如何計算應用程序在iphone中輸入背景時的任務

Question

即使應用程序在iPhone（iOS）中退出活動狀態時進入背景，我如何才能運行任務直至完成任務。

Answer 1

首先，我們需要檢查設備是否支持多任務或NOT？

if([UIDevice currentDevice]respondsToSelector:@selector(isMultitaskingSupported)){ 

    // If the device supports Multitasking we can run the task as :- 

    UIBackgroundTaskIdentifier bgTask; 

    bgTask=[[UIApplication sharedApplication] beginBackgroundTaskWithExpirationHandler:^{ 
     [[UIApplication sharedApplication] endBackgroundTask:bgTask]; 
    }]; 

    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0ul), ^{ 
     for(double i=0; i<99999; i++) 
      NSLog(@"Backgroudn quee"); 

     [[UIApplication sharedApplication] endBackgroundTask:bgTask]; 
    }); 
}