拷贝# IOS网络访问之NSURLSession
NSURLSession是IOS7中新添加的网络访问接口，作用与NSURLConnection一致，在程序在前台时，NSURLSession与NSURLConnection可以互为替代工作。如果用户强制将程序关闭，NSURLSession会断掉。
NSURLSession中关键类有下面几种
1：NSURLSessionConfiguration：用于配置NSURLSession工作模式以及网络设置
工作模式分为下面三种：
普通模式（default）：可以使用缓存
+ (NSURLSessionConfiguration *)defaultSessionConfiguration;
瞬时模式（ephemeral）：不使用缓存
+ (NSURLSessionConfiguration *)ephemeralSessionConfiguration;
后台模式（background）：当按下home键后仍然可以在后台进行上传下载操作，需要通过唯一的identity标示
+ (NSURLSessionConfiguration *)backgroundSessionConfiguration:(NSString *)identifier;
网络设置：
@property BOOL allowsCellularAccess 允许使用蜂窝数据
@property (getter=isDiscretionary) BOOL discretionary YES时表示任务后台运行时自动选择最佳的网络选择（综合考虑网络，电量）
2：NSURLSession：获取NSURLSession有下面几种方式
+ (NSURLSession *)sharedSession 共享的会话，使用全局的Cookie，缓存数据
+ (NSURLSession *)sessionWithConfiguration:(NSURLSessionConfiguration *)configuration 使用配置好的NSURLSessionConfiguration获得会话
+ (NSURLSession *)sessionWithConfiguration:(NSURLSessionConfiguration *)configuration delegate:(id <NSURLSessionDelegate>)delegate delegateQueue:(NSOperationQueue *)queue 与第2中相似，但是指定了委托
3：NSURLSessionTask：会话任务，通过NSURLSession创建，有下面3种常用子类
NSURLSessionDataTask：最普通的网络访问，与NSURLConnection使用方式相似，多用来获取xml或者json，可以通过NSURLSession的以下方法创建
- (NSURLSessionDataTask *)dataTaskWithRequest:(NSURLRequest *)request;
- (NSURLSessionDataTask *)dataTaskWithURL:(NSURL *)url
同时还可以通过block指定回调
- (NSURLSessionDataTask *)dataTaskWithRequest:(NSURLRequest *)request completionHandler:(void (^)(NSData *data, NSURLResponse *response, NSError *error))completionHandler;
- (NSURLSessionDataTask *)dataTaskWithURL:(NSURL *)url completionHandler:(void (^)(NSData *data, NSURLResponse *response, NSError *error))completionHandler;
NSURLSessionDownLoadTask：用来处理下载任务
- (NSURLSessionDownloadTask *)downloadTaskWithRequest:(NSURLRequest *)request;
- (NSURLSessionDownloadTask *)downloadTaskWithURL:(NSURL *)url;
- (NSURLSessionDownloadTask *)downloadTaskWithResumeData:(NSData *)resumeData;
上面3种方法均可通过block设置回调，第三种方法可以实现断点续传
NSURLSessionUploadTask：用来处理上传任务，NSURLSessionDataTask的子类
- (NSURLSessionUploadTask *)uploadTaskWithRequest:(NSURLRequest *)request fromFile:(NSURL *)fileURL
- (NSURLSessionUploadTask *)uploadTaskWithRequest:(NSURLRequest *)request fromData:(NSData *)bodyData
- (NSURLSessionUploadTask *)uploadTaskWithStreamedRequest:(NSURLRequest *)request
上面3种方法同样可以通过block设置回调
创建后的NSURLSessionTask需要调用resume才会执行
4：NSURLSessionDelegate和NSURLSessionTaskDelegate协议
在网络请求的各个阶段都会触发协议的不同方法，具体使用方法可以参照后面例子
**取消链接**
不再需要连接调用Session的invalidateAndCancel直接关闭，或者调用finishTasksAndInvalidate等待当前Task结束后关闭。这时Delegate会收到URLSession:didBecomeInvalidWithError:这个事件。Delegate收到这个事件之后会被解引用
示例1：通过NSSessionDataTask访问网络数据
-(void)viewDidLoad {
[super viewDidLoad];
NSString *urlStr = @"http://localhost/iostest.php";
urlStr = [urlStr stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];
//创建request
NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:[NSURL URLWithString:urlStr]];
request.HTTPMethod = @"POST";
