关于iOS屏幕旋转处理

首先Device orientation中要配置支持方向
其次关键方法如下：
1.是否支持自动旋转

• (BOOL)shouldAutorotate

2.返回支持旋转的方向

• (UIInterfaceOrientationMask)supportedInterfaceOrientations

支持正立竖屏
UIInterfaceOrientationMaskPortrait = (1 << UIInterfaceOrientationPortrait),
支持左横屏
UIInterfaceOrientationMaskLandscapeLeft = (1 << UIInterfaceOrientationLandscapeLeft),
支持右横屏
UIInterfaceOrientationMaskLandscapeRight = (1 << UIInterfaceOrientationLandscapeRight),
支持倒立竖屏
UIInterfaceOrientationMaskPortraitUpsideDown = (1 << UIInterfaceOrientationPortraitUpsideDown),
支持倒立横屏
UIInterfaceOrientationMaskLandscape = (UIInterfaceOrientationMaskLandscapeLeft | UIInterfaceOrientationMaskLandscapeRight),
支持全部
UIInterfaceOrientationMaskAll = (UIInterfaceOrientationMaskPortrait | UIInterfaceOrientationMaskLandscapeLeft | UIInterfaceOrientationMaskLandscapeRight | UIInterfaceOrientationMaskPortraitUpsideDown),
除了倒立竖屏都支持
UIInterfaceOrientationMaskAllButUpsideDown = (UIInterfaceOrientationMaskPortrait | UIInterfaceOrientationMaskLandscapeLeft | UIInterfaceOrientationMaskLandscapeRight),

3.即将旋转时代理回调

• (void)willRotateToInterfaceOrientation:(UIInterfaceOrientation)toInterfaceOrientation duration:(NSTimeInterval)duration

4.完成旋转时代理回调

• (void)didRotateFromInterfaceOrientation:(UIInterfaceOrientation)fromInterfaceOrientation

当转动屏幕后，手机会根据旋转方向进行主动旋转。

被动强制屏幕旋转：
如果想要强制旋转屏幕，比如点击按钮触发式旋转，方法如下：
（但这个方法不太亲和,可能会被拒或者与自动旋转冲突潜在bug）

   NSNumber *resetOrientationTarget = [NSNumber numberWithInt: UIInterfaceOrientationUnknown];

[[UIDevice currentDevice] setValue: resetOrientationTarget forKey:@"orientation"];

NSNumber *orientationTarget = [NSNumber numberWithInt: UIInterfaceOrientationLandscapeLeft];
[[UIDevice currentDevice] setValue: orientationTarget forKey:@"orientation"];