方法一：
[searchBar setValue:@"取消"forKey:@"_cancelButtonText"];
方法二 ：
[[UIBarButtonItem appearanceWhenContainedInInstancesOfClasses:@[[UISearchBar class]]] setTitle:@"取消"];
方法三：
for (id cencelButton in [searchBar.subviews[0] subviews])
{
if([cencelButton isKindOfClass:[UIButton class]])
{
UIButton *btn = (UIButton *)cencelButton;
[btn setTitle:@"取消" forState:UIControlStateNormal];
}
}
