相同的功能，都执行，没有声音

Question

我用谷歌搜索了这个问题，但找不到类似的案例。

我使用本教程播放了 testSound.mp3 - 点击 iPad 模拟器上的按钮时的文件： http://mobileorchard.com/easy-audio-playback-with-avaudioplayer/

如果 playSound-Method 在我的 ViewController.m 中，但不在我的 Sound.m 中（它具有相同的方法），它会以这种方式工作（它播放声音）。 代码被执行（NSLog 说：“Sound.m playSound executed”），但根本没有声音。

我真的很感谢这里的一些帮助，我想我完全被卡住了...... :(

最好的问候， - 茶壶

// ViewController.h

#import <UIKit/UIKit.h>
#import <AVFoundation/AVFoundation.h>
#import "Sound.h"

@interface ViewController : UIViewController {

    AVAudioPlayer *audioPlayer;

}

- (IBAction)pressButton:(id)sender;
- (void)playSound: (NSString*) soundFile volume : (NSInteger) volume repeats : (NSInteger) repeats;

@end

// ViewController.m

#import "ViewController.h"

@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading thea view, typically from a nib.

}

- (void)didReceiveMemoryWarning
{
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

- (IBAction)pressButton:(id)sender {

    NSLog (@"Method: pressButton");

    [self playSound: @"testSound.mp3" volume: 2 repeats: 2 url : url]; //It works!

    Sound *tempSound = [[Sound alloc] init];
    [tempSound playSound: @"testSound.mp3" volume: 2 repeats: 2]; // Doesn't work. -> Says "Sound.m playSound executed", but there is no Sound.

}

- (void)playSound: (NSString*) soundFile volume : (NSInteger) volume repeats : (NSInteger) repeats {

    NSLog(@"ViewControler playSound");

    NSError *error;
    audioPlayer = [[AVAudioPlayer alloc] initWithContentsOfURL:url error:&error];
    audioPlayer.numberOfLoops = -1;

    if (audioPlayer == nil){
        NSLog([error description]);
        NSLog(@"ViewController.m playSound NOT executed");
    }
    else{
        [audioPlayer play];
        NSLog(@"ViewController.m playSound executed");
    } 

}

@end

// 声音.h

#import <Foundation/Foundation.h>
#import <AVFoundation/AVFoundation.h>

@interface Sound : NSObject {
    AVAudioPlayer *audioPlayer;
}

- (void) playSound: (NSString*) soundFile volume : (NSInteger) volume repeats : (NSInteger) repeats;

@end

// 声音.m

#import "Sound.h"

@implementation Sound

- (void)playSound: (NSString*) soundFile volume : (NSInteger) volume repeats : (NSInteger) repeats {

    NSLog(@"Sound playSound");

    NSError *error;
    audioPlayer = [[AVAudioPlayer alloc] initWithContentsOfURL:url error:&error];
    audioPlayer.numberOfLoops = -1;

    if (audioPlayer == nil){
        NSLog([error description]);
        NSLog(@"Sound.m playSound NOT executed");
    }
    else{
        [audioPlayer play];
        NSLog(@"Sound.m playSound executed");
    } 

}

@end

Answer 1

您的代码中有一些不一致之处：playSound: 有一个 NSString 参数，但该方法内部的 AVAudioPlayer 使用了一个 NSURL。然后设置numberOfLoops = -1（意味着无限重复）而不是numberOfLoops = repeat。

但主要问题是这里（假设您使用“自动引用计数”进行编译）

Sound *tempSound = [[Sound alloc] init];
[tempSound playSound: @"testSound.mp3" volume: 2 repeats: 2];

pressButton: 离开时，tempSound 对象被释放，因为不再存在对该对象的强引用。

如果您将实例变量（或属性）sound 添加到视图控制器类，并分配给该类

sound = [[Sound alloc] init];
[sound playSound: @"testSound.mp3" volume: 2 repeats: 2];

那么它应该按预期工作。

或者，您可以通过在对象内部维护“自引用”来防止过早释放 Sound 对象，该对象仅在发出声音时才被删除播放完毕：

@interface Sound () <AVAudioPlayerDelegate>
@property(strong, nonatomic) AVAudioPlayer *audioPlayer;
@property(strong, nonatomic) Sound *selfRef;
@end

@implementation Sound

- (void)playSound:(NSString *)soundFile volume:(NSInteger)volume repeats:(NSInteger)repeats
{
    NSLog(@"Sound playSound");
    NSURL *soundURL = [[NSBundle mainBundle] URLForResource:soundFile withExtension:nil];
    NSError *error;
    self.audioPlayer = [[AVAudioPlayer alloc] initWithContentsOfURL:soundURL error:&error];
    if (self.audioPlayer == nil) {
        NSLog(@"%@", [error description]);
        NSLog(@"Sound.m playSound NOT executed");
    } else{
        self.audioPlayer.numberOfLoops = repeats;
        self.audioPlayer.delegate = self;
        [self.audioPlayer play];
        self.selfRef = self; // self reference to avoid deallocation
        NSLog(@"Sound.m playSound executed");
    }
}

- (void)audioPlayerDidFinishPlaying:(AVAudioPlayer *)player successfully:(BOOL)flag
{
    self.selfRef = nil; // remove self reference
}
@end

当然，你不应该用“无限重复”来做这个！