ios - 通话后如何恢复音乐

Question

我有一个在线音乐播放器。我想给它添加一个功能，如果正在播放歌曲并调用电话(来电或去电)，它应该暂停正在通话的音乐，并且在通话断开后，音乐应该重新开始。

这是我的代码:

////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，插入音量 View 的代码也在那里，然后 UI 中也没有音量 Controller 。为什么会这样？

////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

通话后无法启动音乐。请帮助提供可能的解决方案。

Answer 1

需要在FirstViewController中添加观察者

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

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

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

并且不要忘记删除观察者。