导语

现在NSURLConnection在开发中会使用的越来越少，iOS9已经将NSURLConnection废弃，现在最低版本一般适配iOS7，所以也可以使用。
NSURLConnection相对于NSURLSession,安全性低。NSURLConnection下载有峰值，比较麻烦处理。
尽管适配最低版本iOS7，也可以使用NSURLSession。AFN已经不支持NSURLConnection。
NSURLSession：默认是挂起状态，如果要请求网络，需要开启。

[NSURLSession sharedSession] 获取全局的NSURLSession对象。在iPhone的所有app共用一个全局session.
     NSURLSessionUploadTask -> NSURLSessionDataTask -> NSURLSessionTask
     NSURLSessionDownloadTask -> NSURLSessionTask
     NSURLSessionDownloadTask下载，默认下载到tmp文件夹。下载完成后删除临时文件。所以我们要在删除文件之前，将它移动到Cache里。

NSURLSession详解

NSURLSession基础
NSURLSession代理
NSURLSession大文件下载
NSURLSession断点续传

1.NSURLSession基础

第一种网络请求方法

    //创建URL

    NSURL * url = [NSURL URLWithString:@"http://192.168.1.200/login.php?username=haha&password=123"];

    //创建请求

    //    NSURLRequest * request = [NSURLRequest requestWithURL:url];

    //创建Session

    NSURLSession * session = [NSURLSession sharedSession];

    //创建任务

    NSURLSessionDataTask * task = [session dataTaskWithURL:url completionHandler:^(NSData * _Nullable data, NSURLResponse * _Nullable response, NSError * _Nullable error) {

        NSLog(@"%@",[[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding]);

    }];

    //开启网络任务

    [task resume];

第二种网络请求方法

//创建URL

    NSURL * url = [NSURL URLWithString:@"http://192.168.1.200/login.php?username=haha&password=123"];

    //创建请求

    NSURLRequest * request = [NSURLRequest requestWithURL:url];

    //创建Session

    NSURLSession * session = [NSURLSession sharedSession];

    //创建任务

    NSURLSessionDataTask * task = [session dataTaskWithRequest:request completionHandler:^(NSData * _Nullable data, NSURLResponse * _Nullable response, NSError * _Nullable error) {

        NSLog(@"%@",[[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding]);

    }];

    //开启网络任务

    [task resume];

POST请求

NSURL * url = [NSURL URLWithString:@"http://192.168.1.200/login.php"];

    NSMutableURLRequest * request = [NSMutableURLRequest requestWithURL:url];

    //设置请求方法

    request.HTTPMethod = @"POST";

    //设置请求体

    request.HTTPBody = [@"username=haha&password=123" dataUsingEncoding:NSUTF8StringEncoding];

    [[[NSURLSession sharedSession] dataTaskWithRequest:request completionHandler:^(NSData * _Nullable data, NSURLResponse * _Nullable response, NSError * _Nullable error) {

        NSLog(@"%@",[[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding]);

    }] resume];

下载文件

    NSURL * url = [NSURL URLWithString:[@"http://192.168.1.200/DOM解析.mp4" stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding]];

    NSURLSession * session = [NSURLSession sharedSession];

    NSURLSessionDownloadTask * downloadTask = [session downloadTaskWithURL:url completionHandler:^(NSURL * _Nullable location, NSURLResponse * _Nullable response, NSError * _Nullable error) {

        //location 下载到沙盒的地址

        NSLog(@"下载完成%@",location);

        //response.suggestedFilename 响应信息中的资源文件名

        NSString * cachesPath = [[NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) lastObject] stringByAppendingPathComponent:response.suggestedFilename];

        NSLog(@"缓存地址%@",cachesPath);

        //获取文件管理器

        NSFileManager * mgr = [NSFileManager defaultManager];

        //将临时文件移动到缓存目录下

        //[NSURL fileURLWithPath:cachesPath] 将本地路径转化为URL类型

        //URL如果地址不正确，生成的url对象为空

        [mgr moveItemAtURL:location toURL:[NSURL fileURLWithPath:cachesPath] error:NULL];

    }];

    [downloadTask resume];

2.NSURLSession代理

- (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event {

    //  全局session

    //    NSURLSession * session = [NSURLSession sharedSession];

    //创建自定义session

    //NSURLSessionConfiguration 的 配置

    //[[NSOperationQueue alloc] init] 也可以写成 nil

    NSURL * url = [NSURL URLWithString:@"http://192.168.1.200/login.php?username=haha&password=123"];

    NSURLSession * session = [NSURLSession sessionWithConfiguration:[NSURLSessionConfiguration defaultSessionConfiguration] delegate:self delegateQueue:[[NSOperationQueue alloc] init]];

    NSURLSessionDataTask * task = [session dataTaskWithURL:url];

    [task resume];

}

//接收到服务器响应

- (void)URLSession:(NSURLSession *)session dataTask:(NSURLSessionDataTask *)dataTask

didReceiveResponse:(NSURLResponse *)response

 completionHandler:(void (^)(NSURLSessionResponseDisposition disposition))completionHandler {

    NSLog(@"%s",__FUNCTION__);

    //允许接受服务器回传数据

    completionHandler(NSURLSessionResponseAllow);

}

//接收服务器回传的数据,有可能执行多次

- (void)URLSession:(NSURLSession *)session dataTask:(NSURLSessionDataTask *)dataTask

    didReceiveData:(NSData *)data {

    NSLog(@"%@",[[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding]);

}

//请求成功或失败

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

    NSLog(@"%@",error);

}

3.NSURLSession大文件下载

#import "ViewController.h"

@interface ViewController ()<NSURLSessionDownloadDelegate>

@end

@implementation ViewController

- (void)viewDidLoad {

    [super viewDidLoad];

    // Do any additional setup after loading the view, typically from a nib.

