1.设备横竖屏切换通知
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(orientChange:) name:UIDeviceOrientationDidChangeNotification object:nil];
- (void)orientationDidChange:(NSNotification *)notification
{
UIDeviceOrientation orient = [UIDevice currentDevice].orientation;
//需要重新设置contentSize，contentOffset
_collectionView.contentSize = CGSizeMake(_arrPageModel.count * self.view.frame.size.width,self.view.frame.size.height);
_collectionView.contentOffset = CGPointMake(_currentIndexPath.item * self.view.frame.size.width, 0);
}
