Question

如何在应用程序运行时播放背景音频？

感谢。

Answer 1

好。这是iOS4和iOS上的背景声音解决方案。 iOS5（绝对适用于iOS 5.0.1），我只用AVPlayer测试过它。它也可能适用于MPMusicPlayerController。

必需的框架：

AVFoundation.framework
AudioToolbox.framework

在Info.plist中，对于密钥UIBackgroundModes，请添加audio。

在MyAppDelegate.h：

参考<AVFoundation/AVFoundation.h>＆amp; <AudioToolbox/AudioToolbox.h>

实施协议AVAudioSessionDelegate：

@interface MyAppDelegate : NSObject <UIApplicationDelegate, AVAudioSessionDelegate>

定义方法ensureAudio：

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

在MyAppDelegate.m：

实施ensureAudio方法：

- (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;
}

在application:didFinishLaunchingWithOptions:方法中，在分配根视图控制器之前，运行[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;
}

实施AVAudioSessionDelegate这样的方法：

#pragma mark - AVAudioSessionDelegate

- (void) beginInterruption
{

}

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

- (void) inputIsAvailableChanged:(BOOL)isInputAvailable
{

}

确保您的应用继续在后台运行。如果你愿意，你可以使用ol [[UIApplication sharedApplication] beginBackgroundTaskWithExpirationHandler]，但我认为有更好的方法。

播放实际音频（注意我正在使用ARC，这就是没有release次呼叫的原因）：

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];
 }];

它真的很棒！

Answer 2

如果您还使用自己的应用进行录制 - 那么请不要忘记将setCategory更改为AVAudioSessionCategoryPlayAndRecord。在其他情况下，您将无法录制

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

在iphone上播放背景音频

2 个答案: