统一弹登录页面，有的是在push出来的页面弹登录页面,有的是在present页面弹登录页面
说明 ：
例如：A present B A就是presenting view controller（弹出VC）； B就是presented view controller（被弹出VC）；
解决方案：
//登录
- (void)presentLoginVC
{
PhoneLoginViewController *loginVC = Storyboard(@"Main", @"PhoneLoginViewController");
UINavigationController *loginNav = [[UINavigationController alloc] initWithRootViewController:loginVC];
UIViewController *viewController = [UIApplication sharedApplication].keyWindow.rootViewController;
/* viewController.presentedViewController只有present才有值，push的时候为nil
*/
//防止重复弹
if ([viewController.presentedViewController isKindOfClass:[UINavigationController class]]) {
UINavigationController *navigation = (id)viewController.presentedViewController;
if ([navigation.topViewController isKindOfClass:[PhoneLoginViewController class]]) {
return;
}
}
if (viewController.presentedViewController) {
//要先dismiss结束后才能重新present否则会出现Warning: Attempt to present <UINavigationController: 0x7fdd22262800> on <UITabBarController: 0x7fdd21c33a60> whose view is not in the window hierarchy!就会present不出来登录页面
[viewController.presentedViewController dismissViewControllerAnimated:false completion:^{
[viewController presentViewController:loginNav animated:true completion:nil];
}];
}else {
[viewController presentViewController:loginNav animated:true completion:nil];
}
}
2.Warning once only: Detected a case where constraints ambiguously suggest a height of zero for a tableview cell's content view. We're considering the collapse unintentional and using standard height instead.
这个是自定义cell调用了基类的设置高度的方法，在tableview没有实现- (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath这个代理方法，然后就会出现这个警告。
