本文转载至  http://blog.csdn.net/liuwuguigui/article/details/39494435

1.iPad上使用presentModalViewController，custion size not work on ios8 SDK。使用如下方法解决：

In iOS 8 you can also use UIPresentationController which gives you more customization options.

#define IsiOS8Later ([[[UIDevice currentDevice] systemVersion] doubleValue]>=8.0)?YES:NO

This will Work:

AboutViewController * _aboutViewController = [[AboutViewController alloc] init];_aboutViewController.modalPresentationStyle = UIModalPresentationFormSheet;if(IS_IOS8){   _aboutViewController.preferredContentSize = CGSizeMake(300, 300);}[self presentViewController:_aboutViewController animated:YES completion:nil];

- (void)viewWillLayoutSubviews{    [super viewWillLayoutSubviews];    if(!IS_IOS8)    {        self.view.superview.bounds = CGRectMake(0, 0, 300, 300);    }}