如果控制器的view不是tableView或者ScrollView,最好取消view的扩展
代码的取消如下:
- (instancetype)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
[super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
self.edgesForExtendedLayout=UIRectEdgeNone;
}