Herunterladen einer großen Datei - iPhone SDK

Question

Ich verwende Erica Saduns Methode der asynchronen Downloads (Link hier für die Projektdatei: download), aber ihre Methode funktioniert nicht mit Dateien, die eine große Größe (50 MB oder höher) haben. Wenn ich versuche, eine Datei über 50 MB herunterzuladen, stürzt sie normalerweise aufgrund eines Speicherabsturzes ab. Kann ich diesen Code trotzdem optimieren, damit er auch mit großen Dateien funktioniert? Hier ist der Code, den ich in den Download Klassen haben (die bereits in den Download-Link):

.h

@protocol DownloadHelperDelegate <NSObject> 
@optional 
- (void) didReceiveData: (NSData *) theData; 
- (void) didReceiveFilename: (NSString *) aName; 
- (void) dataDownloadFailed: (NSString *) reason; 
- (void) dataDownloadAtPercent: (NSNumber *) aPercent; 
@end 

@interface DownloadHelper : NSObject 
{ 
    NSURLResponse *response; 
    NSMutableData *data; 
    NSString *urlString; 
    NSURLConnection *urlconnection; 
    id <DownloadHelperDelegate> delegate; 
    BOOL isDownloading; 
} 
@property (retain) NSURLResponse *response; 
@property (retain) NSURLConnection *urlconnection; 
@property (retain) NSMutableData *data; 
@property (retain) NSString *urlString; 
@property (retain) id delegate; 
@property (assign) BOOL isDownloading; 

+ (DownloadHelper *) sharedInstance; 
+ (void) download:(NSString *) aURLString; 
+ (void) cancel; 
@end 

.m

#define DELEGATE_CALLBACK(X, Y) if (sharedInstance.delegate && [sharedInstance.delegate respondsToSelector:@selector(X)]) [sharedInstance.delegate performSelector:@selector(X) withObject:Y]; 
#define NUMBER(X) [NSNumber numberWithFloat:X] 

static DownloadHelper *sharedInstance = nil; 

@implementation DownloadHelper 
@synthesize response; 
@synthesize data; 
@synthesize delegate; 
@synthesize urlString; 
@synthesize urlconnection; 
@synthesize isDownloading; 

- (void) start 
{ 
    self.isDownloading = NO; 

    NSURL *url = [NSURL URLWithString:self.urlString]; 
    if (!url) 
    { 
     NSString *reason = [NSString stringWithFormat:@"Could not create URL from string %@", self.urlString]; 
     DELEGATE_CALLBACK(dataDownloadFailed:, reason); 
     return; 
    } 

    NSMutableURLRequest *theRequest = [NSMutableURLRequest requestWithURL:url]; 
    if (!theRequest) 
    { 
     NSString *reason = [NSString stringWithFormat:@"Could not create URL request from string %@", self.urlString]; 
     DELEGATE_CALLBACK(dataDownloadFailed:, reason); 
     return; 
    } 

    self.urlconnection = [[NSURLConnection alloc] initWithRequest:theRequest delegate:self]; 
    if (!self.urlconnection) 
    { 
     NSString *reason = [NSString stringWithFormat:@"URL connection failed for string %@", self.urlString]; 
     DELEGATE_CALLBACK(dataDownloadFailed:, reason); 
     return; 
    } 

    self.isDownloading = YES; 

    // Create the new data object 
    self.data = [NSMutableData data]; 
    self.response = nil; 

    [self.urlconnection scheduleInRunLoop:[NSRunLoop currentRunLoop] forMode:NSRunLoopCommonModes]; 
} 

- (void) cleanup 
{ 
    self.data = nil; 
    self.response = nil; 
    self.urlconnection = nil; 
    self.urlString = nil; 
    self.isDownloading = NO; 
} 

- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)aResponse 
{ 
    // store the response information 
    self.response = aResponse; 

    // Check for bad connection 
    if ([aResponse expectedContentLength] < 0) 
    { 
     NSString *reason = [NSString stringWithFormat:@"Invalid URL [%@]", self.urlString]; 
     DELEGATE_CALLBACK(dataDownloadFailed:, reason); 
     [connection cancel]; 
     [self cleanup]; 
     return; 
    } 

    if ([aResponse suggestedFilename]) 
     DELEGATE_CALLBACK(didReceiveFilename:, [aResponse suggestedFilename]); 
} 

- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)theData 
{ 
    // append the new data and update the delegate 
    [self.data appendData:theData]; 
    if (self.response) 
    { 
     float expectedLength = [self.response expectedContentLength]; 
     float currentLength = self.data.length; 
     float percent = currentLength/expectedLength; 
     DELEGATE_CALLBACK(dataDownloadAtPercent:, NUMBER(percent)); 
    } 
} 

