在iPhone上播放背景音频

Question

在iPhone上播放背景音频

iphoneaudio

3

我应该如何在应用程序运行时播放后台音频？

谢谢。

- ebaccount

2

如何在我的 iPhone 游戏中播放背景音乐？ - Matthew Flaschen

2个回答

0

如果您的应用程序还用于录音，请不要忘记将setCategory更改为AVAudioSessionCategoryPlayAndRecord。否则，您将无法录制

[[AVAudioSession sharedInstance] setCategory: AVAudioSessionCategoryPlayAndRecord error:&setCategoryErr];

- Kirill Smirnov

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- diachedelic · Accepted Answer

好的。这是一个针对iOS4和iOS5背景音效的解决方案（绝对适用于iOS 5.0.1及以下版本），我只测试了AVPlayer，但它也应该适用于MPMusicPlayerController。

所需框架：

AVFoundation.framework
AudioToolbox.framework

在你的Info.plist中，为键UIBackgroundModes添加audio。

在MyAppDelegate.h中：

reference <AVFoundation/AVFoundation.h> & <AudioToolbox/AudioToolbox.h>

implement the protocol AVAudioSessionDelegate:

@interface MyAppDelegate : NSObject <UIApplicationDelegate, AVAudioSessionDelegate>

define a method ensureAudio:

// Ensures the audio routes are setup correctly
- (BOOL) ensureAudio;

在MyAppDelegate.m文件中：

implement the ensureAudio method:

- (BOOL) ensureAudio
{
    // Registers this class as the delegate of the audio session (to get background sound)
    [[AVAudioSession sharedInstance] setDelegate: self];  

    // Set category
    NSError *categoryError = nil;
    if (![[AVAudioSession sharedInstance] setCategory:AVAudioSessionCategoryPlayback error:&categoryError]) {
        NSLog(@"Audio session category could not be set"); 
        return NO;
    }

    // Activate session
    NSError *activationError = nil;
    if (![[AVAudioSession sharedInstance] setActive: YES error: &activationError]) {
        NSLog(@"Audio session could not be activated");
        return NO;
    }

    // Allow the audio to mix with other apps (necessary for background sound)
    UInt32 doChangeDefaultRoute = 1;
    AudioSessionSetProperty(kAudioSessionProperty_OverrideCategoryMixWithOthers, sizeof(doChangeDefaultRoute), &doChangeDefaultRoute);

    return YES;
}

in the application:didFinishLaunchingWithOptions: method, before you assign the root view controller, run [self ensureAudio]:

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    // Configure audio session
    [self ensureAudio];

    // Add the navigation controller's view to the window and display.
    self.window.rootViewController = self.navigationController;
    [self.window makeKeyAndVisible];

    return YES;
}

implement the AVAudioSessionDelegate methods like this:

#pragma mark - AVAudioSessionDelegate

- (void) beginInterruption
{

}

- (void) endInterruption
{
    // Sometimes the audio session will be reset/stopped by an interruption
    [self ensureAudio];
}

- (void) inputIsAvailableChanged:(BOOL)isInputAvailable
{

}

ensure that your app continues to run in the background. You can use the ol' [[UIApplication sharedApplication] beginBackgroundTaskWithExpirationHandler] if you want, but I think there are better ways.

play the actual audio (note I'm using ARC, that's why there are no release calls):

NSURL * file = [[NSBundle mainBundle] URLForResource:@"beep" withExtension:@"aif"];    
AVURLAsset * asset = [[AVURLAsset alloc] initWithURL:file options:nil];
AVPlayerItem * item = [[AVPlayerItem alloc] initWithAsset:asset];
__block AVPlayer * player = [[AVPlayer alloc]initWithPlayerItem:item];
__block id finishObserver = [[NSNotificationCenter defaultCenter] addObserverForName:AVPlayerItemDidPlayToEndTimeNotification 
                                                                      object:player.currentItem 
                                                                       queue:[NSOperationQueue mainQueue] 
                                                                  usingBlock:^(NSNotification *note) {
    [[NSNotificationCenter defaultCenter] removeObserver:finishObserver];

    // Reference the 'player' variable so ARC doesn't release it until it's
    // finished playing.
    player = nil;
}];

// Trigger asynchronous load
[asset loadValuesAsynchronouslyForKeys:[NSArray arrayWithObject:@"tracks"] completionHandler:^{
    // Start playing the beep (watch out - we're not on the main thread here)!
    [player play];
 }];

And it shooooooooooooould work!