How do I remove unrecognized characters which come back from a web service?

I am working on an app which calls a rest web service. Sometimes the xml responses contain characters which the phone can not display. When displaying these characters, an empty box is di开发者_开发问答splayed instead. I would like to filter out these characters. How can I detect if a character will be able to be displayed on the screen?

Some specific characters include:

http://www.fileformat.info/info/unicode/char/0094/index.htm http://www.fileformat.info/info/unicode/char/0080/index.htm http://www.fileformat.info/info/unicode/char/0092/index.htm

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Android support the following encodings

• Xml.Encoding ISO_8859_1
• Xml.Encoding US_ASCII
• Xml.Encoding UTF_16
• Xml.Encoding UTF_8

US_ASCII shouldn't make any problems.

For ISO_8859_1 you should check wiki for control chars 0x00-0x1f and 0x7f-0x9f and filter them. And of course use a matching font.

Using UTF_8 or 16 is more complex, read Joels The Absolute Minimum Every Software Developer Absolutely, Positively Must Know About Unicode and Character Sets

You might find this mailing list useful.

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First of all, try to get the default charset of your device with:

Charset.defaultCharset();

Then try to get the charset of your XML looking in pseudo-attribute of the XML declaration or in Content-Type header of the HTTP call.
For example:

<?xml version="1.0" encoding="utf-8" ?>

or

Content-Type: text/html; charset=utf-8

If the default charset of your device is different from the charset of XML, you have to pay attention when you handle new strings with:

new String( bytes);

because if you forget to specify the correct encoding, Dalvik will use the default encoding of the device with plausible display errors.
Remember to use:

new String( bytes, encoding);

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It appears I can call Character.isIdentifierIgnorable() on each character and not include it if it is ignorable. Character.isISOControl() will probably also work.