iphone - performFetchWithCompletionHandler 只会被调用

Question

这是我的应用委托(delegate)

 (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{

    [[UIApplication sharedApplication] setMinimumBackgroundFetchInterval:2];

    self.window = [[[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]] autorelease];
    // Override point for customization after application launch.
    self.viewController = [[[ViewController alloc] initWithNibName:@"ViewController" bundle:nil] autorelease];
    UINavigationController *nav=[[[UINavigationController alloc]initWithRootViewController:self.viewController ] autorelease];
    nav.navigationBar.hidden=YES;
    self.window.rootViewController = nav;
    [self.window makeKeyAndVisible];
    return YES;
}

-(void)application:(UIApplication *)application performFetchWithCompletionHandler:(void (^)(UIBackgroundFetchResult))completionHandler
{
    NSLog(@"########### Received Background Fetch ###########");
    //Download  the Content .

     [self sometask]; // i want to do some task here but this method get called only ones when i try to launch application 

    //Cleanup
    completionHandler(UIBackgroundFetchResultNoData);

所以问题是 performFetchWithCompletionHandler 只被调用是的，我已经完成了所有在信息 pList 中的获取和所有但没有帮助请提出一些建议

Answer 1

请注意，只有当系统告诉您执行后台提取时，才应调用此方法。

您可以在此处的 Xcode 中模拟它: