我有一个AVAudioPlayer播放一些音频（呃！）
当用户按下按钮时启动音频。当他们发布它时，我希望音频淡出。
我正在使用界面构建器...所以我试图在“内部触摸”上连接一个功能，使音频在1秒内消失，然后停止。
有任何想法吗？
谢谢
我是这样做的：
-(void)doVolumeFade
{
if (self.player.volume > 0.1) {
self.player.volume = self.player.volume - 0.1;
[self performSelector:@selector(doVolumeFade) withObject:nil afterDelay:0.1];
} else {
// Stop and get the sound ready for playing again
[self.player stop];
self.player.currentTime = 0;
[self.player prepareToPlay];
self.player.volume = 1.0;
}
}
怎么样:(如果时间过去是负面然后淡出声音，否则淡入）
- (void) fadeInOutVolumeOverTime: (NSNumber *)time
{
#define fade_out_steps 0.1
float theVolume = player.volume;
NSTimeInterval theTime = [time doubleValue];
int sign = (theTime >= 0) ? 1 : -1;
// before we call this, if we are fading out, we save the volume
// so that we can restore back to that level in the fade in
if ((sign == 1) &&
((theVolume >= savedVolume) ||
(theTime == 0))) {
player.volume = savedVolume;
}
else if ((sign == -1) && (theVolume <= 0)) {
NSLog(@"fading");
[player pause];
[self performSelector:@selector(fadeInOutVolumeOverTime:) withObject:[NSNumber numberWithDouble:0] afterDelay:1.0];
}
else {
theTime *= fade_out_steps;
player.volume = theVolume + fade_out_steps * sign;
[self performSelector:@selector(fadeInOutVolumeOverTime:) withObject:time afterDelay:fabs(theTime)];
}
}
Swift解决方案：
这里评价最高的答案很棒，但是由于0.1的体积步长太大，它会产生口吃效果。使用0.01可以获得更平滑的淡入淡出效果。
使用此代码，您可以指定希望淡入淡出过渡的持续时间。
let fadeVolumeStep: Float = 0.01
let fadeTime = 0.5 // Fade time in seconds
var fadeVolumeStepTime: Double {
return fadeTime / Double(1.0 / fadeVolumeStep)
}
func fadeOut() {
guard let player = self.player else {
return
}
if !player.playing { return }
func fadeOutPlayer() {
if player.volume > fadeVolumeStep {
player.volume -= fadeVolumeStep
delay(time: fadeVolumeStepTime, closure: {
fadeOutPlayer()
})
} else {
player.stop()
player.currentTime = 0
player.prepareToPlay()
}
}
fadeOutPlayer()
}
func fadeIn() {
guard let player = self.player else {
return
}
if player.playing { return }
player.volume = 0
player.play()
func fadeInPlayer() {
if player.volume <= 1 - fadeVolumeStep {
player.volume += fadeVolumeStep
delay(time: fadeVolumeStepTime, closure: {
fadeInPlayer()
})
} else {
player.volume = 1
}
}
fadeInPlayer()
}
func delay(time delay:Double, closure:()->()) {
dispatch_after(
dispatch_time(
DISPATCH_TIME_NOW,
Int64(delay * Double(NSEC_PER_SEC))
),
dispatch_get_main_queue(), closure)
}
你可以使用fadeTime常数来调整时间。
在Objective-C中试试这个：
NSURL *trackURL = [[NSURL alloc]initFileURLWithPath:@"path to audio track"];
// fade duration in seconds
NSTimeInterval fadeDuration = 0.3;
// duration of the audio track in seconds
NSTimeInterval audioTrackDuration = 5.0;
AVAudioPlayer *audioPlayer = [[AVAudioPlayer alloc] initWithContentsOfURL:trackURL error:nil];
[audioPlayer play];
// first we set the volume to 1 - highest
[audioPlayer setVolume:1.0];
// then to 0 - lowest
[musicAudioPlayer setVolume:0 fadeDuration:audioTrackDuration - fadeDuration];
A very good solution可以从objc.io的Nick Lockwood获得这个问题。它利用Core Animation来定时更改音量，如果需要将UI动画与音量变化（包括交互式动画）同步，则可以派上用场。
Swift有一个AVAudioPlayer方法，你可以用它来淡出，包括iOS 10.0：
var audioPlayer = AVAudioPlayer()
...
