如何为 AVAudioEngine 设置完成处理程序答案

【问题标题】：How to set a completionhandler for AVAudioEngine如何为 AVAudioEngine 设置完成处理程序
【发布时间】：2017-04-06 13:23:47
【问题描述】：

我正在使用这种方法播放音频文件；

-(void)playOnMainThread:(id)参数

{
   [self playAudio];

    AVAudioEngine *engine = [[AVAudioEngine alloc] init];
    AVAudioPlayerNode *node = [[AVAudioPlayerNode alloc] init];
    [engine attachNode:node];
    AVAudioUnitTimePitch *pitch = [[AVAudioUnitTimePitch alloc] init];
    pitch.pitch = 100;
    pitch.rate = 2;
    [engine attachNode:pitch];
    AVAudioMixerNode *mixerNode = engine.mainMixerNode;
    [engine connect:node to:pitch format:[mixerNode outputFormatForBus:0]];
    [engine connect:pitch to:mixerNode format:[mixerNode outputFormatForBus:0]];

    AVAudioFile *audioFile = [[AVAudioFile alloc] initForReading:recorder.url error:&error];
    if (error)
        NSLog(@"AVAudioPlayer error %@, %@", error, [error userInfo]);
    if (audioFile != nil) {
        [node scheduleFile:audioFile atTime:nil completionHandler:nil];
        [engine startAndReturnError:nil];
        [node play];
    }    
}

但是我需要设置一个completionhandler，这是我尝试过的；

-(void)stopTalking:(AVAudioNodeCompletionHandler)handler
//-(void)stopTalking
{

    isPlaying = NO;
    [self unschedule:@selector(RepeatSpeackAction)];

    [self schedule:@selector(StartGAmeCall)];

    [stand setDisplayFrame:[[CCSpriteFrameCache sharedSpriteFrameCache] spriteFrameByName:@"Turn1.png"]];

    if(video==true) {
        cases=1;
        [self addaudiotoDict];
    }

}

我试图通过这样使用它来调用它；

[node scheduleFile:audioFile atTime:nil completionHandler:stopTalking];

如果没有成功，如何调用完成处理程序？

【问题讨论】：

标签： ios objective-c iphone xcode completionhandler

【解决方案1】：

您需要使用 GCD 块，而不是方法，作为 completionHandler 参数：

[node scheduleFile:audioFile atTime:nil completionHandler:^{

    // Your "stopTalking" code goes here...

}];

【讨论】：

【解决方案2】：

以上答案都不适合我，所以这里是我从搜索解决方案中得到的结果

// audioFile here is our original audio

audioPlayerNode.scheduleFile(audioFile, at: nil, completionHandler: {
        print("scheduleFile Complete")

    var delayInSeconds: Double = 0

    if let lastRenderTime = self.audioPlayerNode.lastRenderTime, let playerTime = self.audioPlayerNode.playerTime(forNodeTime: lastRenderTime) {

        if let rate = rate {
            delayInSeconds = Double(audioFile.length - playerTime.sampleTime) / Double(audioFile.processingFormat.sampleRate) / Double(rate!)
        } else {
            delayInSeconds = Double(audioFile.length - playerTime.sampleTime) / Double(audioFile.processingFormat.sampleRate)
        }
    }

    // schedule a stop timer for when audio finishes playing
    DispatchTime.executeAfter(seconds: delayInSeconds) {
        audioEngine.mainMixerNode.removeTap(onBus: 0)
        // Playback has completed
    }

})

【讨论】：