如何在iOS 7中下載文件之前查找文件的大小？

Question

誠徵的iOS 7下載前找到一些服務器上的文件的大小...我有NSURLConnectionDelegate的方法，但它的iOS 4.3

這裏後棄用了這種方法：

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

Answer 1

您應改用NSURLConnectionDataDelegate注：DATADelegate

及其didReceiveResponse:方法發送HEAD request得到公正頭：

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

然後你就可以得到響應大小與@ Port的建議：

long long size = [response expectedContentLength]; 

Answer 2

您可以使用此方法，它是通過下面的委託方法NSURLResponse對象：

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

} 
-(NSURLRequest *)connection:(NSURLConnection *)connection 
     willSendRequest:(NSURLRequest *)request 
     redirectResponse:(NSURLResponse *)response { 
} 

嘗試這樣的..

long long size = [response expectedContentLength]; 

Answer 3

試試這個會有幫助。 。 。 。 。

-(void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse 
                     *)response 
{ 
    NSHTTPURLResponse * pHttpUrlResponse = (NSHTTPURLResponse *) response; 

    if ([response respondsToSelector:@selector(allHeaderFields)]) 
    { 
     NSString * fileLength = [NSString stringWithFormat:@"%lld",[pHttpUrlResponse expectedContentLength]]; 
    }  
} 

編碼快樂:)

Answer 4

試試這個，

NSDictionary *fileAttributes = [[NSFileManager defaultManager] attributesOfItemAtPath:URL error:&attributesError]; 
NSNumber *fileSizeNumber = [fileAttributes objectForKey:NSFileSize]; 
long long fileSize = [fileSizeNumber longLongValue]; 

:)

Answer 5

請使用HEAD方法的請求。例如：

NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url]; 
[request setHTTPMethod:@"HEAD"]; 

該請求將與GET相同，但不返回正文。然後調用

long long size = [response expectedContentLength]; 

與NSURLConnection的完整示例（適用於NSURLSession過的課程）：

NSURL *URL = [NSURL URLWithString:@"http://www.google.com"]; 
NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:URL]; 
[request setHTTPMethod:@"HEAD"]; 
NSHTTPURLResponse *response; 
[NSURLConnection sendSynchronousRequest:request returningResponse:&response error: nil]; 
long long size = [response expectedContentLength]; 
NSLog(@"%lld",size); 

這也是基於Last-Modified頭有條件地下載有用的（假設服務器發送你那）。

if ([response respondsToSelector:@selector(allHeaderFields)]) { 
    NSString *lastModifiedString = [[response allHeaderFields] objectForKey:@"Last-Modified"]; 
} 

Answer 6

對於斯威夫特使用這些步驟，

步驟1：使用NSURLConnectionDataDelegate。

class ViewController: UIViewController,NSURLConnectionDataDelegate { 

步驟2：創建用於連接請求。

var request:NSMutableURLRequest = NSMutableURLRequest(URL: NSURL(string: "http://www.twitter.com")!) 

// Use **HEAD** request to get http header information. 

request.HTTPMethod = "HEAD" 

第3步：創建連接。

var connection:NSURLConnection = NSURLConnection(request: request, delegate: self)! 

第4步：使用委託方法 NSURLConnectionDataDelegate

func connection(connection: NSURLConnection, didReceiveResponse response: NSURLResponse) 
{ 
    var size = response.expectedContentLength 
    println("size : \(size)") 
} 

下面是完整的代碼...

import UIKit 

class ViewController: UIViewController,NSURLConnectionDataDelegate { 

override func viewDidLoad() { 
    super.viewDidLoad() 


    var request:NSMutableURLRequest = NSMutableURLRequest(URL: NSURL(string: "http://www.twitter.com")!) 
    request.HTTPMethod = "HEAD" 

    var connection:NSURLConnection = NSURLConnection(request: request, delegate: self)! 

} 

func connection(connection: NSURLConnection, didReceiveResponse response: NSURLResponse) 
{ 
    var size = response.expectedContentLength 
    println("size : \(size)") 
} 
}