audioPlayer.setVolume(0, fadeDuration: 3)
我使用NSOperation子类解决了这个问题，因此淡化卷不会阻塞主线程。它还允许淡入淡出排队和忘记。这对于播放具有淡入和淡出效果的一次性声音特别有用，因为它们在最后一次淡入淡出完成后被释放。
// Example of MXAudioPlayerFadeOperation in NSOperationQueue
NSOperationQueue *audioFaderQueue = [[NSOperationQueue alloc] init];
[audioFaderQueue setMaxConcurrentOperationCount:1]; // Execute fades serially.
NSString *filePath = [[NSBundle mainBundle] pathForResource:@"bg" ofType:@"mp3"]; // path to bg.mp3
AVAudioPlayer *player = [[[AVAudioPlayer alloc] initWithContentsOfURL:[NSURL fileURLWithPath:filePath] error:NULL] autorelease];
[player setNumberOfLoops:-1];
[player setVolume:0.0];
// Note that delay is delay after last fade due to the Operation Queue working serially.
MXAudioPlayerFadeOperation *fadeIn = [[MXAudioPlayerFadeOperation alloc] initFadeWithAudioPlayer:player toVolume:1.0 overDuration:3.0];
[fadeIn setDelay:2.0];
MXAudioPlayerFadeOperation *fadeDown = [[MXAudioPlayerFadeOperation alloc] initFadeWithAudioPlayer:player toVolume:0.1 overDuration:3.0];
[fadeDown setDelay:0.0];
MXAudioPlayerFadeOperation *fadeUp = [[MXAudioPlayerFadeOperation alloc] initFadeWithAudioPlayer:player toVolume:1.0 overDuration:4.0];
[fadeUp setDelay:0.0];
MXAudioPlayerFadeOperation *fadeOut = [[MXAudioPlayerFadeOperation alloc] initFadeWithAudioPlayer:player toVolume:0.0 overDuration:3.0];
[fadeOut setDelay:2.0];
[audioFaderQueue addOperation:fadeIn]; // 2.0s - 5.0s
[audioFaderQueue addOperation:fadeDown]; // 5.0s - 8.0s
[audioFaderQueue addOperation:fadeUp]; // 8.0s - 12.0s
[audioFaderQueue addOperation:fadeOut]; // 14.0s - 17.0s
[fadeIn release];
[fadeDown release];
[fadeUp release];
[fadeOut release];
对于MXAudioPlayerFadeOperation类代码，请参阅this post。
我最终将一些答案组合在一起并将其转换为Swift，最终以此方法结束：
func fadeVolumeAndPause(){
if self.player?.volume > 0.1 {
self.player?.volume = self.player!.volume - 0.1
var dispatchTime: dispatch_time_t = dispatch_time(DISPATCH_TIME_NOW, Int64(0.1 * Double(NSEC_PER_SEC)))
dispatch_after(dispatchTime, dispatch_get_main_queue(), {
self.fadeVolumeAndPause()
})
} else {
self.player?.pause()
self.player?.volume = 1.0
}
}
这些都是很好的答案，但是它们不涉及指定衰落速率（或者将对数曲线应用于衰落，这有时是期望的），或者指定从衰落的单位减少dB的数量。
这是一个除了我的一个应用程序，删除了一些“花里胡哨”，这与这个问题无关。
请享用！
#define linearToDecibels(linear) (MIN(10,MAX(-100,20.0 * log10(linear))))
