Emoji表情最終會被編碼成Unicode，因此，只要知道Emoji表情的Unicode編碼的范圍，就可以判斷用戶是否輸入了Emoji表情。以下是具體代碼，我這里寫成了NSString的一個分類

- (BOOL)stringContainsEmoji:(NSString *)string
{
    __block BOOL returnValue = NO;
    [string enumerateSubstringsInRange:NSMakeRange(0, [string length])
                               options:NSStringEnumerationByComposedCharacterSequences
                            usingBlock:^(NSString *substring, NSRange substringRange, NSRange enclosingRange, BOOL *stop) {
                                const unichar hs = [substring characterAtIndex:0];
                                if (0xd800 <= hs && hs <= 0xdbff) {
                                    if (substring.length > 1) {
                                        const unichar ls = [substring characterAtIndex:1];
                                        const int uc = ((hs - 0xd800) * 0x400) + (ls - 0xdc00) + 0x10000;
                                        if (0x1d000 <= uc && uc <= 0x1f77f) {
                                            returnValue = YES;
                                            NSLog(@"%@",substring);
                                            [self changeToString:substring];
                                        }
                                    }
                                } else if (substring.length > 1) {
                                    const unichar ls = [substring characterAtIndex:1];
                                    if (ls == 0x20e3) {
                                        returnValue = YES;
                                    }
                                } else {
                                    if (0x2100 <= hs && hs <= 0x27ff) {
                                        returnValue = YES;
                                    } else if (0x2B05 <= hs && hs <= 0x2b07) {
                                        returnValue = YES;
                                    } else if (0x2934 <= hs && hs <= 0x2935) {
                                        returnValue = YES;
                                    } else if (0x3297 <= hs && hs <= 0x3299) {
                                        returnValue = YES;
                                    } else if (hs == 0xa9 || hs == 0xae || hs == 0x303d || hs == 0x3030 || hs == 0x2b55 || hs == 0x2b1c || hs == 0x2b1b || hs == 0x2b50) {
                                        returnValue = YES;
                                    }
                                }
                            }];
    return returnValue;
}

這段代碼并非本人原創(chuàng)，也是取自互聯(lián)網(wǎng)，經(jīng)測試好使，分享給大家。
如果想改變emoij的大小，而不改變文字的大小，我試了一下，用屬性字符串就可以。如果有這樣的需求可以試下。