UIWindow

Contents

1. 1. UIScreen、UIWindow、UIView三者之间的关系
2. 2. 从main.m开始
3. 3. 然后就会执行Appdelegate实例的回调方法，告诉我们UIApplication已经创建完毕
4. 4. 图示: UIApplication、AppDelegate、UIWindow、UIViewController之间的关系
5. 5. UIWindowLevel是系统规定出的window的三个级别
6. 6. UIWindow状态发生变化时，发出如下对应的系统通知
7. 7. 获取window的几种方法
8. 8. UIApplication实例，添加多个UIWindow，并作为keyWindow
9. 9. winodw.hide = NO也是可以显示window，完成将window添加到application
10. 10. -[UIView window]获取的window不一定是keyWindow，而是view当前所在window
11. 11. 查找当前App程序中的主事件keyWindow的代码
12. 12. 获取当前显示的UIViewController
13. 13. 最上层的UIWindow是: UITextEffectsWindow
14. 14. 最终显示UI的容器是UIWindow
15. 15. 将一个View插入到一个superView上如下四种方法

UIScreen、UIWindow、UIView三者之间的关系

• (1) UIScreen为硬件设备的屏幕抽象，其中一个属性是整个屏幕区域bounds

• (2) UIWindow为内容显示提供背景平台，一个App程序必须至少要有一个UIWindow，否则不会显示任何的东西

NS_CLASS_AVAILABLE_IOS(2_0) @interface UIWindow : UIView

.....

@end

可以看到UIWindow继承自UIView，所以可以将其看做成一个UI控件使用即可。

window1 = [[UIWindow alloc] init];
window1.backgroundColor = [UIColor redColor];
window1.rootViewController = [[UIViewController alloc] init];
window1.frame = CGRectMake(20, 70, 200, 200);
window1.hidden = NO;    //或者 [window1 makeKeyAndVisible];
[window1 addSubview:[UIView new]];

• (3) UIView负责绝大部分的内容描画，并负责响应用户的交互、管理子视图，最终被添加到UIWindow上进行显示

通常我们在一个-[UIViewController.view addSubviews:]添加很多UIView对象时，其实最终会自动被添加到所在的keyWindow上进行显示.

- UIScreen 屏幕对象 选取一个window进行显示，并作为主事件keyWindow
- UIWindow for `状态栏`
- root view controller
- subview 1
- subview 2
- .....
- UIWindow for `键盘输入`
- root view controller
- subview 1
- subview 2
- .....
- UIWindow for `Alert弹框`
- root view controller
- subview 1
- subview 2
- .....
- UIWindow for `我们自己创建的各种Window`
- root view controller
- subview 1
- subview 2
- .....

从main.m开始

int main(int argc, char * argv[]) {
@autoreleasepool {
return UIApplicationMain(argc, argv, nil, NSStringFromClass([AppDelegate class]));
}
}

• 完成创建UIApplication对象，来表示一个App程序运行
• 创建UIApplicationDelegate对象，作为UIApplication对象状态改变时回调的对象
• 创建Main NSRunLopp，负责整个App进程的事件接收

---

然后就会执行Appdelegate实例的回调方法，告诉我们UIApplication已经创建完毕

如下是一个AppDelegate如何完成UIWindow、RootViewController的步骤demo

@implementation AppDelegate

#pragma mark - UIApplicationDelegate 实现方法

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

//1. UIApplication实例创建完毕
NSLog(@"application = %@\n", application);

//2. 创建一个UIWdinwo实例
UIWindow *window = [[UIWindow alloc] initWithFrame:[UIScreen mainScreen].bounds];
NSLog(@"windowLevel = %lf\n", window.windowLevel);

//3. 将创建出来的Window实例，设置为UIApplication实例的window
//其实这里是通过设置给AppDelegate完成
self.window = window;

//4. 虽然给AppDelegate添加了一个window，完成间接给UIApplication添加了一个window
//但是UIApplication仍然没有一个keyWindow，也就是可见的window
NSLog(@"appdelegate.keyWindow = %@\n", application.keyWindow);

//5. 那么让添加到UIApplication的window，成为可见的窗口
[self.window setWindowLevel:3000.0];
[self.window makeKeyAndVisible];

//6. 设置keyWindow的背景色
self.window.backgroundColor = [UIColor whiteColor];

//7. 再看UIApplication是否有keyWindow
NSLog(@"appdelegate.keyWindow = %@\n", application.keyWindow);

//8. 再看keyWindow的level
NSLog(@"windowLevel = %lf\n", self.window.windowLevel);

//9. 设置keyWindow的rootViewController
UIViewController *vc = [[UIViewController alloc] init];
self.window.rootViewController = vc;

return YES;
}

//....

