Learning iOS Development UI--Program startup principle

iOS program startup process

UIApplication:

1. Each application has its own UIApplication object, and it is a singleton, and the singleton object can be obtained by [uiapplication sharedapplication]. Common Properties of 2.UIApplication:

@property (nonatomic) Nsinteger applicationiconbadgenumber;

@property (nonatomic,getter=isnetworkactivityindicatorvisible) BOOL networkactivityindicatorvisible;

Common methods of 3.UIApplication:

UIApplication *app = [UIApplication sharedapplication];

You can control the style of the status bar, whether it is displayed (need to modify the system Info.pliast file), Uiviewcontroller can operate

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UIWindow:

1 Common methods:

-(void) Makekeywindow;

Make current UIWindow into Keywindow (main window)

-(void) makekeyandvisible;

Make the current UIWindow into Keywindow and show [UIApplication sharedapplication].windows, the UIWindow list opened in this app, This allows you to touch any of the UIView objects in your app (the keyboard that pops up in a new UIWindow when you normally enter text)

[UIApplication Sharedapplication].keywindow, a UIWindow for receiving keyboard and non-touch message events, and only one uiwindow at a time in a program is Keywindow. If a text box inside a UIWindow cannot enter text, it may be because this uiwindow is not a Keywindow four-object diagram