UIWindow

UIWindow.h文件
    1、    IOS  
/Applications//Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS6.1.sdk/System/Library/Frameworks/UIKit.framework/Headers/UIWindow.h
/Applications//Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator6.1.sdk/System/Library/Frameworks/UIKit.framework/Headers/UIWindow.h

一、UIWindow介绍

[1]、UIWindow是一种特殊的UIView（视图集合中的根view），每个UIWindow都有一个窗口等级（windowlevel）,通常在一个程序中只会有一个UIWindow，可以手动创建多个UIWindow。UIWindow在程序中主要起到三个作用：

　　1、作为容器，包含app显示的所有视图
　　2、传递触摸消息到程序中view和其他对象
　　3、与UIViewController协同工作，方便完成设备方向旋转的支持


[2]、通常我们可以采取两种方法将view添加到UIWindow中：

　　1、addSubview
　　直接将view通过addSubview方式添加到window中，程序负责维护view的生命周期以及刷新，但是并不会为去理会view对应的ViewController，因此采用这种方法将view添加到window以后，我们还要保持view对应的ViewController的有效性，不能过早释放。

　　2、rootViewController
　　rootViewController是UIWindow的一个遍历方法，通过设置该属性为要添加view对应的ViewController，UIWindow将会自动将其view添加到当前window中，同时负责ViewController和view的生命周期的维护，防止其过早释放。


       3、keyWindow ： BOOL 类型，只读，用于判断是否是当前应用的 key window (key window 是指可接收到键盘输入及其他非触摸事件的 UIWindow，一次只能有一个 key window)

       4、windowLevel ：UIWindowLevel 类型，多个 UIWindow 的显示顺序是按照 windowLevel 从高到低排列的，windowLevel 最高的显示在最前面。比如：windowLevel 较高的 UIAlertView 警告窗口会显示在一般窗口的前面。UIWindowLevel 类型的定义如下：


typedef CGFloat UIWindowLevel;
UIKIT_EXTERN const UIWindowLevel UIWindowLevelNormal; //默认等级
UIKIT_EXTERN const UIWindowLevel UIWindowLevelAlert; //UIAlert等级
UIKIT_EXTERN const UIWindowLevel UIWindowLevelStatsBar; //状态栏等级


打印结果如下：
NSLog(@"%f", UIWindowLevelNormal);
NSLog(@"%f", UIWindowLevelAlert);
NSLog(@"%f", UIWindowLevelStatusBar);
2013-03-16 10:00:48.925 iosDemo[1033:11303] 0.000000
2013-03-16 10:00:48.927 iosDemo[1033:11303] 2000.000000
2013-03-16 10:00:48.927 iosDemo[1033:11303] 1000.000000


5、makeKeyWindow ：将当前 UIWindow 设置成应用的 key window。


6、makeKeyAndVisible ：将当前 UIWindow 设置成应用的 key window，并使得 UIWindow 可见；也可以使用 UIView 的 hidden 属性来显示或者隐藏一个 UIWindow。

1、- (void)becomeKeyWindow;                               // override point for subclass. Do not call directly 调用窗口，使之变成关键窗口
2、- (void)resignKeyWindow;                               // override point for subclass. Do not call directly  调用窗口，使之取消关键窗口
3、- (void)makeKeyWindow;   使之成为主窗口 
4、- (void)makeKeyAndVisible;                             // convenience. most apps call this to show the main window and also make it key. otherwise use view hidden property 使之成为主窗口，并且显示
5、- (void)sendEvent:(UIEvent *)event;                    // called by UIApplication to dispatch events to views inside the window 事件拦截分发到指定视图对象

当用户发起一个事件，比如触摸屏幕或者晃动设备，系统产生一个事件，同时投递给UIApplication，而UIApplication则将这个事件传递给特定的UIWindow进行处理(正常情况都一个程序都只有一个UIWindow)，然后由UIWindow将这个事件传递给特定的对象(即first responder)并通过响应链进行处理。虽然都是通过响应链对事件进行处理，但是触摸事件和运动事件在处理上有着明显的不同(主要体现在确定哪个对象才是他们的first responder)：

 窗口坐标系统转化

6、- (CGPoint)convertPoint:(CGPoint)point toWindow:(UIWindow *)window;    // can be used to convert to another window 转化当前窗口一个坐标相对另外一个窗口的坐标
7、- (CGPoint)convertPoint:(CGPoint)point fromWindow:(UIWindow *)window;  // pass in nil to mean screen  转化另外窗口一个坐标相对于当前窗口的坐标
8、- (CGRect)convertRect:(CGRect)rect toWindow:(UIWindow *)window;   转化当前窗口一个矩形坐标相对另外一个窗口的坐标
9、- (CGRect)convertRect:(CGRect)rect fromWindow:(UIWindow *)window; 转化另外窗口一个矩形坐标相对于当前窗口的坐标

