断点下载

  1 #import "ViewController.h"
  2 
  3 @interface ViewController () <NSURLSessionDataDelegate, NSURLSessionDownloadDelegate>
  4 
  5 @property (weak, nonatomic) IBOutlet UIImageView *imgView;
  6 @property (weak, nonatomic) IBOutlet UIProgressView *progressView;
  7 
  8 
  9 /**  下载任务的属性  */
 10 @property (nonatomic, strong) NSURLSessionDownloadTask *task;
 11 
 12 /**  网络请求类  */
 13 @property (nonatomic, strong) NSURLSession *session;
 14 
 15 /**  发送请求类  */
 16 @property (nonatomic, strong) NSURLRequest *request;
 17 
 18 /**  保存已经下载的数据，供继续下载使用  */
 19 @property (nonatomic, strong) NSMutableData *data;
 20 
 21 
 22 @end
 23 
 24 @implementation ViewController
 25 
 26 - (void)viewDidLoad {
 27     [super viewDidLoad];
 28     
 29     // 设置progress的初始值
 30     self.progressView.progress = 0;
 31 }
 32 
 33 
 34 #pragma mark - 开始下载
 35 - (IBAction)start:(id)sender {
 36     
 37     // 下载的url
 38     NSURL *url = [NSURL URLWithString:@"http://www.baidu.com/img/bdlogo.png"];
 39     
 40     // 初始化请求类
 41     self.request = [NSURLRequest requestWithURL:url];
 42     
 43     // 创建NSURLSession
 44     NSURLSessionConfiguration *configuration = [NSURLSessionConfiguration defaultSessionConfiguration];
 45     self.session = [NSURLSession sessionWithConfiguration:configuration delegate:self delegateQueue:[NSOperationQueue mainQueue]];
 46     
 47     // 下载请求任务
 48     self.task = [self.session downloadTaskWithRequest:self.request];
 49     
 50     // 开启
 51     [self.task resume];
 52 }
 53 
 54 
 55 #pragma mark - 暂停下载
 56 - (IBAction)pause:(id)sender {
 57     
 58     if (self.task) {
 59         
 60         __weak typeof(self)weakSelf = self;
 61         // 暂停并保存之前已经下载的内容
 62         [self.task cancelByProducingResumeData:^(NSData * _Nullable resumeData) {
 63             
 64             weakSelf.data = [NSMutableData dataWithData:resumeData];
 65         }];
 66     }
 67     
 68     // 暂停任务
 69     [self.task suspend];
 70 }
 71 
 72 
 73 #pragma mark - 继续下载
 74 - (IBAction)continue:(id)sender {
 75     
 76     // 判断当前有没有任务，是发送请求，还是处理数据
 77     if (self.task != nil) {
 78         
 79         // 说明已经下载，这里要处理的就是数据
 80         self.task = [self.session downloadTaskWithResumeData:self.data];
 81     } else {
 82         
 83         // 此时没有下载任何内容，应该重新发送请求进行下载
 84         self.task = [self.session downloadTaskWithRequest:self.request];
 85     }
 86     
 87     // 启动
 88     [self.task resume];
 89 }
 90 
 91 
 92 #pragma mark - 代理方法
 93 // 下载完成的方法
 94 - (void)URLSession:(NSURLSession *)session downloadTask:(NSURLSessionDownloadTask *)downloadTask didFinishDownloadingToURL:(NSURL *)location {
 95     
 96     NSFileManager *fileManager = [NSFileManager defaultManager];
 97     NSString *path = [[NSHomeDirectory() stringByAppendingPathComponent:@"Documents"] stringByAppendingPathComponent:downloadTask.response.suggestedFilename];
 98     [fileManager moveItemAtPath:location.path toPath:path error:nil];
 99     self.imgView.image = [UIImage imageWithContentsOfFile:path];
100 }
101 
102 
103 - (void)URLSession:(NSURLSession *)session downloadTask:(NSURLSessionDownloadTask *)downloadTask didWriteData:(int64_t)bytesWritten totalBytesWritten:(int64_t)totalBytesWritten totalBytesExpectedToWrite:(int64_t)totalBytesExpectedToWrite {
104     
105     // 下载当前段的数据
106     NSLog(@"bytesWritten = %lld", bytesWritten);
107     
108     // 已经下载的总数据量
109     NSLog(@"totalBytesWritten = %lld", totalBytesWritten);
110     
111     // 总进度
112     NSLog(@"totalBytesExpectedToWrite = %lld", totalBytesExpectedToWrite);
113     
114     // 设置progress的进度值
115     self.progressView.progress = (CGFloat)totalBytesWritten / (CGFloat)totalBytesExpectedToWrite;
116 }
117 
118 @end