項目中之前使用的是AVPlayer直接播放URL地址，但是不知道是相機的wifi不夠穩定還是代碼的問題，app總是出現緩沖卡頓，就考慮改寫成邊下邊播的模式，查過了許多資料，發現大部分都是用的同一種方法
AVAssetResourceLoaderDelegate 代理方法，來看看如何實現
首先要實現兩個必須的代理方法
AVAssetResourceLoaderDelegateObjective-C#pragma mark - AVAssetResourceLoaderDelegate//開始加載- (BOOL)resourceLoader:(AVAssetResourceLoader *)resourceLoader shouldWaitForLoadingOfRequestedResource:(AVAssetResourceLoadingRequest *)loadingRequest { [self addLoadingRequest:loadingRequest]; return YES;}//取消加載- (void)resourceLoader:(AVAssetResourceLoader *)resourceLoader didCancelLoadingRequest:(AVAssetResourceLoadingRequest *)loadingRequest { [self removeLoadingRequest:loadingRequest];}#pragma mark - AVAssetResourceLoaderDelegate//開始加載- (BOOL)resourceLoader:(AVAssetResourceLoader *)resourceLoader shouldWaitForLoadingOfRequestedResource:(AVAssetResourceLoadingRequest *)loadingRequest { [self addLoadingRequest:loadingRequest]; return YES;}//取消加載- (void)resourceLoader:(AVAssetResourceLoader *)resourceLoader didCancelLoadingRequest:(AVAssetResourceLoadingRequest *)loadingRequest { [self removeLoadingRequest:loadingRequest];}然后要定義一個下載類，其實就是分段下載數據的下載器
AVAssetResourceLoaderDelegateObjective-C- (void)start { NSMutableURLRequest * request = [NSMutableURLRequest requestWithURL:[self.requestURL originalSchemeURL] cachePolicy:NSURLRequestReloadIgnoringCacheData timeoutInterval:RequestTimeout]; if (self.requestOffset > 0) { [request addValue:[NSString stringWithFormat:@"bytes=%ld-%ld", self.requestOffset, self.fileLength - 1] forHTTPHeaderField:@"Range"]; } self.session = [NSURLSession sessionWithConfiguration:[NSURLSessionConfiguration defaultSessionConfiguration] delegate:self delegateQueue:[NSOperationQueue mainQueue]]; self.task = [self.session dataTaskWithRequest:request]; [self.task resume];}#pragma mark - NSURLSessionDataDelegate//服務器響應- (void)URLSession:(NSURLSession *)session dataTask:(NSURLSessionDataTask *)dataTask didReceiveResponse:(NSURLResponse *)response completionHandler:(void (^)(NSURLSessionResponseDisposition))completionHandler { if (self.cancel) return; SRQLog(@"response: %@",response); completionHandler(NSURLSessionResponseAllow); NSHTTPURLResponse * httpResponse = (NSHTTPURLResponse *)response; NSString * contentRange = [[httpResponse allHeaderFields] objectForKey:@"Content-Range"]; NSString * fileLength = [[contentRange componentsSeparatedByString:@"/"] lastObject]; self.fileLength = fileLength.integerValue > 0 ? fileLength.integerValue : response.expectedContentLength; if (self.delegate && [self.delegate respondsToSelector:@selector(requestTaskDidReceiveResponse)]) { [self.delegate requestTaskDidReceiveResponse]; }}//服務器返回數據 可能會調用多次- (void)URLSession:(NSURLSession *)session dataTask:(NSURLSessionDataTask *)dataTask didReceiveData:(NSData *)data { if (self.cancel) return; //SRQLog(@"收到響應了: %@",data); self.cacheLength += data.length; if (self.delegate && [self.delegate respondsToSelector:@selector(requestTaskDidUpdateCache)]) { [self.delegate requestTaskDidUpdateCache]; }}//請求完成會調用該方法，請求失敗則error有值- (void)URLSession:(NSURLSession *)session task:(NSURLSessionTask *)task didCompleteWithError:(NSError *)error { if (self.cancel) { SRQLog(@"下載取消"); }else { if (error) { if (self.delegate && [self.delegate respondsToSelector:@selector(requestTaskDidFailWithError:)]) { [self.delegate