NSURLSessionDownloadTask 断点下载

#import "ViewController.h"

#import "ASIHTTPRequest.h"

#import <AFNetworking/AFNetworking.h>

@interface ViewController () <NSURLSessionDownloadDelegate>

@property (strong,
nonatomic) NSURLSessionDownloadTask *resumableTask;  
// 可恢复的下载任务

@property (strong,
nonatomic) NSURLSession *currentSession;   
// 当前会话

/* 用于可恢复的下载任务的数据 */

@property (strong,
nonatomic) NSData *partialData;

@property (weak,
nonatomic) IBOutlet UIProgressView *downloadingProgressView;

@property (weak,
nonatomic) IBOutlet UILabel *currentProgress_label;

@end

@implementation ViewController

- (void)viewDidLoad {

[super
viewDidLoad];

AFHTTPRequestOperationManager *man = [AFHTTPRequestOperationManager
manager];

}

/* 创建当前的session */

- (void)createCurrentSession {

NSURLSessionConfiguration *defaultConfig = [NSURLSessionConfiguration
defaultSessionConfiguration];

self.currentSession = [NSURLSession
sessionWithConfiguration:defaultConfig delegate:self
delegateQueue:nil];

self.currentSession.sessionDescription =
@"fdfd";

}

- (IBAction)download:(id)sender {

if (!self.currentSession) {

[self
createCurrentSession];

}

if (self.partialData) {
// 假设是之前被暂停的任务，就从已经保存的数据恢复下载

self.resumableTask = [self.currentSession
downloadTaskWithResumeData:self.partialData];

}

else {
// 否则创建下载任务

NSString *imageURLStr =
@"http://192.168.1.102/0701.zip";

NSURLRequest *request = [NSURLRequest
requestWithURL:[NSURL
URLWithString:imageURLStr]];

self.resumableTask = [self.currentSession
downloadTaskWithRequest:request];

}

[self.resumableTask
resume];

self.partialData =
nil;

}

- (IBAction)stop:(id)sender {

[self.resumableTask
cancelByProducingResumeData:^(NSData *resumeData) {

// 假设是可恢复的下载任务，应该先将数据保存到partialData中，注意在这里不要调用cancel方法

self.partialData = resumeData;

self.resumableTask =
nil;

NSLog(@"resumeData = %@", resumeData);

[resumeData writeToFile:@"/Users/Mac/Desktop/resumeData"
atomically:YES];

}];

}

- (void)URLSession:(NSURLSession *)session downloadTask:(NSURLSessionDownloadTask *)downloadTask didFinishDownloadingToURL:(NSURL *)location {

NSLog(@"location = %@", location);

// 设置文件的存放目标路径

NSString *documentsPath =
NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,
NSUserDomainMask, YES).firstObject;

NSURL *documentsDirectoryURL = [NSURL
fileURLWithPath:documentsPath];

NSURL *fileURL = [documentsDirectoryURL
URLByAppendingPathComponent:[[downloadTask.response
URL] lastPathComponent]];

// 假设该路径下文件已经存在。就要先将其移除，在移动文件

NSFileManager *fileManager = [NSFileManager
defaultManager];

if ([fileManager fileExistsAtPath:[fileURL
path] isDirectory:NULL]) {

[fileManager removeItemAtURL:fileURL
error:NULL];

}

[fileManager moveItemAtURL:location
toURL:fileURL error:NULL];

}

/* 从fileOffset位移处恢复下载任务 */

- (void)URLSession:(NSURLSession *)session downloadTask:(NSURLSessionDownloadTask *)downloadTask didResumeAtOffset:(int64_t)fileOffset expectedTotalBytes:(int64_t)expectedTotalBytes
{

NSLog(@"NSURLSessionDownloadDelegate: Resume download at %lld", fileOffset);

}

/* 完毕下载任务，不管下载成功还是失败都调用该方法 */

- (void)URLSession:(NSURLSession *)session task:(NSURLSessionTask *)task didCompleteWithError:(NSError *)error {

