Question

在我的应用中，我应该填充核心数据DB，我也想在后台进行

- (void)applicationDidEnterBackground:(UIApplication *)application
{
    if ([[UIDevice currentDevice] respondsToSelector:@selector(isMultitaskingSupported)]) { //Check if our iOS version supports multitasking I.E iOS 4
        if ([[UIDevice currentDevice] isMultitaskingSupported]) { //Check if device supports mulitasking
            UIApplication *application = [UIApplication sharedApplication]; //Get the shared application instance

            __block UIBackgroundTaskIdentifier background_task; //Create a task object

            background_task = [application beginBackgroundTaskWithExpirationHandler: ^ {
                [application endBackgroundTask: background_task]; //Tell the system that we are done with the tasks
                background_task = UIBackgroundTaskInvalid; //Set the task to be invalid

                //System will be shutting down the app at any point in time now
            }];

            //Background tasks require you to use asyncrous tasks

            dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
                //Perform your tasks that your application requires

                DBSync *sync = [DBSync sharedInstance];

                [sync startDownloadDataandUpdateDB];

                [application endBackgroundTask: background_task]; //End the task so the system knows that you are done with what you need to perform
                background_task = UIBackgroundTaskInvalid; //Invalidate the background_task
            });
        }
    }
}

问题在于方法＆＃34; startDownloadDataandUpdateDB＆＃34;被称为，但这种方法在DBSync中调用其他方法，但这些方法不起作用，我不明白

Answer 1

我认为在该方法中进行网络调用并不是一个好习惯。

The documentation 表示您有大约五秒的时间来执行任何任务并返回。

您可能需要查看beginBackgroundTaskWithExpirationHandler

iOS：后台进程和单例

1 个答案: