方式

设置代理 <UITextFieldDelegate,UITextViewDelegate>

xx.delegate = self;

• UITextView

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

/** 如果输入“return”，失去焦点*/
    if([text isEqualToString:@"\n"]){
        [textView resignFirstResponder];
    }
  return YES;
    
}

• UITextField

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string{    
    /** 如果输入的是回撤，直接放弃焦点*/
    if([string isEqualToString:@"\n"]){
        [textField resignFirstResponder];
    }
  return YES;
}