NSURLSession 后台断点下载

#import "AppDelegate.h"#import "LYFBackgroundDownload.h"@interface AppDelegate ()@end@implementation AppDelegate- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions { ???// 后台下载任务在App被杀死后下次进入App仍然有效，所以应该有手机系统管理介入，identifier要拼接上bundlId防止和其他App混淆 ???[[LYFBackgroundDownload sharedManager] registerDownloadTaskWithIdentifier:[NSString stringWithFormat:@"%@.%@", [NSBundle mainBundle].bundleIdentifier, @"LYFBackgroundDownload"]]; ???return YES;}//如果不实现该协议,后台一样可以下载，但是不会调用NSURLSessionDownloadDelegate协议，要等到重新回到前台，那些协议才会一股脑被调用。- (void)application:(UIApplication *)application handleEventsForBackgroundURLSession:(NSString *)identifier completionHandler:(void (^)(void))completionHandler { ???????if ([identifier isEqualToString:[[LYFBackgroundDownload sharedManager] downloadTaskIdentifier]]) { ???????[[LYFBackgroundDownload sharedManager] setCompletionHandler:completionHandler]; ???} ???//在这里调用completionHandler，会使之后的NSURLSessionDownloadDelegate协议只走到didFinishDownloadingToURL，之后的didCompleteWithError,URLSessionDidFinishEventsForBackgroundURLSession不被调用。 ???// ???completionHandler();}- (void)application:(UIApplication *)application didReceiveLocalNotification:(UILocalNotification *)notification { ???[[UIApplication sharedApplication] cancelAllLocalNotifications]; ???if ([[LYFBackgroundDownload sharedManager] isDownloadLocalNotification: notification]) {//在后台点击了弹出的横条通知，或者在前台收到了下载完成通知 ???????UIAlertController *alert = [UIAlertController alertControllerWithTitle:@"下载通知" message:notification.alertBody preferredStyle:UIAlertControllerStyleAlert]; ???????alert.title = @"下载通知"; ???????alert.message = notification.alertBody; ???????UIAlertAction *action = [UIAlertAction actionWithTitle:@"确定" style:UIAlertActionStyleDefault handler:nil]; ???????[alert addAction:action]; ???????[self.window.rootViewController presentViewController:alert animated:YES completion:nil]; ???}}@end

#import <Foundation/Foundation.h>NS_ASSUME_NONNULL_BEGINtypedef void(^CompletionHandlerType)(void);@class LYFBackgroundDownload;@protocol LYFBackgroundDownloadDelegate <NSObject>@optional- (void)LYFBackgroundDownloadProgress:(CGFloat)progress;- (void)LYFBackgroundDownloadDidFinishDownloadingToURL:(NSURL *)location;@end@interface LYFBackgroundDownload : NSObject+ (id)sharedManager;- (void)registerDownloadTaskWithIdentifier:(NSString *)identifier;- (void)setDelegate:(id <LYFBackgroundDownloadDelegate>)delegate;- (void)beginDownloadWithUrl: (NSString *)downloadURLString;- (void)pauseDownload;- (void)continueDownload;- (NSString *)downloadTaskIdentifier;- (void)setCompletionHandler:(CompletionHandlerType )completionHandler;- (BOOL)isDownloadLocalNotification:(UILocalNotification *)localNotification;@endNS_ASSUME_NONNULL_END

#import <UIKit/UIKit.h>#import "LYFBackgroundDownload.h"#import "AppDelegate.h"@interface LYFBackgroundDownload() <NSURLSessionDownloadDelegate>@property (strong, nonatomic) UILocalNotification *localNotification;@property (nonatomic, strong) NSOperationQueue *operationQueue;@property (strong, nonatomic) NSURLSession *backgroundSession;@property (strong, nonatomic) NSString *downloadTaskIdentifier;@property (strong, nonatomic) NSURLSessionDownloadTask *downloadTask;@property (strong, nonatomic) CompletionHandlerType completionHandler;@property (weak, nonatomic) id <LYFBackgroundDownloadDelegate> delegate;@end@implementation LYFBackgroundDownload- (instancetype)init { ???self = [super init]; ???if (self != nil) { ???????[self initLYFBackgroundDownload]; ???