修改UIButton状态，注释NSLog(@"text1：%@",_btn.titleLabel.text);这段结果很不可思议
_btn.titleLabel.text = [NSString stringWithFormat:@"aaaaaa%i",i];
NSLog(@"text1：%@",_btn.titleLabel.text);
NSLog(@"text3：%@",[_btn titleForState:UIControlStateNormal]);
UIButtonTypeSystem
2015-05-21 11:16:10.363 test[6137:504267] text1：aaaaaa4
2015-05-21 11:16:10.363 test[6137:504267] text3：Button111
2015-05-21 11:16:13.368 test[6137:504267] text1：aaaaaa5
2015-05-21 11:16:13.368 test[6137:504267] text3：Button111
UIButtonTypeCustom
2015-05-21 11:17:48.471 test[6260:520944] text1：Button111
2015-05-21 11:17:48.472 test[6260:520944] text3：Button111
2015-05-21 11:17:51.475 test[6260:520944] text1：Button111
2015-05-21 11:17:51.476 test[6260:520944] text3：Button111
UIButtonTypeSystem下面就不闪了，断点情况下会出现原始值
[[_btn class] setAnimationsEnabled:NO];
_btn.titleLabel.text = [NSString stringWithFormat:@"aaaaaa%i",i];
[[_btn class] setAnimationsEnabled:YES];
个人小结论：在引用titleLabel.text的时候 其实会对本身进行一次赋值，默认本身状态下所对应的title值
验证码UIButton状态UIButtonTypeSystem时候一闪闪UIButtonTypeCustom不闪
原文：http://www.cnblogs.com/Leetvin/p/4519904.html