Android自带音乐播放器专辑图片相同的问题

音乐播放器是从MediaProvider中获取音乐和音乐信息的，在插入SD卡后，MediaProvider启动扫描服务，文件解析通过opencore操作，扫描到的媒体文件由MediaProvider来保存到数据库，数据库位于

/data/data/com.android.providers.media/databases/external-*.db

 

 

在扫描时，扫描到的专辑图片存放于

Android/data/com.android.providers.media/albumthumbs/

 

 

专辑图片选用优先选择音乐内嵌专辑图片

 

如果音乐没有内嵌专辑图片，则在音乐目录下搜索（忽略根目录和下载目录）

 

             0 AlbumArt.jpg
             1 AlbumArt*Large.jpg
             2 Any other jpg image with 'albumart' anywhere in the name
             3 Any other jpg image
             4 any other png image

 

 

对于扫描的过程，详细可分析文件：

/android-2.2/packages/providers/MediaProvider/src/com/android/providers/media/MediaProvider.java

 

 

 

 private ParcelFileDescriptor makeThumbInternal(ThumbData d) ---> getCompressedAlbumArt(getContext(), d.path);

 

 

 

如果音频文件中有专辑图片，用音频里的图片，如果没有，则按如下策略选择图片。    

    // Extract compressed image data from the audio file itself or, if that fails,
    // look for a file "AlbumArt.jpg" in the containing directory.

    private static byte[] getCompressedAlbumArt(Context context, String path) {
        byte[] compressed = null;

        try {
            File f = new File(path);
            ParcelFileDescriptor pfd = ParcelFileDescriptor.open(f,
                    ParcelFileDescriptor.MODE_READ_ONLY);

            MediaScanner scanner = new MediaScanner(context);
            compressed = scanner.extractAlbumArt(pfd.getFileDescriptor());
            pfd.close();

            // If no embedded art exists, look for a suitable image file in the
            // same directory as the media file, except if that directory is
            // is the root directory of the sd card or the download directory.
            // We look for, in order of preference:
            // 0 AlbumArt.jpg
            // 1 AlbumArt*Large.jpg
            // 2 Any other jpg image with 'albumart' anywhere in the name
            // 3 Any other jpg image
            // 4 any other png image

           
            if (compressed == null && path != null) {
                int lastSlash = path.lastIndexOf('/');
                if (lastSlash > 0) {

                    String artPath = path.substring(0, lastSlash);
                    String sdroot = Environment.getExternalStorageDirectory().getAbsolutePath();
                    String dwndir = Environment.getExternalStoragePublicDirectory(
                            Environment.DIRECTORY_DOWNLOADS).getAbsolutePath();

                    String bestmatch = null;
                    synchronized (sFolderArtMap) {
                        if (sFolderArtMap.containsKey(artPath)) {
                            bestmatch = sFolderArtMap.get(artPath);
                        } else if (!artPath.equalsIgnoreCase(sdroot) &&
                                !artPath.equalsIgnoreCase(dwndir)) {
                            File dir = new File(artPath);
                            String [] entrynames = dir.list();
                            if (entrynames == null) {
                                return null;
                            }
                            bestmatch = null;
                            int matchlevel = 1000;
                            for (int i = entrynames.length - 1; i >=0; i--) {
                                String entry = entrynames[i].toLowerCase();
                                if (entry.equals("albumart.jpg")) {
                                    bestmatch = entrynames[i];
                                    break;
                                } else if (entry.startsWith("albumart")
                                        && entry.endsWith("large.jpg")
                                        && matchlevel > 1) {
                                    bestmatch = entrynames[i];
                                    matchlevel = 1;
                                } else if (entry.contains("albumart")
                                        && entry.endsWith(".jpg")
                                        && matchlevel > 2) {
                                    bestmatch = entrynames[i];
                                    matchlevel = 2;
                                } else if (entry.endsWith(".jpg") && matchlevel > 3) {
                                    bestmatch = entrynames[i];
                                    matchlevel = 3;
                                } else if (entry.endsWith(".png") && matchlevel > 4) {
                                    bestmatch = entrynames[i];
                                    matchlevel = 4;
                                }
                            }
                            // note that this may insert null if no album art was found
                            sFolderArtMap.put(artPath, bestmatch);
                        }
                    }

                    if (bestmatch != null) {
                        File file = new File(artPath, bestmatch);
                        if (file.exists()) {
                            compressed = new byte[(int)file.length()];
                            FileInputStream stream = null;
                            try {
                                stream = new FileInputStream(file);
                                stream.read(compressed);
                            } catch (IOException ex) {
                                compressed = null;
                            } finally {
                                if (stream != null) {
                                    stream.close();
                                }
                            }
                        }
                    }
                }
            }
        } catch (IOException e) {
        }

        return compressed;
    }