Android Studio Mediaplayer如何淡入和淡出 [英] Android Studio Mediaplayer how to fade in and out

问题描述

我正在使用android studio中的mediaplayer类.我只是想淡出一种声音而淡入另一种声音，而不是使用setVolume(0,0)和setVolume(1,1).

I am working with the mediaplayer class in android studio. I simply want to fade out one sound and fade in the other sound instead of using setVolume(0,0) and setVolume(1,1).

我为此创建了两个媒体播放器，似乎在该线程中找到了一个解决方案:

I have created two mediaplayers for this and it seemed like I found a solution in this thread: Android: How to create fade-in/fade-out sound effects for any music file that my app plays? but I don't know how to use deltaTime.

还有一些其他解决方案，我几乎无法理解.没有一种简单的方法可以淡入淡出两个媒体播放器，我无法想象还没有人需要它，或者每个人都使用强迫性代码来实现它.以及我应该如何使用deltaTime?

There are also some other solutions to this, which I can barely understand. Isn't there an easy way to cross fade two mediaplayers, I can not imagine no one has needed this yet or everyone uses obsessive code to achieve it. And how should I use deltaTime?

推荐答案

看看链接的示例，您将拥有循环调用fadeIn()/fadeOut()，以在一段时间内增大/减小音量. deltaTime 是循环的每次迭代之间的时间.

Looking at the linked example, you would have to call fadeIn()/fadeOut() in a loop, to increase/decrease the volume over a period of time. deltaTime would be the time between each iteration of the loop.

您必须在与主UI线程不同的线程中执行此操作，因此您不会阻止它并导致应用程序崩溃.您可以通过将此循环放入新的Thread/Runnable/Timer中来实现.

You'd have to do this in a separate thread from your main UI thread, so you don't block it and cause your app to crash. You can do this by either putting this loop inside a new Thread/Runnable/Timer.

这是我的淡入淡出示例(您可以为淡入淡出做类似的事情):

Here is my example for fading in (you can do a similar thing for fading out):

float volume = 0;

private void startFadeIn(){
    final int FADE_DURATION = 3000; //The duration of the fade
    //The amount of time between volume changes. The smaller this is, the smoother the fade
    final int FADE_INTERVAL = 250;
    final int MAX_VOLUME = 1; //The volume will increase from 0 to 1
    int numberOfSteps = FADE_DURATION/FADE_INTERVAL; //Calculate the number of fade steps
    //Calculate by how much the volume changes each step
    final float deltaVolume = MAX_VOLUME / (float)numberOfSteps;

    //Create a new Timer and Timer task to run the fading outside the main UI thread
    final Timer timer = new Timer(true);
    TimerTask timerTask = new TimerTask() {
        @Override
        public void run() {
            fadeInStep(deltaVolume); //Do a fade step
            //Cancel and Purge the Timer if the desired volume has been reached
            if(volume>=1f){
                timer.cancel();
                timer.purge();
            }
        }
    };

    timer.schedule(timerTask,FADE_INTERVAL,FADE_INTERVAL);
}

private void fadeInStep(float deltaVolume){
    mediaPlayer.setVolume(volume, volume);
    volume += deltaVolume;

}

在您的情况下，我将不使用两个单独的MediaPlayer对象，而是在渐变之间交换轨道. 示例:

Instead of using two separate MediaPlayer objects, I would in your case use just one and swap the track between the fades. Example:

**Audio track #1 is playing but coming to the end**
startFadeOut();
mediaPlayer.stop();
mediaPlayer.reset();
mediaPlayer.setDataSource(context,audiofileUri);
mediaPlayer.prepare();
mediaPlayer.start();
startFadeIn();
**Audio track #2 has faded in and is now playing**

希望这可以解决您的问题.

Hope this solves your problem.

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