request.HTTPBody = [@"name=zanglitao&gender=male" dataUsingEncoding:NSUTF8StringEncoding];
//创建NSURLSession
NSURLSession *session = [NSURLSession sharedSession];
//创建任务
NSURLSessionDataTask *task = [session dataTaskWithRequest:request completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) {
NSLog(@"%@",[[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding]);
}];
//开始任务
[task resume];
}
示例2：通过NSSessionUploadTask上传文件，流程和NSURLConnection基本一致，关键点也是设置请求头参数和请求体拼接
//自定义一个boundary
#define boundary @"zanglitao"
@interface ZViewController()
@end
@implementation ZViewController
-(void)viewDidLoad {
[super viewDidLoad];
NSMutableURLRequest *request = [[NSMutableURLRequest alloc] initWithURL:[NSURL URLWithString:@"http://localhost/iostest.php"]];
//必须使用POST
request.HTTPMethod = @"POST";
//设置请求体
request.HTTPBody = [self getDataBody];
//设置请求头
[request setValue:[NSString stringWithFormat:@"%d",[self getDataBody].length] forHTTPHeaderField:@"Content-Length"];
[request setValue:[NSString stringWithFormat:@"multipart/form-data; boundary=%@",boundary] forHTTPHeaderField:@"Content-Type"];
NSURLSession *session = [NSURLSession sharedSession];
NSURLSessionUploadTask *task = [session uploadTaskWithRequest:request fromData:[self getDataBody] completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) {
NSLog(@"%@",[[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding]);
}];
[task resume];
}
//获取请求体内容
-(NSData *)getDataBody {
NSMutableData *data = [NSMutableData data];
NSString *top = [NSString stringWithFormat:@"--%@\nContent-Disposition: form-data; name=\"file\"; filename=\"1.png\"\nContent-Type: image/png\n\n",boundary];
NSString *bottom = [NSString stringWithFormat:@"\n--%@--\n\n",boundary];
NSData *content = [NSData dataWithContentsOfFile:[[NSBundle mainBundle] pathForResource:@"1" ofType:@"png"]];
[data appendData:[top dataUsingEncoding:NSUTF8StringEncoding]];
[data appendData:content];
[data appendData:[bottom dataUsingEncoding:NSUTF8StringEncoding]];
return data;
}
@end
示例3：使用NSURLSessionDownLoadTask下载文件
-(void)viewDidLoad {
[super viewDidLoad];
NSURLSession *session = [NSURLSession sharedSession];
NSURLSessionDownloadTask *task = [session downloadTaskWithURL:[NSURL URLWithString:@"http://g.hiphotos.baidu.com/image/pic/item/e61190ef76c6a7efc0a0e1ebfffaaf51f2de667c.jpg"] completionHandler:^(NSURL *location, NSURLResponse *response, NSError *error) {
//下载完成后文件位于location处，我们需要移到沙盒中
NSString *dirPath = [NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) firstObject];
NSString *path = [dirPath stringByAppendingPathComponent:@"1.jpg"];
NSFileManager *manager = [NSFileManager defaultManager];
if ([manager fileExistsAtPath:path isDirectory:NO]) {
[manager removeItemAtPath:path error:nil];
}
[manager moveItemAtPath:[location path] toPath:path error:nil];
}];
//开始任务
[task resume];
}
执行后我们看到沙盒中多了一张名为1.jpg的图片，这是我们下载的图片
上面的代码还有一点问题，就是下载过程中没有进度提示只能干等，我们可以通过设置委托获取下载进度
示例4：使用委托查看下载进度
@interface ZViewController()<NSURLSessionDelegate>
@end
@implementation ZViewController
