/data/data/com.androidia/databases/external-*.db

在扫描时，扫描到的专辑图片存放于

Android/data/com.androidia/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;
}