如何在通話後恢復音樂

Question

我有一個在線音樂播放器。我想添加一項功能，如果正在播放歌曲並進行了呼叫（傳入或傳出），則應暫停正在進行呼叫的音樂，並且在呼叫斷開後，音樂應再次啓動。

這裏是我的代碼：

// // FirstViewController.m

#import "FirstViewController.h" 
CM_EXPORT const CMTime kCMTimeZero; 
@interface FirstViewController() 

@end 


@implementation FirstViewController 
@synthesize metadatas; 
@synthesize toggleButton; 
@synthesize slider; 
@synthesize mpVolumeView = _mpVolumeView; 
@synthesize viewVolume; 

- (void)viewDidLoad 
{ 
    //[super viewDidLoad]; 
    //slider.transform = CGAffineTransformRotate(slider.transform,270.0/180*M_PI); 
    //[slider setMaximumValue:2]; 
    //[slider setMinimumValue:0]; 
    //[slider setSelected:YES]; 


    //[[self mpVolumeView] setBackgroundColor:[UIColor clearColor]]; 

    //MPVolumeView *myVolumeView = [[MPVolumeView alloc] initWithFrame: [[self mpVolumeView] bounds]]; 
    //[[self mpVolumeView] addSubview:myVolumeView]; 
    //toggleIsOn =TRUE; 
    [[UIApplication sharedApplication] beginReceivingRemoteControlEvents]; 
    toggleIsOn=TRUE; 
    MPVolumeView *volumeView = [[MPVolumeView alloc] initWithFrame:self.viewVolume.bounds] ; 

    [self.viewVolume addSubview:volumeView]; 

    [volumeView sizeToFit]; 

} 

- (void)didReceiveMemoryWarning 
{ 
    [super didReceiveMemoryWarning]; 
} 

-(IBAction)playButtonPressed:(id)sender 
{ 



    if(toggleIsOn){ 

     toggleIsOn=!toggleIsOn; 

     player = nil; 
     NSString *stringurl = @""; 
     stringurl = @"http://majestic.wavestreamer.com:6221/listen.pls"; 
     NSURL *url = [NSURL URLWithString:stringurl]; 
     asset = [AVURLAsset URLAssetWithURL:url options:nil]; 
     playerItem = [AVPlayerItem playerItemWithAsset:asset]; 
     player = [AVPlayer playerWithPlayerItem:playerItem]; 
     player.actionAtItemEnd = AVPlayerActionAtItemEndNone; 
     [playerItem addObserver:self forKeyPath:@"timedMetadata" options:NSKeyValueObservingOptionNew context:nil]; 
     [playerItem addObserver:self forKeyPath:@"status" options:NSKeyValueObservingOptionNew context:nil]; 
     [player play]; 

     [self.toggleButton setImage:[UIImage imageNamed:@"reload.png"] forState:UIControlStateNormal]; 
     [[AVAudioSession sharedInstance] setCategory:AVAudioSessionCategoryPlayback error:nil]; 
     [[AVAudioSession sharedInstance] setActive: YES error: nil]; 
     [[UIApplication sharedApplication] beginReceivingRemoteControlEvents]; 
    } 
    else { 

     [self.toggleButton setImage:[UIImage imageNamed:@"playMusic.png"] forState:UIControlStateNormal]; 
     self->player.rate=0.0; 
     toggleIsOn=!toggleIsOn; 



    } 


} 
- (void)viewWillAppear:(BOOL)animated 
{ 
    [super viewWillAppear:animated]; 
} 

- (void)viewDidAppear:(BOOL)animated { 
    [super viewDidAppear:animated]; 
    [[UIApplication sharedApplication] beginReceivingRemoteControlEvents]; 
    [self becomeFirstResponder]; 
} 

- (void)viewWillDisappear:(BOOL)animated { 
    [super viewWillDisappear:animated]; 
    [[UIApplication sharedApplication] endReceivingRemoteControlEvents]; 
    [self resignFirstResponder]; 
} 

- (void)viewDidDisappear:(BOOL)animated 
{ 
    [super viewDidDisappear:animated]; 
} 

- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation 
{ 
    return (interfaceOrientation != UIInterfaceOrientationPortraitUpsideDown); 
} 


- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object 
         change:(NSDictionary *)change context:(void *)context { 

    [playerItem removeObserver:self forKeyPath:keyPath]; 


    if ([keyPath isEqualToString:@"status"]) { 
     AVPlayerItem *pItem = (AVPlayerItem *)object; 
     if (pItem.status == AVPlayerItemStatusReadyToPlay) 
     { 
      metadatas.text = @""; 
     } 
    } 
    if ([keyPath isEqualToString:@"timedMetadata"]) { 
     for (AVAssetTrack *track in playerItem.tracks) { 
      for (AVPlayerItemTrack *item in player.currentItem.tracks) { 
       if ([item.assetTrack.mediaType isEqual:AVMediaTypeAudio]) { 
        NSArray *meta = [playerItem timedMetadata]; 
        for (AVMetadataItem *metaItem in meta) { 