-(void)viewDidLoad {
[super viewDidLoad];
NSURLSessionConfiguration *configuration = [NSURLSessionConfiguration defaultSessionConfiguration];
//使用配置的NSURLSessionConfiguration获取NSSession，并且设置委托
NSURLSession *session = [NSURLSession sessionWithConfiguration:configuration delegate:self delegateQueue:nil];
NSURLSessionDownloadTask *task = [session downloadTaskWithURL:[NSURL URLWithString:@"http://g.hiphotos.baidu.com/image/pic/item/e61190ef76c6a7efc0a0e1ebfffaaf51f2de667c.jpg"] ];
//开始任务
[task resume];
}
- (void)URLSession:(NSURLSession *)session downloadTask:(NSURLSessionDownloadTask *)downloadTask
didWriteData:(int64_t)bytesWritten
totalBytesWritten:(int64_t)totalBytesWritten
totalBytesExpectedToWrite:(int64_t)totalBytesExpectedToWrite {
float percent = (float)totalBytesWritten/totalBytesExpectedToWrite;
NSLog(@"%f",percent);
}
- (void)URLSession:(NSURLSession *)session downloadTask:(NSURLSessionDownloadTask *)downloadTask
didFinishDownloadingToURL:(NSURL *)location {
NSString *dirPath = [NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) firstObject];
NSString *path = [dirPath stringByAppendingPathComponent:@"1.jpg"];
NSFileManager *manager = [NSFileManager defaultManager];
if ([manager fileExistsAtPath:path isDirectory:NO]) {
[manager removeItemAtPath:path error:nil];
}
[manager moveItemAtPath:[location path] toPath:path error:nil];
}
//任务结束
- (void)URLSession:(NSURLSession *)session task:(NSURLSessionTask *)task
didCompleteWithError:(NSError *)error {
NSLog(@"%s",__func__);
}
@end
**2014-11-08 14:11:44.146 IOS****网络请求****[2366:3507] 0.020172**
**2014-11-08 14:11:44.147 IOS****网络请求****[2366:3507] 0.100307**
**2014-11-08 14:11:44.148 IOS****网络请求****[2366:3507] 0.153730**
**2014-11-08 14:11:44.148 IOS****网络请求****[2366:3507] 0.180442**
**2014-11-08 14:11:44.149 IOS****网络请求****[2366:3507] 0.207153**
**2014-11-08 14:11:44.150 IOS****网络请求****[2366:3507] 0.236461**
**2014-11-08 14:11:44.156 IOS****网络请求****[2366:3507] 0.263173**
**2014-11-08 14:11:44.160 IOS****网络请求****[2366:3507] 0.289884**
**2014-11-08 14:11:44.160 IOS****网络请求****[2366:3507] 0.316596**
**2014-11-08 14:11:44.161 IOS****网络请求****[2366:3507] 0.343307**
**2014-11-08 14:11:44.162 IOS****网络请求****[2366:3507] 0.370019**
**2014-11-08 14:11:44.162 IOS****网络请求****[2366:3507] 0.476865**
**2014-11-08 14:11:44.163 IOS****网络请求****[2366:3507] 0.557000**
**2014-11-08 14:11:44.169 IOS****网络请求****[2366:3803] 0.610423**
**2014-11-08 14:11:44.170 IOS****网络请求****[2366:3803] 0.663846**
**2014-11-08 14:11:44.171 IOS****网络请求****[2366:3803] 0.690558**
**2014-11-08 14:11:44.175 IOS****网络请求****[2366:3803] 0.717269**
**2014-11-08 14:11:44.176 IOS****网络请求****[2366:3803] 0.743981**
**2014-11-08 14:11:44.176 IOS****网络请求****[2366:3803] 0.797404**
**2014-11-08 14:11:44.177 IOS****网络请求****[2366:3803] 0.850827**
**2014-11-08 14:11:44.178 IOS****网络请求****[2366:3803] 0.877539**
**2014-11-08 14:11:44.179 IOS****网络请求****[2366:3803] 0.904250**
**2014-11-08 14:11:44.180 IOS****网络请求****[2366:3803] 0.930962**
**2014-11-08 14:11:44.180 IOS****网络请求****[2366:3803] 0.957674**
**2014-11-08 14:11:44.180 IOS****网络请求****[2366:3803] 0.984385**
**2014-11-08 14:11:44.181 IOS****网络请求****[2366:3803] 1.000000**
**2014-11-08 14:11:44.182 IOS****网络请求****[2366:3803] -[ZViewController URLSession:task:didCompleteWithError:]**
下载是个漫长的过程，尤其是对于比较大的文件，所以我们还需要一个取消下载的按钮
