UIApplication

• 是一個應(yīng)用界別的單例對象，獲取此單例對象的方法是

UIapplication *app = [UIApplication shareApplication];

• 一般涌來做一些應(yīng)用界別的操作：app的提醒狂辛润，聯(lián)網(wǎng)狀態(tài)，打開網(wǎng)頁，控制狀態(tài)欄外永。（大多為對象方法）

• 查找設(shè)置一些功能找方法，進(jìn)行一些事件找代理

UIApplation 的delegate

• AppDelegate.m

// 學(xué)習(xí)代理方法拧咳，只需要知道這個什么時候調(diào)用伯顶，這個方法可以用來干嘛
// 程序啟動完成的時候調(diào)用
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
// Override point for customization after application launch.
NSLog(@"%s",__func__);
return YES;
}
// 當(dāng)app失去焦點(diǎn)的時候調(diào)用
- (void)applicationWillResignActive:(UIApplication *)application {
NSLog(@"%s",__func__);
// Sent when the application is about to move from active to inactive state. This can occur for certain types of temporary interruptions (such as an incoming phone call or SMS message) or when the user quits the application and it begins the transition to the background state.
// Use this method to pause ongoing tasks, disable timers, and throttle down OpenGL ES frame rates. Games should use this method to pause the game.
}
// app進(jìn)入后臺的時候調(diào)用
// app忽然打斷的時候，在這里保存一些需要用到的數(shù)據(jù)
- (void)applicationDidEnterBackground:(UIApplication *)application {
NSLog(@"%s",__func__);
// Use this method to release shared resources, save user data, invalidate timers, and store enough application state information to restore your application to its current state in case it is terminated later.
// If your application supports background execution, this method is called instead of applicationWillTerminate: when the user quits.
}
// app進(jìn)入即將前臺
- (void)applicationWillEnterForeground:(UIApplication *)application {
NSLog(@"%s",__func__);
// Called as part of the transition from the background to the inactive state; here you can undo many of the changes made on entering the background.
}
// 當(dāng)app獲取到焦點(diǎn)的時候調(diào)用骆膝，意味著app可以與用戶交互
- (void)applicationDidBecomeActive:(UIApplication *)application {
NSLog(@"%s",__func__);
// Restart any tasks that were paused (or not yet started) while the application was inactive. If the application was previously in the background, optionally refresh the user interface.
}
// app被關(guān)閉的時候調(diào)用
- (void)applicationWillTerminate:(UIApplication *)application {
NSLog(@"%s",__func__);
// Called when the application is about to terminate. Save data if appropriate. See also applicationDidEnterBackground:.
}
// app接收到內(nèi)存警告的時候調(diào)用
// 清空圖片的緩存
- (void)applicationDidReceiveMemoryWarning:(UIApplication *)application
{
NSLog(@"%s",__func__);
}

程序啟動原理

// main -> UIApplicationMain
/*
UIApplicationMain
1.創(chuàng)建UIApplication
2.創(chuàng)建UIApplicationDelegate祭衩，并且成為UIApplication代理
3.開啟主運(yùn)行循環(huán)，保持程序一直在運(yùn)行
4.加載info.plist,判斷有沒有指定main.stroyboard阅签，指定了就加載
加載main.stroyboard做的事情
1.創(chuàng)建窗口
2.加載main.storyboard,并且加載main.storyboard指定的控制器
3.把新創(chuàng)建的控制器作為窗口的跟控制器掐暮，讓窗口顯示出來
*/
int main(int argc, char * argv[]) {
@autoreleasepool {
return UIApplicationMain(argc, argv, nil, NSStringFromClass([AppDelegate class]));
}
}

UIWindow

• UIWindow的創(chuàng)建（模擬main storyboard加載過程）

// 程序啟動完成的時候
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
// Override point for customization after application launch.
// 1.創(chuàng)建窗口,注意窗口必須要有尺寸，尺寸跟屏幕一樣大的尺寸,窗口不要被釋放 appDelegate.h中有強(qiáng)引用的 window政钟，所以使用self.window劫乱，以此保證創(chuàng)建的window不會被銷毀
self.window = [[UIWindow alloc] initWithFrame:[UIScreen mainScreen].bounds];
self.window.backgroundColor = [UIColor redColor];
// 2.創(chuàng)建窗口的跟控制器
UIViewController *vc = [[UIViewController alloc] init];
vc.view.backgroundColor = [UIColor yellowColor];
[vc.view addSubview:[UIButton buttonWithType:UIButtonTypeContactAdd]];
// 如果設(shè)置窗口的跟控制器，默認(rèn)就會把控制器的view添加到窗口上
// 設(shè)置窗口的跟控制器锥涕，默認(rèn)就有旋轉(zhuǎn)功能
self.window.rootViewController = vc;
// [self.window addSubview:vc.view];
// 3.顯示窗口
[self.window makeKeyAndVisible];
return YES;
}