AVAudioPlayer音频播放

AVAudioPlayer类创建的实例可以看作为一个音频播放器，可以播放来自文件或存储的音频数据。
它支持多种音频格式，而且能够进行进度、音量、播放速度等控制。
使用这个类，可以：
1、在指定的时间开始播放音频
2、从文件或内存缓冲区播放音频
3、循环播放

属性	描述
@property(readonly, getter=isPlaying) BOOL playing	是否正在播放，只读
@property float volume	音量大小，范围0~1.0
@property float pan	立体声，-1.0完全左声道，0.0左右声道平衡，1.0完全右声道
@property float rate	播放速率，范围0.5～2.0，1.0时为正常播放，如果需要更改播放速率必须设置enableRate为YES
@property BOOL enableRate	是否可以更改播放速率
@property NSInteger numberOfLoops	重复播放次数，为0时只播放一次，小于0时为无限播放，大于0时表示循环次数
@property(readonly) NSDictionary *settings	音频播放次数信息，只读
@property(readonly) NSUInteger numberOfChannels	与音频播放器相关联的声音通道的数量。（只读）
@property(nonatomic, copy) NSArray *channelAssignments	与音频播放器相关AVAudioSessionChannelDescription对象数组
@property(readonly) NSTimeInterval duration	播放时长
@property NSTimeInterval currentTime	当前播放时长
@property(readonly) NSTimeInterval deviceCurrentTime	输出设备播放音频的时间，注意如果播放中被暂停此时间也会继续累加
@property(readonly) NSURL *url	音频文件路径，只读
@property(readonly) NSData *data	音频数据，只读
@property(getter=isMeteringEnabled) BOOL meteringEnabled	否启用音频测量，默认为NO，一旦启用音频测量可以通过updateMeters方法更新测量值
对象方法	描述
- (instancetype)initWithContentsOfURL:(NSURL *)url  error:(NSError **)outError	使用文件URL初始化播放器，注意这个URL不能是HTTP URL，AVAudioPlayer不支持加载网络媒体流，只能播放本地文件
- (instancetype)initWithData:(NSData *)data error:(NSError **)outError	使用NSData初始化播放器，注意使用此方法时必须文件格式和文件后缀一致，否则出错，所以相比此方法更推荐使用上述方法 或- (instancetype)initWithData:(NSData *)data fileTypeHint:(NSString *)utiString error:(NSError **)outError方法进行初始化
- (BOOL)play	播放音频文件
- (BOOL)playAtTime:(NSTimeInterval)time	在指定的时间开始播放音频
- (void)pause	暂停播放
- (void)stop	停止播放
- (BOOL)prepareToPlay	将音频文件加载到缓冲区
- (float)averagePowerForChannel:(NSUInteger)channelNumber	获得指定声道的分贝平均值，注意如果要获得分贝平均值必须在此之前调用updateMeters方法
- (float)peakPowerForChannel:(NSUInteger)channelNumber	获得指定声道的分贝峰值，注意如果要获得分贝峰值必须在此之前调用updateMeters方法
- (void)updateMeters	更新音频测量值，注意如果要更新音频测量值必须设置meteringEnabled为YES，通过音频测量值可以即时获得音频分贝等信息
代理方法	说明
- (void)audioPlayerDidFinishPlaying:(AVAudioPlayer *)player successfully:(BOOL)flag	播放完成后调用，在这里可以进行一些属性的设置
- (void)audioPlayerDecodeErrorDidOccur:(AVAudioPlayer *)player error:(NSError *)error	音频解码发生错误

AVAudioPlayer的使用比较简单：

1、初始化AVAudioPlayer对象，通常指定本地文件路径

2、设置播放器属性，例如播放次数，音量大小，设置代理等

3、开始播放，调用play方法

下面就是AVAudioPlayer实现的一个简单播放器，它播放本地的音频文件，实现了播放、暂停、显示播放进度，现实播放时间等功能：

#import "JZViewController.h"
#import <AVFoundation/AVFoundation.h>

@interface JZViewController() <AVAudioPlayerDelegate>

@property (nonatomic, strong) AVAudioPlayer * audioPlayer;
@property (nonatomic, strong) UIImageView * imageView;
@property (nonatomic, strong) UIProgressView * progressView;
@property (nonatomic, strong) UILabel * timeLabel;
@property (nonatomic, strong) UILabel * currenttimeLabel;
@property (nonatomic, assign) NSTimer * timer;
@property (nonatomic, assign) int intTime;
@property (nonatomic, assign) int timeNum;
@property (nonatomic, assign) UIButton * button;

@end

@implementation JZViewController

- (void)viewDidLoad
{
    [super viewDidLoad];
    self.title = @"礼物"; //播放音频为 礼物.mp3 钢琴曲
    self.view.backgroundColor = [UIColor whiteColor];
    
    [self.view addSubview:self.imageView];
    
    [self initView];
}

//界面初始化，添加一个view、一个进度条、3个label、一个button
- (void)initView
{
    UIView * view = [[UIView alloc] initWithFrame:CGRectMake(0, [UIScreen mainScreen].bounds.size.height - 150, [UIScreen mainScreen].bounds.size.width, 150)];
    view.backgroundColor = [UIColor colorWithRed:246 / 255.0 green:246 / 255.0 blue:246 / 255.0 alpha:0.9];
    view.alpha = 0.8f;
    [self.view addSubview:view];

