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1、UIWindow的bounds
iOS 7之前Window的bounds不会随着方向而变化，但是到了iOS 8以后，随着设备方向的旋转，window.bounds.size.width和window.bounds.size.height也会相应发生变化。
做个很简单的测试，代码如下：
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions { // Override point for customization after application launch. [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(orientationChanged:) name:UIDeviceOrientationDidChangeNotification object:nil]; return YES; } - (void)orientationChanged:(NSNotification*)noti { UIDeviceOrientation orientation = [UIDevice currentDevice].orientation; NSString *orientationDes = nil; switch (orientation) { case UIDeviceOrientationLandscapeLeft: orientationDes = @"UIInterfaceOrientationLandscapeRight"; break; case UIDeviceOrientationLandscapeRight: orientationDes = @"UIInterfaceOrientationLandscapeLeft"; break; case UIDeviceOrientationPortrait: orientationDes = @"UIInterfaceOrientationPortrait"; break; case UIDeviceOrientationPortraitUpsideDown: orientationDes = @"UIInterfaceOrientationPortraitUpsideDown"; break; default: orientationDes = @""; break; } NSLog(@"system ver: %@, \rorientaion: %@, \rwindow bounds: %@", [UIDevice currentDevice].systemVersion, orientationDes, NSStringFromCGRect(self.window.bounds)); }
示例代码很简单，新建一个工程，然后在delegate中直接添加以上代码即可。
iOS 8上运行结果为：
2014-06-04 09:26:32.016 SviOS8[4143:61114] system ver: 8.0, orientaion: UIInterfaceOrientationLandscapeRight, window bounds: {{0, 0}, {320, 480}} 2014-06-04 09:26:34.788 SviOS8[4143:61114] system ver: 8.0, orientaion: UIInterfaceOrientationPortrait, window bounds: {{0, 0}, {480, 320}} 2014-06-04 09:26:35.791 SviOS8[4143:61114] system ver: 8.0, orientaion: UIInterfaceOrientationLandscapeLeft, window bounds: {{0, 0}, {320, 480}} 2014-06-04 09:26:47.468 SviOS8[4143:61114] system ver: 8.0, orientaion: UIInterfaceOrientationPortraitUpsideDown, window bounds: {{0, 0}, {480, 320}}
iOS 7及之前的版本运行结果为：
2014-06-04 09:39:00.527 SviOS8[4380:70b] system ver: 7.0.3, orientaion: UIInterfaceOrientationLandscapeRight, window bounds: {{0, 0}, {320, 480}} 2014-06-04 09:39:00.895 SviOS8[4380:70b] system ver: 7.0.3, orientaion: UIInterfaceOrientationPortrait, window bounds: {{0, 0}, {320, 480}} 2014-06-04 09:39:01.225 SviOS8[4380:70b] system ver: 7.0.3, orientaion: UIInterfaceOrientationLandscapeLeft, window bounds: {{0, 0}, {320, 480}} 2014-06-04 09:39:11.004 SviOS8[4380:70b] system ver: 7.0.3, orientaion: UIInterfaceOrientationPortraitUpsideDown, window bounds: {{0, 0}, {320, 480}}
通过对比我们可以清晰的看到iOS 8中UIWindow在处理旋转时策略的变更，虽然会因为与之前的版本不同导致现有项目布局存在的bug，但是可以看到iOS 8中的处理方式更加符合我们的预期，在竖向的时候我们就获取到width < height, 在横向则是 width > height，这个符合所见即所得的原则。
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原文地址：http://www.cnblogs.com/allanliu/p/4183352.html