示例5：示例4添加取消下载功能
@interface ZViewController()<NSURLSessionDelegate>
@property(nonatomic,strong)NSURLSessionDownloadTask *task;
@end
@implementation ZViewController
-(void)viewDidLoad {
[super viewDidLoad];
NSURLSessionConfiguration *configuration = [NSURLSessionConfiguration defaultSessionConfiguration];
//使用配置的NSURLSessionConfiguration获取NSSession，并且设置委托
NSURLSession *session = [NSURLSession sessionWithConfiguration:configuration delegate:self delegateQueue:nil];
_task = [session downloadTaskWithURL:[NSURL URLWithString:@"http://yinyueshiting.baidu.com/data2/music/46729925/13125209147600128.mp3?xcode=10d30604371d01ea5cfa24abb2db23a644b52c81891b10c8"] ];
//开始任务
[_task resume];
}
- (void)URLSession:(NSURLSession *)session downloadTask:(NSURLSessionDownloadTask *)downloadTask
didWriteData:(int64_t)bytesWritten
totalBytesWritten:(int64_t)totalBytesWritten
totalBytesExpectedToWrite:(int64_t)totalBytesExpectedToWrite {
float percent = (float)totalBytesWritten/totalBytesExpectedToWrite;
NSLog(@"%f",percent);
}
- (void)URLSession:(NSURLSession *)session downloadTask:(NSURLSessionDownloadTask *)downloadTask
didFinishDownloadingToURL:(NSURL *)location {
NSString *dirPath = [NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) firstObject];
NSString *path = [dirPath stringByAppendingPathComponent:@"1.mp3"];
NSFileManager *manager = [NSFileManager defaultManager];
if ([manager fileExistsAtPath:path isDirectory:NO]) {
[manager removeItemAtPath:path error:nil];
}
[manager moveItemAtPath:[location path] toPath:path error:nil];
}
//任务结束
- (void)URLSession:(NSURLSession *)session task:(NSURLSessionTask *)task
didCompleteWithError:(NSError *)error {
NSLog(@"%s",__func__);
}
- (IBAction)cancelDownload:(id)sender {
[_task cancel];
}
@end
**2014-11-08 14:25:28.351 IOS****网络请求****[2451:3803] 0.000917**
**2014-11-08 14:25:28.359 IOS****网络请求****[2451:3507] 0.008676**
**2014-11-08 14:25:28.370 IOS****网络请求****[2451:1303] 0.010250**
**2014-11-08 14:25:28.379 IOS****网络请求****[2451:5407] 0.018904**
**2014-11-08 14:25:28.393 IOS****网络请求****[2451:3507] 0.022838**
**2014-11-08 14:25:28.393 IOS****网络请求****[2451:3507] 0.023625**
**2014-11-08 14:25:28.405 IOS****网络请求****[2451:3507] 0.030705**
**2014-11-08 14:25:28.405 IOS****网络请求****[2451:3507] 0.034639**
**2014-11-08 14:25:28.409 IOS****网络请求****[2451:1303] 0.035032**
**2014-11-08 14:25:28.414 IOS****网络请求****[2451:5407] 0.035426**
**2014-11-08 14:25:28.436 IOS****网络请求****[2451:3507] 0.035819**
**2014-11-08 14:25:28.479 IOS****网络请求****[2451:3507] -[ZViewController URLSession:task:didCompleteWithError:]**
当按下取消按钮时下载停止，同时任务结束的方法被触发
当然现实中更常见的方式是任务停止下载后还能恢复下载
示例6：暂停与恢复
- (IBAction)pauseDownload:(id)sender {
