UIInterfaceOrientation方向枚举：
UIInterfaceOrientationPortrait //home健在下UIInterfaceOrientationPortraitUpsideDown //home健在上
UIInterfaceOrientationLandscapeLeft //home健在左UIInterfaceOrientationLandscapeRight //home健在右
旋转屏幕时触发的函数：
//旋转方向发生改变时
-(void)willAnimateRotationToInterfaceOrientation:(UIInterfaceOrientation)toInterfaceOrientation duration:(NSTimeInterval)duration {
}
//视图旋转动画前一半发生之前自动调用
-(void)willAnimateFirstHalfOfRotationToInterfaceOrientation:(UIInterfaceOrientation)toInterfaceOrientation duration:(NSTimeInterval)duration {
}
//视图旋转动画后一半发生之前自动调用
-(void)willAnimateSecondHalfOfRotationFromInterfaceOrientation:(UIInterfaceOrientation)fromInterfaceOrientation duration:(NSTimeInterval)duration {
}
//视图旋转之前自动调用
-(void)willRotateToInterfaceOrientation:(UIInterfaceOrientation)toInterfaceOrientation duration:(NSTimeInterval)duration {
}
//视图旋转完成之后自动调用
-(void)didRotateFromInterfaceOrientation:(UIInterfaceOrientation)fromInterfaceOrientation {
}
//视图旋转动画前一半发生之后自动调用
-(void)didAnimateFirstHalfOfRotationToInterfaceOrientation:(UIInterfaceOrientation)toInterfaceOrientation {
}