The use of nsoperation (download-related) images and files are both resumable images gradually displayed.

//// Imagedownloader. h // nsoperationtest /// created by YDC on 11-10-29. // copyright 2011 _ mycompanyname __. all rights reserved. // # import <Foundation/Foundation. h> @ protocol imagedownloaderdelegate; @ interface imagedownloader: nsoperation {nsurlrequest * _ request; nsurlconnection * _ connection; nsmutabledata * _ data; bool _ isfinished; bool _ canceled;}-(ID) initwithurlstring :( nsstring *) URL; @ property (readonly) nsdata * data; @ property (nonatomic, assign) ID <imagedownloaderdelegate> delegate; @ property (nonatomic, strong) nsobject * delpara; @ property (nonatomic, strong) implements * cancelledlock; @ end @ protocol imagedownloaderdelegate @ optional // The image download is completed.-(void) imagedidfinished :( uiimage *) image para :( nsobject *) OBJ; @ end

//// Imagedownloader. M // nsoperationtest /// created by YDC on 11-10-29. // copyright 2011 _ mycompanyname __. all rights reserved. // # import "imagedownloader. H "@ implementation imagedownloader-(ID) initwithurlstring :( nsstring *) URL {self = [self init]; If (Self) {assert (URL! = Nil); _ Request = [[nsurlrequest alloc] initwithurl: [nsurl urlwithstring: url]; _ DATA = [nsmutabledata data];} return self ;}- (void) start {If (! [Self iscancelled]) {[nsthread sleepfortimeinterval: 3]; // process events asynchronously, and set proxy _ connection = [nsurlconnection connectionwithrequest: _ Request delegate: Self]; while (_ connection! = Nil) {[[nsunloop currentrunloop] runmode: nsdefaultrunloopmode beforedate: [nsdate distantfuture] ;}}# Pragma mark nsurlconnection delegate method // receives data (incremental) -(void) connection :( nsurlconnection *) connection didreceivedata :( nsdata *) Data {[_ DATA appenddata: Data]; If (self. delegate! = Nil) {uiimage * IMG = [[uiimage alloc] initwithdata: Self. data]; [_ delegate imagedidfinished: IMG para: Self. delpara] ;}}- (void) connectiondidfinishloading :( nsurlconnection *) connection {If (self. delegate! = Nil) {uiimage * IMG = [[uiimage alloc] initwithdata: Self. data]; [_ delegate imagedidfinished: IMG para: Self. delpara];} _ connection = nil;}-(void) connection: (nsurlconnection *) connection didfailwitherror: (nserror *) error {_ connection = nil;}-(void) cancelonrequestthread {[[self cancelledlock] Lock]; If ([self iscancelled]) {[[self cancelledlock] unlock]; return;} [self willchangevalueforkey: @ "iscancelled"]; _ canceled = yes; [self didchangevalueforkey: @ "iscancelled"]; [[self cancelledlock] unlock];}-(bool) iscancelled {bool result; [[self cancelledlock] Lock]; Result = _ canceled; [[self cancelledlock] unlock]; return result;}-(bool) isconcurrent {return yes;}-(bool) isexecuting {return _ connection = nil;}-(bool) isfinished {return _ connection = nil;} @ end

@ Property (strong, nonatomic) nsoperationqueue * queue;

 NSString *newUrl = [NSString stringWithFormat:@"http://static2.dmcdn.net/static/video/666/645/43546666:jpeg_preview_source.jpg?%d",(int)[NSDate timeIntervalSinceReferenceDate]];    ImageDownloader *imageDownloader = [[ImageDownloader alloc]initWithURLString:newUrl];    imageDownloader.delegate = self;    [self.queue addOperation:imageDownloader];

[[NSOperationQueue mainQueue] addOperationWithBlock:^{        self.urlConnection = [NSURLConnection connectionWithRequest:request delegate:self];    }];

Resumable download

NSMutableURLRequest *fileRequest = [NSMutableURLRequest requestWithURL:self.downloadURL                                                               cachePolicy:NSURLRequestUseProtocolCachePolicy                                                           timeoutInterval:kFileDefaultTimeout];

If the file exists, resumable upload

_startFileSize = [[fm attributesOfItemAtPath:self.pathToFile error:nil] fileSize];        NSString *range = [NSString stringWithFormat:@"bytes=%lld-", _startFileSize];        [fileRequest setValue:range forHTTPHeaderField:@"Range"];

Then start the download

  _connection = [[NSURLConnection alloc] initWithRequest:fileRequest                                                  delegate:self                                          startImmediately:NO];    if (self.connection) {        [self.connection scheduleInRunLoop:[NSRunLoop mainRunLoop]                                   forMode:NSDefaultRunLoopMode];        [self willChangeValueForKey:@"isExecuting"];        [self.connection start];        [self didChangeValueForKey:@"isExecuting"];    }

The use of nsoperation (download-related) images and files are both resumable images gradually displayed.