} ???return self;}+ (id)sharedManager { ???static LYFBackgroundDownload *staticInstance = nil; ???static dispatch_once_t onceToken; ???????dispatch_once(&onceToken, ^{ ???????staticInstance = [[self alloc] init]; ???}); ???return staticInstance;}- (void)registerDownloadTaskWithIdentifier: (NSString *)identifier { ???_downloadTaskIdentifier = identifier; ???_backgroundSession = [self backgroundURLSession]; ???_localNotification.userInfo = @{_downloadTaskIdentifier: _downloadTaskIdentifier};}- (void)setDelegate:(id<LYFBackgroundDownloadDelegate>)delegate { ???_delegate = delegate;}- (void)setCompletionHandler: (CompletionHandlerType )completionHandler { ???_completionHandler = completionHandler;}- (NSString *)downloadTaskIdentifier { ???return _downloadTaskIdentifier;}- (BOOL)isDownloadLocalNotification: (UILocalNotification *)localNotification { ???return [_localNotification.userInfo[_downloadTaskIdentifier] isEqualToString:localNotification.userInfo[_downloadTaskIdentifier]];}- (void)initLYFBackgroundDownload ?{ ???[self registerUserNotification]; ???[self initLocalNotification];}- (NSURLSession *)backgroundSession { ???if (_backgroundSession) { ???????return _backgroundSession; ???} ???return [self backgroundURLSession];}- (NSURLSession *)backgroundURLSession { ???static NSURLSession *session = nil; ???static dispatch_once_t onceToken; ???dispatch_once(&onceToken, ^{ ???????NSURLSessionConfiguration* sessionConfig = nil; ???????sessionConfig = [NSURLSessionConfiguration backgroundSessionConfigurationWithIdentifier:self.downloadTaskIdentifier]; ???????self.operationQueue = [[NSOperationQueue alloc] init]; ???????//队列可同时执行的任务数为1,即串行 ???????self.operationQueue.maxConcurrentOperationCount = 1; ???????//允许蜂窝网络下载 ???????sessionConfig.allowsCellularAccess = YES; ???????????????__weak __typeof(self) weakSelf = self; ???????//iOS9之前很多框架的delegate都是强引用：@property (nullable, readonly, retain) id <NSURLSessionDelegate> delegate ???????session = [NSURLSession sessionWithConfiguration:sessionConfig ???????????????????????????????????????????????delegate:weakSelf ??????????????????????????????????????????delegateQueue:self.operationQueue]; ???????????}); ???????return session;}#pragma mark - LYFBackgroundDownload- (void)beginDownloadWithUrl:(NSString *)downloadURLString { ???__weak __typeof(self) weakSelf = self; ???dispatch_semaphore_t semaphore = dispatch_semaphore_create(0); ???//如果backgroundSession已经有downloadTask，就继续，如果没有，就添加。保证backgroundSession最多只有一个downloadTask ???[self.backgroundSession getTasksWithCompletionHandler:^(NSArray *dataTasks, NSArray *uploadTasks, NSArray *downloadTasks) { ???????// ???????for (NSURLSessionDataTask *task in dataTasks) { ???????// ???????} ???????// ???????// ???????for (NSURLSessionUploadTask *uploadTask in uploadTasks) { ???????// ???????} ???????NSAssert(downloadTasks.count <= 1, @"后台下载任务超过1个"); ???????if (downloadTasks.count == 0) { ???????????NSURL *downloadURL = [NSURL URLWithString:downloadURLString]; ???????????NSURLRequest *request = [NSURLRequest requestWithURL:downloadURL]; ???????????weakSelf.downloadTask = [self.backgroundSession downloadTaskWithRequest:request]; ???????} else { ???????????weakSelf.downloadTask= downloadTasks[0]; ???????} ???????dispatch_semaphore_signal(semaphore); ???????????}]; ???dispatch_semaphore_wait(semaphore, DISPATCH_TIME_FOREVER); ???[self.downloadTask resume];}- (void)pauseDownload { ???[self.downloadTask suspend];}- (void)continueDownload { ???