AVAudioPlayer不播放mp3？

Question

我希望我的AVAudioPlayer播放一些mp3文件。 它播放其中一些，但我有一個無法播放的文件！

要播放該文件，我將其在我的設備上下載到應用程序文件夾中並以這種方式初始化：

[[AVAudioPlayer alloc] initWithContentsOfURL:soundPath error:nil];

怎么播放文件？ 為什么不玩？

鏈接到文件： abc.mp3

編輯：

（這是顯示錯誤的代碼。代碼中有一個自述文件。嘗試使用該設備。）

***.pch

#import <Availability.h>

#ifndef __IPHONE_4_0
#warning "This project uses features only available in iOS SDK 4.0 and later."
#endif

#ifdef __OBJC__
    #import <UIKit/UIKit.h>
    #import <Foundation/Foundation.h>
    #import <SystemConfiguration/SystemConfiguration.h>
    #import <MobileCoreServices/MobileCoreServices.h>
    #import <AVFoundation/AVFoundation.h>
    #import <AudioToolbox/AudioToolbox.h>
#endif



ViewController.h

#import <UIKit/UIKit.h>
#import "AFNetworking.h"

@interface SCRViewController : UIViewController <AVAudioPlayerDelegate>
{
    UIButton *button;
    __block UIProgressView *view;
    NSOperationQueue *queue;
    __block BOOL isFile;
    UIButton *play;
    NSString *path;
    AVAudioPlayer *_player;
}

@end


ViewController.m

#import "ViewController.h"

@implementation SCRViewController

- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.

    button = [UIButton buttonWithType:UIButtonTypeCustom];
    [button setBackgroundColor:[UIColor yellowColor]];
    [button setFrame:CGRectMake(50, 50, 220, 50)];
    [button addTarget:self action:@selector(download) forControlEvents:UIControlEventTouchUpInside];
    [button setTitle:@"Download" forState:UIControlStateNormal];
    [button setTitleColor:[UIColor blackColor] forState:UIControlStateNormal];
    [button setTitleColor:[UIColor redColor] forState:UIControlStateHighlighted];
    [self.view addSubview:button];

    play = [UIButton buttonWithType:UIButtonTypeCustom];
    [play setBackgroundColor:[UIColor yellowColor]];
    [play setFrame:CGRectMake(50, 150, 220, 50)];
    [play addTarget:self action:@selector(play) forControlEvents:UIControlEventTouchUpInside];
    [play setTitle:@"Play" forState:UIControlStateNormal];
    [play setTitleColor:[UIColor blackColor] forState:UIControlStateNormal];
    [play setTitleColor:[UIColor redColor] forState:UIControlStateHighlighted];
    [self.view addSubview:play];

    self->view = [[UIProgressView alloc] initWithProgressViewStyle:UIProgressViewStyleDefault];
    self->view.frame = CGRectMake(10, 120, 300, 20);
    [self->view setProgress:0];
    [self.view addSubview:self->view];

    queue = [[NSOperationQueue alloc] init];

    isFile = NO;
}

- (void) download
{
    [button setBackgroundColor:[UIColor brownColor]];
    [button setTitleColor:[UIColor whiteColor] forState:UIControlStateDisabled];
    [button setEnabled:NO];

    NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:@"http://iwheelbuy.com/abc.mp3"]];

    //-------------------------------------------------------
    //-------------------------------------------------------
    // READ ME
    //-------------------------------------------------------
    //-------------------------------------------------------
    // Test in on device
    // I have uploaded another song for you. You can change link to http://iwheelbuy.com/def.mp3 and check the result
    // def.mp3 works fine on the device
    //-------------------------------------------------------
    //-------------------------------------------------------