requestTaskDidFailWithError:error]; } }else { //可以緩存則保存文件 if (self.cache) { [FileHandle cacheTempFileWithFileName:[NSString fileNameWithURL:self.requestURL]]; } if (self.delegate && [self.delegate respondsToSelector:@selector(requestTaskDidFinishLoadingWithCache:)]) { [self.delegate requestTaskDidFinishLoadingWithCache:self.cache]; } } }}- (void)start { NSMutableURLRequest * request = [NSMutableURLRequest requestWithURL:[self.requestURL originalSchemeURL] cachePolicy:NSURLRequestReloadIgnoringCacheData timeoutInterval:RequestTimeout]; if (self.requestOffset > 0) { [request addValue:[NSString stringWithFormat:@"bytes=%ld-%ld", self.requestOffset, self.fileLength - 1] forHTTPHeaderField:@"Range"]; } self.session = [NSURLSession sessionWithConfiguration:[NSURLSessionConfiguration defaultSessionConfiguration] delegate:self delegateQueue:[NSOperationQueue mainQueue]]; self.task = [self.session dataTaskWithRequest:request]; [self.task resume];}#pragma mark - NSURLSessionDataDelegate//服務器響應- (void)URLSession:(NSURLSession *)session dataTask:(NSURLSessionDataTask *)dataTask didReceiveResponse:(NSURLResponse *)response completionHandler:(void (^)(NSURLSessionResponseDisposition))completionHandler { if (self.cancel) return; SRQLog(@"response: %@",response); completionHandler(NSURLSessionResponseAllow); NSHTTPURLResponse * httpResponse = (NSHTTPURLResponse *)response; NSString * contentRange = [[httpResponse allHeaderFields] objectForKey:@"Content-Range"]; NSString * fileLength = [[contentRange componentsSeparatedByString:@"/"] lastObject]; self.fileLength = fileLength.integerValue > 0 ? fileLength.integerValue : response.expectedContentLength; if (self.delegate && [self.delegate respondsToSelector:@selector(requestTaskDidReceiveResponse)]) { [self.delegate requestTaskDidReceiveResponse]; }}//服務器返回數據 可能會調用多次- (void)URLSession:(NSURLSession *)session dataTask:(NSURLSessionDataTask *)dataTask didReceiveData:(NSData *)data { if (self.cancel) return; //SRQLog(@"收到響應了: %@",data); self.cacheLength += data.length; if (self.delegate && [self.delegate respondsToSelector:@selector(requestTaskDidUpdateCache)]) { [self.delegate requestTaskDidUpdateCache]; }}//請求完成會調用該方法，請求失敗則error有值- (void)URLSession:(NSURLSession *)session task:(NSURLSessionTask *)task didCompleteWithError:(NSError *)error { if (self.cancel) { SRQLog(@"下載取消"); }else { if (error) { if (self.delegate && [self.delegate respondsToSelector:@selector(requestTaskDidFailWithError:)]) { [self.delegate requestTaskDidFailWithError:error]; } }else { //可以緩存則保存文件 if (self.cache) { [FileHandle cacheTempFileWithFileName:[NSString fileNameWithURL:self.requestURL]]; } if (self.delegate && [self.delegate respondsToSelector:@selector(requestTaskDidFinishLoadingWithCache:)]) { [self.delegate requestTaskDidFinishLoadingWithCache:self.cache]; } } }}最后將拿到的數據塞進AVAssetResourceLoaderDelegate代理中，交還給AVPlayer，就可以播放了
