直接上代码吧
通过改变的字符,判断是否存在回车
swift版

func textView(textView: UITextView,shouldChangeTextInRange range: NSRange,replacementText text: String) -> Bool {
        if text == "\n"
        {
            self.inputView.resignFirstResponder()
            return false
        }
        return true
    }

OC版

-(BOOL)textView:(UITextView *)textView shouldChangeTextInRange:(NSRange)range replacementText:(NSString *)text
{
    if ([text isEqualToString:@"\n"]) {
        [self.inputView resignFirstResponder];
        return NO;
    }
    return YES;
}