[self.downloadTask resume];}#pragma mark - NSURLSessionDownloadDelegate- (void)URLSession:(NSURLSession *)session ?????downloadTask:(NSURLSessionDownloadTask *)downloadTaskdidFinishDownloadingToURL:(NSURL *)location { ???????NSLog(@"downloadTask:%lu didFinishDownloadingToURL:%@", (unsigned long)downloadTask.taskIdentifier, location); ???????// 用 NSFileManager 将文件复制到应用的存储中 ???NSString *locationString = [location path]; ???NSString *finalLocation = [[NSSearchPathForDirectoriesInDomains(NSDocumentDirectory , NSUserDomainMask, YES) lastObject] stringByAppendingPathComponent:[NSString stringWithFormat:@"%lufile",(unsigned long)downloadTask.taskIdentifier]]; ???NSError *error; ???[[NSFileManager defaultManager] moveItemAtPath:locationString toPath:finalLocation error:&error]; ???????NSLog(@"finalLocation = %@", finalLocation); ???__weak __typeof(self) weakSlef = self; ???dispatch_async(dispatch_get_main_queue(), ^{ ???????if ([weakSlef.delegate respondsToSelector:@selector(LYFBackgroundDownloadDidFinishDownloadingToURL:)]) { ???????????[weakSlef.delegate LYFBackgroundDownloadDidFinishDownloadingToURL:[NSURL fileURLWithPath:finalLocation]]; ???????} ???});}//downloadTaskWithResumeData会触发调用该方法- (void)URLSession:(NSURLSession *)session downloadTask:(NSURLSessionDownloadTask *)downloadTask didResumeAtOffset:(int64_t)fileOffset expectedTotalBytes:(int64_t)expectedTotalBytes { ???????NSLog(@"fileOffset:%lld expectedTotalBytes:%lld",fileOffset,expectedTotalBytes);}//进入后台后将不再触发- (void)URLSession:(NSURLSession *)session ?????downloadTask:(NSURLSessionDownloadTask *)downloadTask ?????didWriteData:(int64_t)bytesWritten totalBytesWritten:(int64_t)totalBytesWrittentotalBytesExpectedToWrite:(int64_t)totalBytesExpectedToWrite { ????CGFloat progress = (CGFloat)totalBytesWritten / totalBytesExpectedToWrite; ???NSLog(@"downloadTask:%lu percent:%.2f%%",(unsigned long)downloadTask.taskIdentifier,progress * 100); ???__weak __typeof(self) weakSlef = self; ???dispatch_async(dispatch_get_main_queue(), ^{ ???????if ([weakSlef.delegate respondsToSelector:@selector(LYFBackgroundDownloadProgress:)]) { ???????????[weakSlef.delegate LYFBackgroundDownloadProgress:progress]; ???????} ???});}- (void)URLSessionDidFinishEventsForBackgroundURLSession:(NSURLSession *)session { ???NSLog(@"Background URL session %@ finished events.\n", session); ???NSString *identifier = session.configuration.identifier; ???if ([identifier isEqualToString:_downloadTaskIdentifier]) { ???????// 调用在 -application:handleEventsForBackgroundURLSession: 中保存的 handler ???????if (_completionHandler) { ???????????NSLog(@"Calling completion handler for session %@", identifier); ???????????_completionHandler(); ???????} ???}}/* * 该方法下载成功和失败都会回调，只是失败的是error是有值的， * 在下载失败时，error的userinfo属性可以通过NSURLSessionDownloadTaskResumeData * 这个key来取到resumeData(和上面的resumeData是一样的)，再通过resumeData恢复下载 *///下载完成//?函数里可以做：//1.发出下载完成的本地通知，如果在后台就可以发本地通知，在前台不可以显示本地通知，可以由didReceiveLocalNotification里面来处理本地通知//2.因为在后台是不会更新下载进度的，所有这个函数里要处理把进度改为100%//?断点下载处理：//如果app退出（发现Xcode重新编译不算app退出），下次进入app会触发该方法，error不为空，可以进行断点下载工作//这里app退出，重新进入调用该函数也说明了NSURLSession的多任务是由系统管理，所以NSURLSessionConfiguration的identifier要包含bundle id，以防止和其他app混淆。- (void)URLSession:(NSURLSession *)session ?????????????task:(NSURLSessionTask *)taskdidCompleteWithError:(NSError *)error { ???NSLog(@"didCompleteWithError"); ???if ([session.configuration.identifier isEqualToString:_downloadTaskIdentifier]) { ???????if (error) { ???????????if ([error.userInfo objectForKey:NSURLSessionDownloadTaskResumeData]) { ???????????????NSData *resumeData = [error.userInfo objectForKey:NSURLSessionDownloadTaskResumeData]; ???????????????