Android MediaPlayer 字幕同步

Android从API16中更新对字幕追踪的支持，具体是下面几个方法。

Added in API level 16

public void addTimedTextSource (Context context, Uri uri, String mimeType)
public void addTimedTextSource (String path, String mimeType)
public void addTimedTextSource (FileDescriptor fd, long offset, long length, String mimeType)
public void addTimedTextSource (FileDescriptor fd, String mimeType)
以第二方法为例，先看下API注释：

Added in API level 16
Adds an external timed text source file. Currently supported format is SubRip with the file extension .srt, case insensitive. Note that a single external timed text source may contain multiple tracks in it. One can find the total number of available tracks using getTrackInfo() to see what additional tracks become available after this method call.

大致意思就是，MediaPlayer支持外置文件显示字幕，但是现在只支持.SRT格式。这个文件可能有多个追踪器在追踪它，可以通过调用getTrackInfo（）方法来获得所有的追踪器。

TrackInfo 共有四种类型，未知，视频，音频，字幕。

Added in API level 16
public static final int MEDIA_TRACK_TYPE_UNKNOWN = 0;
        public static final int MEDIA_TRACK_TYPE_VIDEO = 1;
        public static final int MEDIA_TRACK_TYPE_AUDIO = 2;
        public static final int MEDIA_TRACK_TYPE_TIMEDTEXT = 3;

使用
在调用的时候，经常遇到这个错误：

03-29 14:42:38.675: W/System.err(21382): java.lang.RuntimeException: failure code: -38
03-29 14:42:38.675: W/System.err(21382): at android.media.MediaPlayer.invoke(MediaPlayer.java:644)
03-29 14:42:38.675: W/System.err(21382): at android.media.MediaPlayer.addTimedTextSource(MediaPlayer.java:1814)
03-29 14:42:38.675: W/System.err(21382): at android.media.MediaPlayer.addTimedTextSource(MediaPlayer.java:1778)
03-29 14:42:38.675: W/System.err(21382): at android.media.MediaPlayer.addTimedTextSource(MediaPlayer.java:1710)
03-29 14:42:38.675: W/System.err(21382): at com.demo.devin.fragment.QosDemoFragment$VideoHolder.onPrepared(QosDemoFragment.java:224)

API中告诉我们会抛这些Exception：

Added in API level 16

Throws:
IOException - if the file cannot be accessed or is corrupted.
IllegalArgumentException - if the mimeType is not supported.
IllegalStateException - if called in an invalid state.

经过试验，在OnPrepared的时候调用没有问题！

但是只是调用这个方法是无法工作的，还需要注册响应的listener和调用selectTrack方法。

具体代码如下：（在OnPrepared回调中）

[java] view plaincopyprint?
<SPAN style="WHITE-SPACE: pre"> </SPAN>try
            {
                mMediaPlayer.addTimedTextSource(srtPath,
                        MediaPlayer.MEDIA_MIMETYPE_TEXT_SUBRIP);

                TrackInfo[] trackInfos = mMediaPlayer.getTrackInfo();

                if (trackInfos != null && trackInfos.length > 0)
                {
                    for (int i = 0; i < trackInfos.length; i++)
                    {
                        final TrackInfo info = trackInfos[i];

                        Log.w(TAG, "TrackInfo: " + info.getTrackType() + " "
                                + info.getLanguage());

                        if (info.getTrackType() == TrackInfo.MEDIA_TRACK_TYPE_AUDIO)
                        {
                            // mMediaPlayer.selectTrack(i);
                        }
                        else if (info.getTrackType() == TrackInfo.MEDIA_TRACK_TYPE_TIMEDTEXT)
                        {
                            mMediaPlayer.selectTrack(i);
                        }
                    }
                }
            }
            catch (Exception e)
            {
                e.printStackTrace();
            }

try
            {
                mMediaPlayer.addTimedTextSource(srtPath,
                        MediaPlayer.MEDIA_MIMETYPE_TEXT_SUBRIP);

TrackInfo[] trackInfos = mMediaPlayer.getTrackInfo();

                if (trackInfos != null && trackInfos.length > 0)
                {
                    for (int i = 0; i < trackInfos.length; i++)
                    {

补充：移动开发 , Android ,