iphone - iOS xcode4 AVQueuePlayer 不播放声音

Question

我正在尝试在 iPhone4 上使用 AVQueuePlayer 播放 .m4a 声音文件，但没有声音。
如果我使用相同的文件尝试 AudioServicesPlaySystemSound，则一切正常。

这是代码。

(AVFoundation framework is installed.)

    #import <AVFoundation/AVFoundation.h> 

-(void) play_sound_file: (NSString *) sound_file_m4a
{
    printf("\n play_sound_file 1: '%s' ", [sound_file_m4a UTF8String] );


        AVPlayerItem *sound_file = [[AVPlayerItem alloc] initWithURL:[NSURL URLWithString:[[NSBundle mainBundle] pathForResource:sound_file_m4a ofType:@"m4a"]]]; 
        AVQueuePlayer *player = [AVQueuePlayer queuePlayerWithItems:[NSArray arrayWithObjects:sound_file, nil]];  

        [player play]; 

        return;
}

2012 年 8 月 28 日的最新代码.......
(注意:两个声音文件都适用于 AudioServicesPlaySystemSound)

AVPlayerItem *sound_file1 = [[AVPlayerItem alloc] initWithURL:[NSURL fileURLWithPath:[[NSBundle mainBundle] pathForResource:[[NSString alloc] initWithFormat:@"Hold still"] ofType:@"m4a"]]]; 

AVPlayerItem *sound_file2 = [[AVPlayerItem alloc] initWithURL:[NSURL fileURLWithPath:[[NSBundle mainBundle] pathForResource:[[NSString alloc] initWithFormat:@"Press go"] ofType:@"m4a"]]];     

AVQueuePlayer *player = [AVQueuePlayer queuePlayerWithItems: [NSArray arrayWithObjects:sound_file1, sound_file2,  nil]];  

[player play]; 

Answer 1

我在你上一篇文章中对我的回答的评论中解释了如何解决这个问题。这可能不起作用的原因之一是因为您将一项传递给 arrayWithObjects:这需要不止一项。另一个可能导致它不起作用的事情是，如果您试图在模拟器中运行它，AVQueuePlayer 之间存在已知的兼容性问题。和模拟器。

还:

代替

AVPlayerItem *sound_file = [[AVPlayerItem alloc] initWithURL:[NSURL URLWithString:[[NSBundle mainBundle] pathForResource:sound_file_m4a ofType:@"m4a"]]]; 

和

AVPlayerItem *sound_file = [[AVPlayerItem alloc] initWithURL:[NSURL fileURLWithPath:[[NSBundle mainBundle] pathForResource:[[NSString alloc] initWithFormat:@"sound_file_m4a"] ofType:@"m4a"]]];

编辑:下面是如何按顺序播放音频文件的示例。

在你的头文件中:

#import <AVFoundation/AVFoundation.h>

AVAudioPlayer *data;
NSArray *arrayOfTracks;
NSUInteger currentTrackNumber;

然后在您的实现文件中:

- (void)viewDidLoad
{
    [super viewDidLoad];
    arrayOfTracks = [[NSArray alloc] initWithObjects:@"1",@"2",@"3", nil];//Do NOT include file extension here
    currentTrackNumber = 0;
}
- (void)startPlaying
{
    if (data) {
        [data stop];
        //[data release]; if project isn't using Automatic Reference Counting
        data = nil;
    }
    data = [[AVAudioPlayer alloc] initWithContentsOfURL:[NSURL fileURLWithPath:[[NSBundle mainBundle] pathForResource:[[NSString alloc] initWithString:[arrayOfTracks objectAtIndex:currentTrackNumber]] ofType:@"m4a"]] error:NULL];
    data.delegate = self;
    [data play];
}

- (void)audioPlayerDidFinishPlaying:(AVAudioPlayer *)player successfully:(BOOL)flag
{
    if (flag) {
        if (currentTrackNumber < [arrayOfTracks count] - 1) {
            currentTrackNumber ++;
            if (data) {
                [data stop];
                //[data release]; if project isn't using Automatic Reference Counting
                data = nil;
            }
            data = [[AVAudioPlayer alloc] initWithContentsOfURL:[NSURL fileURLWithPath:[[NSBundle mainBundle] pathForResource:[[NSString alloc] initWithString:[arrayOfTracks objectAtIndex:currentTrackNumber]] ofType:@"m4a"]] error:NULL];
            data.delegate = self;
            [data play];
        }
    }
}