@end

打印结果

2015-09-04 21:33:10.271 UICodes[17470:269909] application = <UIApplication: 0x7f95b9c04550>
2015-09-04 21:33:10.285 UICodes[17470:269909] windowLevel = 0.000000
2016-09-04 21:33:10.285 UICodes[17470:269909] appdelegate.keyWindow = (null)
2015-09-04 21:33:10.287 UICodes[17470:269909] appdelegate.keyWindow = <UIWindow: 0x7f95b9e38630; frame = (0 0; 375 667); gestureRecognizers = <NSArray: 0x7f95b9d19410>; layer = <UIWindowLayer: 0x7f95b9e1c740>>
2015-09-04 21:33:10.287 UICodes[17470:269909] windowLevel = 3000.000000

对如上代码总结

• 1、最终显示元素，依赖一个keyWindow

• 2、让一个normalWindow可见，必须执行-[UIWindow makeKeyAndVisible]（错误的）

这样既让window可见，但是又称为了keyWindow，但是有时候可能只需要让window显示而已:

_myWindow = [[UIWindow alloc] initWithFrame:CGRectMake(20, 80, 100, 100)];
_myWindow.backgroundColor = [UIColor redColor];

//让其显示
_myWindow.hidden = NO;

• 3、keyWindow.level = normalWindow.level = 0.0

• 4、UIWindow实例，是通过我们设置给AppDelegate单例，达到间接的设置给UIApplication实例

• 5、UIApplication会读取AppDelegate实例的window属性指向的UIWindow实例

---

图示: UIApplication、AppDelegate、UIWindow、UIViewController之间的关系

---

UIWindowLevel是系统规定出的window的三个级别

• (1) Normal = 0

UIKIT_EXTERN const UIWindowLevel UIWindowLevelNormal;

• (2) StatusBar = 1000

UIKIT_EXTERN const UIWindowLevel UIWindowLevelStatusBar;

• (3) Alert = 2000

UIKIT_EXTERN const UIWindowLevel UIWindowLevelAlert;

从上面三个值可以看出，三个级别的大小

Alert > StatusBar > Normal

而UIApplication实例，是根据-[UIWindow windowLevel]值的大小来排序显示，值越大就显示在越靠上面

我们还可以任意指定一个window的level

[window setWindowLevel:9999.0];

---

UIWindow状态发生变化时，发出如下对应的系统通知

//成为可见
UIKIT_EXTERN NSString *const UIWindowDidBecomeVisibleNotification; // nil

//成为隐藏
UIKIT_EXTERN NSString *const UIWindowDidBecomeHiddenNotification;  // nil

//成为主事件窗口
UIKIT_EXTERN NSString *const UIWindowDidBecomeKeyNotification;     // nil

//失去成为主事件窗口
UIKIT_EXTERN NSString *const UIWindowDidResignKeyNotification;     // nil

---

获取window的几种方法

主要获取window的方式

• (1) [UIApplication sharedApplication].keyWindow
• (2) [UIApplication sharedApplication].windows
• (3) [UIApplication sharedApplication].delegate.window

[UIApplication sharedApplication].keyWindow >>>>>> 国家主席

• 记录当前App程序唯一的一个能够接收事件的主窗口
• 记录的窗口是App程序的所有子窗口中，最牛逼的一个主事件窗口
• iOS并没有提供一种叫做keyWindow的api类，所以window创建的时候，都是一样的
• 而是在App程序内所有的window中选出一个window，作为App程序的的keyWindow
• 注意，避免直接使用[UIApplication sharedApplication].keyWindow，因为很有可能是系统的window，而不是我们自己的window
• Status Bar Window
• UItextFiled Keyboard Window
• Alert Window
• …..等等系统window

[UIApplication sharedApplication].windows >>>>>> 候选者

• 记录了App程序的所有的候选window
• 一旦某个UIView实例所在的windiw被系统推选为keyWindow，那么就成功竞选成国家主席
• 任何UIWindow不是一开始就是keyWindow，最开始都是normalWindow。只是某一个Window内部UIView实例触发事件时，然后系统将这个window提升为主事件keyWindow。

