24-NSURLSession的用法

说明：NSURLSession实在IOS7推出的一种新技术,用来代替NSURLConnection.
利用NSURLSession可以更加方便的实现与服务器的交互，更方便的下载上传文件。
NSURLSession的常用方法：

// 常用的类方法
+ (NSURLSession *)sharedSession;
+ (NSURLSession *)sessionWithConfiguration:(NSURLSessionConfiguration *)configuration;
+ (NSURLSession *)sessionWithConfiguration:(NSURLSessionConfiguration *)configuration delegate:(id <NSURLSessionDelegate>)delegate delegateQueue:(NSOperationQueue *)queue;

// 任务：任何一个请求都是任务
// NSURLSessionDataTask : 普通的GET\POST请求
// NSURLSessionDownloadTask : 文件下载
// NSURLSessionUploadTask : 文件上传
// 下面是常用的创建任务的方法
/* 
 * NSURLSessionTask objects are always created in a suspended state and
 * must be sent the -resume message before they will execute.
 */

/* Creates a data task with the given request. The request may have a body stream. */
- (NSURLSessionDataTask *)dataTaskWithRequest:(NSURLRequest *)request;

/* Creates a data task to retrieve the contents of the given URL. */
- (NSURLSessionDataTask *)dataTaskWithURL:(NSURL *)url;

/* Creates an upload task with the given request. The body of the request will be created from the file referenced by fileURL */
- (NSURLSessionUploadTask *)uploadTaskWithRequest:(NSURLRequest *)request fromFile:(NSURL *)fileURL;

/* Creates an upload task with the given request. The body of the request is provided from the bodyData. */
- (NSURLSessionUploadTask *)uploadTaskWithRequest:(NSURLRequest *)request fromData:(NSData *)bodyData;

/* Creates an upload task with the given request. The previously set body stream of the request (if any) is ignored and the URLSession:task:needNewBodyStream: delegate will be called when the body payload is required. */
- (NSURLSessionUploadTask *)uploadTaskWithStreamedRequest:(NSURLRequest *)request;

/* Creates a download task with the given request. */
- (NSURLSessionDownloadTask *)downloadTaskWithRequest:(NSURLRequest *)request;

/* Creates a download task to download the contents of the given URL. */
- (NSURLSessionDownloadTask *)downloadTaskWithURL:(NSURL *)url;

/* Creates a download task with the resume data. If the download cannot be successfully resumed, URLSession:task:didCompleteWithError: will be called. */
- (NSURLSessionDownloadTask *)downloadTaskWithResumeData:(NSData *)resumeData;

当需要有下载进度时，需要使用协议，实现NSURLSessionDownloadDelegate方法。

下面是利用NSURLSession实现的下载代码：

//
// ViewController.m
// NSURLSession-的使用
//
// Created by apple on 15-5-20.
// Copyright (c) 2015年 zzu. All rights reserved.
//

#import "ViewController.h"

@interface ViewController ()<NSURLSessionDownloadDelegate>

@property (nonatomic,strong) NSURLSession *session;

@end

@implementation ViewController



// 任务：任何一个请求都是任务
// NSURLSessionDataTask : 普通的GET\POST请求
// NSURLSessionDownloadTask : 文件下载
// NSURLSessionUploadTask : 文件上传
- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
}

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
// NSString *caches = [NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) lastObject];
// NSLog(@"%@",caches);

    [self downloadTask2];
}

/** * 下载任务：不能看到下载进度 */
- (void)downloadTask
{
    NSURLSession *session = [NSURLSession sharedSession];
    NSURL *url = [NSURL URLWithString:@"http://localhost:8080/MJServer/resources/images/minion_01.png"];
    // 创建一个下载task
    NSURLSessionDownloadTask *task = [session downloadTaskWithURL:url completionHandler:^(NSURL *location, NSURLResponse *response, NSError *error) {
        // location ： 临时文件的路径（下载好的文件）
        NSString *caches = [NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) lastObject];
        NSString *file = [caches stringByAppendingPathComponent:response.suggestedFilename];
        // 将临时文件剪切或复制caches文件
        NSFileManager *mgr = [NSFileManager defaultManager];
        [mgr moveItemAtPath:location.path toPath:file error:nil];
    }];
    // 开始任务
    [task resume];
}

- (void)downloadTask2
{
    NSURLSessionConfiguration *cfg = [NSURLSessionConfiguration defaultSessionConfiguration];
    // 得到session对象
    NSURLSession *session = [NSURLSession sessionWithConfiguration:cfg delegate:self delegateQueue:[NSOperationQueue mainQueue]];
    // 创建一个下载task
    NSURL *url= [NSURL URLWithString:@"http://localhost:8080/MJServer/resources/videos/test.zip"];
    NSURLSessionDownloadTask *task = [session downloadTaskWithURL:url];
    // 开始任务
    [task resume];
    // 如果下载任务设置了completionHandle这个block，也实现了下载的代理方法，则优先执行block
}

#pragma mark - <NSURLSessionDownloadDelegate>协议的方法

// 下载完毕后调用
// location : 临时文件的路径 （下载好的文件）
- (void)URLSession:(NSURLSession *)session downloadTask:(NSURLSessionDownloadTask *)downloadTask didFinishDownloadingToURL:(NSURL *)location
{
    NSString *caches = [NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) lastObject];
    NSString *file = [caches stringByAppendingPathComponent:downloadTask.response.suggestedFilename];

