iOS在下载前获取文件大小_Ios_Download_Size_Nsurlsession_Nsurlsessiondownloadtask

iOS在下载前获取文件大小

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iOS在下载前获取文件大小,ios,download,size,nsurlsession,nsurlsessiondownloadtask,Ios,Download,Size,Nsurlsession,Nsurlsessiondownloadtask,我找不到适合我的解决方案。但是我需要得到我正在下载的视频的文件大小，这样我才能确保用户的手机上有足够的空间来下载我的想法是检查视频的大小，然后如果用户有空间，我会下载它。有什么建议吗 NSURL *url = [NSURL URLWithString:stringURL]; NSURLRequest *request = [NSURLRequest requestWithURL:url]; NSURLSession *session = [NSURLSession sharedSession]

我找不到适合我的解决方案。但是我需要得到我正在下载的视频的文件大小，这样我才能确保用户的手机上有足够的空间来下载

我的想法是检查视频的大小，然后如果用户有空间，我会下载它。有什么建议吗

NSURL *url = [NSURL URLWithString:stringURL];
NSURLRequest *request = [NSURLRequest requestWithURL:url];
NSURLSession *session = [NSURLSession sharedSession];

NSURLSessionDownloadTask *downloadTask = [session downloadTaskWithRequest:request completionHandler:^(NSURL *location, NSURLResponse *response, NSError *error) {...}];

使用此函数可获取URL的远程大小。请注意，此函数是同步的，将阻止线程，因此从不同于主线程的线程调用它：

extension NSURL {
    var remoteSize: Int64 {
        var contentLength: Int64 = NSURLSessionTransferSizeUnknown
        let request = NSMutableURLRequest(URL: self, cachePolicy: NSURLRequestCachePolicy.ReloadIgnoringLocalAndRemoteCacheData, timeoutInterval: 30.0);
        request.HTTPMethod = "HEAD";
        request.timeoutInterval = 5;
        let group = dispatch_group_create()
        dispatch_group_enter(group)
        NSURLSession.sharedSession().dataTaskWithRequest(request, completionHandler: { (data, response, error) -> Void in
            contentLength = response?.expectedContentLength ?? NSURLSessionTransferSizeUnknown
            dispatch_group_leave(group)
        }).resume()
        dispatch_group_wait(group, dispatch_time(DISPATCH_TIME_NOW, Int64(5 * NSEC_PER_SEC)))
        return contentLength
    }
}

let size = url.remoteSize

然后在与主线程不同的线程上，在需要的任何位置调用remoteSize变量：

extension NSURL {
    var remoteSize: Int64 {
        var contentLength: Int64 = NSURLSessionTransferSizeUnknown
        let request = NSMutableURLRequest(URL: self, cachePolicy: NSURLRequestCachePolicy.ReloadIgnoringLocalAndRemoteCacheData, timeoutInterval: 30.0);
        request.HTTPMethod = "HEAD";
        request.timeoutInterval = 5;
        let group = dispatch_group_create()
        dispatch_group_enter(group)
        NSURLSession.sharedSession().dataTaskWithRequest(request, completionHandler: { (data, response, error) -> Void in
            contentLength = response?.expectedContentLength ?? NSURLSessionTransferSizeUnknown
            dispatch_group_leave(group)
        }).resume()
        dispatch_group_wait(group, dispatch_time(DISPATCH_TIME_NOW, Int64(5 * NSEC_PER_SEC)))
        return contentLength
    }
}

let size = url.remoteSize

使用此函数可获取URL的远程大小。请注意，此函数是同步的，将阻止线程，因此从不同于主线程的线程调用它：

extension NSURL {
    var remoteSize: Int64 {
        var contentLength: Int64 = NSURLSessionTransferSizeUnknown
        let request = NSMutableURLRequest(URL: self, cachePolicy: NSURLRequestCachePolicy.ReloadIgnoringLocalAndRemoteCacheData, timeoutInterval: 30.0);
        request.HTTPMethod = "HEAD";
        request.timeoutInterval = 5;
        let group = dispatch_group_create()
        dispatch_group_enter(group)
        NSURLSession.sharedSession().dataTaskWithRequest(request, completionHandler: { (data, response, error) -> Void in
            contentLength = response?.expectedContentLength ?? NSURLSessionTransferSizeUnknown
            dispatch_group_leave(group)
        }).resume()
        dispatch_group_wait(group, dispatch_time(DISPATCH_TIME_NOW, Int64(5 * NSEC_PER_SEC)))
        return contentLength
    }
}

let size = url.remoteSize

然后在与主线程不同的线程上，在需要的任何位置调用remoteSize变量：

extension NSURL {
    var remoteSize: Int64 {
        var contentLength: Int64 = NSURLSessionTransferSizeUnknown
        let request = NSMutableURLRequest(URL: self, cachePolicy: NSURLRequestCachePolicy.ReloadIgnoringLocalAndRemoteCacheData, timeoutInterval: 30.0);
        request.HTTPMethod = "HEAD";
        request.timeoutInterval = 5;
        let group = dispatch_group_create()
        dispatch_group_enter(group)
        NSURLSession.sharedSession().dataTaskWithRequest(request, completionHandler: { (data, response, error) -> Void in
            contentLength = response?.expectedContentLength ?? NSURLSessionTransferSizeUnknown
            dispatch_group_leave(group)
        }).resume()
        dispatch_group_wait(group, dispatch_time(DISPATCH_TIME_NOW, Int64(5 * NSEC_PER_SEC)))
        return contentLength
    }
}