二 、UIWindow.h分析

//  UIWindow.h
//  UIKit
//
//  Copyright (c) 2005-2012, Apple Inc. All rights reserved.
//


#import <Foundation/Foundation.h>基础框架入口
#import <CoreGraphics/CoreGraphics.h>绘图入口
#import <UIKit/UIView.h>视图对象
#import <UIKit/UIApplication.h>提供IOS程序运行期的协作和控制
#import <UIKit/UIKitDefines.h>一些宏定义


typedef CGFloat UIWindowLevel; 32位则为float | 64位为double


@class UIEvent, UIScreen, NSUndoManager, UIViewController; //UIEvent 触摸事件，运动事件
//UIScreen 屏幕处理
//NSUndoManager  记录撤销，修改操作的消息//UIViewController 视图控制器
NS_CLASS_AVAILABLE_IOS(2_0) @interface UIWindow : UIView {
  @package
    id                       _delegate;
    CGFloat                  _windowLevel;
    CGFloat                  _windowSublevel;
    id                       _layerContext;
    UIView                  *_lastMouseDownView;
    UIView                  *_lastMouseEnteredView;
    UIResponder             *_firstResponder;
    id                       _fingerInfo;
    id                       _touchData;
    UIInterfaceOrientation   _viewOrientation;
    UIView                  *_exclusiveTouchView;
    NSUndoManager           *_undoManager;
    UIScreen                *_screen;
    CALayer                 *_transformLayer;
    NSMutableArray          *_rotationViewControllers;
    UIViewController        *_rootViewController;
    UIColor                 *_savedBackgroundColor;
    NSMutableSet            *_subtreeMonitoringViews;
    NSMutableSet            *_tintViews;
    id                      _currentTintView;
    struct {
unsigned int delegateWillRotate:1;
        unsigned int delegateDidRotate:1;
        unsigned int delegateWillAnimateFirstHalf:1;
        unsigned int delegateDidAnimationFirstHalf:1;
        unsigned int delegateWillAnimateSecondHalf:1;
        unsigned int autorotatesToPortrait:1;
        unsigned int autorotatesToPortraitUpsideDown:1;
        unsigned int autorotatesToLandscapeLeft:1;
        unsigned int autorotatesToLandscapeRight:1;
        unsigned int dontBecomeKeyOnOrderFront:1;
        unsigned int output:1;
        unsigned int inGesture:1;
        unsigned int bitsPerComponent:4;
        unsigned int autorotates:1;
        unsigned int isRotating:1;
        unsigned int isUsingOnePartRotationAnimation:1;
        unsigned int isHandlingContentRotation:1;
        unsigned int disableAutorotationCount:4;
        unsigned int needsAutorotationWhenReenabled:1;
        unsigned int forceTwoPartRotationAnimation:1;
        unsigned int orderKeyboardInAfterRotating:1;
        unsigned int roundedCorners:4;
        unsigned int resizesToFullScreen:1;
        unsigned int keepContextInBackground:1;
        unsigned int ignoreSetHidden:1;
        unsigned int forceVisibleOnInit:1;
        unsigned int settingFirstResponder:1;
        unsigned int legacyOrientationChecks:1;
        unsigned int windowResizedToFullScreen:1;
    } _windowFlags;

    id _windowController;
}


@property(nonatomic,retain) UIScreen *screen NS_AVAILABLE_IOS(3_2);  // default is [UIScreen mainScreen]. changing the screen may be an expensive operation and should not be done in performance-sensitive code


@property(nonatomic) UIWindowLevel windowLevel;                   // default = 0.0
@property(nonatomic,readonly,getter=isKeyWindow) BOOL keyWindow;
- (void)becomeKeyWindow;                               // override point for subclass. Do not call directly 调用窗口，使之变成关键窗口
- (void)resignKeyWindow;                               // override point for subclass. Do not call directly 调用窗口，使之取消关键窗口


- (void)makeKeyWindow;     使之成为主窗口
- (void)makeKeyAndVisible;                             // convenience. most apps call this to show the main window and also make it key. otherwise use view hidden property 使之成为主窗口，并且显示


@property(nonatomic,retain) UIViewController *rootViewController NS_AVAILABLE_IOS(4_0);  // default is nil 


- (void)sendEvent:(UIEvent *)event;                    // called by UIApplication to dispatch events to views inside the window 事件拦截分发到指定视图对象
当用户发起一个事件，比如触摸屏幕或者晃动设备，系统产生一个事件，同时投递给UIApplication，而UIApplication则将这个事件传递给特定的UIWindow进行处理(正常情况都一个程序都只有一个UIWindow)，然后由UIWindow将这个事件传递给
特定的对象(即first responder)
并通过响应链进行处理。虽然都是通过响应链对事件进行处理，但是触摸事件和运动事件在处理上有着明显的不同(主要体现在确定哪个对象才是他们的first responder)：