    AFHTTPRequestOperation *operation = [[AFHTTPRequestOperation alloc] initWithRequest:request];

    path = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0];
    path = [path stringByAppendingPathComponent:@"song"];

    if ( [[NSFileManager defaultManager] fileExistsAtPath:path])
        [[NSFileManager defaultManager] removeItemAtPath:path error:nil];

    operation.outputStream = [NSOutputStream outputStreamToFileAtPath:path append:NO];
    [operation setCompletionBlockWithSuccess:^(AFHTTPRequestOperation *operation, id responseObject)
     {
         isFile = YES;
     } failure:^(AFHTTPRequestOperation *operation, NSError *error)
     {
         //
     }];
    [operation setDownloadProgressBlock:^(NSUInteger bytesRead, long long totalBytesRead, long long totalBytesExpectedToRead)
     {
         CGFloat done = (CGFloat)((int)totalBytesRead);
         CGFloat expected = (CGFloat)((int)totalBytesExpectedToRead);
         CGFloat progress = done / expected;
         self->view.progress = progress;
     }];
    [queue addOperation:operation];
}

- (void) play
{
    if (isFile)
    {
        NSError *error = nil;
        NSURL *url = [NSURL fileURLWithPath:path];
        _player = [[AVAudioPlayer alloc] initWithContentsOfURL:url error:&error];
        if(error || !_player)
        {
            UIAlertView *alert = [[UIAlertView alloc] initWithTitle:nil message:[error description] delegate:nil cancelButtonTitle:@"Try def.mp3" otherButtonTitles:nil];
            [alert show];
        }
        else
        {
            [_player play]; // plays fine
            [[AVAudioSession sharedInstance] setCategory:AVAudioSessionCategoryPlayback error:nil];
            [[AVAudioSession sharedInstance] setActive: YES error: nil];
        }
    }
    else
    {
        UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Warning" message:@"Download the file plz" delegate:nil cancelButtonTitle:@"Ok" otherButtonTitles: nil];
        [alert show];
    }
}

@end

Answer 1

非ARC

您必須在播放期間保留它，因為它不會保留自己。 一旦解除分配，它將立即停止播放。

弧

您需要在類中保存AVAudioPlayer實例。 並在它停止播放后釋放它。 例如，

#import <AVFoundation/AVFoundation.h>

@interface TAViewController () <AVAudioPlayerDelegate> {
    AVAudioPlayer *_somePlayer;   // strong reference
}
@end

@implementation TAViewController

- (IBAction)playAudio:(id)sender
{
    NSURL *url = [[NSBundle mainBundle] URLForResource:@"kogmawjoke" withExtension:@"mp3"];
    _somePlayer = [[AVAudioPlayer alloc] initWithContentsOfURL:url error:NULL];
    _somePlayer.delegate = self;
    [_somePlayer play];
}

- (void)audioPlayerDidFinishPlaying:(AVAudioPlayer *)player successfully:(BOOL)flag
{
    if (player == _somePlayer) {
        _somePlayer = nil;
    }
}

@end

Answer 2

http://bugreport.apple.com

Engineering已根據以下信息確定此問題的行為符合預期：

可以使用附加的示例應用程序進行重新編譯，但這是AudioFile的預期行為。

問題是AVAudioPlayer正在使用沒有文件擴展名的url進行初始化，並且相應的文件沒有有效的ID3標記。沒有文件擴展名或有效數據，我們無法確定正確的文件格式，因此這些文件將無法打開這是一種預期的行為。

在附帶的示例代碼中：

path = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0];

path = [path stringByAppendingPathComponent:@"song"];

- >路徑將是這樣的：

在/ var /移動/應用/ 2FFD0147-E56B-47D4-B143-A9F19BE92818 /文件/歌曲

- >注意：最后沒有文件擴展名。

與具有有效標記大小（0x927）的def.mp3不同，abc.mp3具有無效的ID3標記大小（0x2EE）。 因此，當這些被指定為“...。/ song”而沒有任何擴展時，AudioFile只查看數據並找到def.mp3的有效同步字，但不能找到abc.mp3。

但是，用stringByAppendingPathComponent:@"song"替換stringByAppendingPathComponent:@"song" stringByAppendingPathComponent:@"song.mp3"成功為abc.mp3，並且可以幫助其他一般的mp3文件。

我們認為這個問題已經結束 如果您對此問題有任何疑問或疑慮，請直接更新您的報告（ http://bugreport.apple.com ）。

感謝您抽出寶貴時間通知我們此問題。