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：

 1 #import "RootViewController.h"
 2 #import "ListViewController.h"
 3 @interface RootViewController ()
 4
 5 @end
 6
 7 @implementation RootViewController
 8
 9 - (void)viewDidLoad {
10     [super viewDidLoad];
11     // Do any additional setup after loading the view from its nib.
12     self.slider_Process.minimumValue=0;
13     if (self.songName.length==0) {
14         self.songName=@"蓝莲花";
15     }
16     self.lblTitle.text=self.songName;
17     //找歌曲路径
18     NSString *path=[[NSBundle mainBundle]pathForResource:@"蓝莲花" ofType:@"mp3"];
19     //路径格式转换
20     NSURL *URL=[NSURL fileURLWithPath:path];
21     player=[[AVAudioPlayer alloc] initWithContentsOfURL:URL error:nil];
22     player.delegate=self;
23     //把播放的歌曲加到缓存中
24     [player prepareToPlay];
25
26     //添加观察者(通知中心)
27     [[NSNotificationCenter defaultCenter]  addObserver:self selector:@selector(songNameChange:) name:@"changeMusic" object:nil];
28
29 }
30 -(void)songNameChange:(NSNotification *)sender{
31     //获取歌曲名字.sender onject获得通知者的值
32     self.songName=[sender object];
33     self.lblTitle.text=self.songName;
34
35     NSString *strPath=[[NSBundle mainBundle] pathForResource:_songName ofType:@".mp3"];
36     NSURL  *URL=[NSURL fileURLWithPath:strPath];//从文件
37 //    NSURL *URL=[NSURL URLWithString:strPath];//从网上转换路径
38     if (player!=nil) {
39         player=nil;
40     }
41     player=[[AVAudioPlayer alloc] initWithContentsOfURL:URL error:nil];
42     player.delegate=self;
43     [player play];
44
45     //更新页面
46     //播放时声音的值就是音量滑块的值
47     [player setVolume:_slider_Volume.value];
48     //每隔一秒更新播放时间
49     [NSTimer scheduledTimerWithTimeInterval:1 target:self selector:@selector(updateTime) userInfo:nil repeats:YES];
50 }
51 //更新播放时间
52 -(void)updateTime{
53     //获取播放歌曲的总时长，获取到的是秒数
54     NSTimeInterval allTime=player.duration;
55     int minute=allTime/60;
56     int second=(int)allTime%60;
57     //获取当前播放的时间的分、秒
58     NSTimeInterval currentTime=player.currentTime;
59     int currentMintue=currentTime/60;
60     int currentSecond=(int)currentTime%60;
61     //把当前时间和总时间格式化为一个字符串
62     NSString *strCurrentTime=[NSString stringWithFormat:@"%.2d:%.2d",currentMintue,currentSecond];
63     NSString *strAllTime=[NSString stringWithFormat:@"/%.2d:%.2d",minute,second];
64     self.lblTime.text=[NSString stringWithFormat:@"%@%@",strCurrentTime,strAllTime];
65
66     self.slider_Process.value=player.currentTime/player.duration;  //进度条随播放移动
67 }
68 #pragma mark - 实现音频播放协议里的函数
69 -(void)audioPlayerDidFinishPlaying:(AVAudioPlayer *)player successfully:(BOOL)flag{
70     NSLog(@"当前歌曲播放完毕");
71 }
72 -(void)audioPlayerDecodeErrorDidOccur:(AVAudioPlayer *)player error:(NSError *)error{
73     NSLog(@"播放器出现异常");
74 }
75 - (void)didReceiveMemoryWarning {
76     [super didReceiveMemoryWarning];
77     // Dispose of any resources that can be recreated.
78 }

在ListViewController.h文件中：

 1 #import "ListViewController.h"
 2
 3 @interface ListViewController ()
 4
 5 @end
 6
 7 @implementation ListViewController
 8
 9 - (void)viewDidLoad {
10     [super viewDidLoad];
11     // Do any additional setup after loading the view from its nib.
12     [self initData];
13     [self createTableView];
14 }
15 -(void)initData{
16     dataAry=[[NSMutableArray alloc] init];
17     //从沙盒中读取数据
18     NSString *strPath=[[NSBundle mainBundle]pathForResource:@"musicList" ofType:@".plist"];
19     NSArray *ary=[NSArray arrayWithContentsOfFile:strPath];
20     [dataAry addObjectsFromArray:ary];
21 }
22 -(void)createTableView{
23     tv=[[UITableView alloc] initWithFrame:CGRectMake(0, 20, 375, 600) style:UITableViewStylePlain];
24     UIImageView *iv=[[UIImageView alloc] initWithFrame:tv.frame];
25     iv.image=[UIImage imageNamed:@"king1"];
26     [tv setBackgroundView:iv];
27     tv.delegate=self;
28     tv.dataSource=self;
29     [self.view addSubview:tv];
30 }
31 -(NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section{
32     return dataAry.count;
33 }
34 -(UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath{
35     NSString *identifier=@"song";
36     UITableViewCell *cell=[tableView dequeueReusableCellWithIdentifier:identifier];
37     if (!cell) {
38         cell=[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:identifier];
39     }
40     cell.textLabel.text=dataAry[indexPath.row];
41     cell.backgroundColor=[UIColor clearColor];
42     return cell;
43 }
44 -(void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath{
45     //获得选中行的歌曲名字
46     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
51 }
52 - (void)didReceiveMemoryWarning {
53     [super didReceiveMemoryWarning];
54     // Dispose of any resources that can be recreated.
55 }

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。