ios断点续传:NSURLSession和NSURLSessionDataTask实现

苹果提供的NSURLSessionDownloadTask虽然能实现断点续传，但是有些情况是无法处理的，比如程序强制退出或没有调用

cancelByProducingResumeData取消方法，这时就无法断点续传了。

使用NSURLSession和NSURLSessionDataTask实现断点续传的过程是：

1、配置NSMutableURLRequest对象的Range请求头字段信息

2、创建使用代理的NSURLSession对象

3、使用NSURLSession对象和NSMutableURLRequest对象创建NSURLSessionDataTask对象，启动任务。

4、在NSURLSessionDataDelegate的didReceiveData方法中追加获取下载数据到目标文件。

下面是具体实现，封装了一个续传管理器。可以直接拷贝到你的工程里，也可以参考我提供的DEMO：http://pan.baidu.com/s/1c0BHToW

//

//  MQLResumeManager.h

//

//  Created by MQL on 15/10/21.

//  Copyright © 2015年. All rights reserved.

//

#import <Foundation/Foundation.h>

@interface MQLResumeManager : NSObject

/**

 *  创建断点续传管理对象，启动下载请求

 *

 *  @param url          文件资源地址

 *  @param targetPath   文件存放路径

 *  @param success      文件下载成功的回调块

 *  @param failure      文件下载失败的回调块

 *  @param progress     文件下载进度的回调块

 *

 *  @return 断点续传管理对象

 *

 */

+(MQLResumeManager*)resumeManagerWithURL:(NSURL*)url

                                targetPath:(NSString*)targetPath

                                success:(void (^)())success

                                failure:(void (^)(NSError*error))failure

                               progress:(void (^)(longlongtotalReceivedContentLength,longlong totalContentLength))progress;

/**

 *  启动断点续传下载请求

 */

-(void)start;

/**

 *  取消断点续传下载请求

 */

-(void)cancel;