    NSLog(@"%@",NSSearchPathForDirectoriesInDomains(, , ));

}

- (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event {

    NSURLSession * session = [NSURLSession sessionWithConfiguration:[NSURLSessionConfiguration defaultSessionConfiguration] delegate:self delegateQueue:[[NSOperationQueue alloc] init]];

    NSURLSessionDownloadTask * task = [session downloadTaskWithURL:[NSURL URLWithString:[@"http://192.168.1.200/DOM解析.mp4"stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding]]];

    [task resume];

}

/*

 监测临时文件下载的数据大小，当每次写入临时文件时，就会调用一次

 bytesWritten 单次写入多少

 totalBytesWritten  已经写入了多少

 totalBytesExpectedToWrite 文件总大小

 */

- (void)URLSession:(NSURLSession *)session downloadTask:(NSURLSessionDownloadTask *)downloadTask

      didWriteData:(int64_t)bytesWritten

 totalBytesWritten:(int64_t)totalBytesWritten

totalBytesExpectedToWrite:(int64_t)totalBytesExpectedToWrite {

    //打印下载百分比

    NSLog(@"%f",totalBytesWritten * 1.0 / totalBytesExpectedToWrite);

}

//下载完成

- (void)URLSession:(NSURLSession *)session downloadTask:(NSURLSessionDownloadTask *)downloadTask

didFinishDownloadingToURL:(NSURL *)location {

    NSString * cachesPath = [[NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) lastObject] stringByAppendingPathComponent:downloadTask.response.suggestedFilename];

    NSFileManager * mgr = [NSFileManager defaultManager];

    [mgr moveItemAtURL:location toURL:[NSURL fileURLWithPath:cachesPath] error:NULL];

}

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

    NSLog(@"%@",error);

}

4.NSURLSession断点续传

#import "ViewController.h"

@interface ViewController ()<NSURLSessionDownloadDelegate>

@property (nonatomic, strong) NSURLSessionDownloadTask * task;

@property (nonatomic, strong) NSData * resumeData;

@property (nonatomic, strong) NSURLSession * session;

@end

@implementation ViewController

//故事板中开始按钮的响应方法

- (IBAction)start:(id)sender {

    NSURLSession * session = [NSURLSession sessionWithConfiguration:[NSURLSessionConfiguration defaultSessionConfiguration] delegate:self delegateQueue:[[NSOperationQueue alloc] init]];

    self.session = session;

    self.task = [session downloadTaskWithURL:[NSURL URLWithString:[@"http://192.168.1.68/丁香花.mp3"stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding]]];

    [self.task resume];

}

//故事板中暂停按钮的响应方法

- (IBAction)pause:(id)sender {

    //暂停就是将任务挂起

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

        //保存已下载的数据

        self.resumeData = resumeData;

    }];

}

//继续按钮的响应方法

- (IBAction)resume:(id)sender {

    //可以使用ResumeData创建任务

    self.task = [self.session downloadTaskWithResumeData:self.resumeData];

    //开启继续下载

    [self.task resume];

}

- (void)viewDidLoad {

    [super viewDidLoad];

    // Do any additional setup after loading the view, typically from a nib.

    NSLog(@"%@",NSSearchPathForDirectoriesInDomains(, , ));

}

/*

 监测临时文件下载的数据大小，当每次写入临时文件时，就会调用一次

 bytesWritten 单次写入多少

 totalBytesWritten  已经写入了多少

 totalBytesExpectedToWrite 文件总大小

 */

- (void)URLSession:(NSURLSession *)session downloadTask:(NSURLSessionDownloadTask *)downloadTask

      didWriteData:(int64_t)bytesWritten

 totalBytesWritten:(int64_t)totalBytesWritten

totalBytesExpectedToWrite:(int64_t)totalBytesExpectedToWrite {

    //打印下载百分比

    NSLog(@"%f",totalBytesWritten * 1.0 / totalBytesExpectedToWrite);

}

//下载完成

- (void)URLSession:(NSURLSession *)session downloadTask:(NSURLSessionDownloadTask *)downloadTask

didFinishDownloadingToURL:(NSURL *)location {

    NSString * cachesPath = [[NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) lastObject] stringByAppendingPathComponent:downloadTask.response.suggestedFilename];

    NSFileManager * mgr = [NSFileManager defaultManager];

    [mgr moveItemAtURL:location toURL:[NSURL fileURLWithPath:cachesPath] error:NULL];

}

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

    NSLog(@"%@",error);

}