小编Mic*_*chi的帖子

自从在iOS 8上测试我的应用程序以来,我发现一个关于视图控制器初始化和演示的工作真的很慢.

我曾经在iOS 6和7上使用类似的代码:

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    ....

    [self.window setRootViewController:_rootController];
    [self.window makeKeyAndVisible];

    // Conditions

    if (#first launch condition#) {
        // quite small controller containing Welcome showcase
        WelcomeViewController *w = ....
        [_rootViewController presentViewController:w animated:NO];
    }

    else if (#last opened item condition#) {
        // pretty big container, root view controller contains
        // a grid view which opens Item detail container the same way
        ItemDetailController *item = ....
        [_rootViewController presentViewController:item animated:NO];
    }

}

在iOS 8中,这变成了一个非常缓慢的地狱.根视图控制器现在可以看到0.5-1秒,然后立即重新绘制屏幕.此外,演示文稿的缓慢开始引起Unbalanced calls to begin/end appearance …

我使用上下文UIWindow在我的应用程序中切换key ，以提供更简洁的流程-欢迎窗口=>具有项目列表的主屏幕<=>带有汉堡菜单和物品的项目容器。

函数示例如下：

- (void)updateKeyWindow:(UIWindow *)window withTransition:(WindowTransition)transition
{
    UIWindow *originalWindow = _keyWindow;
    _keyWindow = window;

    window.alpha = 0;
    [originalWindow resignKeyWindow];
    [originalWindow resignFirstResponder];
    originalWindow.userInteractionEnabled = NO;
    [window makeKeyAndVisible];
    window.transform = (transition == WindowTransitionFlyDown) ? CGAffineTransformMakeScale(1.02, 1.02) :
                       (transition == WindowTransitionFlyUp)   ? CGAffineTransformMakeScale(.96, .96) :
                                                                 CGAffineTransformIdentity;

//  [UIView animateWithDuration:.24 animations:^{

        window.alpha = 1;
        originalWindow.alpha = 0;
        window.transform = CGAffineTransformIdentity;
        originalWindow.transform = (transition == WindowTransitionFlyDown) ? CGAffineTransformMakeScale(.96, .96) :
                                   (transition == WindowTransitionFlyUp)   ? CGAffineTransformMakeScale(1.02, 1.02) :
                                                                             CGAffineTransformIdentity;

//  } completion:^(BOOL b){ …