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[操作系统]iOS 大文件断点下载


iOS 在下载大文件的时候,可能会因为网络或者人为等原因,使得下载中断,那么如何能够进行断点下载呢?

// resumeData的文件路径#define XMGResumeDataFile [[NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) lastObject] stringByAppendingPathComponent:@"resumeData.tmp"]#import "ViewController.h"@interface ViewController () <NSURLSessionDownloadDelegate>/** 下载任务 */@property (nonatomic, strong) NSURLSessionDownloadTask *task;/** 保存上次的下载信息 */@property (nonatomic, strong) NSData *resumeData;/** session */@property (nonatomic, strong) NSURLSession *session;@end

 

 

@implementation ViewController/** session */- (NSURLSession *)session{  if (!_session) {    _session = [NSURLSession sessionWithConfiguration:[NSURLSessionConfiguration defaultSessionConfiguration] delegate:self delegateQueue:[[NSOperationQueue alloc] init]];  }  return _session;}/** * 开始下载 */- (IBAction)start:(id)sender {    self.task = [self.session downloadTaskWithURL:[NSURL URLWithString:@"http://120.25.226.186:32812/resources/videos/minion_01.mp4"]];  [self.task resume];}/** * 暂停下载 */- (IBAction)pause:(id)sender {  // 一旦这个task被取消了,就无法再恢复  [self.task cancelByProducingResumeData:^(NSData *resumeData) {    self.resumeData = resumeData;  }];}/** * 继续下载 */- (IBAction)goOn:(id)sender {  self.task = [self.session downloadTaskWithResumeData:self.resumeData];  [self.task resume];}#pragma mark - <NSURLSessionDownloadDelegate>- (void)URLSession:(NSURLSession *)session task:(NSURLSessionTask *)task didCompleteWithError:(NSError *)error{  NSLog(@"didCompleteWithError");    // 保存恢复数据  self.resumeData = error.userInfo[NSURLSessionDownloadTaskResumeData];}- (void)URLSession:(NSURLSession *)session downloadTask:(NSURLSessionDownloadTask *)downloadTask didResumeAtOffset:(int64_t)fileOffset expectedTotalBytes:(int64_t)expectedTotalBytes{  NSLog(@"didResumeAtOffset");}/** * 每当写入数据到临时文件时,就会调用一次这个方法 * totalBytesExpectedToWrite:总大小 * totalBytesWritten: 已经写入的大小 * bytesWritten: 这次写入多少 */- (void)URLSession:(NSURLSession *)session downloadTask:(NSURLSessionDownloadTask *)downloadTask didWriteData:(int64_t)bytesWritten totalBytesWritten:(int64_t)totalBytesWritten totalBytesExpectedToWrite:(int64_t)totalBytesExpectedToWrite{  NSLog(@"--------%f", 1.0 * totalBytesWritten / totalBytesExpectedToWrite);}/** * * 下载完毕就会调用一次这个方法 */- (void)URLSession:(NSURLSession *)session downloadTask:(NSURLSessionDownloadTask *)downloadTask didFinishDownloadingToURL:(NSURL *)location{  // 文件将来存放的真实路径  NSString *file = [[NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) lastObject] stringByAppendingPathComponent:downloadTask.response.suggestedFilename];    // 剪切location的临时文件到真实路径  NSFileManager *mgr = [NSFileManager defaultManager];  [mgr moveItemAtURL:location toURL:[NSURL fileURLWithPath:file] error:nil];}@end