Detect if a unicode character is supported?

Question

I'm trying to put together a small android app that can randomly return an emoji to the user. My intention is to just use actual unicode emoji characters, and return them as unicode string characters.

I built a full array of unicode strings that could be randomly chosen from, and many will display correctly. However some are showing up as unsupported characters (a rectangle with an x through it).

Obviously not every platform will support every unicode emoji character, but if possible I'd like a way to determine what is and isn't a supported character. The ideal would be to query for a list of supported characters, but being able to test individual characters would also do the job just fine.

Answer 1

Also check out Paint.hasGlyph(String), which was added in API level 23. You can use this to test if a character like an emoji has a glyph available.

This is what the documentation says:

boolean hasGlyph (String string)

Determine whether the typeface set on the paint has a glyph supporting the string. The simplest case is when the string contains a single character, in which this method determines whether the font has the character. In the case of multiple characters, the method returns true if there is a single glyph representing the ligature. For example, if the input is a pair of regional indicator symbols, determine whether there is an emoji flag for the pair.

Finally, if the string contains a variation selector, the method only returns true if the fonts contains a glyph specific to that variation.

Checking is done on the entire fallback chain, not just the immediate font referenced.

See also

• How to detect emoji support on Android by code

Answer 2

So, when you talk about a character being "unsupported", it sounds like what you mean is that the current font doesn't have a glyph for the character (and either the application doesn't have fallback logic to find a different font that does, or the system doesn't have any font that does).

In regular Java, this is pretty easy: given an instance of java.awt.Font, you can see if it has a glyph for a given Unicode character by using the canDisplay method.

The Android APIs, for whatever reason, don't seem to expose a way to figure out what font you're actually working with. (android.graphics.Typeface keeps that information private: see "Check the family of a Typeface object in Android".) However, you might at least try something like new java.awt.Font("SansSerif", java.awt.Font.PLAIN, 12) to get a basic 12-point sans-serif font. You'll want to test, of course, to see if that gives a usable approximation for the emoji that the real font will be able to display.