@end

  1 //
  2
  3 //  MQLResumeManager.m
  4
  5 //
  6
  7 //  Created by MQL on 15/10/21.
  8
  9 //  Copyright © 2015年. All rights reserved.
 10
 11 //
 12
 13
 14
 15 #import "MQLResumeManager.h"
 16
 17
 18
 19 typedef void (^completionBlock)();
 20
 21 typedef void (^progressBlock)();
 22
 23
 24
 25 @interface MQLResumeManager ()<NSURLSessionDelegate,NSURLSessionTaskDelegate>
 26
 27
 28
 29 @property (nonatomic,strong)NSURLSession *session;   //注意一个session只能有一个请求任务
 30
 31 @property(nonatomic,readwrite,retain)NSError *error;//请求出错
 32
 33 @property(nonatomic,readwrite,copy)completionBlockcompletionBlock;
 34
 35 @property(nonatomic,readwrite,copy)progressBlock progressBlock;
 36
 37
 38
 39 @property (nonatomic,strong)NSURL *url;          //文件资源地址
 40
 41 @property (nonatomic,strong)NSString *targetPath;//文件存放路径
 42
 43 @property longlong totalContentLength;            //文件总大小
 44
 45 @property longlong totalReceivedContentLength;    //已下载大小
 46
 47
 48
 49 /**
 50
 51  *  设置成功、失败回调block
 52
 53  *
 54
 55  *  @param success 成功回调block
 56
 57  *  @param failure 失败回调block
 58
 59  */
 60
 61 - (void)setCompletionBlockWithSuccess:(void (^)())success
 62
 63                               failure:(void (^)(NSError*error))failure;
 64
 65
 66
 67 /**
 68
 69  *  设置进度回调block
 70
 71  *
 72
 73  *  @param progress
 74
 75  */
 76
 77 -(void)setProgressBlockWithProgress:(void (^)(longlongtotalReceivedContentLength,longlong totalContentLength))progress;
 78
 79
 80
 81 /**
 82
 83  *  获取文件大小
 84
 85  *  @param path 文件路径
 86
 87  *  @return 文件大小
 88
 89  *
 90
 91  */
 92
 93 - (long long)fileSizeForPath:(NSString *)path;
 94
 95
 96
 97 @end
 98
 99
100
101 @implementation MQLResumeManager
102
103
104
105 /**
106
107  *  设置成功、失败回调block
108
109  *
110
111  *  @param success 成功回调block
112
113  *  @param failure 失败回调block
114
115  */
116
117 - (void)setCompletionBlockWithSuccess:(void (^)())success
118
119                               failure:(void (^)(NSError*error))failure{
120
121
122
123     __weak typeof(self) weakSelf =self;
124
125     self.completionBlock = ^ {
126
127
128
129         dispatch_async(dispatch_get_main_queue(), ^{
130
131
132
133             if (weakSelf.error) {
134
135                 if (failure) {
136
137                     failure(weakSelf.error);
138
139                 }
140
141             } else {
142
143                 if (success) {
144
145                     success();
146
147                 }
148
149             }
150
151
152
153         });
154
155     };
156
157 }
158
159
160
161 /**
162
163  *  设置进度回调block
164
165  *
166
167  *  @param progress
168
169  */
170
171 -(void)setProgressBlockWithProgress:(void (^)(longlongtotalReceivedContentLength,longlong totalContentLength))progress{
172
173
174
175     __weak typeof(self) weakSelf =self;
176
177     self.progressBlock = ^{
178
179
180
181         dispatch_async(dispatch_get_main_queue(), ^{
182
183
184
185             progress(weakSelf.totalReceivedContentLength, weakSelf.totalContentLength);
186
187         });
188
189     };
190
191 }
192
193
194
195 /**
196
197  *  获取文件大小
198
199  *  @param path 文件路径
200
201  *  @return 文件大小
202
203  *
204
205  */
206
207 - (long long)fileSizeForPath:(NSString *)path {
208
209
210
211     long long fileSize =0;
212
213     NSFileManager *fileManager = [NSFileManagernew];// not thread safe
214
215     if ([fileManager fileExistsAtPath:path]) {
216
217         NSError *error = nil;
218
219         NSDictionary *fileDict = [fileManagerattributesOfItemAtPath:path error:&error];
220
221         if (!error && fileDict) {
222
223             fileSize = [fileDict fileSize];
224
225         }
226
227     }
228
229     return fileSize;
230
231 }
232
233
234
235 /**
236
237  *  创建断点续传管理对象，启动下载请求
238
239  *
240
241  *  @param url          文件资源地址
242
243  *  @param targetPath   文件存放路径
244
245  *  @param success      文件下载成功的回调块
246
247  *  @param failure      文件下载失败的回调块
248
249  *  @param progress     文件下载进度的回调块
250
251  *
252
253  *  @return 断点续传管理对象
254
255  *
256
257  */
258
259 +(MQLResumeManager*)resumeManagerWithURL:(NSURL*)url
260
261                               targetPath:(NSString*)targetPath
262
263                                  success:(void (^)())success
264
265                                  failure:(void (^)(NSError*error))failure
266
267                                 progress:(void (^)(longlongtotalReceivedContentLength,longlong totalContentLength))progress{
268
269
270
271     MQLResumeManager *manager = [[MQLResumeManageralloc]init];
272
273
274
275     manager.url = url;
276
277     manager.targetPath = targetPath;
278
279     [managersetCompletionBlockWithSuccess:successfailure:failure];
280
281     [manager setProgressBlockWithProgress:progress];
282
283
284
285     manager.totalContentLength =0;
286
287     manager.totalReceivedContentLength =0;
288
289
290
291     return manager;
292
293 }
294
295
296
297 /**
298
299  *  启动断点续传下载请求
300
301  */
302
303 -(void)start{
304
305
306
307     NSMutableURLRequest *request = [[NSMutableURLRequestalloc]initWithURL:self.url];
308
309
310
311     longlong downloadedBytes =self.totalReceivedContentLength = [selffileSizeForPath:self.targetPath];
312
313     if (downloadedBytes > 0) {
314
315
316
317         NSString *requestRange = [NSStringstringWithFormat:@"bytes=%llu-", downloadedBytes];
318
319         [request setValue:requestRangeforHTTPHeaderField:@"Range"];
320
321     }else{
322
323
324
325         int fileDescriptor =open([self.targetPathUTF8String],O_CREAT |O_EXCL |O_RDWR,0666);
326
327         if (fileDescriptor > 0) {
328
329             close(fileDescriptor);
330
331         }
332
333     }
334
335
336
337     NSURLSessionConfiguration *sessionConfiguration = [NSURLSessionConfigurationdefaultSessionConfiguration];
338
339     NSOperationQueue *queue = [[NSOperationQueuealloc]init];
340
341     self.session = [NSURLSessionsessionWithConfiguration:sessionConfigurationdelegate:selfdelegateQueue:queue];
342
343
344
345     NSURLSessionDataTask *dataTask = [self.sessiondataTaskWithRequest:request];
346
347     [dataTask resume];
348
349 }
350
351
352
353 /**
354
355  *  取消断点续传下载请求
356
357  */
358
359 -(void)cancel{
360
361
362
363     if (self.session) {
364
365
366
367         [self.sessioninvalidateAndCancel];
368
369         self.session =nil;
370
371     }
372
373 }
374
375
376
377 #pragma mark -- NSURLSessionDelegate
378
379 /* The last message a session delegate receives.  A session will only become
380
381  * invalid because of a systemic error or when it has been
382
383  * explicitly invalidated, in which case the error parameter will be nil.
384
385  */
386
387 - (void)URLSession:(NSURLSession *)session didBecomeInvalidWithError:(nullableNSError *)error{
388
389
390
391     NSLog(@"didBecomeInvalidWithError");
392
393 }
394
395
396
397 #pragma mark -- NSURLSessionTaskDelegate
398
399 /* Sent as the last message related to a specific task.  Error may be
400
401  * nil, which implies that no error occurred and this task is complete.
402
403  */
404
405 - (void)URLSession:(NSURLSession *)session task:(NSURLSessionTask*)task
406
407 didCompleteWithError:(nullable NSError *)error{
408
409
410
411     NSLog(@"didCompleteWithError");
412
413
414
415     if (error == nil &&self.error ==nil) {
416
417
418
419         self.completionBlock();
420
421
422
423     }else if (error !=nil){
424
425
426
427         if (error.code != -999) {
428
429
430
431             self.error = error;
432
433             self.completionBlock();
434
435         }
436
437
438
439     }else if (self.error !=nil){
440
441
442
443         self.completionBlock();
444
445     }
446
447
448
449
450
451 }
452
453
454
455 #pragma mark -- NSURLSessionDataDelegate
456
457 /* Sent when data is available for the delegate to consume.  It is
458
459  * assumed that the delegate will retain and not copy the data.  As
460
461  * the data may be discontiguous, you should use
462
463  * [NSData enumerateByteRangesUsingBlock:] to access it.
464
465  */
466
467 - (void)URLSession:(NSURLSession *)session dataTask:(NSURLSessionDataTask *)dataTask
468
469     didReceiveData:(NSData *)data{
470
471
472
473     //根据status code的不同，做相应的处理
474
475     NSHTTPURLResponse *response = (NSHTTPURLResponse*)dataTask.response;
476
477     if (response.statusCode ==200) {
478
479
480
481         self.totalContentLength = dataTask.countOfBytesExpectedToReceive;
482
483
484
485     }else if (response.statusCode ==206){
486
487
488
489         NSString *contentRange = [response.allHeaderFieldsvalueForKey:@"Content-Range"];
490
491         if ([contentRange hasPrefix:@"bytes"]) {
492
493             NSArray *bytes = [contentRangecomponentsSeparatedByCharactersInSet:[NSCharacterSetcharacterSetWithCharactersInString:@" -/"]];
494
495             if ([bytes count] == 4) {
496
497                 self.totalContentLength = [[bytesobjectAtIndex:3]longLongValue];
498
499             }
500
501         }
502
503     }else if (response.statusCode ==416){
504
505
506
507         NSString *contentRange = [response.allHeaderFieldsvalueForKey:@"Content-Range"];
508
509         if ([contentRange hasPrefix:@"bytes"]) {
510
511             NSArray *bytes = [contentRangecomponentsSeparatedByCharactersInSet:[NSCharacterSetcharacterSetWithCharactersInString:@" -/"]];
512
513             if ([bytes count] == 3) {
514
515
516
517                 self.totalContentLength = [[bytesobjectAtIndex:2]longLongValue];
518
519                 if (self.totalReceivedContentLength==self.totalContentLength) {
520
521
522
523                     //说明已下完
524
525
526
527                     //更新进度
528
529                     self.progressBlock();
530
531                 }else{
532
533
534
535                     //416 Requested Range Not Satisfiable
536
537                     self.error = [[NSErroralloc]initWithDomain:[self.urlabsoluteString]code:416userInfo:response.allHeaderFields];
538
539                 }
540
541             }
542
543         }
544
545         return;
546
547     }else{
548
549
550
551         //其他情况还没发现
552
553         return;
554
555     }
556
557
558
559     //向文件追加数据
560
561     NSFileHandle *fileHandle = [NSFileHandlefileHandleForUpdatingAtPath:self.targetPath];
562
563     [fileHandle seekToEndOfFile]; //将节点跳到文件的末尾
564
565
566
567     [fileHandle writeData:data];//追加写入数据
568
569     [fileHandle closeFile];
570
571
572
573     //更新进度
574
575     self.totalReceivedContentLength += data.length;
576
577     self.progressBlock();
578
579 }
580
581
582
583
584
585 @end

