在實際開發中，遇到在UITextView的frame等於當前控制器的View的frame的情況下，然后運行的時候，發現控制器的Frame的高度y值會從導航條的位置64變化到0。
導致UITextView的frame也跟着一起移動。
這個問題本質其實就是iOS7View被導航欄遮擋問題，於是經過百度搜索到答案。特此下面 復制拷貝 做個簡單的筆記：
self.navigationController.navigationBar.translucent = NO;
如果在iPad上用了split view，並且設置了UINavigationBar的background image，現象為狀態欄一直是一片漆黑
UINavigationController will alter the height of its UINavigationBar to either 44 points or 64 points, depending on a rather strange and undocumented set of constraints. If the UINavigationController detects that the top of its view’s frame is visually contiguous with its UIWindow’s top, then it draws its navigation bar with a height of 64 points. If its view’s top is not contiguous with the UIWindow’s top (even if off by only one point), then it draws its navigation bar in the “traditional” way with a height of 44 points. This logic is performed by UINavigationController even if it is several children down inside the view controller hierarchy of your application. There is no way to prevent this behavior.
意思就是UINavigationBar的高度會自行調整為44或者64，沒有確定的預測方法。而之前作為UINavigationBar背景的圖片是44高度的。最后換了張64高度，上面留了20px透明的圖片搞定
網友還有一種解決辦法
IOS7的視圖有個邊緣延伸的屬性：edgesForExtendedLayout，
其默認值是UIExtendedEdgeAll。
只要將其改成UIExtendedEdgeNone即可，要注意的是在IOS7以下版本會出現bug。
所以在UIViewController 的viewDidLoad里加上下面代碼就完美解決了這個問題
if( ([[[UIDevice currentDevice] systemVersion] doubleValue]>=7.0)) {
self.edgesForExtendedLayout = UIRectEdgeNone;
self.extendedLayoutIncludesOpaqueBars = NO;
self.modalPresentationCapturesStatusBarAppearance = NO;
}