申请域网站,贵州省住房和城乡建设局网站首页,中小企业网站建设新闻,数字营销包括哪些方面三种方式使得iOS程序即使在关闭或崩溃的情况下也能够在后台持续进行一些任务#xff0c;比如更新程序界面快照#xff0c;下载文件等。这三个方法分别是Background Fetch#xff0c;Remote Notification和NSURLSession的backgroundSessionConfiguration Background Fetch 开…三种方式使得iOS程序即使在关闭或崩溃的情况下也能够在后台持续进行一些任务比如更新程序界面快照下载文件等。这三个方法分别是Background FetchRemote Notification和NSURLSession的backgroundSessionConfiguration Background Fetch 开启 首先在info plist文件中开启UIBackgroundModes的Background fetch。或者手动编辑这个值 keyUIBackgroundModes/key
arraystringfetch/string
/array iOS默认不进行background fetch需要设置一个时间的间隔 - (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{//UIApplicationBackgroundFetchIntervalMinimum表示尽可能频繁去获取如果需要指定至少多少时间更新一次就需要给定一个时间值[application setMinimumBackgroundFetchInterval:UIApplicationBackgroundFetchIntervalMinimum];return YES; } 最后在App Delegate里实现下面的方法这个方法只能在30秒内完成。 - (void) application:(UIApplication *)application
performFetchWithCompletionHandler:(void (^)(UIBackgroundFetchResult))completionHandler
{NSURLSessionConfiguration *sessionConfiguration [NSURLSessionConfiguration defaultSessionConfiguration];NSURLSession *session [NSURLSession sessionWithConfiguration:sessionConfiguration]; NSURL *url [[NSURL alloc] initWithString:http://yourserver.com/data.json]; NSURLSessionDataTask *task [session dataTaskWithURL:url completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) { if (error) { completionHandler(UIBackgroundFetchResultFailed); return; } // 解析响应/数据以决定新内容是否可用 BOOL hasNewData ... if (hasNewData) { completionHandler(UIBackgroundFetchResultNewData); } else { completionHandler(UIBackgroundFetchResultNoData); } }]; // 开始任务 [task resume]; } 测试 通过查看UIApplication的applicationState - (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{NSLog(Launched in background %d, UIApplicationStateBackground application.applicationState); return YES; } Remote Notification 在普通的远程通知里带上content-available标志就可以在通知用户同时在后台进行更新。通知结构如下 {aps : {content-available : 1 }, content-id : 42 } 接收一条带有content-available的通知会调用下面的方法 - (void)application:(UIApplication *)applicationdidReceiveRemoteNotification:(NSDictionary *)userInfofetchCompletionHandler:(void (^)(UIBackgroundFetchResult))completionHandler
{NSLog(Remote Notification userInfo is %, userInfo); NSNumber *contentID userInfo[content-id]; // 根据 content ID 进行操作 completionHandler(UIBackgroundFetchResultNewData); } 利用NSURLSession进行background transfer task 使用[NSURLSessionConfiguration backgroundSessionConfiguration]创建一个后台任务当应用退出后崩溃或进程被关掉都还是会运行。 范例先处理一条远程通知并将NSURLSessionDownloadTask添加到后台传输服务队列。 - (NSURLSession *)backgroundURLSession
{static NSURLSession *session nil;static dispatch_once_t onceToken; dispatch_once(onceToken, ^{ NSString *identifier io.objc.backgroundTransferExample; NSURLSessionConfiguration* sessionConfig [NSURLSessionConfiguration backgroundSessionConfiguration:identifier]; session [NSURLSession sessionWithConfiguration:sessionConfig delegate:self delegateQueue:[NSOperationQueue mainQueue]]; }); return session; } - (void) application:(UIApplication *)application didReceiveRemoteNotification:(NSDictionary *)userInfo fetchCompletionHandler:(void (^)(UIBackgroundFetchResult))completionHandler { NSLog(Received remote notification with userInfo %, userInfo); NSNumber *contentID