The most important application delegate methods in iOS are those that handle key events in the app's lifecycle. These methods are part of the UIApplicationDelegate protocol and are crucial for managing transitions between different states of the app. Here are the seven most important application delegate methods:
application:willFinishLaunchingWithOptions:
This method is called when the launch process is initiated. It is the first opportunity to execute any code within the app[1].
application:didFinishLaunchingWithOptions:
This method is called when the launch process is nearly complete. It is the last opportunity to prepare the interface and make any final adjustments before the app’s windows are displayed[1][4].
applicationDidBecomeActive:
This method is called when the application has become active. It is also invoked each time the app returns to an active state from an inactive state, such as after a phone call or SMS[1][4].
applicationWillResignActive:
This method is called when the app 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[1][4].
applicationDidEnterBackground:
This method is called when the app enters the background. The app has approximately five seconds to perform tasks and return. If the method does not return within this time, the application is terminated[1][4].
applicationWillEnterForeground:
This method is called as the app is preparing to move from the background to the foreground. It gives the developer an opportunity to re-establish the settings of the previous running state before the app becomes active[1][4].
applicationWillTerminate:
This method is called when the app is about to terminate. It is an opportunity to save data and perform any necessary cleanup. This method is also called when t...
