textview的限制字符和回收键盘

textView的代理方法中实现下面：

- (BOOL)textView:(UITextView *)textView shouldChangeTextInRange:(NSRange)range replacementText:(NSString *)text

{

#define MY_MAX 200

    if ((textView.text.length - range.length + text.length) > MY_MAX)

    {

        NSString *substring = [text substringToIndex:MY_MAX - (textView.text.length - range.length)];

        NSMutableString *lastString = [textView.text mutableCopy];

        [lastString replaceCharactersInRange:range withString:substring];

        textView.text = [lastString copy];

        return NO;

    }else if ([@"\n" isEqualToString:text]){

        [textView resignFirstResponder];

        return NO;

    }else{

        return YES;

    }

}