 

经验证，如果app后台能运行，datatask是支持后台传输的。
让您的app成为后台运行app非常简单：

#import "AppDelegate.h"
static UIBackgroundTaskIdentifier bgTask;

@interface AppDelegate ()

@end

@implementation AppDelegate

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
    // Override point for customization after application launch.
    return YES;
}

- (void)applicationDidEnterBackground:(UIApplication *)application {
    
    [self getBackgroundTask];
}

- (void)applicationWillEnterForeground:(UIApplication *)application {
    
    [self endBackgroundTask];
}

/**
 *  获取后台任务
 */
-(void)getBackgroundTask{
    
    NSLog(@"getBackgroundTask");
    UIBackgroundTaskIdentifier tempTask = [[UIApplication sharedApplication] beginBackgroundTaskWithExpirationHandler:^{
        
    }];
    
    if (bgTask != UIBackgroundTaskInvalid) {
        
        [self endBackgroundTask];
    }
    
    bgTask = tempTask;
    
    [self performSelector:@selector(getBackgroundTask) withObject:nil afterDelay:120];
}

/**
 *  结束后台任务
 */
-(void)endBackgroundTask{
    
    [[UIApplication sharedApplication] endBackgroundTask:bgTask];
    bgTask = UIBackgroundTaskInvalid;
}

@end