iOS 在特定时间停止音频播放（AVAudioPlayer 结束时间）

Question

我只想播放音频文件的一部分。这个音频文件包含 232 个口语单词，我有一本字典，其中包含每个单词的开始时间。所以我有开始和停止时间，我只是找不到在给定时间停止或播放文件一段时间的方法。任何可以帮助我的建议和/或示例代码将不胜感激，谢谢杰森。

所以我找到了解决方案，我如何获得 endTime 存在问题，但我确定我可以解决它。

//Prepare to play
[audioPlayer prepareToPlay];

//Get current time from the array using selected word
audioPlayer.currentTime = [[wordsDict objectForKey:selectedWord] floatValue]; 

//Find end time  - this is a little messy for now
int currentIndex = 0;
int count = 0;

for (NSString* item in wordsKeys) {
    if ([item isEqualToString: selectedWord]) {
        currentIndex = count+1;
    }
    count++;
}

//Store found end time
endTime  = [[wordsDict objectForKey:[wordsKeys objectAtIndex:currentIndex]] floatValue];

//Start Timer
NSTimer * myAudioTimer = [NSTimer scheduledTimerWithTimeInterval:0.1
                                                             target:self
                                                           selector:@selector(checkCurrentTime)
                                                           userInfo:nil
                                                            repeats:YES]
//Now play audio
[audioPlayer play];



//Stop at endTime
- (void) checkCurrentTime {
if(audioPlayer.playing && audioPlayer.currentTime >= endTime)
    [audioPlayer stop];
}

Answer 1

这应该做你想做的事。你不需要一个重复的计时器来让玩家崩溃。

NSString *myAudioFileInBundle = @"words.mp3";
NSTimeInterval wordStartsAt = 1.8;
NSTimeInterval wordEndsAt = 6.5;
NSString *filePath = [[[NSBundle mainBundle] bundlePath] stringByAppendingPathComponent:myAudioFileInBundle];
NSURL *myFileURL = [NSURL fileURLWithPath:filePath];
AVAudioPlayer *myPlayer = [[AVAudioPlayer alloc]initWithContentsOfURL:myFileURL error:nil];
if (myPlayer) 
{
    [myPlayer setCurrentTime:wordStartsAt];
    [myPlayer prepareToPlay];
    [myPlayer play];
    [NSTimer scheduledTimerWithTimeInterval:wordEndsAt-wordStartsAt target:myPlayer.autorelease selector:@selector(stop) userInfo:nil repeats:NO];

}

Answer 2

尝试使用 AVPlayer 并利用

addBoundaryTimeObserverForTimes:queue:usingBlock:

它的作用：在正常播放期间遍历指定时间时请求调用块。

https://developer.apple.com/library/prerelease/ios/documentation/AVFoundation/Reference/AVPlayer_Class/index.html#//apple_ref/occ/instm/AVPlayer/addBoundaryTimeObserverForTimes:queue:usingBlock:

Answer 3

AVAudioPlayer 为您提供了一些可以使用的简洁属性：

• currentTime：在播放过程中，您可以依赖此属性。

• playAtTime：从预定义的时间开始播放。

---

但首先我会为此编写一些帮助程序：

@interface Word {
    double startTime;
    double endTime;
}

@property double startTime;  
@property double endTime;  

@end

这只是一个简单地使用以下方法的类。

- (void)playWord:(Word *)aWord {

    self.avPlayer.playAtTime = aWord.startTime;
    [avPlayer prepareToPlay];
    [avPlayer play];

    while (avPlayer.playing) {
        /*
        This while loop could be dangerous as it could go on for a long time.
        But because we're just evaluating words, it won't be as much power draining
        */

        if(avPlayer.currentTime >= aWord.endTime;
        [avPlayer stop];
    }
}

我建议您使用数组或任何其他机制来自动切换到下一个单词。也许您还可以添加上一个和下一个按钮来处理用户输入。

如果这对你有用，请告诉我。

HTH