//通过之前保存的resumeData，获取断点的NSURLSessionTask，调用resume恢复下载 ???????????????NSLog(@"self.resumeData.length = %ld, %@", resumeData.length, session.configuration.identifier); ???????????????// ???????????self.downloadTask = [self.backgroundSession downloadTaskWithCorrectResumeData:self.resumeData]; ???????????????self.downloadTask = [self.backgroundSession downloadTaskWithResumeData: resumeData]; ???????????????[self.downloadTask resume]; ???????????} ???????} else { ???????????dispatch_async(dispatch_get_main_queue(), ^{ ???????????????[self sendLocalNotification]; ???????????????//更新进度条 ???????????????if ([self.delegate respondsToSelector:@selector(LYFBackgroundDownloadProgress:)]) { ???????????????????[self.delegate LYFBackgroundDownloadProgress:1]; ???????????????} ???????????}); ???????} ???}}#pragma mark - Local Notification- (void)registerUserNotification { ???if ([[UIApplication sharedApplication] respondsToSelector:@selector(registerUserNotificationSettings:)]) { ???????UIUserNotificationType type = ?UIUserNotificationTypeAlert | UIUserNotificationTypeBadge | UIUserNotificationTypeSound; ???????UIUserNotificationSettings *settings = [UIUserNotificationSettings settingsForTypes:type ????????????????????????????????????????????????????????????????????????????????categories:nil]; ???????[[UIApplication sharedApplication] registerUserNotificationSettings:settings]; ???}}- (void)initLocalNotification { ???self.localNotification = [[UILocalNotification alloc] init]; ???self.localNotification.fireDate = [[NSDate date] dateByAddingTimeInterval:5]; ???self.localNotification.alertAction = nil; ???self.localNotification.soundName = UILocalNotificationDefaultSoundName; ???self.localNotification.alertBody = @"下载完成了！"; ???// ???self.localNotification.applicationIconBadgeNumber = 1; ???// ???self.localNotification.repeatInterval = 0;}- (void)sendLocalNotification { ???[[UIApplication sharedApplication] scheduleLocalNotification:self.localNotification];}@end

#import "ViewController.h"#import "LYFBackgroundDownload.h"@interface ViewController () <LYFBackgroundDownloadDelegate>@property (strong, nonatomic) IBOutlet UIProgressView *downloadProgress;@property (weak, nonatomic) IBOutlet UILabel *progressLabel;@property (weak, nonatomic) IBOutlet UIImageView *imageView;@end@implementation ViewController- (void)viewDidLoad { ???[super viewDidLoad]; ???// Do any additional setup after loading the view, typically from a nib. ???[[LYFBackgroundDownload sharedManager] setDelegate: self];}- (void)updateDownloadProgress:(CGFloat)progress { ???self.progressLabel.text = [NSString stringWithFormat:@"%.2f%%",progress * 100]; ???self.downloadProgress.progress = progress;}#pragma mark Method- (IBAction)download:(id)sender {// ???[[LYFBackgroundDownload sharedManager] beginDownloadWithUrl:@"https://www.baidu.com/img/bdlogo.png"]; ???[[LYFBackgroundDownload sharedManager] beginDownloadWithUrl:@"https://www.apple.com/105/media/cn/iphone-x/2017/01df5b43-28e4-4848-bf20-490c34a926a7/films/feature/iphone-x-feature-cn-20170912_1280x720h.mp4"];}- (IBAction)pauseDownlaod:(id)sender { ???[[LYFBackgroundDownload sharedManager] pauseDownload];}- (IBAction)continueDownlaod:(id)sender { ???[[LYFBackgroundDownload sharedManager] continueDownload];}#pragma mark LYFBackgroundDownloadDelegate- (void)LYFBackgroundDownloadProgress:(CGFloat)progress { ???[self updateDownloadProgress:progress];}- (void)LYFBackgroundDownloadDidFinishDownloadingToURL:(NSURL *)location { ???self.imageView.image = [UIImage imageWithContentsOfFile:[location path]];}@end