         NSString *source = metaItem.stringValue; 
         metadatas.text = source; 
        } 
       } 
      } 
     } 
    } 

    [self.toggleButton setImage:[UIImage imageNamed:toggleIsOn ? @"playMusic.png" :@"stop.png"] forState:UIControlStateNormal]; 

} 


-(IBAction)fbButtonPressed:(id)sender 
{ 

    NSURL *url = [NSURL URLWithString:@"http://www.facebook.com"]; 

    if (![[UIApplication sharedApplication] openURL:url]) 
     NSLog(@"%@%@",@"Failed to open url:",[url description]); 
} 


-(IBAction)inButtonPressed:(id)sender 
{ 

    NSURL *url = [NSURL URLWithString:@"http://www.linkedin.com"]; 

    if (![[UIApplication sharedApplication] openURL:url]) 
     NSLog(@"%@%@",@"Failed to open url:",[url description]); 
} 

-(IBAction)tweetButtonPressed:(id)sender 
{ 

    NSURL *url = [NSURL URLWithString:@"http://www.twitter.com"]; 

    if (![[UIApplication sharedApplication] openURL:url]) 
     NSLog(@"%@%@",@"Failed to open url:",[url description]); 
} 
-(IBAction) sliderChanged:(id)sender 
{ 


} 

- (NSUInteger)supportedInterfaceOrientations{ 
    return UIInterfaceOrientationMaskPortrait; 
} 

@end 

此外，用於插入體積視圖的代碼是存在的，則還沒有音量控制器在UI中。爲什麼這樣。？

// // FirstViewController.m

#import <UIKit/UIKit.h> 
#import <AVFoundation/AVFoundation.h> 
#import <MediaPlayer/MediaPlayer.h> 

@class AVPlayer; 
@class AVPlayerItem; 

@interface FirstViewController : UIViewController 
{ 

    UIView *viewVolume; 
    AVAsset *asset; 
    AVPlayerItem *playerItem; 
    AVPlayer *player; 
    NSURL *mURL; 
    MPVolumeView *_mpVolumeView; 
    IBOutlet UILabel *metadatas; 
    IBOutlet UIButton *toggleButton; 
    BOOL toggleIsOn; 
    IBOutlet UISlider *slider; 


} 

-(IBAction)playButtonPressed:(id)sender; 
-(IBAction)fbButtonPressed:(id)sender; 
-(IBAction)inButtonPressed:(id)sender; 
-(IBAction)tweetButtonPressed:(id)sender; 
-(IBAction) sliderChanged:(id)sender; 
@property (strong, nonatomic) IBOutlet UISlider *slider; 
@property (nonatomic, retain) IBOutlet MPVolumeView *mpVolumeView; 
@property (nonatomic, retain) IBOutlet UILabel *metadatas; 
@property (nonatomic, retain) IBOutlet UIButton *toggleButton; 
@property (nonatomic, strong) IBOutlet UIView *viewVolume; 

@end 

時無法調用後，開始音樂。請幫助解決可能的問題。

Answer 1

轉到您的appDelegate文件，在那裏您會發現UIApplicationDelegate方法自動爲您執行。

只需在方法中添加音樂暫停和恢復代碼，其他所有內容都將相應處理。只要確保您可以從應用程序代理訪問您的音樂實例播放器。

- (void)applicationWillResignActive:(UIApplication *)application 
{ 
    // Sent when the application is about to move from active to inactive state. This can occur for certain types of temporary interruptions (such as an incoming phone call or SMS message) or when the user quits the application and it begins the transition to the background state. 
    // Use this method to pause ongoing tasks, disable timers, and throttle down OpenGL ES frame rates. Games should use this method to pause the game. 
} 

- (void)applicationDidEnterBackground:(UIApplication *)application 
{ 
    // Use this method to release shared resources, save user data, invalidate timers, and store enough application state information to restore your application to its current state in case it is terminated later. 
    // If your application supports background execution, this method is called instead of applicationWillTerminate: when the user quits. 
} 

- (void)applicationWillEnterForeground:(UIApplication *)application 
{ 
    // Called as part of the transition from the background to the active state; here you can undo many of the changes made on entering the background. 
} 

- (void)applicationDidBecomeActive:(UIApplication *)application 
{ 
    // Restart any tasks that were paused (or not yet started) while the application was inactive. If the application was previously in the background, optionally refresh the user interface. 
} 

Answer 2

您需要在添加觀察者FirstViewController

- (void)viewWillAppear:(BOOL)animated 
{ 
    [super viewWillAppear:animated]; 

    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(resumePlayMusic)  name:UIApplicationDidBecomeActiveNotification object:nil]; 
} 

- (void) resumePlayMusic 
{ 
    ....... 
} 

而且不要忘記刪除觀察者。