NSURLSessionDataTask

#import "ViewController.h"

@interface ViewController ()<NSURLSessionDelegate,NSURLSessionTaskDelegate,NSURLSessionDataDelegate>

@property (weak, nonatomic) IBOutlet UIImageView *imageView;

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

@property (nonatomic,strong) NSURLSession * session;

@property (nonatomic,strong) NSURLSessionDataTask * dataTask;

@property (nonatomic,strong) NSMutableData * imageData;

@property (nonatomic,assign) long long length;

@end

@implementation ViewController

- (void)viewDidLoad {

[super viewDidLoad];

}

-(NSURLSession *)session{

if (_session == nil) {

NSURLSessionConfiguration * config = [NSURLSessionConfiguration defaultSessionConfiguration];

self.session = [NSURLSession sessionWithConfiguration:config delegate:self delegateQueue:[NSOperationQueue mainQueue]];

}

return _session;

}

-(NSURLSessionDataTask *)dataTask{

if (_dataTask ==nil) {

NSURL * url = [NSURL URLWithString:@"http://img1.3lian.com/2015/a1/124/d/181.jpg"];

self.dataTask = [self.session dataTaskWithURL:url];

}

return _dataTask;

}

- (IBAction)suspendenButtonDidClicked:(UIButton *)sender {

if (self.dataTask.state == NSURLSessionTaskStateRunning) {

[self.dataTask suspend];

}

}

- (IBAction)resumeButtonDidClicked:(UIButton *)sender {

[self.dataTask resume];

}

- (IBAction)cancelButtonDidClicked:(UIButton *)sender {

if (_dataTask) {

if (self.dataTask.state == NSURLSessionTaskStateRunning||NSURLSessionTaskStateSuspended) {

[self.dataTask cancel];

self.dataTask=nil;

self.session = nil;

[self.progress setProgress:0 animated:NO];

}

}

}

//获取服务器返回的响应信息

-(void)URLSession:(NSURLSession *)session dataTask:(NSURLSessionDataTask *)dataTask didReceiveResponse:(NSURLResponse *)response completionHandler:(void (^)(NSURLSessionResponseDisposition))completionHandler{

//转换

NSHTTPURLResponse * httpResponse = (NSHTTPURLResponse *)response;

NSLog(@"%@",[httpResponse allHeaderFields]);

//获取资源大小

self.length = httpResponse.expectedContentLength;

NSLog(@"responce");

if (_length!=-1) {

//继续下载或上传

self.imageData = [NSMutableData dataWithCapacity:(NSUInteger)_length];

completionHandler(NSURLSessionResponseAllow);

}else{

completionHandler(NSURLSessionResponseCancel);

[self.dataTask cancel];

self.dataTask = nil;

}

}

//一个数据包过来了

-(void)URLSession:(NSURLSession *)session dataTask:(NSURLSessionDataTask *)dataTask didReceiveData:(nonnull NSData *)data{

NSLog(@"receive data");

//将当前的数据添加到imageData中

[self.imageData appendData:data];

float rate = data.length/(_length*1.0);

[self.progress setProgress:(_progress.progress +rate) animated:NO];

}

//下载完毕

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

NSLog(@"complete");

if (error) {

NSLog(@"error");

}else{

UIImage * img = [UIImage imageWithData:_imageData];

self.imageView.image = img;

}

self.session = nil;

self.dataTask = nil;

}

@end