iOS UIKit ：UIWindow

iOS UIKit ：UIWindow

UIQWindow定义了一个window对象来管理views。一个软件只能有一个window。window的主要职能使为view提供显示取和向view传递事件。想要改变软件显示的内容，你可以改变window的root view。

UIWindow的screen属性指定了window的显示属性包括： bounds, mode, and brightness.

window  notifications用来监听 window 和 screen的 改变，包括：

 UIWindowDidBecomeVisibleNotification
UIWindowDidBecomeHiddenNotification
UIWindowDidBecomeKeyNotification
UIWindowDidResignKeyNotification  

UIWindow继承自UIView，关于这一点可能有点逻辑障碍，画框怎么继承自画布呢？不要过于去专牛角尖，画框的形状不就是跟画布一样吗？拿一块画布然后用一些方法把它加强，是不是可以当一个画框用呢？这也是为什么 一个view可以直接加到另一个view上去的原因了。 一个应用程序只能有一个画框。

看一下系统的初始化过程（在application didFinishLauchingWithOptions里面）：

- (BOOL)application:(UIApplication *)application willFinishLaunchingWithOptions:(NSDictionary * )launchOptions {
   UIWindow  *window =  [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
   myViewController  =  [[MyViewController alloc] init];
   window.rootViewController  =  myViewController;
   [window makeKeyAndVisible];
     return   YES;
} 

创建一个 an external display：

- ( void  )checkForExistingScreenAndInitializeIfPresent
{
      if  ([[UIScreen screens] count] >  1  )
    {
          //   Get the screen object that represents the external display. 
        UIScreen *secondScreen = [[UIScreen screens] objectAtIndex: 1  ];
          //   Get the screen's bounds so that you can create a window of the correct size. 
        CGRect screenBounds =  secondScreen.bounds;
 
        self.secondWindow  =  [[UIWindow alloc] initWithFrame:screenBounds];
        self.secondWindow.screen  =  secondScreen;
 
          //   Set up initial content to display...
          //   Show the window. 
        self.secondWindow.hidden =  NO;
    }
}

 - ( void  )setUpScreenConnectionNotificationHandlers
{
    NSNotificationCenter  *center =  [NSNotificationCenter defaultCenter];
 
    [center addObserver:self selector:@selector(handleScreenDidConnectNotification:)
            name:UIScreenDidConnectNotification   object  :nil];
    [center addObserver:self selector:@selector(handleScreenDidDisconnectNotification:)
            name:UIScreenDidDisconnectNotification   object  :nil];
}

 - ( void )handleScreenDidConnectNotification:(NSNotification* )aNotification
{
    UIScreen  *newScreen = [aNotification  object  ];
    CGRect screenBounds  =  newScreen.bounds;
 
      if  (! self.secondWindow)
    {
        self.secondWindow  =  [[UIWindow alloc] initWithFrame:screenBounds];
        self.secondWindow.screen  =  newScreen;
 
          //   Set the initial UI for the window. 
     }
}
 
 - ( void )handleScreenDidDisconnectNotification:(NSNotification* )aNotification
{
      if   (self.secondWindow)
    {
          //   Hide and then delete the window. 
        self.secondWindow.hidden =  YES;
        self.secondWindow  =  nil;
 
    }
 
} 

 

 

 

分类:  iOS

标签:  iOSUIKit

作者： Leo_wl

　　　　

出处： http://www.cnblogs.com/Leo_wl/

　　　　

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