exoplayer2 显示内嵌字幕

要在ExoPlayer 2中显示内嵌字幕，您可以使用以下步骤：

创建一个DefaultTrackSelector对象，并将其分配给您的ExoPlayer实例：

DefaultTrackSelector trackSelector = new DefaultTrackSelector();
player = ExoPlayerFactory.newSimpleInstance(context, trackSelector);

使用MediaSource对象创建您的ExoPlayer实例：

MediaSource mediaSource = new ExtractorMediaSource.Factory(dataSourceFactory)
        .createMediaSource(uri);
player.prepare(mediaSource);

如果您的媒体文件包含内嵌字幕，则它们将自动加载。您可以使用以下代码检查当前媒体源是否包含字幕轨道：

MappedTrackInfo mappedTrackInfo = trackSelector.getCurrentMappedTrackInfo();
if (mappedTrackInfo != null) {
    int rendererIndex = ...; // The index of the renderer for which you want to check the track selection.
    int trackType = C.TRACK_TYPE_TEXT;
    TrackGroupArray trackGroups = mappedTrackInfo.getTrackGroups(rendererIndex);
    if (trackGroups.length > 0) {
        TrackGroup trackGroup = trackGroups.get(0);
        for (int i = 0; i < trackGroup.length; i++) {
            Format format = trackGroup.getFormat(i);
            if (format.sampleMimeType != null && format.sampleMimeType.startsWith("text/")) {
                // This track group contains a text track.
            }
        }
    }
}

如果您想手动选择字幕轨道，您可以使用以下代码：

MappedTrackInfo mappedTrackInfo = trackSelector.getCurrentMappedTrackInfo();
if (mappedTrackInfo != null) {
    int rendererIndex = ...; // The index of the renderer for which you want to select a track.
    int trackType = C.TRACK_TYPE_TEXT;
    TrackGroupArray trackGroups = mappedTrackInfo.getTrackGroups(rendererIndex);
    if (trackGroups.length > 0) {
        int trackIndex = ...; // The index of the track you want to select.
        DefaultTrackSelector.ParametersBuilder builder = trackSelector.buildUponParameters();
        builder.setRendererDisabled(rendererIndex, false);
        builder.setSelectionOverride(rendererIndex, trackGroups, new DefaultTrackSelector.SelectionOverride(trackIndex, 0));
        trackSelector.setParameters(builder.build());
    }
}

这将启用指定的渲染器，并选择指定的轨道。请注意，此代码仅选择单个轨道。如果您想同时选择多个轨道，请参阅ExoPlayer文档中的更多信息