NSURLConnection如何获取剩余时间信息

Question

我有一个表格单元格，我必须获取有关我正在下载的文件的更多信息，我设法得到了所有我需要但剩下的时间

这是我想要做的一个例子，除了时间计算之外，我已经完成了所有工作

获取文件大小：

fileSize = [NSNumber numberWithLongLong:[response expectedContentLength]]/(1024*1024);

下载：

[_responseData length]/(1024*1024)

速度：

 double speed = [_responseData length] / ([NSDate timeIntervalSinceReferenceDate] - start);

其中start也是

中设置的[NSDate timeIntervalSinceReferenceDate]

- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response 

剩余时间：???

问题：如何计算剩余时间？

Answer 1

我想你需要做的是处理connection:didReceiveData:委托方法。

@property (atomic, strong) NSDate *lastCheckDate;
@property (atomic, strong) NSDate *startDate;
@property (atomic, strong) NSNumber *fileSize;
@property (atomic, strong) NSNumber *sizeLeft;

- (void) connection:(NSURLConnection *) connection didReceiveData:(NSData *) data
{
    NSDate *now = [NSDate date];
    double dt = [now timeIntervalSinceDate:_lastCheckDate]; // time since last check
    self.lastCheckDate = now;
    double db = [data length]; // bytes received
    double speed = db / dt;
    self.sizeLeft = self.sizeLeft - [NSNumber numberWithDouble:db];
    double averageSpeed = [(_fileSize - _sizeLeft) doubleValue] / [now timeIntervalSinceDate:_startDate];
    // time left, based on current speed
    double timeLeftCurrent = [sizeLeft doubleValue] / speed;
    // time left, based on average speed
    double timeLeftAverage = [sizeLeft doubleValue] / averageSpeed;
}

Answer 2

在#kender的帮助下，我设法回答了我的问题

@interface TableViewController ()
{
    NSTimeInterval start; 
}
@property (atomic, strong) NSNumber *sizeLeft;


- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response 
{
//in this method we get the file size and the start time 
   start = [NSDate timeIntervalSinceReferenceDate];
   NSNumber *fileSize;
  if ([response expectedContentLength] == NSURLResponseUnknownLength) 
  {
    // unknown content size
    fileSize = @0;
  }
  else 
  {
    fileSize = [NSNumber numberWithLongLong:[response expectedContentLength]];
  }
  self.sizeLeft = fileSize;
}


- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data 
{
    // _responseData is an NSData that i use to get the size i already downloaded
    [_responseData appendData:data]; 
    double speed = [_responseData length] / ([NSDate timeIntervalSinceReferenceDate] - start);
    self.sizeLeft = [NSNumber numberWithDouble:[_sizeLeft doubleValue]  - [data length]] ;
    // time based on current speed
    double timeLeft = [_sizeLeft doubleValue] / speed; 
    NSLog(@"time  %.2f",timeLeft);
}