播放声音,等待它完成播放并继续(iphone)

Question

我是iphone和Objective c的新手,到目前为止,我已经能够编写一些小例子了.

我想播放声音,并在示例完成播放后继续使用其余代码,即:

printf("hello");
playASound["file.wav"];
printf("world");

实际上我得到了:打印你好,同时播放文件和打印世界,但我想要的是:打印你好,播放文件,打印世界......所以,问题是我如何得到它？

谢谢

顺便说一句.这是playASound代码:

-(void) playASound: (NSString *) file {

    //Get the filename of the sound file:
    NSString *path = [NSString stringWithFormat:@"%@/%@",
                      [[NSBundle mainBundle] resourcePath],
                      file];

    SystemSoundID soundID;
    //Get a URL for the sound file
    NSURL *filePath = [NSURL fileURLWithPath:path isDirectory:NO];
    AudioServicesCreateSystemSoundID((CFURLRef)filePath, &soundID);
    //play the file
    AudioServicesPlaySystemSound(soundID);
}

Answer 1

从文档:

讨论此功能播放短音(持续时间不超过30秒).因为声音可能会播放几秒钟,所以此功能是异步执行的.要知道声音何时播放完毕,请调用AudioServicesAddSystemSoundCompletion函数以注册回调函数.

因此,您需要将您的功能分解为两部分:一个调用PlayASound并打印"Hello"的函数,以及一个在声音播放完毕后由系统调用并打印"World" 的函数.

// Change PlayASound to return the SystemSoundID it created
-(SystemSoundID) playASound: (NSString *) file {

    //Get the filename of the sound file:
    NSString *path = [NSString stringWithFormat:@"%@/%@",
                      [[NSBundle mainBundle] resourcePath],
                      file];

    SystemSoundID soundID;
    //Get a URL for the sound file
    NSURL *filePath = [NSURL fileURLWithPath:path isDirectory:NO];
    AudioServicesCreateSystemSoundID((CFURLRef)filePath, &soundID);
    //play the file
    AudioServicesPlaySystemSound(soundID);
    return soundID;
}

-(void)startSound
{
   printf("Hello");
    SystemSoundID id = [self playASound:@"file.wav"];
    AudioServicesAddSystemSoundCompletion (
       id,
       NULL,
       NULL,
       endSound,
       NULL
   );
}

void endSound (
   SystemSoundID  ssID,
   void           *clientData
)
{
   printf("world\n");
}

另请参阅AudioServicesAddSystemSoundCompletion和AudioServicesSystemSoundCompletionProc的文档.