如何用一个按钮暂停/播放多个MediaPlayer对象？

Question

我有一个按钮，我想用这个按钮控制多个MediaPlayer对象。在示例中，用户从列表中选择了3个声音，当他们正在播放时，用户点击暂停图标按钮，所有声音都应该暂停（并且暂停按钮的资源应该更改为播放图标）。如果用户再次点击播放图标，所有的声音应该继续。

如果我删除代码中的其他部分，我可以实现暂停声音，这是当前正在播放，但如果我再次单击播放按钮，声音将不会播放，什么也不会发生。

我得XML：

<LinearLayout
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:orientation="horizontal">

    <ImageButton
        android:id="@+id/stop_all_sound"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:background="@android:color/transparent"
        android:src="@drawable/pause_button" />
</LinearLayout>

我的代码：

    stop_all_sound.setOnClickListener {
        // List of sounds
        val list = arrayListOf(sound1, sound2, sound3, sound4)
        // List for playing sounds
        val playingSounds = arrayListOf<MediaPlayer>()

        list.forEach { sound ->
            if (sound.isPlaying) {
                // If sound is playing add it to the playingSounds list
                playingSounds.add(sound)

                for (playingSound in playingSounds) {
                    // Pause that playing sounds currently
                    playingSound.pause()
                    stop_all_sound.setImageResource(R.drawable.play_button)
                }
            }
            // I couldn't figured out this part. I guess playingSounds list is empty
            else {
                for (playingSound in playingSounds) {
                    playingSound.start()
                    stop_all_sound.setImageResource(R.drawable.pause_button)
                }
            }
        }
    }

为了更清楚地说明，假设有一个MediaPlayer列表和一个按钮

• 如果没有MediaPlayer处于播放状态，则按钮的图标将为play_button，否则为pause_button

当按下按钮时，我希望MediaPlayer的以下行为：

• 如果没有MediaPlayer正在播放，并且没有MediaPlayer处于暂停状态，则所有MediaPlayer都将开始播放
• 如果没有MediaPlayer正在播放，而某些MediaPlayer处于暂停状态，则所有暂停的MediaPlayer都将开始播放
• 如果某些MediaPlayer正在播放，而没有MediaPlayer处于暂停状态，则所有正在播放的MediaPlayer都将暂停

Answer 1

var buttonIcon: Int = R.drawable.play_button

val playList = PlayList { isPlaying ->
    buttonIcon =
        if (isPlaying) R.drawable.pause_button
        else R.drawable.play_button
    stop_all_sound.setImageResource(buttonIcon)
}

stop_all_sound.setOnClickListener {
    // List of sounds
    val list = arrayListOf(sound1, sound2, sound3, sound4)
    if (playList.isEmpty()) {
        buttonIcon = R.drawable.play_button
        list.forEach { sound ->
            if (sound.isPlaying) {
                playList.add(sound)
                buttonIcon = R.drawable.pause_button
            }
        }
        if (playList.isEmpty()) list.forEach { playList.add(it) }
    }
    when (buttonIcon) {
        R.drawable.play_button -> playList.play()
        R.drawable.pause_button -> playList.pause()
    }
}

// PlayList class

class PlayList(private val playingState: (Boolean) -> Unit) {
    private val soundList = mutableListOf<MediaPlayer>()

    fun isEmpty() = soundList.isEmpty()

    fun add(sound: MediaPlayer) {
        sound.setOnCompletionListener {
            soundList.remove(it)
            if (soundList.isEmpty()) playingState(false)
        }
        soundList.add(sound)
    }

    fun play() {
        soundList.forEach {
            it.start()
        }
        playingState(true)
    }

    fun pause() {
        soundList.forEach {
            if (it.isPlaying) it.pause()
        }
        playingState(false)
    }
}

我可以从你的问题中找出以下测试用例,

1. 用户选择歌曲列表
2. 如果没有播放歌曲，用户按“播放/暂停”按钮播放所有选定的歌曲
3. 用户按“播放/暂停”按钮以停止当前正在播放的所有歌曲

在上述情况下，我可能会做以下操作：

var buttonIcon = R.drawable.play_button

val playList = PlayList(arrayListOf(sound1, sound2, sound3, sound4)) { isPlaying ->
    if (isPlaying) {
        buttonIcon = R.drawable.pause_button
        stop_all_sound.setImageResource(buttonIcon)
    } else {
        buttonIcon = R.drawable.play_button
        stop_all_sound.setImageResource(buttonIcon)
    }
}

stop_all_sound.setOnClickListener {
    when(buttonIcon) {
        R.drawable.play_button -> playList.play()
        R.drawable.pause_button -> playList.pause()
    }
}

playlist类

class PlayList(
    private val soundList: List<MediaPlayer>,
    private val playingState: (Boolean) -> Unit
) {
    private var nowPlayingCount = 0

    init {
        soundList.forEach {
            it.setOnCompletionListener {
                nowPlayingCount = nowPlayingCount.dec()
                if (nowPlayingCount == 0) playingState(false)
            }
        }
    }

    fun play() {
        soundList.forEach {
            it.start()
        }
        playingState(true)
        nowPlayingCount = soundList.size
    }

    fun pause() {
        soundList.forEach {
            if (it.isPlaying) it.pause()
        }
        playingState(false)
        nowPlayingCount = 0
    }
}