1. When you press the home button, the iOS APP still exists for a period of time. At this time, you can immediately restore the APP to its original state by clicking the APP. 2. Cold start refers to the process of starting from scratch after the App is killed.

Optimization solution for hot start: 1. Data optimization: Asynchronously process time-consuming operations.

dispatch_queue_t globalQueue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0); Dispatch_async (globalQueue, ^{dispatch_queue_t mainQueue = dispatch_get_main_queue(); // asynch_dispatch_async (mainQueue, ^{NSLog(@" update UI ")); }); });Copy the code

NSUserDefaults produces a plist file in the Library folder, and loads the entire plist configuration file into memory. Therefore, very frequent access to a large amount of data may also lead to APP startup lag.

IOS App Startup Performance Optimization ios-performance-Optimization [iOS Performance check]