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>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</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>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</data>
<key>NSURLSessionResumeServerDownloadDate</key>
<string>Sat, 16 May 2015 06:03:42 GMT</string>
</dict>
</plist>