版本記錄

前言

ios系統(tǒng)中有很多方式可以播放音頻文件，這里我們就詳細(xì)的說明下播放音樂文件的原理和實(shí)例。

功能需求

播放本地音樂，實(shí)現(xiàn)播放MP3類型的音樂聲頻文件。

功能實(shí)現(xiàn)

下面我們就直接看一下代碼。

1. 一個重要的音頻播放的類

下面看一下AVAudioPlayer這個類。

#import <AVFoundation/AVBase.h>
#import <AVFoundation/AVAudioFormat.h>
#import <Foundation/Foundation.h>
#import <AVFAudio/AVAudioSettings.h>

#if (TARGET_OS_IPHONE && __has_include(<AVFoundation/AVAudioSession.h>))
#import <AVFAudio/AVAudioSession.h>
#endif // #if TARGET_OS_EMBEDDED

#import <Availability.h>

NS_ASSUME_NONNULL_BEGIN

@class NSData, NSURL, NSError;
#if (TARGET_OS_IPHONE && __has_include(<AVFoundation/AVAudioSession.h>))
@class AVAudioSessionChannelDescription;
#endif
@protocol AVAudioPlayerDelegate;

NS_CLASS_AVAILABLE(10_7, 2_2) __WATCHOS_AVAILABLE(3_0)
@interface AVAudioPlayer : NSObject {
@private
    id _impl;
}

/* For all of these init calls, if a return value of nil is given you can check outError to see what the problem was.
 If not nil, then the object is usable for playing
*/

/* all data must be in the form of an audio file understood by CoreAudio */
- (nullable instancetype)initWithContentsOfURL:(NSURL *)url error:(NSError **)outError;
- (nullable instancetype)initWithData:(NSData *)data error:(NSError **)outError;

/* The file type hint is a constant defined in AVMediaFormat.h whose value is a UTI for a file format. e.g. AVFileTypeAIFF. */
/* Sometimes the type of a file cannot be determined from the data, or it is actually corrupt. The file type hint tells the parser what kind of data to look for so that files which are not self identifying or possibly even corrupt can be successfully parsed. */
- (nullable instancetype)initWithContentsOfURL:(NSURL *)url fileTypeHint:(NSString * __nullable)utiString error:(NSError **)outError NS_AVAILABLE(10_9, 7_0);
- (nullable instancetype)initWithData:(NSData *)data fileTypeHint:(NSString * __nullable)utiString error:(NSError **)outError NS_AVAILABLE(10_9, 7_0);

/* transport control */
/* methods that return BOOL return YES on success and NO on failure. */
- (BOOL)prepareToPlay;  /* get ready to play the sound. happens automatically on play. */
- (BOOL)play;           /* sound is played asynchronously. */
- (BOOL)playAtTime:(NSTimeInterval)time NS_AVAILABLE(10_7, 4_0); /* play a sound some time in the future. time is an absolute time based on and greater than deviceCurrentTime. */
- (void)pause;          /* pauses playback, but remains ready to play. */
- (void)stop;           /* stops playback. no longer ready to play. */

/* properties */

@property(readonly, getter=isPlaying) BOOL playing; /* is it playing or not? */

@property(readonly) NSUInteger numberOfChannels;
@property(readonly) NSTimeInterval duration; /* the duration of the sound. */

#if !TARGET_OS_IPHONE
/* the UID of the current audio device (as a string) */
@property(copy, nullable) NSString *currentDevice API_AVAILABLE(macos(10.13));
#endif

/* the delegate will be sent messages from the AVAudioPlayerDelegate protocol */ 
@property(assign, nullable) id<AVAudioPlayerDelegate> delegate;

/* one of these properties will be non-nil based on the init... method used */
@property(readonly, nullable) NSURL *url; /* returns nil if object was not created with a URL */
@property(readonly, nullable) NSData *data; /* returns nil if object was not created with a data object */

