You wrap this around your existing input stream, and it filters out the invalid characters. Note that you could easily do more damage to the XML, or end up with nonsense XML, but equally it may allow you to get out the data you need or to more easily see where the problems lie.

I use to filter it with a regex, but the trick is not trying to get and replace the accents. It depends on the encode and you don't want to change the content.
Try to insert the content of the tags into this tags
Like this
<title>My title</title>
<link>http://mylink.com</link>
<description>My description</description>
To this
<title><![CDATA[My title]]></title>
<link><![CDATA[http://milynk.com]]></link>
<description><![CDATA[My Description]]></description>
The regex shouldn't be very hard to figure out. It works for me, hope it helps for you.

The problem with UTF-8 is that it is a multibyte encoding. As such it needs a way to indicate when a character is formed by more than one byte (maybe two, three, four, ...). The way of doing this is by reserving some byte values to signal multibyte characters. Thus encoding follows some basic rules:
One byte characters have no MSB set (codes compatible with 7-bit ASCII).
Two byte characters are represented by sequence: 110xxxxx 10xxxxxx
Three bytes: 1110xxxx 10xxxxxx 10xxxxxx
Four bytes: 11110xxx 10xxxxxx 10xxxxxx 10xxxxxx
Your problem is that you may be reading some character string supposedly encoded as UTF-8 (as the XML encoding definition states) but the byte chunk might not be really encoded in UTF-8 (it is a common mistake to declare something as UTF-8 but encoding text with a different encoding such as Cp1252). Your XML parser tries to interpret byte chunks as UTF-8 characters but finds something that does not fit the encoding rules (illegal character). I.e. two bytes with two most significate bytes set would bring an illegal encoding error: 110xxxxx must be always followed by 10xxxxxx (values such as 01xxxxxx 11xxxxxx 00xxxxxx would be illegal).
This problem does not arise when non-variable length encodings are used. I.e. if you state in your XML declaration that your file uses Windows-1252 encoding but you end up using ANSI your only problem will be that non-ASCII characters (values > 127) will render incorrectly.
The solution:
Try to detect encoding by other means.
If you will always be reading data from same source you could sample some files and use an advanced text editor that tries to infer actual encoding of the file (i.e. notepad++, jEdit, etc.).
Do it programatically. Preprocess raw bytes before doing any actual xml processing.
Force actual encoding at the XML processor
Alternatively if you do not mind about non-ASCII characters (no matter if strange symbols appear now and then) you could go directly to step 2 and force XML processing to any ASCII compatible 8-byte fixed length encoding (ANSI, any Windows-XXXX codepage, Mac-Roman encoding, etc.). With your present code you just could try:
XmlPullParser parser = Xml.newPullParser();
parser.setInput(url.open(), "ISO-8859-1");

Calling setInput(istream, null) already means for the pull parser to try to detect the encoding on its own. It obviously fails, due to the fact that there is an actual problem with the file. So it's not like your code is wrong - you can't be expected to be able to parse all incorrect documents, whether ill-formed or with wrong encodings.
If however it's mandatory that you try to parse this particular document, what you can do is modify your parsing code so it's in a function that takes the encoding as a parameter and is wrapped in a try/catch block. The first time through, do not specify an encoding, and if you get an encoding error, relaunch it with ISO-8859-1. If it's mandatory to have it succeed, repeat for other encodings, otherwise call it quits after two.

Before parsing your XML, you may tweak it, and manually remove the accents before you parse it.
Maybe not the best solution so far, but it will do the job.