[UIApplication sharedApplication].delegate.window >>> App程序创建时创建的root window

• 获取的永远都是单例window，并且是App程序的主window

---

UIApplication实例，添加多个UIWindow，并作为keyWindow

static UIWindow *window1;
static UIWindow *window2;
static UIWindow *window3;

@implementation AppDelegate

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
//主Window
UIWindow *window = [[UIWindow alloc] initWithFrame:[UIScreen mainScreen].bounds];
self.window = window;
self.window.backgroundColor = [UIColor grayColor];
HomePage_RootViewController *vc = [[HomePage_RootViewController alloc] init];
vc.title = @"HomePage";
UINavigationController *nav = [[UINavigationController alloc] initWithRootViewController:vc];
self.window.rootViewController = nav;
[self.window makeKeyAndVisible];

//window1
window1 = [[UIWindow alloc] init];
window1.backgroundColor = [UIColor redColor];
window1.rootViewController = [[UIViewController alloc] init];
window1.origin = CGPointMake(5, 70);
window1.width = 180;
window1.height = 180;
[window1 makeKeyAndVisible];

//window2
window2 = [[UIWindow alloc] init];
window2.backgroundColor = [UIColor blueColor];
window2.rootViewController = [[UIViewController alloc] init];
window2.origin = CGPointMake(50, 180);
window2.width = 180;
window2.height = 180;
[window2 makeKeyAndVisible];

//window3
window3 = [[UIWindow alloc] init];
window3.backgroundColor = [UIColor yellowColor];
window3.rootViewController = [[UIViewController alloc] init];
window3.origin = CGPointMake(100, 100);
window3.width = 180;
window3.height = 180;
[window3 makeKeyAndVisible];

return YES;
}

可以看到，越晚执行makeKeyAndVisible方法出现在最上面显示，但实际上是因为window对象被创建的顺序，也就是添加到UIApplication对象的顺序。

上面代码中我们并没使用-[UIApplication addWindow:]这样类似的代码，就只是创建了UIWindow对象，然后执行-[UIWindow makeKeyAndVisible]就显示出来了。也就是说-[UIWindow makeKeyAndVisible]就相当于-[UIApplication addWindo w:]。那么最晚执行addWindow:的自然就在最上面。

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
//主Window
self.window = [[UIWindow alloc] initWithFrame:[UIScreen mainScreen].bounds];
self.window.backgroundColor = [UIColor grayColor];
UIViewController *vc = [[UIViewController alloc] init];
vc.title = @"HomePage";
UINavigationController *nav = [[UINavigationController alloc] initWithRootViewController:vc];
self.window.rootViewController = nav;
[self.window makeKeyAndVisible];

//window1 redColor
window1 = [[UIWindow alloc] init];
window1.backgroundColor = [UIColor redColor];
window1.rootViewController = [[UIViewController alloc] init];
window1.frame = CGRectMake(20, 70, 200, 200);

//window2 blueColor
window2 = [[UIWindow alloc] init];
window2.backgroundColor = [UIColor blueColor];
window2.rootViewController = [[UIViewController alloc] init];
window2.frame = CGRectMake(100, 100, 200, 200);

//window3 yellowColor
window3 = [[UIWindow alloc] init];
window3.backgroundColor = [UIColor yellowColor];
window3.rootViewController = [[UIViewController alloc] init];
window3.frame = CGRectMake(80, 200, 200, 200);

// 改变添加window的顺序
[window3 makeKeyAndVisible];
[window2 makeKeyAndVisible];
[window1 makeKeyAndVisible];

// 打印windows
NSLog(@"application.windows = %@", [UIApplication sharedApplication].windows);
NSLog(@"application.keyWindow = %@", [UIApplication sharedApplication].keyWindow);

return YES;
}

最晚执行makeKeyAndVisible的红色window，显示在最上面。

---

winodw.hide = NO也是可以显示window，完成将window添加到application

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
//主Window
self.window = [[UIWindow alloc] initWithFrame:[UIScreen mainScreen].bounds];
self.window.backgroundColor = [UIColor grayColor];
UIViewController *vc = [[UIViewController alloc] init];
vc.title = @"HomePage";
UINavigationController *nav = [[UINavigationController alloc] initWithRootViewController:vc];
self.window.rootViewController = nav;
[self.window makeKeyAndVisible];