NSLog(@"NSURLSessionDownloadDelegate: Complete task");

NSLog(@"下载失败：%@", error);

}

/* 运行下载任务时有数据写入 */

- (void)URLSession:(NSURLSession *)session downloadTask:(NSURLSessionDownloadTask *)downloadTask didWriteData:(int64_t)bytesWritten  totalBytesWritten:(int64_t)totalBytesWritten
totalBytesExpectedToWrite:(int64_t)totalBytesExpectedToWrite
// 期望收到的全部data字节数

{

// 计算当前下载进度并更新视图

double downloadProgress = totalBytesWritten / (double)totalBytesExpectedToWrite;

[self setDownloadProgress:downloadProgress];

}

/* 依据下载进度更新视图 */

- (void)setDownloadProgress:(double)progress {

NSString *progressStr = [NSString
stringWithFormat:@"%.1f", progress *
100];

progressStr = [progressStr stringByAppendingString:@"%"];

NSLog(@"progressStr = %@", progressStr);

dispatch_async(dispatch_get_main_queue(), ^{

self.downloadingProgressView.progress = progress;

self.currentProgress_label.text = progressStr;

});

}

@end

[self.currentSession downloadTaskWithResumeData:self.partialData];

通过resumeData的原因例如以下是resumeData内容

resumeData内容例如以下

<?xml version="1.0" encoding="UTF-8"?

