blocks|key|4485359|text|找到了解决方案。我声明了一个名为signal的视图控制器属性。我说signal：==？-然后在viewDidLoad中，我放了一个if语句，如果signal+==+nil，只播放背景歌曲。然后，在我的其他视图控制器中，我对其进行了设置，以便当它们分割回mainviewcontroller时，信号属性=+false。然后，歌曲将不会再次播放，一切都将正常工作。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4485360|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

Found a solution. I declared a view controller property called signal. I said signal: Bool? - Then in viewDidLoad I put an if statement to only play the background song if signal == nil. Then, in my other view controllers I set it so that when they segue back to the mainviewcontroller, the signal property = false. Then, the song won't play again and everything works correctly.

blocks|key|4484404|text|我想你应该在你的AppDelegate.swift文件中试试。在application(.....didFinishLaunchingWithOptions.....){}方法中定义AVAudioPlayer()和.play()|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4484405|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

I think you should try in you AppDelegate.swift file.
In the method application(.....didFinishLaunchingWithOptions.....){} define your AVAudioPlayer() and .play()

blocks|key|4485414|text|我是这样做的。将此代码添加到您希望音乐开始播放的类场景之外的任何位置。你甚至可以创建一个全新的Swift文件，然后在其中添加以下代码(导入AVFoundation)|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4485415|var+backgroundMusicPlayer:+AVAudioPlayer!

func+playBackgroundMusic(filename:+String)+{

++++//The+location+of+the+file+and+its+type
++++let+url+=+NSBundle.mainBundle().URLForResource(filename,+withExtension:+"mp3")

++++//Returns+an+error+if+it+can't+find+the+file+name
++++if+(url+==+nil)+{
++++++++println("Could+not+find+the+file+\(filename)")
++++}

++++var+error:+NSError?+=+nil

++++//Assigns+the+actual+music+to+the+music+player
++++backgroundMusicPlayer+=+AVAudioPlayer(contentsOfURL:+url,+error:+&error)

++++//Error+if+it+failed+to+create+the+music+player
++++if+backgroundMusicPlayer+==+nil+{
++++println("Could+not+create+audio+player:+\(error!)")
++++return
++++}

++++//A+negative+means+it+loops+forever
++++backgroundMusicPlayer.numberOfLoops+=+-1
++++backgroundMusicPlayer.prepareToPlay()
++++backgroundMusicPlayer.play()
}|code-block|syntax|javascript|4485416|完成后，转到didMoveToView函数并使用文件名调用该函数。|4485417|playBackgroundMusic("IntroMusic")|4485418|我刚刚测试了它，切换场景后它工作得很好。|4485419|entityMap^0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Q|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|R|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|S|8|@]|9|@]|A|$]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

Here's how I did mine. Add this code anywhere OUTSIDE the class scene where you want the music to start playing. You can even make a whole new Swift file and just add this code in there (import AVFoundation) 

<pre><code>var backgroundMusicPlayer: AVAudioPlayer!

func playBackgroundMusic(filename: String) {

 //The location of the file and its type
 let url = NSBundle.mainBundle().URLForResource(filename, withExtension: "mp3")

 //Returns an error if it can't find the file name
 if (url == nil) {
 println("Could not find the file \(filename)")
 }

 var error: NSError? = nil

 //Assigns the actual music to the music player
 backgroundMusicPlayer = AVAudioPlayer(contentsOfURL: url, error: &amp;error)

 //Error if it failed to create the music player
 if backgroundMusicPlayer == nil {
 println("Could not create audio player: \(error!)")
 return
 }

 //A negative means it loops forever
 backgroundMusicPlayer.numberOfLoops = -1
 backgroundMusicPlayer.prepareToPlay()
 backgroundMusicPlayer.play()
}
</code></pre>

After you have that, go to the didMoveToView function and call the function with the name of the file.

<pre><code>playBackgroundMusic("IntroMusic")
</code></pre>

I just tested it and it works perfect after switching scenes.

blocks|key|4485448|text|只需添加"numberofLoops+=+-1“，它将在后台无限播放。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4485449|示例(Swift)：|4485450|func+playBackgroundMusic()+{
++++do+{
++++++++if+let+bundle+=+NSBundle.mainBundle().pathForResource("someMP3file",+ofType:+"mp3")+{
++++++++++++let+alertSound+=+NSURL(fileURLWithPath:+bundle)
++++++++++++try+AVAudioSession.sharedInstance().setCategory(AVAudioSessionCategoryPlayback)
++++++++++++try+AVAudioSession.sharedInstance().setActive(true)
++++++++++++try+audioPlayer+=+AVAudioPlayer(contentsOfURL:+alertSound)
++++++++++++audioPlayer.numberOfLoops+=+-1
++++++++++++audioPlayer.prepareToPlay()
++++++++++++audioPlayer.play()

++++++++}
++++}+catch+{
++++++++print(error)
++++}
}|code-block|syntax|javascript|4485451|玩得开心。|4485452|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|N|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|O|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|P|8|@]|9|@]|A|$]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

Just add "numberofLoops = -1" an its plays infinitly in the background. 

Example (Swift): 

<pre><code>func playBackgroundMusic() {
 do {
 if let bundle = NSBundle.mainBundle().pathForResource("someMP3file", ofType: "mp3") {
 let alertSound = NSURL(fileURLWithPath: bundle)
 try AVAudioSession.sharedInstance().setCategory(AVAudioSessionCategoryPlayback)
 try AVAudioSession.sharedInstance().setActive(true)
 try audioPlayer = AVAudioPlayer(contentsOfURL: alertSound)
 audioPlayer.numberOfLoops = -1
 audioPlayer.prepareToPlay()
 audioPlayer.play()

 }
 } catch {
 print(error)
 }
}
</code></pre>

Have fun.

blocks|key|4484473|text|对于swift+4：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4484474|func+playBackgroundMusic()+{
++++++++let+aSound+=+NSURL(fileURLWithPath:+Bundle.main.path(forResource:+"music",+ofType:+"mp3")!)
++++++++do+{
++++++++++++audioPlayer+=+try+AVAudioPlayer(contentsOf:aSound+as+URL)
++++++++++++audioPlayer!.numberOfLoops+=+-1
++++++++++++audioPlayer!.prepareToPlay()
++++++++++++audioPlayer!.play()
++++++++}+catch+{
++++++++++++print("Cannot+play+the+file")
++++++++}
++++}|code-block|syntax|javascript|4484475|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

for swift 4:

<pre><code>func playBackgroundMusic() {
 let aSound = NSURL(fileURLWithPath: Bundle.main.path(forResource: "music", ofType: "mp3")!)
 do {
 audioPlayer = try AVAudioPlayer(contentsOf:aSound as URL)
 audioPlayer!.numberOfLoops = -1
 audioPlayer!.prepareToPlay()
 audioPlayer!.play()
 } catch {
 print("Cannot play the file")
 }
 }
</code></pre>

I want the user to be able to open the app and have music start playing. I want the user to be able to go any view controller and return back to the initial one without the music stopping. I want it to loop indefinitely. 

I have tried to put in the <code>viewDidLoad</code> method of the initial view controller for it to start playing. What happens is, the user leaves the initial view controller and when they come back, the music starts playing again, overlapping the original copy. 

To remedy this, I put an if statement checking if the sound is already to playing to not launch another copy and the viewDidLoad method completely ignores the if statement and plays it again anyways. I also tried using <code>viewDid/WillAppear</code>. I have tried putting the sound in the app delegate in the <code>applicationDidLaunchWithOptions</code> method and I got complete silence.

Play background music in app?

Swift

我希望用户能够打开应用程序，并有音乐开始播放。我希望用户能够转到任何视图控制器，并在音乐不停止的情况下返回到初始视图控制器。我想让它无限循环。我已经尝试将初始视图控制器的viewDidLoad方法放入其中，让它开始播放。发生的情况是，用户离开初始视图控制器，当他们回来时，音乐再次开始播放，与原始副本重叠。为了纠正这个问...

问是否在应用程序中播放背景音乐？
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问是否在应用程序中播放背景音乐？
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