@property float pan NS_AVAILABLE(10_7, 4_0); /* set panning. -1.0 is left, 0.0 is center, 1.0 is right. */
@property float volume; /* The volume for the sound. The nominal range is from 0.0 to 1.0. */
- (void)setVolume:(float)volume fadeDuration:(NSTimeInterval)duration API_AVAILABLE(macos(10.12), ios(10.0), watchos(3.0), tvos(10.0)); /* fade to a new volume over a duration */

@property BOOL enableRate NS_AVAILABLE(10_8, 5_0); /* You must set enableRate to YES for the rate property to take effect. You must set this before calling prepareToPlay. */
@property float rate NS_AVAILABLE(10_8, 5_0); /* See enableRate. The playback rate for the sound. 1.0 is normal, 0.5 is half speed, 2.0 is double speed. */


/*  If the sound is playing, currentTime is the offset into the sound of the current playback position.  
If the sound is not playing, currentTime is the offset into the sound where playing would start. */
@property NSTimeInterval currentTime;

/* returns the current time associated with the output device */
@property(readonly) NSTimeInterval deviceCurrentTime NS_AVAILABLE(10_7, 4_0);

/* "numberOfLoops" is the number of times that the sound will return to the beginning upon reaching the end. 
A value of zero means to play the sound just once.
A value of one will result in playing the sound twice, and so on..
Any negative number will loop indefinitely until stopped.
*/
@property NSInteger numberOfLoops;

/* settings */
@property(readonly) NSDictionary<NSString *, id> *settings NS_AVAILABLE(10_7, 4_0); /* returns a settings dictionary with keys as described in AVAudioSettings.h */

/* returns the format of the audio data */
@property(readonly) AVAudioFormat *format API_AVAILABLE(macos(10.12), ios(10.0), watchos(3.0), tvos(10.0));

/* metering */

@property(getter=isMeteringEnabled) BOOL meteringEnabled; /* turns level metering on or off. default is off. */

- (void)updateMeters; /* call to refresh meter values */

- (float)peakPowerForChannel:(NSUInteger)channelNumber; /* returns peak power in decibels for a given channel */
- (float)averagePowerForChannel:(NSUInteger)channelNumber; /* returns average power in decibels for a given channel */

#if (TARGET_OS_IPHONE && __has_include(<AVFoundation/AVAudioSession.h>))
/* The channels property lets you assign the output to play to specific channels as described by AVAudioSession's channels property */
/* This property is nil valued until set. */
/* The array must have the same number of channels as returned by the numberOfChannels property. */
@property(nonatomic, copy, nullable) NSArray<AVAudioSessionChannelDescription *> *channelAssignments NS_AVAILABLE(10_9, 7_0); /* Array of AVAudioSessionChannelDescription objects */
#endif

@end

2. 一個代理AVAudioPlayerDelegate

下面看一下這個關(guān)于音頻播放的代理方法。

/* A protocol for delegates of AVAudioPlayer */
__WATCHOS_AVAILABLE(3_0)
@protocol AVAudioPlayerDelegate <NSObject>
@optional 
/* audioPlayerDidFinishPlaying:successfully: is called when a sound has finished playing. This method is NOT called if the player is stopped due to an interruption. */
- (void)audioPlayerDidFinishPlaying:(AVAudioPlayer *)player successfully:(BOOL)flag;

/* if an error occurs while decoding it will be reported to the delegate. */
- (void)audioPlayerDecodeErrorDidOccur:(AVAudioPlayer *)player error:(NSError * __nullable)error;

#if TARGET_OS_IPHONE

/* AVAudioPlayer INTERRUPTION NOTIFICATIONS ARE DEPRECATED - Use AVAudioSession instead. */

/* audioPlayerBeginInterruption: is called when the audio session has been interrupted while the player was playing. The player will have been paused. */
- (void)audioPlayerBeginInterruption:(AVAudioPlayer *)player NS_DEPRECATED_IOS(2_2, 8_0);

