1.在viewdidload中添加一個(gè)默認(rèn)字體的lable

placeHoderLable = [[UILabel alloc]initWithFrame:CGRectMake(3, 3, DeviceWidth-6, 40)];//根據(jù)情況調(diào)節(jié)位置
placeHoderLable.enabled = NO;
placeHoderLable.text = @"請(qǐng)?jiān)谶@里輸入您要預(yù)測(cè)的內(nèi)容，您的預(yù)言需要經(jīng)過(guò)其他用戶的審核才能發(fā)布。";
placeHoderLable.numberOfLines=0;
placeHoderLable.font =  [UIFont systemFontOfSize:12];
placeHoderLable.textColor = [UIColor lightGrayColor];
[_myTextView addSubview:placeHoderLable];
_myTextView.delegate=self;//記得設(shè)置textview的代理
_myTextView.returnKeyType=UIReturnKeyDone;

2.在textview的代理方法中實(shí)現(xiàn)以下代碼

-(void)textViewDidChange:(UITextView *)textView
      {
        if ([_myTextView.text length] == 0) {
            [placeHoderLable setHidden:NO];
        }else{
            [placeHoderLable setHidden:YES];
        }
    }

- (BOOL)textView:(UITextView *)textView shouldChangeTextInRange:(NSRange)range replacementText:                                (NSString *)text
{
    if([text isEqualToString:@"\n"]){

        [textView resignFirstResponder];

        return NO;

    }
    if (range.location>=100)
    {
        _yuNumLable.text=@"還能輸入0字";
        return  NO;
    }
    else
    {
        _yuNumLable.text=[NSString stringWithFormat:@"還能輸入%lu字",100-range.location];
        return YES;
    }
}