- (void)connectionDidFinishLoading:(NSURLConnection *)connection 
{ 
    // finished downloading the data, cleaning up 
    self.response = nil; 

    // Delegate is responsible for releasing data 
    if (self.delegate) 
    { 
     NSData *theData = [self.data retain]; 
     DELEGATE_CALLBACK(didReceiveData:, theData); 
    } 
    [self.urlconnection unscheduleFromRunLoop:[NSRunLoop currentRunLoop] forMode:NSRunLoopCommonModes]; 
    [self cleanup]; 
} 

- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error 
{ 
    self.isDownloading = NO; 
    NSLog(@"Error: Failed connection, %@", [error localizedDescription]); 
    DELEGATE_CALLBACK(dataDownloadFailed:, @"Failed Connection"); 
    [self cleanup]; 
} 

+ (DownloadHelper *) sharedInstance 
{ 
    if(!sharedInstance) sharedInstance = [[self alloc] init]; 
    return sharedInstance; 
} 

+ (void) download:(NSString *) aURLString 
{ 
    if (sharedInstance.isDownloading) 
    { 
     NSLog(@"Error: Cannot start new download until current download finishes"); 
     DELEGATE_CALLBACK(dataDownloadFailed:, @""); 
     return; 
    } 

    sharedInstance.urlString = aURLString; 
    [sharedInstance start]; 
} 

+ (void) cancel 
{ 
    if (sharedInstance.isDownloading) [sharedInstance.urlconnection cancel]; 
} 
@end 

Und schließlich ist dies, wie ich das schreiben Datei mit den zwei Klassen darüber:

- (void) didReceiveData: (NSData *) theData 
{ 
    if (![theData writeToFile:self.savePath atomically:YES]) 
     [self doLog:@"Error writing data to file"]; 

    [theData release]; 

} 

Wenn jemand mir helfen könnte, wäre ich so froh!

Danke,

Kevin

Answer 1

Ersetzen Sie die In-Memory-NSData *data mit einem NSOutputStream *stream. In -start den Strom erzeugen, um es zu anhängen und öffnen:

stream = [[NSOutputStream alloc] initToFileAtPath:path append:YES]; 
[stream open]; 

Da die Daten in kommt, schreiben Sie es in den Stream:

NSUInteger left = [theData length]; 
NSUInteger nwr = 0; 
do { 
    nwr = [stream write:[theData bytes] maxLength:left]; 
    if (-1 == nwr) break; 
    left -= nwr; 
} while (left > 0); 
if (left) { 
    NSLog(@"stream error: %@", [stream streamError]); 
} 

Wenn Sie fertig sind, schließen Sie den Strom:

[stream close]; 

Ein besserer Ansatz wäre, den Datenstrom zusätzlich zum Daten-Ivar hinzuzufügen, den Helfer als Delegaten des Datenstroms festzulegen, eingehende Daten im Daten-Ivar zu puffern und dann den Inhalt des Daten-Ivar an den Helfer-wh auszugeben Immer dann, wenn der Stream dem Helfer sein raumverfügbares Ereignis sendet und es aus dem Datenbereich löscht.

Answer 2

Ich habe eine leichte Änderung an dem obigen Code.

Verwenden Sie diese Funktion, es funktioniert gut für mich.

- (void) didReceiveData: (NSData*) theData 
{ 
    NSOutputStream *stream=[[NSOutputStream alloc] initToFileAtPath:self.savePath append:YES]; 
    [stream open]; 
    percentage.hidden=YES; 
    NSString *str=(NSString *)theData; 
    NSUInteger left = [str length]; 
    NSUInteger nwr = 0; 
    do { 
     nwr = [stream write:[theData bytes] maxLength:left]; 
     if (-1 == nwr) break; 
     left -= nwr; 
    } while (left > 0); 
    if (left) { 
     NSLog(@"stream error: %@", [stream streamError]); 
    } 
    [stream close]; 
} 

Answer 3

Versuchen Sie . Und:

NSString *yourFileURL=@"http://yourFileURL.zip"; 
NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:yourFileURL]]; 
AFURLConnectionOperation *operation = [[AFHTTPRequestOperation alloc] initWithRequest:request]; 

NSString *cacheDir = [NSSearchPathForDirectoriesInDomains 
          (NSCachesDirectory, NSUserDomainMask, YES) objectAtIndex:0]; 
NSString *filePath = [cacheDir stringByAppendingPathComponent: 
         @"youFile.zip"]; 

operation.outputStream = [NSOutputStream outputStreamToFileAtPath:filePath append:NO]; 

[operation setDownloadProgressBlock:^(NSUInteger bytesRead, long long totalBytesRead, long long totalBytesExpectedToRead) { 
    //show here your downloading progress if needed 
}]; 

[operation setCompletionBlock:^{ 
    NSLog(@"File successfully downloaded"); 
}]; 

[operation start];