#define decibelsToLinear(decibels) (pow (10, (0.05 * decibels)))
#define fadeInfoId(n) [fadeInfo objectForKey:@#n]
#define fadeInfoObject(NSObject,n) ((NSObject*) fadeInfoId(n))
#define fadeInfoFloat(n) [fadeInfoId(n) floatValue]
#define useFadeInfoObject(n) * n = fadeInfoId(n)
#define useFadeInfoFloat(n) n = fadeInfoFloat(n)
#define setFadeInfoId(n,x) [fadeInfo setObject:x forKey:@#n]
#define setFadeInfoFloat(n,x) setFadeInfoId(n,[NSNumber numberWithFloat:x])
#define setFadeInfoFlag(n) setFadeInfoId(n,[NSNumber numberWithBool:YES])
#define saveFadeInfoId(n) setFadeInfoId(n,n)
#define saveFadeInfoFloat(n) setFadeInfoFloat(n,n)
#define fadeAVAudioPlayer_default nil
#define fadeAVAudioPlayer_linearFade @"linearFade"
#define fadeAVAudioPlayer_fadeToStop @"fadeToStop"
#define fadeAVAudioPlayer_linearFadeToStop @"linearFadeToStop"
-(void) fadeAVAudioPlayerTimerEvent:(NSTimer *) timer {
NSMutableDictionary *fadeInfo = timer.userInfo;
NSTimeInterval elapsed = 0 - [fadeInfoObject(NSDate,startTime) timeIntervalSinceNow];
NSTimeInterval useFadeInfoFloat(fadeTime);
float useFadeInfoFloat(fadeToLevel);
AVAudioPlayer useFadeInfoObject(player);
double linear;
if (elapsed>fadeTime) {
if (fadeInfoId(stopPlaybackAtFadeTime)) {
[player stop];
linear = fadeInfoFloat(fadeFromLevel);
} else {
linear = fadeToLevel;
}
[timer invalidate];
[fadeInfo release];
} else {
if (fadeInfoId(linearCurve)) {
float useFadeInfoFloat(fadeFromLevel);
float fadeDelta = fadeToLevel-fadeFromLevel;
linear = fadeFromLevel + (fadeDelta * (elapsed/fadeTime));
} else {
float useFadeInfoFloat(fadeToDB);
float useFadeInfoFloat(fadeFromDB);
float fadeDelta = fadeToDB-fadeFromDB;
float decibels = fadeFromDB + (fadeDelta * (elapsed/fadeTime));
linear = decibelsToLinear(decibels);
}
}
[player setVolume: linear];
//[self displayFaderLevelForMedia:player];
//[self updateMediaVolumeLabel:player];
}
-(void) fadeAVAudioPlayerLinear:(AVAudioPlayer *)player over:(NSTimeInterval) fadeTime fadeToLevel:(float) fadeToLevel fadeMode:(NSString*)fadeMode {
NSMutableDictionary *fadeInfo = [[NSMutableDictionary alloc ]init];
saveFadeInfoId(player);
float fadeFromLevel = player.volume;// to optimize macros put value in var, so we don't call method 3 times.
