1.在viewDidLoad中添加一个默认字体的Lable

placeHoderLable = [[UILabel alloc]initWithFrame:CGRectMake(3,3, DeviceWidth-6,40)];//根据情况调节位置placeHoderLable.enabled=NO;

placeHoderLable.text=@"请在这里输入您要预测的内容。";

placeHoderLable.numberOfLines=0;

placeHoderLable.font=  [UIFontsystemFontOfSize:12];

placeHoderLable.textColor= [UIColorlight GrayColor];

[_myTextView addSubview:placeHoderLable];

_myTextView.delegate=self;//记得设置textview的代理_myTextView.returnKeyType=UIReturnKeyDone;

2.在textView的代理方法中实现以下代码

-(void)textViewDidChange:(UITextView*)textView

{     if([_myTextView.textlength] ==0) {

       [placeHoderLable setHidden:NO];

      }else {

        [placeHoderLable setHidden:YES];

    }

}

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

{

       if([text isEqualToString:@"\n"]|| ([text isEqualToString:@""])

    {

      [textView resignFirstResponder];

     returnNO;

   }

if(range.location>=200){

_yuNumLable.text=@"还能输入0字" ;

returnNO;

}else{

_yuNumLable.text=[NSStringstringWithFormat:@"还能输入%lu字",200-range.location];

returnYES;

  }

}