[_task suspend];
}
- (IBAction)continueDownload:(id)sender {
[_task resume];
}
有时候我们暂停了任务然后退出了程序，如果希望下次进入程序后还能继续下载，那就需要实现断点下载功能，在NSURLConnection中可以利用请求头的Range参数实现断点下载，在NSURLSession中实现断点下载更加简单
示例7：断点下载
@interface ZViewController()<NSURLSessionDelegate>
@property (strong, nonatomic)NSURLSessionDownloadTask *task;
//存储已下载的数据
@property(nonatomic,strong)NSData *data;
@end
@implementation ZViewController
-(void)viewDidLoad {
[super viewDidLoad];
NSURLSessionConfiguration *configuration = [NSURLSessionConfiguration defaultSessionConfiguration];
//使用配置的NSURLSessionConfiguration获取NSSession，并且设置委托
NSURLSession *session = [NSURLSession sessionWithConfiguration:configuration delegate:self delegateQueue:nil];
_task = [session downloadTaskWithURL:[NSURL URLWithString:@"http://yinyueshiting.baidu.com/data2/music/46729925/13125209147600128.mp3?xcode=10d30604371d01ea5cfa24abb2db23a644b52c81891b10c8"] ];
//开始任务
[_task resume];
}
- (void)URLSession:(NSURLSession *)session downloadTask:(NSURLSessionDownloadTask *)downloadTask
didWriteData:(int64_t)bytesWritten
totalBytesWritten:(int64_t)totalBytesWritten
totalBytesExpectedToWrite:(int64_t)totalBytesExpectedToWrite {
float percent = (float)totalBytesWritten/totalBytesExpectedToWrite;
NSLog(@"%f",percent);
}
- (void)URLSession:(NSURLSession *)session downloadTask:(NSURLSessionDownloadTask *)downloadTask
didFinishDownloadingToURL:(NSURL *)location {
NSString *dirPath = [NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) firstObject];
NSString *path = [dirPath stringByAppendingPathComponent:@"1.mp3"];
NSFileManager *manager = [NSFileManager defaultManager];
if ([manager fileExistsAtPath:path isDirectory:NO]) {
[manager removeItemAtPath:path error:nil];
}
[manager moveItemAtPath:[location path] toPath:path error:nil];
}
//任务结束
- (void)URLSession:(NSURLSession *)session task:(NSURLSessionTask *)task
didCompleteWithError:(NSError *)error {
NSLog(@"%s",__func__);
}
- (IBAction)pauseDownload:(id)sender {
[_task cancelByProducingResumeData:^(NSData *resumeData) {
_task = nil;
_data = resumeData;
}];
}
- (IBAction)continueDownload:(id)sender {
NSURLSessionConfiguration *configuration = [NSURLSessionConfiguration defaultSessionConfiguration];
NSURLSession *session = [NSURLSession sessionWithConfiguration:configuration delegate:self delegateQueue:nil];
_task = [session downloadTaskWithResumeData:_data];
[_task resume];
}
@end
示例8：后台下载
@implementation ZViewController
-(void)viewDidLoad {
[super viewDidLoad];
NSURLSession *session = [self session];
NSURLSessionDownloadTask *task = [session downloadTaskWithURL:[NSURL URLWithString:@"http://yinyueshiting.baidu.com/data2/music/46729925/13125209147600128.mp3?xcode=10d30604371d01ea5cfa24abb2db23a644b52c81891b10c8"] ];
//开始任务
[task resume];
}
//后台会话(保证只有一个后台会话)
-(NSURLSession *)session {
static NSURLSession *session;
static dispatch_once_t token;
dispatch_once(&token, ^{
//后台下载
NSURLSessionConfiguration *configuration = [NSURLSessionConfiguration backgroundSessionConfiguration:@"zang"];
