多媒体之本地音乐的播放(利用观察者模式传值)及播放中控件的变化

在RootViewController的m文件里：

#import "RootViewController.h"
#import "ListViewController.h"
@interface RootViewController ()

@end

@implementation RootViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view from its nib.
    self.slider_Process.minimumValue=0;
    if (self.songName.length==0) {
        self.songName=@"蓝莲花";
    }
    self.lblTitle.text=self.songName;
    //找歌曲路径
    NSString *path=[[NSBundle mainBundle]pathForResource:@"蓝莲花" ofType:@"mp3"];
    //路径格式转换
    NSURL *URL=[NSURL fileURLWithPath:path];
    player=[[AVAudioPlayer alloc] initWithContentsOfURL:URL error:nil];
    player.delegate=self;
    //把播放的歌曲加到缓存中
    [player prepareToPlay];
    
    //添加观察者(通知中心)
27     [[NSNotificationCenter defaultCenter]  addObserver:self selector:@selector(songNameChange:) name:@"changeMusic" object:nil];
28     
}
30 -(void)songNameChange:(NSNotification *)sender{
    //获取歌曲名字.sender onject获得通知者的值
    self.songName=[sender object];
    self.lblTitle.text=self.songName;
    
    NSString *strPath=[[NSBundle mainBundle] pathForResource:_songName ofType:@".mp3"];
    NSURL  *URL=[NSURL fileURLWithPath:strPath];//从文件
//    NSURL *URL=[NSURL URLWithString:strPath];//从网上转换路径
    if (player!=nil) {
        player=nil;
    }
    player=[[AVAudioPlayer alloc] initWithContentsOfURL:URL error:nil];
    player.delegate=self;
    [player play];
    
    //更新页面
    //播放时声音的值就是音量滑块的值
    [player setVolume:_slider_Volume.value];
    //每隔一秒更新播放时间
    [NSTimer scheduledTimerWithTimeInterval:1 target:self selector:@selector(updateTime) userInfo:nil repeats:YES];
}
//更新播放时间
-(void)updateTime{
    //获取播放歌曲的总时长，获取到的是秒数
    NSTimeInterval allTime=player.duration;
    int minute=allTime/60;
    int second=(int)allTime%60;
    //获取当前播放的时间的分、秒
    NSTimeInterval currentTime=player.currentTime;
    int currentMintue=currentTime/60;
    int currentSecond=(int)currentTime%60;
    //把当前时间和总时间格式化为一个字符串
    NSString *strCurrentTime=[NSString stringWithFormat:@"%.2d:%.2d",currentMintue,currentSecond];
    NSString *strAllTime=[NSString stringWithFormat:@"/%.2d:%.2d",minute,second];
    self.lblTime.text=[NSString stringWithFormat:@"%@%@",strCurrentTime,strAllTime];
    
    self.slider_Process.value=player.currentTime/player.duration;  //进度条随播放移动
}
#pragma mark - 实现音频播放协议里的函数
-(void)audioPlayerDidFinishPlaying:(AVAudioPlayer *)player successfully:(BOOL)flag{
    NSLog(@"当前歌曲播放完毕");
}
-(void)audioPlayerDecodeErrorDidOccur:(AVAudioPlayer *)player error:(NSError *)error{
    NSLog(@"播放器出现异常");
}
- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

在ListViewController.h文件中：

#import "ListViewController.h"

@interface ListViewController ()

@end

@implementation ListViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view from its nib.
    [self initData];
    [self createTableView];
}
-(void)initData{
    dataAry=[[NSMutableArray alloc] init];
    //从沙盒中读取数据
    NSString *strPath=[[NSBundle mainBundle]pathForResource:@"musicList" ofType:@".plist"];
    NSArray *ary=[NSArray arrayWithContentsOfFile:strPath];
    [dataAry addObjectsFromArray:ary];
}
-(void)createTableView{
    tv=[[UITableView alloc] initWithFrame:CGRectMake(0, 20, 375, 600) style:UITableViewStylePlain];
    UIImageView *iv=[[UIImageView alloc] initWithFrame:tv.frame];
    iv.image=[UIImage imageNamed:@"king1"];
    [tv setBackgroundView:iv];
    tv.delegate=self;
    tv.dataSource=self;
    [self.view addSubview:tv];
}
-(NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section{
    return dataAry.count;
}
-(UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath{
    NSString *identifier=@"song";
    UITableViewCell *cell=[tableView dequeueReusableCellWithIdentifier:identifier];
    if (!cell) {
        cell=[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:identifier];
    }
    cell.textLabel.text=dataAry[indexPath.row];
    cell.backgroundColor=[UIColor clearColor];
    return cell;
}
-(void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath{
    //获得选中行的歌曲名字
    NSString *songName=dataAry[indexPath.row];
47     //把名字传回到第一个页面(Root页面)采用观察者模式
48     [[NSNotificationCenter defaultCenter] postNotificationName:@"changeMusic" object:songName];
49     [self dismissViewControllerAnimated:NO completion:nil];
50     
}
- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

实现效果：

此例利用Xib快速构建UI并添加控件事件等。实现本地音乐的播放、及播放中各控件如何变化和利用KVC-KVO观察者传值。