//window1 redColor
window1 = [[UIWindow alloc] init];
window1.backgroundColor = [UIColor redColor];
window1.rootViewController = [[UIViewController alloc] init];
window1.frame = CGRectMake(20, 70, 200, 200);

//window2 blueColor
window2 = [[UIWindow alloc] init];
window2.backgroundColor = [UIColor blueColor];
window2.rootViewController = [[UIViewController alloc] init];
window2.frame = CGRectMake(100, 100, 200, 200);

//window3 yellowColor
window3 = [[UIWindow alloc] init];
window3.backgroundColor = [UIColor yellowColor];
window3.rootViewController = [[UIViewController alloc] init];
window3.frame = CGRectMake(80, 200, 200, 200);

//    [window3 makeKeyAndVisible];
//    [window2 makeKeyAndVisible];
//    [window1 makeKeyAndVisible];

//    window3.hidden = NO;
//    window2.hidden = NO;
//    window1.hidden = NO;

window1.hidden = NO;
window2.hidden = NO;
window3.hidden = NO;

// 打印windows
NSLog(@"application.windows = %@", [UIApplication sharedApplication].windows);
NSLog(@"application.keyWindow = %@", [UIApplication sharedApplication].keyWindow);

return YES;
}

可以看到和之前makeKeyAndVisble的效果一样的，但是并不是keyWindow。

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
//主Window
self.window = [[UIWindow alloc] initWithFrame:[UIScreen mainScreen].bounds];
self.window.backgroundColor = [UIColor grayColor];
UIViewController *vc = [[UIViewController alloc] init];
vc.title = @"HomePage";
UINavigationController *nav = [[UINavigationController alloc] initWithRootViewController:vc];
self.window.rootViewController = nav;
[self.window makeKeyAndVisible];

//window1 redColor
window1 = [[UIWindow alloc] init];
window1.backgroundColor = [UIColor redColor];
window1.rootViewController = [[UIViewController alloc] init];
window1.frame = CGRectMake(20, 70, 200, 200);

//window2 blueColor
window2 = [[UIWindow alloc] init];
window2.backgroundColor = [UIColor blueColor];
window2.rootViewController = [[UIViewController alloc] init];
window2.frame = CGRectMake(100, 100, 200, 200);

//window3 yellowColor
window3 = [[UIWindow alloc] init];
window3.backgroundColor = [UIColor yellowColor];
window3.rootViewController = [[UIViewController alloc] init];
window3.frame = CGRectMake(80, 200, 200, 200);

//    [window3 makeKeyAndVisible];
//    [window2 makeKeyAndVisible];
//    [window1 makeKeyAndVisible];

window3.hidden = NO;
window2.hidden = NO;
window1.hidden = NO;

//    window1.hidden = NO;
//    window2.hidden = NO;
//    window3.hidden = NO;

// 打印windows
NSLog(@"application.windows = %@", [UIApplication sharedApplication].windows);
NSLog(@"application.keyWindow = %@", [UIApplication sharedApplication].keyWindow);

return YES;
}

---

-[UIView window]获取的window不一定是keyWindow，而是view当前所在window

• 当前UIView实例所在window，如果刚好是keyWindow，那么调用次方返回的就是keyWindow

• 如果UIView实例是键盘View的某一个subview，那么通过view.window返回的就是键盘的window，而并非keyWindow

查找当前App程序中的主事件keyWindow的代码

@interface UIWindow (Tools)

+ (UIWindow *)findKeyWindow {

//逆序遍历 当前应用程序的`所有的UIWindow实例`，然后依次找出keyWindow
NSEnumerator *frontToBackWindows = [UIApplication.sharedApplication.windows reverseObjectEnumerator];

//记录找到的keyWindow实例
UIWindow *keyWindow = nil;

//遍历当前App所有的UIWindow对象
for (UIWindow *window in frontToBackWindows){

//条件1. 是否处于当前主屏幕
BOOL windowOnMainScreen = window.screen == UIScreen.mainScreen;

//条件2. 屏幕是否可见
BOOL windowIsVisible = !window.hidden && window.alpha > 0;

//条件3. 屏幕的优先级为normal（排除AlertView所在的Window、排除StatusBar所在的Window）
BOOL windowLevelNormal = window.windowLevel == UIWindowLevelNormal;