/* audioPlayerEndInterruption:withOptions: is called when the audio session interruption has ended and this player had been interrupted while playing. */
/* Currently the only flag is AVAudioSessionInterruptionFlags_ShouldResume. */
- (void)audioPlayerEndInterruption:(AVAudioPlayer *)player withOptions:(NSUInteger)flags NS_DEPRECATED_IOS(6_0, 8_0);

- (void)audioPlayerEndInterruption:(AVAudioPlayer *)player withFlags:(NSUInteger)flags NS_DEPRECATED_IOS(4_0, 6_0);

/* audioPlayerEndInterruption: is called when the preferred method, audioPlayerEndInterruption:withFlags:, is not implemented. */
- (void)audioPlayerEndInterruption:(AVAudioPlayer *)player NS_DEPRECATED_IOS(2_2, 6_0);

#endif // TARGET_OS_IPHONE

@end

NS_ASSUME_NONNULL_END

需要對音頻的處理，都可以在這里進(jìn)行。

3. 開啟后臺播放模式

開啟后臺播放模式，有兩種方式。

第一種方式就是按照下面進(jìn)行設(shè)置。

也可以在plist文件中添加鍵值對

有這些就可以了嗎？不，還不夠，還需要添加幾句代碼。

    AVAudioSession *session = [AVAudioSession sharedInstance];
    [session setActive:YES error:nil];
    [session setCategory:AVAudioSessionCategoryPlayback error:nil];

有這些就夠了，就可以在后臺播放指定的音樂文件。

4. 代碼實(shí)現(xiàn)

下面就看一下代碼實(shí)現(xiàn)。

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

@interface ViewController () <AVAudioPlayerDelegate>

@property (weak, nonatomic) IBOutlet UIButton *startPlay;
@property (nonatomic, strong) AVAudioPlayer *audioPlayer;


@end

@implementation ViewController

#pragma mark - Override Base Function

- (void)viewDidLoad
{
    [super viewDidLoad];
    
    AVAudioSession *session = [AVAudioSession sharedInstance];
    [session setActive:YES error:nil];
    [session setCategory:AVAudioSessionCategoryPlayback error:nil];
}

#pragma mark - Action && Notification

- (IBAction)startPlayButtonDidClick:(UIButton *)sender
{
    // 1.獲取要播放音頻文件的URL
    NSURL *fileURL = [[NSBundle mainBundle]URLForResource:@"music" withExtension:@".mp3"];
    
    // 2.創(chuàng)建 AVAudioPlayer 對象
    self.audioPlayer = [[AVAudioPlayer alloc]initWithContentsOfURL:fileURL error:nil];
    
    // 3.打印歌曲信息
    NSString *msg = [NSString stringWithFormat:@"音頻文件聲道數(shù):%ld\n 音頻文件持續(xù)時間:%g",self.audioPlayer.numberOfChannels,self.audioPlayer.duration];
    NSLog(@"%@",msg);
    
    // 4.設(shè)置循環(huán)播放
    self.audioPlayer.numberOfLoops = -1;
    
    //這句話如果不需要在代理方法里面處理什么是不要設(shè)置代理的
    self.audioPlayer.delegate = self;
    
    // 5.開始播放
    [self.audioPlayer play];
}

#pragma mark - AVAudioPlayerDelegate

- (void)audioPlayerDecodeErrorDidOccur:(AVAudioPlayer *)player error:(NSError *)error
{
    NSLog(@"player = %@", player);
    NSLog(@"error = %@", error);
}

- (void)audioPlayerDidFinishPlaying:(AVAudioPlayer *)player successfully:(BOOL)flag
{
    NSLog(@"player = %@", player);
    NSLog(@"flag = %d", flag);
}

@end

功能效果

下面我們就看一下功能效果。

本人親測，這個是可以正常在后臺播放音樂的，不能給出音樂文件示意圖了，只能給一個界面提示了。

參考文章

1. iOS音頻播放的幾種方式

后記

未完，待續(xù)~~~