How can I keep background music playing when switching ViewControllers? - ios

Question

I currently have a SettingsViewController which handles starting/stopping music and adjusting the musics volume.
Is it possible to make the music stay on after unwinding the SettingsViewController? And after turning on the music and switching ViewControllers, can I re-open the SettingsViewController and turn off the music as well? Please let me know the limitations.
Here is the code for my SettingsViewController.h
#import <UIKit/UIKit.h>
#import <AVFoundation/AVFoundation.h>
#interface SettingsViewController : UIViewController <AVAudioPlayerDelegate>
{
AVAudioPlayer *audioPlayer;
IBOutlet UISwitch *Switch;
IBOutlet UISlider *Slider;
}
-(IBAction)Switch:(UISwitch *)sender;
-(IBAction)Slider:(UISlider *)sender;
#end
And here is the code for my SettingsViewController.m
#import "SettingsViewController.h"
#interface SettingsViewController ()
#end
#implementation SettingsViewController
-(IBAction)Switch:(UISwitch *)sender{
NSUserDefaults *standardDefaults = [NSUserDefaults standardUserDefaults];
if(sender.tag == 0){
if(sender.on){
[standardDefaults setObject:#"On" forKey:#"keyName"];
//choosing and setting the music file
NSString *music = [[NSBundle mainBundle]pathForResource:#"bgmusic1" ofType:#"mp3"];
audioPlayer = [[AVAudioPlayer alloc]initWithContentsOfURL:[NSURL fileURLWithPath:music] error:NULL];
audioPlayer.delegate = self;
audioPlayer.numberOfLoops= -1; //sets the music to loop infinitely
[audioPlayer play]; //plays the music
} else if (sender.on == 0){
[standardDefaults setObject:#"Off" forKey:#"keyName"];
[audioPlayer stop]; //stops the music
}
}
[standardDefaults synchronize];
}
-(IBAction)Slider:(UISlider *)sender{
audioPlayer.volume = sender.value / 100.0; //will adjust the volume of the music according the slider value
}
- (void)viewDidLoad {
[super viewDidLoad];
// Do any additional setup after loading the view.
}
- (void)didReceiveMemoryWarning {
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
Let me know what needs to be modified!

Answer 1

Do that in your AppDelegate.
To access it from anywhere, import it's .h file in your ViewControllers .m file and access it with
MyAppDelegate *appDelegate = (MyAppDelegate *)[[UIApplication sharedApplication] delegate];
Make the audioplayer to a property in your AppDelegate.h to allow public access (for e.g. your other viewControllers)
#interface AppDelegate: NSAppDelegate
{
IBOutlet UISwitch *Switch;
IBOutlet UISlider *Slider;
}
#property AVAudioPlayer *audioPlayer; // <------
-(IBAction)Switch:(UISwitch *)sender;
-(IBAction)Slider:(UISlider *)sender;
#end
Then adjust each call of your audioplayer in the m file to adopt the change in your h file.
//Instead of [audioplayer doSomething] write...
[self.audioplayer doSomething];
// in modern objective-c you can use also
[_audioplayer doSomething];
To call your audioplayer from other ViewControllers then implement the first mentioned code and call your player like so
[appDelegate.audioplayer doSomething]

Answer 2

Because your audioPlayer will be release when its parent SettingsViewController released.
So you should add it to global and you can make it with Singleton Pattern.
Create BackgroundPlayer.h
#interface BackgroundPlayer: NSObject {
AVAudioPlayer *audioPlayer;
}
+ (id)sharedManager;
#end
and BackgroundPlayer.m
#implementation BackgroundPlayer
static BackgroundPlayer* sharedInstance = nil;
+ (BackgroundPlayer*) sharedInstance {
if (sharedInstance == nil) {
sharedInstance = [[super allocWithZone:NULL] init];
}
return sharedInstance;
}
- (id)init
{
self = [super init];
return self;
}
-(void)playAudio:(NSString *) audioPath
{
audioPlayer = [[AVAudioPlayer alloc]initWithContentsOfURL:[NSURL fileURLWithPath:audioPath] error:NULL];
audioPlayer.delegate = self;
audioPlayer.numberOfLoops= -1; //sets the music to loop infinitely
[audioPlayer play]; //plays the music
}
-(void)setVolum:(float) volum {
if (audioPlayer) {
audioPlayer.volume = sender.value / 100.0;
}
}
Then you just call
NSString *music = [[NSBundle mainBundle]pathForResource:#"bgmusic1" ofType:#"mp3"];
[[BackgroundPlayersharedInstance] playAudio:music];