/*
Window有三个优先级

排序: Normal < StatusBar < Alert

1. Level层级相同的时候，只有第一个设置为KeyWindow的显示出来 [window makeKeyAndVisible]
2. Level层级不相同的时候，最高Level的始终显示在最前面

UIKIT_EXTERN const UIWindowLevel UIWindowLevelNormal;
UIKIT_EXTERN const UIWindowLevel UIWindowLevelAlert;
UIKIT_EXTERN const UIWindowLevel UIWindowLevelStatusBar;
*/

//找到正常显示的Window
if (windowOnMainScreen && windowIsVisible && windowLevelNormal) {
keyWindow = window;
break;
}
}

return keyWindow;
}

@end

获取当前显示的UIViewController

• 第一步、找到找到接收事件的主窗口 – keyWindow
• 第二步、获取keyWindow 的 rootVIewController

- (UIViewController *)getCurrentVC  
{  
UIViewController *result = nil;  

//第一步、找到接收事件的主窗口
UIWindow * window = [[UIApplication sharedApplication] keyWindow];  

if (window.windowLevel != UIWindowLevelNormal)  
{  
NSArray *windows = [[UIApplication sharedApplication] windows];  

for(UIWindow * tmpWin in windows)  
{  
if (tmpWin.windowLevel == UIWindowLevelNormal)  
{  
window = tmpWin;  
break;  
}  
}  
}  

//第二步、 根据主事件窗口内的subview，找到当前屏幕出现的控制器对象

//1. 取出window上所有subviews中的`最上面`的一个subview   
UIView *frontView = [[window subviews] objectAtIndex:0];  

//2. subview是否有下一个事件处理对象
id nextResponder = [frontView nextResponder];  

//3. 根据有没有下一个事件处理对象，来判断返回哪一个viewController
if ([nextResponder isKindOfClass:[UIViewController class]]) {

//3.1 找到了subview的事件处理对象UIViewController，将找到的这个控制器对象返回
result = nextResponder;  

} else {

//3.2 未找到susbview的事件处理对象，那么将window.rootViewController作为找到的控制器对象返回
result = window.rootViewController;  
}

return result;  
}

---

最上层的UIWindow是: UITextEffectsWindow

id window = [[UIApplication sharedApplication].windows lastObject];

---

最终显示UI的容器是UIWindow

• 系统将UIViewController实例内部的UIView实例及所有subviews，全部复制到当前接收时间的keyWindow上进行显示

• 举例: UITableViewController、UINavigationController如何显示在UIWindow的

• UINavigationController实例的UIView提供
• 提供两个UI控件，并且添加到UITableView上
• 顶部导航栏 UINavigationBar
• 底部工具栏 UIToolBar
• 提供两个栈结构
• UIViewController实例栈

• UITabBarButtonItem实例栈

• UITableViewController

• 将内部的UITableView实例，添加到UIWindow实例上
• iOS7后，以window的左上角(0,0)为坐标系原点
• 如果将某些UI添加到UITableView上的最顶部，以(0,0)为坐标系原点

• 但是会随着UITableView滚动一起滚动

• 而UINavigationBar、UIToolBar、UITableView

• 最终都是添加到 UIViewController实例的UIView实例 中

• UITableViewController是继承自UIViewController，只是多了一个UITableView和实现了UITableViewDelegate和UITableViewDataSource的方法

• 最后负责显示所有UI控件的容器

• UIWindow实例
• 并且是keyWindow当前显示的、接收事件的主窗口
• 将UIViewController实例的UIView实例中的，所有的subviews，都复制添加到keyWindow进行显示、接收事件

---

将一个View插入到一个superView上如下四种方法

//1. 添加到最上面
addSubview:

//2. 添加到指定层次
insertSubview:atIndex:

//3. 将subview调整 或 添加 到最上面
insertSubview:aboveSubview:

//4. 将subview调整 或 添加 到最下面
insertSubview:belowSubview:

比如、将UILabel添加到导航栏控制器navigationBar的下面

- (void)setupTopLabel {

_label = [[UILabel alloc] init];
_label.font = [UIFont systemFontOfSize:17.f];
_label.backgroundColor = [UIColor redColor];

_label.originX = 0;
_label.width = [UIScreen mainScreen].bounds.size.width;
_label.height = 44;
_label.originY = 64 - _label.height;

//将UILabel添加到导航栏控制器navigationBar的下面
[self.navigationController.view insertSubview:_label belowSubview:self.navigationController.navigationBar];
}