新的iOS 8的麻烦

Question

我正在尝试学习新的CoreAudio iOS 8的API，并且似乎无法在我的设备上产生任何声音。我正在使用来自WWDC会话502的代码，另外，我认为启动音频会话是个好主意。

#import "AppDelegate.h"
#import <AVFoundation/AVFoundation.h>

@interface AppDelegate ()


@end

@implementation AppDelegate


- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:    (NSDictionary *)launchOptions {
// Override point for customization after application launch.
AVAudioSession *session = [AVAudioSession sharedInstance];
NSError *error;
[session setCategory:AVAudioSessionCategoryPlayback error:&error];


AVAudioEngine *engine = [[AVAudioEngine alloc] init];
AVAudioPlayerNode *player = [[AVAudioPlayerNode alloc] init];
[engine attachNode:player];

NSURL *fileURL = [[NSBundle mainBundle] URLForResource:@"mySound" withExtension:@"aif"];
AVAudioFile *file = [[AVAudioFile alloc] initForReading:fileURL error:&error];
if (error) {
    NSLog(@"error getting audio file");
}

AVAudioMixerNode *mainMixer = [engine mainMixerNode];
// just to be safe
mainMixer.outputVolume = 1;
[engine connect:player to:mainMixer format:file.processingFormat];
[player scheduleFile:file atTime:nil completionHandler:nil];

if ([engine startAndReturnError:&error]) {
    NSLog(@"engine succsessful %@", error);
} else {
    NSLog(@"error starting engine: %@", error);
}
[player play];




return YES;

}

我遗漏了什么？

谢谢!

Answer 1

engine在你听到任何消息之前就被释放了。将引擎添加为类成员，这样，一旦didFinishLaunching返回，它就不会被丢弃

#import "AppDelegate.h"
#import <AVFoundation/AVFoundation.h>

@interface AppDelegate ()
    AVAudioEngine *engine;
@end

@implementation AppDelegate


- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:    (NSDictionary *)launchOptions {
// Override point for customization after application launch.
AVAudioSession *session = [AVAudioSession sharedInstance];
NSError *error;
[session setCategory:AVAudioSessionCategoryPlayback error:&error];


engine = [[AVAudioEngine alloc] init];
AVAudioPlayerNode *player = [[AVAudioPlayerNode alloc] init];
[engine attachNode:player];

NSURL *fileURL = [[NSBundle mainBundle] URLForResource:@"mySound" withExtension:@"aif"];
AVAudioFile *file = [[AVAudioFile alloc] initForReading:fileURL error:&error];
if (error) {
    NSLog(@"error getting audio file");
}

AVAudioMixerNode *mainMixer = [engine mainMixerNode];
// just to be safe
mainMixer.outputVolume = 1;
[engine connect:player to:mainMixer format:file.processingFormat];
[player scheduleFile:file atTime:nil completionHandler:nil];

if ([engine startAndReturnError:&error]) {
    NSLog(@"engine succsessful %@", error);
} else {
    NSLog(@"error starting engine: %@", error);
}
[player play];

return YES;
}

AVAudioSession是不必要的。