IOS后台运行代码

Question

Firebase * ref = nil;


NSInteger iid = [[API sharedInstance] userid];
NSString * path = [NSString stringWithFormat:  @"http://example.firebaseIO.com/user/%d/conversations", iid];

ref = [[Firebase alloc] initWithUrl:path];


if(ref) {

    NSString * path = [NSString stringWithFormat: @"http://example.firebaseIO.com/conversations"];
    Firebase * conv = [[Firebase alloc] initWithUrl: path];

    [ref observeEventType:FEventTypeChildAdded withBlock:^(FDataSnapshot *snapshot) {

        // name of conversation
        NSString * name = snapshot.name;
        Firebase * ref1 = [conv childByAppendingPath: name];

        [ref1 observeSingleEventOfType:FEventTypeValue withBlock:^(FDataSnapshot *snapshot) {

            if(snapshot.value != [NSNull null] && ![snapshot.value isKindOfClass: [NSString class]])
            {
                FDataSnapshot * chatsnapshot = [snapshot childSnapshotForPath: @"chats"];

                NSInteger numChatMessages = chatsnapshot.childrenCount;
                numberOfTotalChatMessages += numChatMessages;

                NSMutableDictionary *m = [snapshot.value mutableCopy];
                [m setValue: snapshot.name forKey: @"ref_name"];

                NSInteger current_user = [[API sharedInstance] userid];
                NSString * userpath = [NSString stringWithFormat: @"users/%d", current_user];
                FDataSnapshot * usersnapshot = [snapshot childSnapshotForPath: userpath];

                if(usersnapshot.value != [NSNull null] && ![usersnapshot.value isKindOfClass: [NSString class]])
                {
                    NSDictionary * userdict = usersnapshot.value;
                    NSInteger numUserMessagesRead = [userdict[@"numOfMessages"] intValue];

                    numberOfMessagesRead += numUserMessagesRead;

                    if(numberOfTotalChatMessages > numberOfMessagesRead) {
                        [m setValue: @"true" forKey: @"bubble"];
                    }
                }

                [self.chats addObject: m];

                NSNumber * index = [NSNumber numberWithInt: self.chats.count - 1];
                [read setValue: index forKey: snapshot.name];

                PLRightMenuViewController * rightPanel = (PLRightMenuViewController *) self.viewController.rightPanel;
                [rightPanel.tableView reloadData];

                self.numChats = numberOfTotalChatMessages - numberOfMessagesRead;
                [[UIApplication sharedApplication] setApplicationIconBadgeNumber: self.numChats];

            }
        }];

    }];


    [ref observeEventType:FEventTypeChildChanged withBlock:^(FDataSnapshot *snapshot) {

        NSString * name = snapshot.name;
        Firebase * ref1 = [conv childByAppendingPath: name];

        [ref1 observeSingleEventOfType:FEventTypeValue withBlock:^(FDataSnapshot *snapshot)
        {
            if(snapshot.value != [NSNull null] && ![snapshot.value isKindOfClass: [NSString class]])
            {
                numberOfTotalChatMessages += 1;

                NSMutableDictionary *m = [snapshot.value mutableCopy];
                [m setValue: snapshot.name forKey: @"ref_name"];
                [m setValue: @"true" forKey: @"bubble"];
                [self.chats addObject: m];


                if([read objectForKey: snapshot.name])
                {
                    NSInteger index = [[read objectForKey: snapshot.name] intValue];
                    [self.chats removeObjectAtIndex: index];

                     NSNumber * index1 = [NSNumber numberWithInt: self.chats.count - 1];
                    [read setValue: index1 forKey: snapshot.name];
                }

                self.numChats = numberOfTotalChatMessages - numberOfMessagesRead;
                [[UIApplication sharedApplication] setApplicationIconBadgeNumber: self.numChats];


                PLRightMenuViewController * rightPanel = (PLRightMenuViewController *) self.viewController.rightPanel;
                [rightPanel.tableView reloadData];
            }
        }];

    }];
}

我有上面的代码，它基本上使用 firebase 检查任何新的聊天对话并更改应用程序徽章编号。如何在应用程序后台运行代码，以便无论是否有人当前使用该应用程序，都可以更改应用程序徽章编号？

基本上，我怎样才能在后台运行上面的代码？我应该在 Appdelegate 中进行哪些更改？

Answer 1

除非你作弊，否则你不能。目前 iOS 或 Apple 分别不允许应用程序进入后台，只有极少数例外。例如定位服务或播放音频。

有些人通过假装播放某种声音来作弊。

到目前为止，您必须使用推送通知来通知应用收到的消息并更新徽章。

或者……等待 iOS 7 发布。假设您有一个开发者帐户，您已经可以访问文档和预览/测试版资源并做好准备，直到 iOS 7 和 SDK 等成为 GA。

Answer 2

// @interface

// Declare Private property
@property (nonatomic) UIBackgroundTaskIdentifier backgroundTask;

//@end
// ...