float fadeFromDB = linearToDecibels(fadeFromLevel);
float fadeToDB = linearToDecibels(fadeToLevel);
saveFadeInfoFloat(fadeFromLevel);
saveFadeInfoFloat(fadeToLevel);
saveFadeInfoFloat(fadeToDB);
saveFadeInfoFloat(fadeFromDB);
saveFadeInfoFloat(fadeTime);
setFadeInfoId(startTime,[NSDate date]);
if([fadeMode isEqualToString:fadeAVAudioPlayer_fadeToStop]||[fadeMode isEqualToString:fadeAVAudioPlayer_linearFadeToStop]){
setFadeInfoFlag(stopPlaybackAtFadeTime);
}
if([fadeMode isEqualToString:fadeAVAudioPlayer_linearFade]||[fadeMode isEqualToString:fadeAVAudioPlayer_linearFadeToStop]){
setFadeInfoFlag(linearCurve);
}
[NSTimer scheduledTimerWithTimeInterval:0.05 target:self selector:@selector(fadeAVAudioPlayerTimerEvent:) userInfo:fadeInfo repeats:YES];
}
-(void) fadeAVAudioPlayer:(AVAudioPlayer *)player over:(NSTimeInterval) fadeTime fadeToDB:(float) fadeToDB fadeMode:(NSString*)fadeMode {
[self fadeAVAudioPlayerLinear:player over:fadeTime fadeToLevel:decibelsToLinear(fadeToDB) fadeMode:fadeMode ];
}
-(void) fadeoutAVAudioPlayer:(AVAudioPlayer *)player {
[self fadeAVAudioPlayerLinear:player over:5.0 fadeToLevel:0 fadeMode:fadeAVAudioPlayer_default];
}
-(void) fadeinAVAudioPlayer:(AVAudioPlayer *)player {
[self fadeAVAudioPlayerLinear:player over:5.0 fadeToLevel:0 fadeMode:fadeAVAudioPlayer_default];
}
我在Swift写了一个帮助类，用于进出AvAudioPlayer。您可以使用对数体积函数来实现更渐进的淡入淡出效果。
let player = AVAudioPlayer(contentsOfURL: soundURL, error: nil)
let fader = iiFaderForAvAudioPlayer(player: player)
fader.fadeIn()
fader.fadeOut()
这是一个演示应用程序：https://github.com/evgenyneu/sound-fader-ios
swift 3的扩展灵感来自最投票的答案。对于那些喜欢复制粘贴的人:)
extension AVAudioPlayer {
func fadeOut() {
if volume > 0.1 {
// Fade
volume -= 0.1
perform(#selector(fadeOut), with: nil, afterDelay: 0.1)
} else {
// Stop and get the sound ready for playing again
stop()
prepareToPlay()
volume = 1
}
}
}
我喜欢Ambroise Collon的答案，所以我投票了，但是Swift是静态类型的，所以performSelector：方法要落在路边，也许另外一种可能是调度异步（在这个版本中我还添加了目标卷作为参数）
func dispatchDelay(delay:Double, closure:@escaping ()->()) {
DispatchQueue.main.asyncAfter(deadline: DispatchTime.now() + delay, execute: closure)
}
extension AVAudioPlayer {
func fadeOut(vol:Float) {
if volume > vol {
//print("vol is : \(vol) and volume is: \(volume)")
dispatchDelay(delay: 0.1, closure: {
[weak self] in
guard let strongSelf = self else { return }
strongSelf.volume -= 0.01
strongSelf.fadeOut(vol: vol)
})
} else {
volume = vol
}
}
func fadeIn(vol:Float) {
if volume < vol {
dispatchDelay(delay: 0.1, closure: {
[weak self] in
guard let strongSelf = self else { return }
strongSelf.volume += 0.01
strongSelf.fadeIn(vol: vol)
})
} else {
volume = vol
}
}
}
在我看来，这是对NSOperationQueue的下降使用。
因此，这是我的解决方案：
-(void) fadeIn
{
if (self.currentPlayer.volume >= 1.0f) return;
else {
self.currentPlayer.volume+=0.10;
__weak typeof (self) weakSelf = self;
[NSThread sleepForTimeInterval:0.2f];
[self.fadingQueue addOperationWithBlock:^{
NSLog(@"fading in %.2f", self.currentPlayer.volume);
[weakSelf fadeIn];
}];
}
}
-(void) fadeOut
{
if (self.currentPlayer.volume <= 0.0f) return;
else {
self.currentPlayer.volume -=0.1;
__weak typeof (self) weakSelf = self;
[NSThread sleepForTimeInterval:0.2f];
[self.fadingQueue addOperationWithBlock:^{
NSLog(@"fading out %.2f", self.currentPlayer.volume);
[weakSelf fadeOut];
}];
}
}