下载音频，在IOS设备上播放

在IOS上可以用MPMoviePlayerViewController实现在线播放音频，但是当网络不理想的情况下客户体验总不是太好，所以采用了，先下载下来，然后播放。

 

1.下载音频

    NSString *soundhttpURL = [[NSString alloc] initWithFormat:@"http://114.112.55.2:6080/audio/question/audio_"];
    NSString *qid = [currentQuestion objectForKey:@"qid"];
    NSString *soundURLStr = [NSString stringWithFormat:@"%@%@%@",soundhttpURL,qid,@".wav"];
    NSURL *soundURL = [NSURL URLWithString:soundURLStr];
    NSLog(@"soundURL:%@",soundURL);
    
    NSDate *date = [NSDate date];
	NSMutableURLRequest *theRequest = [NSMutableURLRequest requestWithURL:soundURL];
	NSURLResponse *response;
	NSError *error;
	NSData* result = [NSURLConnection sendSynchronousRequest:theRequest returningResponse:&response error:&error];
    NSLog(@"Response expects %lld bytes", [response expectedContentLength]);
	NSLog(@"Response suggested file name: %@", [response suggestedFilename]);
	if ([response suggestedFilename])
		self.savePath = [DEST_PATH stringByAppendingString:[response suggestedFilename]];
	
	if (!result)
		NSLog(@"Error downloading data: %@.", [error localizedDescription]);
	else if ([response expectedContentLength] < 0)
		NSLog(@"Error with download. Carrier redirect?");
	else
	{
		NSLog(@"Download succeeded.");
		NSLog(@"Read %d bytes", result.length);
		NSLog(@"Elapsed time: %0.2f seconds.", -1*[date timeIntervalSinceNow]);
		[result writeToFile:self.savePath atomically:YES];
		NSLog(@"Data written to file: %@.", self.savePath);
	}
[self performSelectorOnMainThread:@selector(playQuestionSound:) withObject:soundURL waitUntilDone:NO];//播放问题音频

 2.播放音频

- (void) playQuestionSound:(NSURL *)soundURL {
    //播放问题音频
    [[AVAudioSession sharedInstance] setCategory: AVAudioSessionCategoryPlayback error: nil];
    [[AVAudioSession sharedInstance] setActive: YES error: nil];
    NSURL *fileURL = [NSURL fileURLWithPath:self.savePath];
    player = [[AVAudioPlayer alloc] initWithContentsOfURL: fileURL error: nil];
    [fileURL release];
    [player setVolume:15.0];
    [player play];
}