窗口坐标系统转化

- (CGPoint)convertPoint:(CGPoint)point toWindow:(UIWindow *)window;    // can be used to convert to another window 转化一个坐标到另外窗口
- (CGPoint)convertPoint:(CGPoint)point fromWindow:(UIWindow *)window;  // pass in nil to mean screen 转化一个坐标从另外窗口
- (CGRect)convertRect:(CGRect)rect toWindow:(UIWindow *)window; 转化一个矩形到另外窗口
- (CGRect)convertRect:(CGRect)rect fromWindow:(UIWindow *)window; 转化一个矩形从另外窗口


@end


UIKIT_EXTERN const UIWindowLevel UIWindowLevelNormal; 默认等级
UIKIT_EXTERN const UIWindowLevel UIWindowLevelAlert; UIAlert等级
UIKIT_EXTERN const UIWindowLevel UIWindowLevelStatusBar; 状态栏等级


UIKIT_EXTERN NSString *const UIWindowDidBecomeVisibleNotification; // nil 通知对象窗口为可见
UIKIT_EXTERN NSString *const UIWindowDidBecomeHiddenNotification;  // nil通知对象窗口为隐藏
UIKIT_EXTERN NSString *const UIWindowDidBecomeKeyNotification;     // nil 通知对象窗口为重要
UIKIT_EXTERN NSString *const UIWindowDidResignKeyNotification;     // nil  通知对象窗口取消主窗口状态


// Each notification includes a nil object and a userInfo dictionary containing the
// begining and ending keyboard frame in screen coordinates. Use the various UIView and
// UIWindow convertRect facilities to get the frame in the desired coordinate system.
// Animation key/value pairs are only available for the "will" family of notification.
UIKIT_EXTERN NSString *const UIKeyboardWillShowNotification;通知键盘对象视图即将加载
UIKIT_EXTERN NSString *const UIKeyboardDidShowNotification; 通知键盘对象视图完全加载
UIKIT_EXTERN NSString *const UIKeyboardWillHideNotification;  通知键盘对象视图即将隐藏
UIKIT_EXTERN NSString *const UIKeyboardDidHideNotification;  通知键盘对象视图完全隐藏


UIKIT_EXTERN NSString *const UIKeyboardFrameBeginUserInfoKey        NS_AVAILABLE_IOS(3_2); // NSValue of CGRect 指明键盘动画之前的框架，键盘将要显示时，显示之前把框架传递给这个动画;键盘已经显示即将隐藏时，键盘消失之前将这个框架传递给一个隐藏动画。包含一个CGRct类型值。
UIKIT_EXTERN NSString *const UIKeyboardFrameEndUserInfoKey          NS_AVAILABLE_IOS(3_2); // NSValue of CGRect 指明动画完成后的键盘框架，键盘将要显示时，键盘完全显示后把框架传递给键盘;键盘已经显示即将隐藏时，键盘隐藏后将这个框架传递给一个键盘。包含一个CGRct类型值。
UIKIT_EXTERN NSString *const UIKeyboardAnimationDurationUserInfoKey NS_AVAILABLE_IOS(3_0); // NSNumber of double 指明键盘显示和隐藏动画所用时间，包好一个NSNumber类型值（double）
UIKIT_EXTERN NSString *const UIKeyboardAnimationCurveUserInfoKey    NS_AVAILABLE_IOS(3_0); // NSNumber of NSUInteger (UIViewAnimationCurve)指明动画类型，用来显示和隐藏键盘，包含了一个NSnumber类型值（NSUInteger）


// Like the standard keyboard notifications above, these additional notifications include
// a nil object and begin/end frames of the keyboard in screen coordinates in the userInfo dictionary.
UIKIT_EXTERN NSString *const UIKeyboardWillChangeFrameNotification  NS_AVAILABLE_IOS(5_0);键盘即将改变布局发出通知
UIKIT_EXTERN NSString *const UIKeyboardDidChangeFrameNotification   NS_AVAILABLE_IOS(5_0);键盘已经改变布局后发出通知


// These keys are superseded by UIKeyboardFrameBeginUserInfoKey and UIKeyboardFrameEndUserInfoKey.
UIKIT_EXTERN NSString *const UIKeyboardCenterBeginUserInfoKey   NS_DEPRECATED_IOS(2_0, 3_2); 键盘开始动画之前的起始坐标
UIKIT_EXTERN NSString *const UIKeyboardCenterEndUserInfoKey     NS_DEPRECATED_IOS(2_0, 3_2); 键盘动画后的坐标
UIKIT_EXTERN NSString *const UIKeyboardBoundsUserInfoKey        NS_DEPRECATED_IOS(2_0, 3_2); 包含的矩形只能用于取得尺寸信息