IOS断点续传技术

断点续传

@interface ViewController ()

{
__weak IBOutlet UIProgressView *_progressView;

__weak IBOutlet UILabel *rateLab;NSURLConnection *myConnection;NSFileHandle *myFileHandle; //文件句柄, 操作文件(对文件进行读写 )//记录当前已经有多少数据了long long currentFileSize;//文件总大小long long totalFileSize;

}
@end

• (void)viewDidLoad {
  [super viewDidLoad];

  //每次进入, 先判断文件是否存在,如果存在则获取已经下载的大小, 否则创建文件
  NSFileManager *fileManager = [NSFileManager defaultManager];
  if ([fileManager fileExistsAtPath:[self getFilePath]]) {

  NSDictionary *attributesDict = [fileManager attributesOfItemAtPath:[self getFilePath] error:nil];currentFileSize = [attributesDict[NSFileSize] longLongValue];NSLog(@\"已经下载了:%lldKB\", currentFileSize/1024);

  }
  else {
  [fileManager createFileAtPath:[self getFilePath] contents:nil attributes:nil];
  }

  //获取保存在本地的文件总大小, 更新进度值
  NSNumber *totalSize = [[NSUserDefaults standardUserDefaults] objectForKey:@“totalFileSize”];
  if (totalSize) {
  totalFileSize = [totalSize longLongValue];
  _progressView.progress = (currentFileSize)*1.0 / totalFileSize;
  rateLab.text = [NSString stringWithFormat:@\”%.02f%%\”, (currentFileSize)*1.0 / totalFileSize * 100];
  }

}

#pragma mark – 开始下载

• (IBAction)start:(id)sender {

  NSString *urlStr = DownloadURL;

  NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:[NSURL URLWithString:urlStr]];

  //根据文件已下载的大小,设置下载范围,从后面开始开始下载
  NSString *range = [NSString stringWithFormat:@“bytes=%lld-”, currentFileSize];
  [request setValue:range forHTTPHeaderField:@“RANGE”];

  myConnection = [NSURLConnection connectionWithRequest:request delegate:self];

}

#pragma mark – NSURLConnectionDataDelegate

• (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
  {
  NSLog(@“接收到服务器响应”);

  //计算文件总大小
  totalFileSize = response.expectedContentLength + currentFileSize;

  //将文件总大小保存在本地,下次进入App可以直接获取
  [[NSUserDefaults standardUserDefaults] setObject:@(totalFileSize) forKey:@“totalFileSize”];
  NSLog(@“文件总大小:%lldM”, totalFileSize/1024/1024);

  myFileHandle = [NSFileHandle fileHandleForUpdatingAtPath:[self getFilePath]];

  //将文件的指针移动到最后
  [myFileHandle seekToEndOfFile];
  }

• (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
  {
  NSLog(@“接收到数据”);
  currentFileSize = currentFileSize+data.length;

  _progressView.progress = (currentFileSize)*1.0 / totalFileSize;
  rateLab.text = [NSString stringWithFormat:@\”%.02f%%\”, (currentFileSize)*1.0 / totalFileSize * 100];

  //将data添加到文件的后面
  [myFileHandle writeData:data];
  }

• (void)connectionDidFinishLoading:(NSURLConnection *)connection
  {
  NSLog(@“接收完成!”);

  [myFileHandle closeFile];

}

• (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error
  {
  [myFileHandle closeFile];

  NSLog(@\”%@\”, error);

}

#pragma mark – 暂停(取消下载)

• (IBAction)stop:(id)sender {

  [myConnection cancel];
  [myFileHandle closeFile];
  }

#pragma mark – 文件路径
-(NSString *)getFilePath
{
NSString *filePath = [NSHomeDirectory() stringByAppendingPathComponent:@“Documents”];

filePath = [filePath stringByAppendingPathComponent:@\"qq.dmg\"];NSLog(@\"filePath:%@\", filePath);return filePath;

}

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