
If you have ever traded messages with someone using your smartphone – which is basically everyone – you have probably run into a problem where someone sends you an emoji that just displays as a blank box or a box with an X through it. This happens due to incompatibilities with fonts supported by an operating system and can be quite frustrating. Google's Android developers think they have figured out a way around this that will separate emoji display from the operating system and put more control in the hands of developers to open up the world of emojis to their users.
A new EmojiCompat support library is being rolled out by Android's developers that “aims to keep Android devices up to date with the latest emoji.” The new library will work on devices going back to Android 4.4 enabling devices running these older versions of Android to display new Emojis that have been released subsequent to their last operating system update. According to Google, the new support library can be configured to work with either bundled or downloaded fonts.
The new support library uses the CharSequence code for any given emoji and replaces it with an “EmojiSpan” for any emojis that are currently missing on the target device. That EmojiSpan can then be used to render the emoji glyph or image.

Adding this new emoji support will be up to developers, but should be a fairly easy update. We expect Google at a minimum to add this to their own half-dozen messaging apps. At least one issue is unclear from the information shared by the Android developers and that is exactly which emoji glyphs will ultimately be displayed – a manufacturer's own glyphs like what Samsung, LG or HTC might supply on their devices or Google's system glyphs.
source: Android Developers