let size = url.remoteSize

SWIFT 3：

extension NSURL {
    var remoteSize: Int64 {
        var contentLength: Int64 = NSURLSessionTransferSizeUnknown
        let request = NSMutableURLRequest(url: self as URL, cachePolicy: NSURLRequest.CachePolicy.reloadIgnoringLocalAndRemoteCacheData, timeoutInterval: 30.0);
        request.httpMethod = "HEAD";
        request.timeoutInterval = 5;
        let group = DispatchGroup()
        group.enter()
        URLSession.shared.dataTask(with: request as URLRequest, completionHandler: { (data, response, error) -> Void in
            contentLength = response?.expectedContentLength ?? NSURLSessionTransferSizeUnknown
            group.leave()
        }).resume()

        return contentLength
    }
}

SWIFT 3：

extension NSURL {
    var remoteSize: Int64 {
        var contentLength: Int64 = NSURLSessionTransferSizeUnknown
        let request = NSMutableURLRequest(url: self as URL, cachePolicy: NSURLRequest.CachePolicy.reloadIgnoringLocalAndRemoteCacheData, timeoutInterval: 30.0);
        request.httpMethod = "HEAD";
        request.timeoutInterval = 5;
        let group = DispatchGroup()
        group.enter()
        URLSession.shared.dataTask(with: request as URLRequest, completionHandler: { (data, response, error) -> Void in
            contentLength = response?.expectedContentLength ?? NSURLSessionTransferSizeUnknown
            group.leave()
        }).resume()

        return contentLength
    }
}

Swift 3: 因为您正在调用dataTask，所以不能使用块外的值，所以请这样使用它

 var contentLength: Int64 = NSURLSessionTransferSizeUnknown
                let request = NSMutableURLRequest(url: url as URL, cachePolicy: NSURLRequest.CachePolicy.reloadIgnoringLocalAndRemoteCacheData, timeoutInterval: 30.0);
                request.httpMethod = "HEAD";
                request.timeoutInterval = 5;
                let group = DispatchGroup()
                group.enter()
                URLSession.shared.dataTask(with: request as URLRequest, completionHandler: { (data, response, error) -> Void in
                    contentLength = response?.expectedContentLength ?? NSURLSessionTransferSizeUnknown
//Here you should use the value
                    print("contentLength",contentLength)
                    group.leave()
                }).resume()

Swift 3: 因为您正在调用dataTask，所以不能使用块外的值，所以请这样使用它

 var contentLength: Int64 = NSURLSessionTransferSizeUnknown
                let request = NSMutableURLRequest(url: url as URL, cachePolicy: NSURLRequest.CachePolicy.reloadIgnoringLocalAndRemoteCacheData, timeoutInterval: 30.0);
                request.httpMethod = "HEAD";
                request.timeoutInterval = 5;
                let group = DispatchGroup()
                group.enter()
                URLSession.shared.dataTask(with: request as URLRequest, completionHandler: { (data, response, error) -> Void in
                    contentLength = response?.expectedContentLength ?? NSURLSessionTransferSizeUnknown
//Here you should use the value
                    print("contentLength",contentLength)
                    group.leave()
                }).resume()

以下是其他答案的一个变体，它使用函数（在Swift 4中）在检索大小时调用闭包：

func getDownloadSize(url: URL, completion: @escaping (Int64, Error?) -> Void) {
    let timeoutInterval = 5.0
    var request = URLRequest(url: url,
                             cachePolicy: .reloadIgnoringLocalAndRemoteCacheData,
                             timeoutInterval: timeoutInterval)
    request.httpMethod = "HEAD"
    URLSession.shared.dataTask(with: request) { (data, response, error) in
        let contentLength = response?.expectedContentLength ?? NSURLSessionTransferSizeUnknown
        completion(contentLength, error)
    }.resume()
}

以下是如何使用此功能：

let url = URL(string: "https://upload.wikimedia.org/wikipedia/commons/7/70/Example.png")!
getDownloadSize(url: url, completion: { (size, error) in
    if error != nil {
        print("An error occurred when retrieving the download size: \(error.localizedDescription)")
    } else {
        print("The download size is \(size).")
    }
})

以下是其他答案的一个变体，它使用函数（在Swift 4中）在检索大小时调用闭包：

func getDownloadSize(url: URL, completion: @escaping (Int64, Error?) -> Void) {
    let timeoutInterval = 5.0
    var request = URLRequest(url: url,
                             cachePolicy: .reloadIgnoringLocalAndRemoteCacheData,
                             timeoutInterval: timeoutInterval)
    request.httpMethod = "HEAD"
    URLSession.shared.dataTask(with: request) { (data, response, error) in
        let contentLength = response?.expectedContentLength ?? NSURLSessionTransferSizeUnknown
        completion(contentLength, error)
    }.resume()
}

以下是如何使用此功能：

let url = URL(string: "https://upload.wikimedia.org/wikipedia/commons/7/70/Example.png")!
getDownloadSize(url: url, completion: { (size, error) in
    if error != nil {
        print("An error occurred when retrieving the download size: \(error.localizedDescription)")
    } else {
        print("The download size is \(size).")
    }
})

看@RayKing增加超时，现在是5秒，你可以像这样增加你所需要的吗？DispatchQueue.main.asyncAfter（截止日期：.now（）+15）{print（NSURL（fileURLWithPath:track.url！）.remoteSize）}此时仍然会得到-1@RayKing在调度组等待中更改5。我注意到在swift 3版本中，作者省略了这行代码unusable@RayKing增加超时时间，现在是5秒，你可以像这样增加你所需要的时间吗？DispatchQueue.main.asyncAfter（截止日期：.now（）+15）{print（NSURL（fileURLWithPath:track.url！）.remoteSize）}此时仍然会得到-1@RayKing在调度组等待中更改5。我注意到在swift 3版本中，作者省略了这一行，这使得代码无法使用