導入媒體工作階段

應用程式準備播放媒體時，請建立 MediaSession 。下列程式碼片段是設定適當回呼和旗標的範例：

Kotlin

session = MediaSession(this, "MusicService").apply {
    setCallback(MediaSessionCallback())
    setFlags(
        MediaSession.FLAG_HANDLES_MEDIA_BUTTONS or MediaSession.FLAG_HANDLES_TRANSPORT_CONTROLS
    )
}

Java

session = new MediaSession(this, "MusicService");
session.setCallback(new MediaSessionCallback());
session.setFlags(MediaSession.FLAG_HANDLES_MEDIA_BUTTONS |
        MediaSession.FLAG_HANDLES_TRANSPORT_CONTROLS);

啟動媒體工作階段

請務必在開始播放時呼叫 setActive(true)。應用程式也必須要求音訊焦點，詳情請參閱「管理音訊焦點」。相關步驟如以下範例所示：

Kotlin

fun handlePlayRequest() {
    tryToGetAudioFocus()

    if (!session.isActive) {
        session.isActive = true
    }
    // ...
}

Java

private void handlePlayRequest() {

    tryToGetAudioFocus();

    if (!session.isActive()) {
        session.setActive(true);
    }
    ...
}

更新播放狀態

更新 MediaSession 中的播放狀態，反映目前媒體的狀態：

Kotlin

private fun updatePlaybackState() {
    val position: Long =
        mediaPlayer
            ?.takeIf { it.isPlaying }
            ?.currentPosition?.toLong()
            ?: PlaybackState.PLAYBACK_POSITION_UNKNOWN

    val stateBuilder = PlaybackState.Builder()
        .setActions(getAvailableActions()).apply {
            setState(mState, position, 1.0f)
        }
    session.setPlaybackState(stateBuilder.build())
}

private fun getAvailableActions(): Long {
    var actions = (
        PlaybackState.ACTION_PLAY_PAUSE
            or PlaybackState.ACTION_PLAY_FROM_MEDIA_ID
            or PlaybackState.ACTION_PLAY_FROM_SEARCH
        )

    playingQueue?.takeIf { it.isNotEmpty() }?.apply {
        actions = if (mState == PlaybackState.STATE_PLAYING) {
            actions or PlaybackState.ACTION_PAUSE
        } else {
            actions or PlaybackState.ACTION_PLAY
        }
        if (currentIndexOnQueue > 0) {
            actions = actions or PlaybackState.ACTION_SKIP_TO_PREVIOUS
        }
        if (currentIndexOnQueue < size - 1) {
            actions = actions or PlaybackState.ACTION_SKIP_TO_NEXT
        }
    }
    return actions
}

Java

private void updatePlaybackState() {
    long position = PlaybackState.PLAYBACK_POSITION_UNKNOWN;
    if (mediaPlayer != null && mediaPlayer.isPlaying()) {
        position = mediaPlayer.getCurrentPosition();
    }
    PlaybackState.Builder stateBuilder = new PlaybackState.Builder()
            .setActions(getAvailableActions());
    stateBuilder.setState(mState, position, 1.0f);
    session.setPlaybackState(stateBuilder.build());
}

private long getAvailableActions() {
    long actions = PlaybackState.ACTION_PLAY_PAUSE |
            PlaybackState.ACTION_PLAY_FROM_MEDIA_ID |
            PlaybackState.ACTION_PLAY_FROM_SEARCH;
    if (playingQueue == null || playingQueue.isEmpty()) {
        return actions;
    }
    if (mState == PlaybackState.STATE_PLAYING) {
        actions |= PlaybackState.ACTION_PAUSE;
    } else {
        actions |= PlaybackState.ACTION_PLAY;
    }
    if (currentIndexOnQueue > 0) {
        actions |= PlaybackState.ACTION_SKIP_TO_PREVIOUS;
    }
    if (currentIndexOnQueue < playingQueue.size() - 1) {
        actions |= PlaybackState.ACTION_SKIP_TO_NEXT;
    }
    return actions;
}

更新媒體中繼資料

使用 setMetadata() 方法設定 MediaMetadata。每個播放的物件只會呼叫這個方法一次。您可以透過這個方法，向媒體工作階段提供媒體相關資訊，包括標題、副標題、藝人、藝術作品等。以下範例專為音樂設計，並假設曲目的資料儲存在自訂資料類別 MediaData 中：

Kotlin

private fun updateMetadata(myData: MediaData) {
    val metadataBuilder = MediaMetadata.Builder().apply {
        // To provide most control over how an item is displayed set the
        // display fields in the metadata
        putString(MediaMetadata.METADATA_KEY_DISPLAY_TITLE, myData.displayTitle)
        putString(MediaMetadata.METADATA_KEY_DISPLAY_SUBTITLE, myData.displaySubtitle)
        putString(MediaMetadata.METADATA_KEY_DISPLAY_ICON_URI, myData.artUri)
        // And at minimum the title and artist for legacy support
        putString(MediaMetadata.METADATA_KEY_TITLE, myData.title)
        putString(MediaMetadata.METADATA_KEY_ARTIST, myData.artist)
        // A small bitmap for the artwork is also recommended
        putBitmap(MediaMetadata.METADATA_KEY_ART, myData.artBitmap)
        // Add any other fields you have for your data as well
    }
    session.setMetadata(metadataBuilder.build())
}

Java

private void updateMetadata(MediaData myData) {
    MediaMetadata.Builder metadataBuilder = new MediaMetadata.Builder();
    // To provide most control over how an item is displayed set the
    // display fields in the metadata
    metadataBuilder.putString(MediaMetadata.METADATA_KEY_DISPLAY_TITLE,
            myData.displayTitle);
    metadataBuilder.putString(MediaMetadata.METADATA_KEY_DISPLAY_SUBTITLE,
            myData.displaySubtitle);
    metadataBuilder.putString(MediaMetadata.METADATA_KEY_DISPLAY_ICON_URI,
            myData.artUri);
    // And at minimum the title and artist for legacy support
    metadataBuilder.putString(MediaMetadata.METADATA_KEY_TITLE,
            myData.title);
    metadataBuilder.putString(MediaMetadata.METADATA_KEY_ARTIST,
            myData.artist);
    // A small bitmap for the artwork is also recommended
    metadataBuilder.putBitmap(MediaMetadata.METADATA_KEY_ART,
            myData.artBitmap);
    // Add any other fields you have for your data as well
    session.setMetadata(metadataBuilder.build());
}
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