detect keyboard mode chagne

     [[NSNotificationCenter defaultCenter] addObserver:self
                                                 selector:@selector(changeInputMode:)
                                                     name:UITextInputCurrentInputModeDidChangeNotification object:nil];
                                                     
- (void)changeInputMode:(NSNotification*)notification
{
    NSString *inputMethod = [[UITextInputMode currentInputMode] primaryLanguage]; //判断当前键盘类型， emoji en-US en-HANS
    
    if ([inputMethod isEqualToString:@"emoji"]) {
     }
}

检测键盘状态改变。