userInfo[content-id]; NSString *downloadURLString [NSString stringWithFormat:http://yourserver.com/downloads/%d.mp3, [contentID intValue]]; NSURL* downloadURL [NSURL URLWithString:downloadURLString]; NSURLRequest *request [NSURLRequest requestWithURL:downloadURL]; NSURLSessionDownloadTask *task [[self backgroundURLSession] downloadTaskWithRequest:request]; task.taskDescription [NSString stringWithFormat:Podcast Episode %d, [contentID intValue]]; //执行resume保证开始了任务 [task resume]; completionHandler(UIBackgroundFetchResultNewData); } 下载完成后调用NSURLSessionDownloadDelegate的委托方法这些委托方法全部是必须实现的。了解所有类型session task的生命周期可以参考官方文档https://developer.apple.com/library/ios/documentation/cocoa/Conceptual/URLLoadingSystem/NSURLSessionConcepts/NSURLSessionConcepts.html#//apple_ref/doc/uid/10000165i-CH2-SW42 #Pragma Mark - NSURLSessionDownloadDelegate- (void) URLSession:(NSURLSession *)sessiondownloadTask:(NSURLSessionDownloadTask *)downloadTaskdidFinishDownloadingToURL:(NSURL *)location
{NSLog(downloadTask:% didFinishDownloadingToURL:%, downloadTask.taskDescription, location); // 必须用 NSFileManager 将文件复制到应用的存储中因为临时文件在方法返回后会被删除 // ... // 通知 UI 刷新 } - (void) URLSession:(NSURLSession *)session downloadTask:(NSURLSessionDownloadTask *)downloadTask didResumeAtOffset:(int64_t)fileOffset expectedTotalBytes:(int64_t)expectedTotalBytes { } - (void) URLSession:(NSURLSession *)session downloadTask:(NSURLSessionDownloadTask *)downloadTask didWriteData:(int64_t)bytesWritten totalBytesWritten:(int64_t)totalBytesWritten totalBytesExpectedToWrite:(int64_t)totalBytesExpectedToWrite { } 后台的任务完成后如果应用没有在前台运行需要实现UIApplication的两个delegate让系统唤醒应用 - (void) application:(UIApplication *)applicationhandleEventsForBackgroundURLSession:(NSString *)identifier completionHandler:(void (^)())completionHandler
{// 你必须重新建立一个后台 seesiong 的参照// 否则 NSURLSessionDownloadDelegate 和 NSURLSessionDelegate 方法会因为// 没有 对 session 的 delegate 设定而不会被调用。参见上面的 backgroundURLSession NSURLSession *backgroundSession [self backgroundURLSession]; NSLog(Rejoining session with identifier % %, identifier, backgroundSession); // 保存 completion handler 以在处理 session 事件后更新 UI [self addCompletionHandler:completionHandler forSession:identifier]; } - (void)URLSessionDidFinishEventsForBackgroundURLSession:(NSURLSession *)session { NSLog(Background URL session % finished events. , session); if (session.configuration.identifier) { // 调用在 -application:handleEventsForBackgroundURLSession: 中保存的 handler [self callCompletionHandlerForSession:session.configuration.identifier]; } } - (void)addCompletionHandler:(CompletionHandlerType)handler forSession:(NSString *)identifier { if ([self.completionHandlerDictionary objectForKey:identifier]) { NSLog(Error: Got multiple handlers for a single session identifier. This should not happen. ); } [self.completionHandlerDictionary setObject:handler forKey:identifier]; } - (void)callCompletionHandlerForSession: (NSString *)identifier { CompletionHandlerType handler [self.completionHandlerDictionary objectForKey: identifier]; if (handler) { [self.completionHandlerDictionary removeObjectForKey: identifier]; NSLog(Calling completion handler for session %, identifier); handler(); } }原文地址 转载于:https://www.cnblogs.com/pandas/p/4334871.html
