运用时：

            UICollectionViewFlowLayout *layout = [[UICollectionViewFlowLayout alloc] init];
            self.mediaView = [[UICustomCollectionView alloc] initWithFrame:CGRectMake(10, 10, Main_Screen_Width-2*15, 80) collectionViewLayout:layout];

4：模拟器改为Ipad userInterfaceIdiom没有效果的解决方法 

将模拟器改为Ipad时，调用[[UIDevice currentDevice] userInterfaceIdiom]==UIUserInterfaceIdiomPad判断设备是否为Ipad，但程序并未做出正确的判断，后来做出如下设置：

PROJECT->Build Settings->Deployment->Targeted Device Family->iPhone/iPad

再次调试程序，成功识别出设备