// Copy into
//@implementation 

- (void)setupBackgrounding {
    [[NSNotificationCenter defaultCenter] addObserver: self selector: @selector(appBackgrounding:)
                                                 name: UIApplicationDidEnterBackgroundNotification
                                               object: nil];
    [[NSNotificationCenter defaultCenter] addObserver: self selector: @selector(appForegrounding:)
                                                 name: UIApplicationWillEnterForegroundNotification
                                               object: nil];
}

- (void)appBackgrounding: (NSNotification *)notification {
    [self keepAlive];
}

- (void) keepAlive {
    self.backgroundTask = [[UIApplication sharedApplication] beginBackgroundTaskWithExpirationHandler:^{
        [[UIApplication sharedApplication] endBackgroundTask:self.backgroundTask];
        self.backgroundTask = UIBackgroundTaskInvalid;
        [self keepAlive];
    }];
}

- (void)appForegrounding: (NSNotification *)notification {
    if (self.backgroundTask != UIBackgroundTaskInvalid) {
        [[UIApplication sharedApplication] endBackgroundTask:self.backgroundTask];
        self.backgroundTask = UIBackgroundTaskInvalid;
    }
}

Answer 3

您可以使用这些方法，将后台任务运行更多时间..

- (UIBackgroundTaskIdentifier)beginBackgroundTaskWithExpirationHandler:(void(^)(void))handler  NS_AVAILABLE_IOS(4_0);
- (void)endBackgroundTask:(UIBackgroundTaskIdentifier)identifier NS_AVAILABLE_IOS(4_0);

- (BOOL)setKeepAliveTimeout:(NSTimeInterval)timeout handler:(void(^)(void))keepAliveHandler NS_AVAILABLE_IOS(4_0);
- (void)clearKeepAliveTimeout NS_AVAILABLE_IOS(4_0);



- (void)getDataFromServer

    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{

        [self beginBackgroundUpdateTask];

        NSURLResponse * response = nil;
        NSError  * error = nil;
        NSData * responseData = [NSURLConnection sendSynchronousRequest: request returningResponse: &response error: &error];

        // Do something with the result

        [self endBackgroundUpdateTask];
    });
}
- (void) beginBackgroundUpdateTask
{
    self.backgroundUpdateTask = [[UIApplication sharedApplication] beginBackgroundTaskWithExpirationHandler:^{
        [self endBackgroundUpdateTask];
    }];
}

- (void) endBackgroundUpdateTask
{
    [[UIApplication sharedApplication] endBackgroundTask: self.backgroundUpdateTask];
    self.backgroundUpdateTask = UIBackgroundTaskInvalid;
}

如果你想让你的应用程序保持活力，你可以使用这个：-

- (void)applicationDidEnterBackground:(UIApplication *)application 
{
    // Use this method to release shared resources, save user data, invalidate timers, and store
    // enough application state information to restore your application to its current state in case
    // it is terminated later.
    // 
    // If your application supports background execution,
    // called instead of applicationWillTerminate: when the user quits.

    if ([application respondsToSelector:@selector(setKeepAliveTimeout:handler:)]) 
    {
        [application setKeepAliveTimeout:600 handler:^{

            DDLogVerbose(@"KeepAliveHandler");

            // Do other keep alive stuff here.
        }];
    }
}

它可能会帮助你.. 在 iOS 7 中可能有更好的方法来做到这一点......

Answer 4

您需要使用Apple Push Notification服务，通常缩写为APN。

Answer 5

您可以使用推送通知来做到这一点，这是一个很好的解释。
example http://www.raywenderlich.com/32960/apple-push-notification-services-in-ios-6-tutorial-part-1
注意：您需要一个 APNS 来通知您的应用程序。
在 iOS7 中，带有 fetchAPI 的功能允许您在后台工作，但请注意，您的应用程序不会在后台运行，因为系统将决定何时允许应用程序在后台运行。
在 iOS7 中还有另外一件事叫做静默推送通知，它可以让你在通知到来时更新你的视图，这意味着如果你的应用程序在后台并且通知来了，你可以在后台更改应用程序徽章编号。