configuration.discretionary = YES;
//使用配置的NSURLSessionConfiguration获取NSSession，并且设置委托
session = [NSURLSession sessionWithConfiguration:configuration delegate:self delegateQueue:nil];
});
return session;
}
- (void)URLSession:(NSURLSession *)session downloadTask:(NSURLSessionDownloadTask *)downloadTask
didWriteData:(int64_t)bytesWritten
totalBytesWritten:(int64_t)totalBytesWritten
totalBytesExpectedToWrite:(int64_t)totalBytesExpectedToWrite {
float percent = (float)totalBytesWritten/totalBytesExpectedToWrite;
NSLog(@"%f",percent);
}
- (void)URLSession:(NSURLSession *)session downloadTask:(NSURLSessionDownloadTask *)downloadTask
didFinishDownloadingToURL:(NSURL *)location {
NSString *dirPath = [NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) firstObject];
NSString *path = [dirPath stringByAppendingPathComponent:@"1.mp3"];
NSFileManager *manager = [NSFileManager defaultManager];
if ([manager fileExistsAtPath:path isDirectory:NO]) {
[manager removeItemAtPath:path error:nil];
}
[manager moveItemAtPath:[location path] toPath:path error:nil];
}
//任务结束
- (void)URLSession:(NSURLSession *)session task:(NSURLSessionTask *)task
didCompleteWithError:(NSError *)error {
NSLog(@"%s",__func__);
}
@end
启动程序后按下home键发现下载进度信息不再更新，静候片刻再进入程序发现沙盒中多了1.mp3，使用backgroundSessionConfiguration可以使我们的下载任务运行在后台
我们也可以通过委托在文件下载完后进行界面更新
示例9：后台下载任务监控
当在后台下载完成后会触发AppDelegate的一个方法
此方法包含一个competionHandler（此操作表示应用完成所有处理工作），通常我们会保存此对象；直到最后一个任务完成，此时会重新通过会话标识（上面sessionConfig中设置的）找到对应的会话并调用NSURLSession的-(void)URLSessionDidFinishEventsForBackgroundURLSession:(NSURLSession *)session代理方法，在这个方法中通常可以进行UI更新，并调用completionHandler通知系统已经完成所有操作
- (void)application:(UIApplication *)application handleEventsForBackgroundURLSession:(NSString *)identifier completionHandler:(void (^)())completionHandler {
NSLog(@"%@:download complete",identifier);
self.handler = completionHandler;
}
**2014-11-08 16:35:38.553 IOS****网络请求****[5149:1303] 0.018046**
**2014-11-08 16:35:38.554 IOS****网络请求****[5149:1303] 0.018117**
**2014-11-08 16:35:38.632 IOS****网络请求****[5149:3d07] 0.036427**
**2014-11-08 16:35:38.633 IOS****网络请求****[5149:3d07] 0.036606**
**2014-11-08 16:35:38.719 IOS****网络请求****[5149:4707] 0.054916**
**2014-11-08 16:35:38.719 IOS****网络请求****[5149:4707] 0.055094**
**2014-11-08 16:35:38.813 IOS****网络请求****[5149:1303] 0.073583**
**2014-11-08 16:35:38.814 IOS****网络请求****[5149:1303] 0.092072**
**2014-11-08 16:35:38.881 IOS****网络请求****[5149:3d07] 0.110560**
**2014-11-08 16:35:46.697 IOS****网络请求****[5149:607] zang:download complete**
**2014-11-08 16:35:46.701 IOS****网络请求****[5149:1303] -[ZViewController URLSession:downloadTask:didFinishDownloadingToURL:]**
**2014-11-08 16:35:46.703 IOS****网络请求****[5149:1303] -[ZViewController URLSession:task:didCompleteWithError:]**
**2014-11-08 16:35:46.703 IOS****网络请求****[5149:1303] -[ZViewController URLSessionDidFinishEventsForBackgroundURLSession:]**
执行程序后按下home键，静静等待下载完成后发现虽然程序处于后台，但委托的3个方法均得到了执行
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