检查自定义字体是否可以显示字符

I have a custom font which is displaying the box character. The font I am using does not support all languages apparently. I want to check if the String I am about to display can be displayed by my custom font. If it cannot then I want to use the standard Android font (which I know can display the characters). I can't find a method to check if my Typeface can display a particular String though. I am sure I have seen a method around that does this somewhere. Anyone know?I have a custom font which is displaying the bo