Question

我想在我的游戏中播放背景音乐（理想情况下我喜欢它淡入/淡出但我希望它先播放）

我已经查看了SO的各种答案，我的代码看起来似乎正确但由于某种原因文件没有播放，实际上它在AVAudioPlayer *player行崩溃（没有有用的输出）。如果我继续在[player play]行再次崩溃，但error为0。

再次更新

GameViewController.h

@property (nonatomic, retain) AVAudioPlayer *player;

GameViewController.m

@synthesize player; // the player object

viewDidLoad中：

NSString *soundFilePath = [[NSBundle mainBundle] pathForResource: @"bgtrack" ofType: @"mp3"];
NSURL *fileURL = [[NSURL alloc] initFileURLWithPath: soundFilePath];

player = [[AVAudioPlayer alloc] initWithContentsOfURL:fileURL error: nil]; // breaks here
[player prepareToPlay];

我包括

#import <AudioToolbox/AudioToolbox.h>
#import <AVFoundation/AVFoundation.h>

更新

根据评论，我尝试直接从Apple Dev中心复制/粘贴代码。我正在使用最新的XCode 4和iOS 6.1模拟器。

当它崩溃时，我没有得到它触及断点的信息。该文件包含在捆绑包中

Answer 1

您需要存储对player的强引用（可能在您的视图控制器的ivar中）。如果您只是将代码放入-viewDidLoad方法或某些内容而不强烈引用它，那么发生的事情就是玩家在有机会开始播放之前会被解除分配。例如：

@interface MyViewController : UIViewController

@end

@implementation MyViewController
{
    AVAudioPlayer* player;
}

- (void)viewDidLoad
{
    [super viewDidLoad];

    NSString *soundFilePath = [[NSBundle mainBundle] pathForResource:@"YourMP3FileName" ofType:@"mp3"];
    NSURL *soundFileURL = [NSURL fileURLWithPath:soundFilePath];
    NSError *error;
    player = [[AVAudioPlayer alloc] initWithContentsOfURL:soundFileURL error:&error];
    player.numberOfLoops = -1; //infinite
    player.currentTime = 139;// 2:19;

    [player play];
}

@end

这对我来说很好，但是如果player不是视图控制器的ivar，我就没有声音。

或者，我掀起了下面的课程，这个课程将作为一个单一的＆＃34;＆＃34; AVAudioPlayer。对于numberOfLoops为-1（无限）的情况，这显然会出现问题，因为这意味着它永远不会停止播放或消失，但如果您想要播放一次然后播放，则可能会使事情变得更容易一些走开，不需要随身携带它。

<强> OneShotAVAudioPlayer.h

#import <AVFoundation/AVFoundation.h>

@interface OneShotAVAudioPlayer : AVAudioPlayer
@end

<强> OneShotAVAudioPlayer.m

#import "OneShotAVAudioPlayer.h"
#import <AVFoundation/AVFoundation.h>
#import <objc/runtime.h>

@interface OneShotAVAudioPlayer () <AVAudioPlayerDelegate>
@property(weak) id<AVAudioPlayerDelegate> p_exogenousDelegate;
@end

@implementation OneShotAVAudioPlayer

static void * const OneShotAVAudioPlayerKey = (void*)&OneShotAVAudioPlayerKey;

- (id)initWithContentsOfURL:(NSURL *)url error:(NSError **)outError
{
    if (self = [super initWithContentsOfURL:url error:outError])
    {
        // Retain ourself
        objc_setAssociatedObject(self, OneShotAVAudioPlayerKey, self, OBJC_ASSOCIATION_RETAIN);
        [super setDelegate: self];
    }
    return self;
}

- (id)initWithData:(NSData *)data error:(NSError **)outError;
{
    if (self = [super initWithData:data error:outError])
    {
                    // Retain ourself
        objc_setAssociatedObject(self, OneShotAVAudioPlayerKey, self, OBJC_ASSOCIATION_RETAIN);
        [super setDelegate: self];
    }
    return self;
}

- (void)setDelegate:(id<AVAudioPlayerDelegate>)delegate
{
    self.p_exogenousDelegate = delegate;
}

- (id<AVAudioPlayerDelegate>)delegate
{
    return self.p_exogenousDelegate;
}

- (void)audioPlayerDidFinishPlaying:(AVAudioPlayer *)player successfully:(BOOL)flag
{
    @try
    {
        if ([self.p_exogenousDelegate respondsToSelector: _cmd])
            [self.p_exogenousDelegate audioPlayerDidFinishPlaying:player successfully:flag];
    }
    @finally
    {
        // Make a strong ref so we stay alive through the scope of this function
        typeof(self) keepAlive = self;
        // Give up the self retain
        objc_setAssociatedObject(keepAlive, OneShotAVAudioPlayerKey, nil, OBJC_ASSOCIATION_RETAIN);
        // Push in the "real" (outside) delegate, cause our job is done here.
        [super setDelegate: self.p_exogenousDelegate];
    }
}

- (void)audioPlayerDecodeErrorDidOccur:(AVAudioPlayer *)player error:(NSError *)error
{
    @try
    {
        if ([self.p_exogenousDelegate respondsToSelector: _cmd])
            [self.p_exogenousDelegate audioPlayerDecodeErrorDidOccur:player error:error];
    }
    @finally
    {
        // Make a strong ref so we stay alive through the scope of this function
        typeof(self) keepAlive = self;
        // Give up the self retain
        objc_setAssociatedObject(keepAlive, OneShotAVAudioPlayerKey, nil, OBJC_ASSOCIATION_RETAIN);
        // Push in the "real" (outside) delegate, cause our job is done here.
        [super setDelegate: self.p_exogenousDelegate];
    }
}

- (BOOL)respondsToSelector:(SEL)aSelector
{
    BOOL retVal = [super respondsToSelector: aSelector];
    if (!retVal)
    {
        struct objc_method_description method = protocol_getMethodDescription(@protocol(AVAudioPlayerDelegate), aSelector, YES, YES);
        if (method.name)
        {
            retVal = [self.p_exogenousDelegate respondsToSelector: aSelector];
        }
    }
    return retVal;
}

- (id)forwardingTargetForSelector:(SEL)aSelector
{
    id retVal = [super forwardingTargetForSelector:aSelector];
    if (!retVal)
    {
        struct objc_method_description method = protocol_getMethodDescription(@protocol(AVAudioPlayerDelegate), aSelector, YES, YES);
        if (method.name && [self.p_exogenousDelegate respondsToSelector: aSelector])
        {
            retVal = self.p_exogenousDelegate;
        }
    }
    return retVal;
}

- (void)setNumberOfLoops:(NSInteger)numberOfLoops
{
    if (numberOfLoops < 0)
    {
        NSLog(@"Warning! You have set an infinite loop count for an instance of %@ (%p). This means the instance will effectively be leaked.", NSStringFromClass([self class]), self);
    }
    [super setNumberOfLoops: numberOfLoops];
}

@end

发布here as a gist。

Answer 2

如果玩家为零，则将玩家ivar提升为强大的属性并记录[error description]。

如果它崩溃了肯定是错的。您是否添加了异常断点？

无法在iPhone游戏中播放mp3文件

2 个答案: