如何在应用程序运行时播放背景音频?
Thanks.
好的。这是 iOS4 和 iOS5 上背景声音的解决方案(绝对适用于 iOS 5.0.1),我仅使用 AVPlayer 对其进行了测试。它可能也适用于 MPMusicPlayerController。
所需框架:
AVFoundation.framework
AudioToolbox.framework
In your Info.plist
,对于关键UIBackgroundModes
, add audio
.
In MyAppDelegate.h
:
- 参考
<AVFoundation/AVFoundation.h>
& <AudioToolbox/AudioToolbox.h>
-
实施协议AVAudioSessionDelegate
:
@interface MyAppDelegate : NSObject <UIApplicationDelegate, AVAudioSessionDelegate>
-
定义一个方法ensureAudio
:
// Ensures the audio routes are setup correctly
- (BOOL) ensureAudio;
In MyAppDelegate.m
:
-
实施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:
方法,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
像这样的方法:
#pragma mark - AVAudioSessionDelegate
- (void) beginInterruption
{
}
- (void) endInterruption
{
// Sometimes the audio session will be reset/stopped by an interruption
[self ensureAudio];
}
- (void) inputIsAvailableChanged:(BOOL)isInputAvailable
{
}
确保您的应用程序继续在后台运行。你可以使用ol'[[UIApplication sharedApplication] beginBackgroundTaskWithExpirationHandler]
如果你愿意的话,但我认为还有更好的方法。
-
播放实际的音频(注意我使用的是 ARC,这就是为什么没有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];
}];
它可以工作!
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