iOS 5.1实现旋转屏幕

在iOS6.1之前。Xcode不能自动旋转屏幕，只有通过程序控制旋转勒。。。。

- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation {

return (interfaceOrientation ==UIInterfaceOrientationLandscapeLeft || interfaceOrientation ==UIInterfaceOrientationLandscapeRight ); }