    // 将临时文件剪切或复制到caches文件夹
    NSFileManager *mgr = [NSFileManager defaultManager];
    [mgr moveItemAtPath:location.path toPath:file error:nil];
}

// 恢复下载时调用
- (void)URLSession:(NSURLSession *)session downloadTask:(NSURLSessionDownloadTask *)downloadTask didResumeAtOffset:(int64_t)fileOffset expectedTotalBytes:(int64_t)expectedTotalBytes
{

}

//每当下载完一部分数据时，就会调用
// bytesWriten : 本次调用写了多少数据
// totalBytesWritten : 累计写了多少数据到沙盒中
// totalBytesExceptedToWrite : 文件总长度
- (void)URLSession:(NSURLSession *)session downloadTask:(NSURLSessionDownloadTask *)downloadTask didWriteData:(int64_t)bytesWritten totalBytesWritten:(int64_t)totalBytesWritten totalBytesExpectedToWrite:(int64_t)totalBytesExpectedToWrite
{
    double progress = (double)totalBytesWritten /  totalBytesExpectedToWrite;
    NSLog(@"下载进度----- %f",progress);
}

@end

带断点续传功能的问文件下载：

//
// ZQViewController.m
//

#import "ZQViewController.h"

@interface ZQViewController () <NSURLSessionDownloadDelegate, NSURLSessionDataDelegate>
@property (weak, nonatomic) IBOutlet UIProgressView *progressView;
- (IBAction)download:(UIButton *)sender;

@property (nonatomic, strong) NSURLSessionDownloadTask *task;
@property (nonatomic, strong) NSData *resumeData;
@property (nonatomic, strong) NSURLSession *session;
@end

@implementation HMViewController

- (NSURLSession *)session
{
    if (!_session) {
        // 获得session
        NSURLSessionConfiguration *cfg = [NSURLSessionConfiguration defaultSessionConfiguration];
        self.session = [NSURLSession sessionWithConfiguration:cfg delegate:self delegateQueue:[NSOperationQueue mainQueue]];
    }
    return _session;
}

- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.

}

- (IBAction)download:(UIButton *)sender {
    // 按钮状态取反
    sender.selected = !sender.isSelected;

    if (self.task == nil) { // 开始（继续）下载
        if (self.resumeData) { // 恢复
            [self resume];
        } else { // 开始
            [self start];
        }
    } else { // 暂停
        [self pause];
    }
}

/** * 从零开始 */
- (void)start
{
    // 1.创建一个下载任务
    NSURL *url = [NSURL URLWithString:@"http://192.168.15.172:8080/MJServer/resources/videos/minion_01.mp4"];
    self.task = [self.session downloadTaskWithURL:url];

    // 2.开始任务
    [self.task resume];
}

/** * 恢复（继续） */
- (void)resume
{
    // 传入上次暂停下载返回的数据，就可以恢复下载
    self.task = [self.session downloadTaskWithResumeData:self.resumeData];

    // 开始任务
    [self.task resume];

    // 清空
    self.resumeData = nil;
}

/** * 暂停 */
- (void)pause
{
    __weak typeof(self) vc = self;
    [self.task cancelByProducingResumeData:^(NSData *resumeData) {
        // resumeData : 包含了继续下载的开始位置\下载的url
        vc.resumeData = resumeData;
        vc.task = nil;
    }];
}

#pragma mark - NSURLSessionDownloadDelegate
- (void)URLSession:(NSURLSession *)session downloadTask:(NSURLSessionDownloadTask *)downloadTask
didFinishDownloadingToURL:(NSURL *)location
{
    NSString *caches = [NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) lastObject];
    // response.suggestedFilename ： 建议使用的文件名，一般跟服务器端的文件名一致
    NSString *file = [caches stringByAppendingPathComponent:downloadTask.response.suggestedFilename];

    // 将临时文件剪切或者复制Caches文件夹
    NSFileManager *mgr = [NSFileManager defaultManager];

    // AtPath : 剪切前的文件路径
    // ToPath : 剪切后的文件路径
    [mgr moveItemAtPath:location.path toPath:file error:nil];
}

- (void)URLSession:(NSURLSession *)session downloadTask:(NSURLSessionDownloadTask *)downloadTask
      didWriteData:(int64_t)bytesWritten
 totalBytesWritten:(int64_t)totalBytesWritten
totalBytesExpectedToWrite:(int64_t)totalBytesExpectedToWrite
{
    NSLog(@"获得下载进度--%@", [NSThread currentThread]);
    // 获得下载进度
    self.progressView.progress = (double)totalBytesWritten / totalBytesExpectedToWrite;
}

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

}

//- (void)URLSession:(NSURLSession *)session dataTask:(NSURLSessionDataTask *)dataTask didReceiveData:(NSData *)data
//{
//
//}
//
//- (void)URLSession:(NSURLSession *)session dataTask:(NSURLSessionDataTask *)dataTask didReceiveResponse:(NSURLResponse *)response completionHandler:(void (^)(NSURLSessionResponseDisposition))completionHandler
//{
//
//}
@end