>

<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">

<plist version="1.0">

<dict>

<key>NSURLSessionDownloadURL</key>

<string>http://192.168.1.102/0701.zip</string>

<key>NSURLSessionResumeBytesReceived</key>

<integer>47271936</integer>

<key>NSURLSessionResumeCurrentRequest</key>

<data>

YnBsaXN0MDDUAQIDBAUGcnNYJHZlcnNpb25YJG9iamVjdHNZJGFyY2hpdmVyVCR0b3AS

AAGGoK8QGAcIP0BGR05PUFFSU1Q1VVZiY2RlZmdobVUkbnVsbN8QGwkKCwwNDg8QERIT

FBUWFxgZGhscHR4fICEiIyQlJicoKSUrLC0nLycmJiYkNTYmOCY6Jjw9PlMkMTJSJDNT

JDI1UyQxN1IkNFMkMjFTJDEzViRjbGFzc1IkNVMkMThSJDZTJDIyUyQxNFIkN1MkMTlT

JDEwUiQ4UiQwUyQxNVMkMjNSJDlTJDExUiQxUyQyNFMkMTZSJDJTJDIwgAiAAoAAgAeA

A4AOgAKAF4AGgAyAB4APgAeAAIAAgACACBACgAqAAIAJgAAQCYAAgAsQFoANCNNBEEIm

REVXTlMuYmFzZVtOUy5yZWxhdGl2ZYAAgAWABF8QHWh0dHA6Ly8xOTIuMTY4LjEuMTAy

LzA3MDEuemlw0khJSktaJGNsYXNzbmFtZVgkY2xhc3Nlc1VOU1VSTKJMTVVOU1VSTFhO

U09iamVjdCNATgAAAAAAABAACREBhCMAAAAAAAAAACMAAAAAAAAAABP//////////1NH

RVTTV1gQWV1hV05TLmtleXNaTlMub2JqZWN0c6NaW1yAEIARgBKjXl9ggBOAFIAVgBZf

EA9BY2NlcHQtRW5jb2RpbmdWQWNjZXB0XxAPQWNjZXB0LUxhbmd1YWdlXWd6aXAsIGRl

ZmxhdGVTKi8qVWVuLXVz0khJaWpcTlNEaWN0aW9uYXJ5omtsXE5TRGljdGlvbmFyeVhO

U09iamVjdNJISW5vXE5TVVJMUmVxdWVzdKJwcVxOU1VSTFJlcXVlc3RYTlNPYmplY3Rf

EA9OU0tleWVkQXJjaGl2ZXLRdHVUcm9vdIABAAgAEQAaACMALQAyADcAUgBYAJEAlQCY

AJwAoACjAKcAqwCyALUAuQC8AMAAxADHAMsAzwDSANUA2QDdAOAA5ADnAOsA7wDyAPYA

+AD6APwA/gEAAQIBBAEGAQgBCgEMAQ4BEAESARQBFgEYARoBHAEeASABIgEkASYBKAEq

ASwBLQE0ATwBSAFKAUwBTgFuAXMBfgGHAY0BkAGWAZ8BqAGqAasBrgG3AcAByQHNAdQB

3AHnAesB7QHvAfEB9QH3AfkB+wH9Ag8CFgIoAjYCOgJAAkUCUgJVAmICawJwAn0CgAKN

ApYCqAKrArAAAAAAAAACAQAAAAAAAAB2AAAAAAAAAAAAAAAAAAACsg==

</data>

<key>NSURLSessionResumeEntityTag</key>

<string>"c04546-5c3ca3fe-5162cb9046b80"</string>

<key>NSURLSessionResumeInfoLocalPath</key>

<string>/Users/Mac/Library/Developer/CoreSimulator/Devices/E460928F-4469-41A7-B94E-8E6372A96C89/data/Containers/Data/Application/8E686354-BA1D-408E-8124-56AC07CD7287/tmp/CFNetworkDownload_brs2kY.tmp</string>

<key>NSURLSessionResumeInfoVersion</key>

<integer>1</integer>

<key>NSURLSessionResumeOriginalRequest</key>

<data>

YnBsaXN0MDDUAQIDBAUGTk9YJHZlcnNpb25YJG9iamVjdHNZJGFyY2hpdmVyVCR0b3AS

AAGGoK4HCDM0OjtCQ0RFRkdISVUkbnVsbN8QFQkKCwwNDg8QERITFBUWFxgZGhscHR4f

ICEfIyQlICAoKCgeLC0uKDAxMlMkMTJSJDNTJDE3UiQ0UyQxM1YkY2xhc3NSJDVTJDE4

UiQ2UyQxNFIkN1MkMTlTJDEwUiQ4UiQwUyQxNVIkOVMkMTFSJDFTJDE2UiQygAiAAoAH

gAOAAoANgAaADIAHgAeAAIAAgACACBACgAqACYAAEAmACxAQCNM1DjYoODlXTlMuYmFz

ZVtOUy5yZWxhdGl2ZYAAgAWABF8QHWh0dHA6Ly8xOTIuMTY4LjEuMTAyLzA3MDEuemlw

0jw9Pj9aJGNsYXNzbmFtZVgkY2xhc3Nlc1VOU1VSTKJAQVVOU1VSTFhOU09iamVjdCNA

TgAAAAAAABAACREBgCMAAAAAAAAAACMAAAAAAAAAABP//////////9I8PUpLXE5TVVJM

UmVxdWVzdKJMTVxOU1VSTFJlcXVlc3RYTlNPYmplY3RfEA9OU0tleWVkQXJjaGl2ZXLR

UFFUcm9vdIABAAgAEQAaACMALQAyADcARgBMAHkAfQCAAIQAhwCLAJIAlQCZAJwAoACj

AKcAqwCuALEAtQC4ALwAvwDDAMYAyADKAMwAzgDQANIA1ADWANgA2gDcAN4A4ADiAOQA

5gDoAOoA7ADuAPAA8QD4AQABDAEOARABEgEyATcBQgFLAVEBVAFaAWMBbAFuAW8BcgF7

AYQBjQGSAZ8BogGvAbgBygHNAdIAAAAAAAACAQAAAAAAAABSAAAAAAAAAAAAAAAAAAAB

1A==

</data>

<key>NSURLSessionResumeServerDownloadDate</key>

<string>Sat, 16 May 2015 06:03:42 GMT</string>

</dict>

</plist>

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