AVAssetResourceLoaderDelegateObjective-C- (BOOL)finishLoadingWithLoadingRequest:(AVAssetResourceLoadingRequest *)loadingRequest { //填充信息 CFStringRef contentType = UTTypeCreatePreferredIdentifierForTag(kUTTagClassMIMEType, (__bridge CFStringRef)(MimeType), NULL); loadingRequest.contentInformationRequest.contentType = CFBridgingRelease(contentType); loadingRequest.contentInformationRequest.byteRangeAccessSupported = YES; loadingRequest.contentInformationRequest.contentLength = self.requestTask.fileLength; //讀文件，填充數據 NSUInteger cacheLength = self.requestTask.cacheLength; NSUInteger requestedOffset = loadingRequest.dataRequest.requestedOffset; if (loadingRequest.dataRequest.currentOffset != 0) { requestedOffset = loadingRequest.dataRequest.currentOffset; } NSUInteger canReadLength = cacheLength - (requestedOffset - self.requestTask.requestOffset); NSUInteger respondLength = MIN(canReadLength, loadingRequest.dataRequest.requestedLength); //SRQLog(@"好不容易填充一次"); [loadingRequest.dataRequest respondWithData:[FileHandle readTempFileDataWithOffset:requestedOffset - self.requestTask.requestOffset length:respondLength]]; //如果完全響應了所需要的數據，則完成 NSUInteger nowendOffset = requestedOffset + canReadLength; NSUInteger reqEndOffset = loadingRequest.dataRequest.requestedOffset + loadingRequest.dataRequest.requestedLength; if (nowendOffset >= reqEndOffset) { [loadingRequest finishLoading]; return YES; } return NO;}- (void)player{ self.resouerLoader = [[ResourceLoader alloc] init]; self.asset = [AVURLAsset URLAssetWithURL:[self.videoUrl customSchemeURL] options:nil]; [self.asset.resourceLoader setDelegate:self.resouerLoader queue:dispatch_get_main_queue()]; _playerItem = [AVPlayerItem playerItemWithAsset:self.asset]; _players = [AVPlayer playerWithPlayerItem:_playerItem];}- (BOOL)finishLoadingWithLoadingRequest:(AVAssetResourceLoadingRequest *)loadingRequest { //填充信息 CFStringRef contentType = UTTypeCreatePreferredIdentifierForTag(kUTTagClassMIMEType, (__bridge CFStringRef)(MimeType), NULL); loadingRequest.contentInformationRequest.contentType = CFBridgingRelease(contentType); loadingRequest.contentInformationRequest.byteRangeAccessSupported = YES; loadingRequest.contentInformationRequest.contentLength = self.requestTask.fileLength; //讀文件，填充數據 NSUInteger cacheLength = self.requestTask.cacheLength; NSUInteger requestedOffset = loadingRequest.dataRequest.requestedOffset; if (loadingRequest.dataRequest.currentOffset != 0) { requestedOffset = loadingRequest.dataRequest.currentOffset; } NSUInteger canReadLength = cacheLength - (requestedOffset - self.requestTask.requestOffset); NSUInteger respondLength = MIN(canReadLength, loadingRequest.dataRequest.requestedLength); //SRQLog(@"好不容易填充一次"); [loadingRequest.dataRequest respondWithData:[FileHandle readTempFileDataWithOffset:requestedOffset - self.requestTask.requestOffset length:respondLength]]; //如果完全響應了所需要的數據，則完成 NSUInteger nowendOffset = requestedOffset + canReadLength; NSUInteger reqEndOffset = loadingRequest.dataRequest.requestedOffset + loadingRequest.dataRequest.requestedLength; if (nowendOffset >= reqEndOffset) { [loadingRequest finishLoading]; return YES; } return NO;}- (void)player{ self.resouerLoader = [[ResourceLoader alloc] init]; self.asset = [AVURLAsset URLAssetWithURL:[self.videoUrl customSchemeURL] options:nil]; [self.asset.resourceLoader setDelegate:self.resouerLoader queue:dispatch_get_main_queue()]; _playerItem = [AVPlayerItem playerItemWithAsset:self.asset]; _players = [AVPlayer playerWithPlayerItem:_playerItem];}注意：此方法服務器端最好支持Range頭，這樣才是分段下載。
總結
以上所述是小編給大家介紹的iOS 邊下邊播的實現代碼，希望對大家有所幫助，如果大家有任何疑問請給我留言，小編會及時回復大家的。在此也非常感謝大家對武林網網站的支持！
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