    UIProgressView * progressView = [[UIProgressView alloc] initWithFrame:CGRectMake(40, 50, [UIScreen mainScreen].bounds.size.width - 80, 0)];
    self.progressView = progressView;
    [view addSubview:progressView];
    
    UILabel * timeLabel = [[UILabel alloc] initWithFrame:CGRectMake([UIScreen mainScreen].bounds.size.width - 40, 40, 40, 20)];
    timeLabel.backgroundColor = [UIColor clearColor];
    timeLabel.font = [UIFont systemFontOfSize:11];
    timeLabel.textAlignment = NSTextAlignmentCenter;
    self.timeLabel = timeLabel;
    [view addSubview:timeLabel];
    
    UILabel * currentTimeLabel = [[UILabel alloc] initWithFrame:CGRectMake(0, 40, 40, 20)];
    currentTimeLabel.backgroundColor = [UIColor clearColor];
    currentTimeLabel.font = [UIFont systemFontOfSize:11];
    currentTimeLabel.textAlignment = NSTextAlignmentCenter;
    self.currenttimeLabel = currentTimeLabel;
    [view addSubview:currentTimeLabel];
    
    UILabel * label = [[UILabel alloc] initWithFrame:CGRectMake(0, 0, [UIScreen mainScreen].bounds.size.width, 50)];
    label.backgroundColor = [UIColor clearColor];
    label.text = @"礼物";
    label.textAlignment = NSTextAlignmentCenter;
    [view addSubview:label];
    
    UIButton * button = [[UIButton alloc] initWithFrame:CGRectMake([UIScreen mainScreen].bounds.size.width / 2 - 30, 70, 60, 60)];
    button.backgroundColor = [UIColor clearColor];
    [button setImage:[UIImage imageNamed:@"start.jpg"] forState:UIControlStateNormal];
    [button addTarget:self action:@selector(clickButton:) forControlEvents:UIControlEventTouchUpInside];
    self.button = button;
    button.tag = 10;
    [view addSubview:button];
}

//初始化imageView，添加背景图片
- (UIImageView *)imageView
{
    if(!_imageView){
        UIImage * image = [UIImage imageNamed:@"sjz.jpg"];
        UIImageView * imageView = [[UIImageView alloc] initWithImage:image];
        imageView.frame = [UIScreen mainScreen].bounds;
        _imageView = imageView;
    }
    return _imageView;
}

//懒加载，创建audioPlayer
- (AVAudioPlayer *)audioPlayer
{
    if(!_audioPlayer){
        NSString * urlStr = [[NSBundle mainBundle] pathForResource:@"礼物.mp3" ofType:nil];
        NSURL * url = [NSURL fileURLWithPath:urlStr];
        NSError * error = nil;
        _audioPlayer = [[AVAudioPlayer alloc] initWithContentsOfURL:url error:&error];
        //设置播放属性
        _audioPlayer.numberOfLoops = 0;
        _audioPlayer.delegate = self;
        [_audioPlayer prepareToPlay];  //加载音频文件到缓存
        
        
        if(error){
            NSLog(@"初始化播放器过程发生错误，错误信息:%@", error.localizedDescription);
            return nil;
        }
        
    }
    return _audioPlayer;
}

//点击button后调用的方法，播放、暂停音乐
- (void)clickButton:(UIButton *)sender
{
    if(sender.tag == 10){
        sender.tag = 20;
        [sender setImage:[UIImage imageNamed:@"stop.jpg"] forState:UIControlStateNormal];
        [self.audioPlayer play];
        self.timer.fireDate = [NSDate distantPast];
    }else{
        sender.tag = 10;
        [sender setImage:[UIImage imageNamed:@"start.jpg"] forState:UIControlStateNormal];
        [self.audioPlayer pause];
        self.timer.fireDate = [NSDate distantFuture];
    }
}

//初始化定时器
- (NSTimer *)timer
{
    if(!_timer){
        _timer = [NSTimer scheduledTimerWithTimeInterval:1.0f target:self selector:@selector(updateTimeAddProgress) userInfo:nil repeats:YES];
        self.timeNum = (int)self.audioPlayer.duration;
    }
    return _timer;
}

//定时器的调用方法，在这里更新进度条，并且更新时间
- (void)updateTimeAddProgress
{
    float progress = self.audioPlayer.currentTime / self.audioPlayer.duration;
    [self.progressView setProgress:progress animated:YES];
    
    self.intTime++;
    NSString * str = [NSString stringWithFormat:@"%.2d:%.2d", self.intTime / 60, self.intTime % 60];
    self.currenttimeLabel.text = str;
    
    self.timeNum--;
    NSString * strTime = [NSString stringWithFormat:@"%.2d:%.2d", self.timeNum / 60, self.timeNum % 60];
    self.timeLabel.text = strTime;
}

//代理方法，做一些播放完成后的处理，删除掉定时器，button图片的更改、停止音乐播放等
- (void)audioPlayerDidFinishPlaying:(AVAudioPlayer *)player successfully:(BOOL)flag
{
    self.intTime = 0;
    [self.audioPlayer stop];
    [self.timer invalidate];
    self.timer = nil;
    
    self.button.tag = 10;
    [self.button setImage:[UIImage imageNamed:@"start.jpg"] forState:UIControlStateNormal];
}

@end