#import "AFNetworking.h"

 @interface ViewController (){ // 下載句柄 NSURLSessionDownloadTask *_downloadTask;} 

#import <UIKit/UIKit.h>@interface ViewController : UIViewController// 下載文件顯示@property (weak, nonatomic) IBOutlet UIImageView *imageView;// 下載進度條顯示@property (weak, nonatomic) IBOutlet UIProgressView *progressView;@end

@interface ViewController (){ // 下載句柄 NSURLSessionDownloadTask *_downloadTask;} 

- (void)downFileFromServer{ //遠程地址 NSURL *URL = [NSURL URLWithString:@"http://www.baidu.com/img/bdlogo.png"]; //默認配置 NSURLSessionConfiguration *configuration = [NSURLSessionConfiguration defaultSessionConfiguration];  //AFN3.0+基于封住URLSession的句柄 AFURLSessionManager *manager = [[AFURLSessionManager alloc] initWithSessionConfiguration:configuration];  //請求 NSURLRequest *request = [NSURLRequest requestWithURL:URL];  //下載Task操作 _downloadTask = [manager downloadTaskWithRequest:request progress:^(NSProgress * _Nonnull downloadProgress) {    // @property int64_t totalUnitCount;  需要下載文件的總大小  // @property int64_t completedUnitCount; 當前已經下載的大小    // 給Progress添加監聽 KVO  NSLog(@"%f",1.0 * downloadProgress.completedUnitCount / downloadProgress.totalUnitCount);  // 回到主隊列刷新UI  dispatch_async(dispatch_get_main_queue(), ^{  // 設置進度條的百分比    self.progressView.progress = 1.0 * downloadProgress.completedUnitCount / downloadProgress.totalUnitCount;  });  } destination:^NSURL * _Nonnull(NSURL * _Nonnull targetPath, NSURLResponse * _Nonnull response) {    //- block的返回值, 要求返回一個URL, 返回的這個URL就是文件的位置的路徑   NSString *cachesPath = [NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) lastObject];  NSString *path = [cachesPath stringByAppendingPathComponent:response.suggestedFilename];  return [NSURL fileURLWithPath:path];  } completionHandler:^(NSURLResponse * _Nonnull response, NSURL * _Nullable filePath, NSError * _Nullable error) {  //設置下載完成操作  // filePath就是你下載文件的位置，你可以解壓，也可以直接拿來使用    NSString *imgFilePath = [filePath path];// 將NSURL轉成NSString  UIImage *img = [UIImage imageWithContentsOfFile:imgFilePath];  self.imageView.image = img;  }];} 

- (IBAction)stopDownloadBtnClick:(id)sender { //暫停下載 [_downloadTask suspend];}- (IBAction)startDownloadBtnClick:(id)sender { //開始下載 [_downloadTask resume];} 

- (void)viewDidLoad { [super viewDidLoad];  //網絡監控句柄 AFNetworkReachabilityManager *manager = [AFNetworkReachabilityManager sharedManager];  //要監控網絡連接狀態，必須要先調用單例的startMonitoring方法 [manager startMonitoring];  [manager setReachabilityStatusChangeBlock:^(AFNetworkReachabilityStatus status) {  //status:  //AFNetworkReachabilityStatusUnknown   = -1, 未知  //AFNetworkReachabilityStatusNotReachable  = 0, 未連接  //AFNetworkReachabilityStatusReachableViaWWAN = 1, 3G  //AFNetworkReachabilityStatusReachableViaWiFi = 2, 無線連接  NSLog(@"%d", status); }];  //準備從遠程下載文件. -> 請點擊下面開始按鈕啟動下載任務 [self downFileFromServer]; }