取消第一响应

field.returnKeyType = UIReturnKeyDone;

[field addTarget:self action:@selector(onKeyBoardDown:) forControlEvents:UIControlEventEditingDidEndOnExit];// 取消第一响应

-(void)onKeyBoardDown:(id)sender{

    [sender resignFirstResponder];

}

原文：http://www.cnblogs.com/pjl111/p/4196415.html