Android开发——MediaProvider源码分析
转自http://www.cnblogs.com
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MediaProvider包括五个类：
- com.android.providers.media.MediaProvider
- com.android.providers.media.MediaScannerCursor
- com.android.providers.media.MediaScannerReceiver
- com.android.providers.media.MediaScannerService
- com.android.providers.media.MediaThumbRequest
1.MediaProvider
此类继承ContentProvider，实现一个内容提供者。主要用于创建媒体库的数据库表。有自己创建过ContentProvider的同学相信都比较清楚的。
特别说明一下在MediaProvider中有个广播接收者，代码如下：
1: private BroadcastReceiver mUnmountReceiver = new BroadcastReceiver() {
2:
@Override 3: public void onReceive(Context context, Intent intent) {
4: if (intent.getAction().equals(Intent.ACTION_MEDIA_EJECT)) {
5: // Remove the external volume and then notify all cursors backed by
6: // data on that volume
7: detachVolume(Uri.parse("content://media/external" ));
8:
sFolderArtMap.clear(); 9:
MiniThumbFile.reset(); 10:
} 11:
} 12:
}; 此接收者是用来接收Sdcard卸载的广播。当Sdcard从手机中分离出来的时候，Sdcard中的媒体文件相对应的数据库将无法操作。
1: private void detachVolume(Uri uri) {
2: //判断是否是同一个进程
3: if (Process.supportsProcesses() && Binder.getCallingPid() != Process.myPid()) {
4: throw new SecurityException(
5: "Opening and closing databases not allowed." );
6:
} 7: //此方法只是操作Sdcard的媒体数据库，不支持手机内存的媒体数据库
8:
String volume = uri.getPathSegments().get(0); 9: if (INTERNAL_VOLUME.equals(volume)) {
10: throw new UnsupportedOperationException(
11: "Deleting the internal volume is not allowed" );
12: } else if (!EXTERNAL_VOLUME.equals(volume)) {
13: throw new IllegalArgumentException(
14: "There is no volume named " + volume);
15:
} 16:
17:
synchronized (mDatabases) { 18:
DatabaseHelper database = mDatabases.get(volume); 19: if (database == null )
return ;
21: try {
22: // touch the database file to show it is most recently used
23: File file = new File(database.getReadableDatabase().getPath());
24:
file.setLastModified(System.currentTimeMillis()); 25: } catch (SQLException e) {
26: Log.e(TAG, "Can't touch database file" , e);
27:
} 28: //移除数据库
29:
mDatabases.remove(volume); 30:
database.close(); 31:
} 32:
33: getContext().getContentResolver().notifyChange(uri, null );
34: if (LOCAL_LOGV) Log.v(TAG, "Detached volume: " + volume);
35:
} 注意移除数据库并非删除数据库文件（*.db）,mDatabases是一个HashMap<String,DatabaseHelper>,移除的含义是暂时无法操作，也可以说说是查询返回的数据都是空的。
2.MediaScannerCursor
一个自定义游标，用来查询媒体文件的扫描状态。主要有一个volume字段，用来区分是内置媒体数据库还是Sdcard的媒体数据库。
3.MediaScannerReceiver
此类实现广播接收者。接收到广播的时候对手机的媒体文件进行扫描。
1: public class MediaScannerReceiver extends BroadcastReceiver
2:
{ 3: private final static String TAG = "MediaScannerReceiver" ;
4:
5:
@Override 6: public void onReceive(Context context, Intent intent) {
7:
String action = intent.getAction(); 8:
Uri uri = intent.getData(); 9:
String externalStoragePath = Environment.getExternalStorageDirectory().getPath(); 10: //系统启动完毕
11: if (action.equals(Intent.ACTION_BOOT_COMPLETED)) {
12: // scan internal storage
13:
scan(context, MediaProvider.INTERNAL_VOLUME); 14: } else {
15: if (uri.getScheme().equals("file" )) {
16: // handle intents related to external storage
17:
String path = uri.getPath(); 18: if (action.equals(Intent.ACTION_MEDIA_MOUNTED/*Sdcard挂载广播*/ ) &&
19:
externalStoragePath.equals(path)) { 20:
scan(context, MediaProvider.EXTERNAL_VOLUME); 21: } else if (action.equals(Intent.ACTION_MEDIA_SCANNER_SCAN_FILE/*单个文件扫描广播*/ ) &&
22: path != null && path.startsWith(externalStoragePath + "/" )) {
23:
scanFile(context, path); 24:
} 25:
} 26:
} 27:
} 扫描分为两种三种情况：
a,启动完毕扫面手机内存中的媒体文件
b.sdcard挂载完毕扫描扩展卡的媒体文件
c,扫描单个文件
应用实例：我们可以发送不同的广播让系统去扫描媒体文件。当需要扫描单个文件的时候需要设置一些参数，如下：
1: /**
2: * 扫描文件
3: *
4: * @param filePath 文件路径
5: * @author http://t.sina.com.cn/halzhang
6: */
7: public void scanOneFile(final String filePath) {
8: Intent intent = new Intent(Intent.ACTION_MEDIA_SCANNER_SCAN_FILE);
9: Uri uri = Uri.parse("file://" + filePath);
10:
intent.setData(uri); 11:
sendBroadcast(intent); 12:
} 接着看一下scan 和scenFile 两个方法：
1: private void scan(Context context, String volume/*内置卡或者外置卡*/ ) {
2: Bundle args = new Bundle();
3: args.putString("volume" , volume);
4:
context.startService( 5: new Intent(context, MediaScannerService.class ).putExtras(args));
6:
} 7:
8: private void scanFile(Context context, String path/*文件路径*/ ) {
9: Bundle args = new Bundle();
10: args.putString("filepath" , path);
11:
context.startService( 12: new Intent(context, MediaScannerService.class ).putExtras(args));
13:
} 两个方法都是启动MediaScannerService去扫描媒体文件的。
关于MediaScannerSerive且听下回分解。
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在 上一篇文章中说到系统当接收到扫描请求广播的时候就会调用scan或者scanFile去扫描手机（手机内存和sdcard）中的媒体文件。这两个方法都 是启动MediaScannerService这个服务来完成扫描任务的。接下来我们来看看MediaScannerService是怎么工作的……
4.MediaScannerService（MSS）
MSS实现了Runnable，所以必然的需要实现run方法了，代码如下：
1: public void run()
2:
{ 3: // reduce priority below other background threads to avoid interfering
4: // with other services at boot time.
5:
Process.setThreadPriority(Process.THREAD_PRIORITY_BACKGROUND + 6:
Process.THREAD_PRIORITY_LESS_FAVORABLE); 7:
Looper.prepare(); 8:
9:
mServiceLooper = Looper.myLooper(); 10: mServiceHandler = new ServiceHandler();
11:
12:
Looper.loop(); 13:
} 在run方法中设置了线程的优先级，优先级比较低，主要为了避免跟其他服务抢夺资源。还有就是利用looper对ServiceHandler的消息进行循环控制。
接着看一下ServiceHandler 的实现代码：
1: private final class ServiceHandler extends Handler
2:
{ 3:
@Override 4: public void handleMessage(Message msg)
5:
{ 6:
Bundle arguments = (Bundle) msg.obj; 7: //获取文件路径
8: String filePath = arguments.getString("filepath" );
9:
10: try {
11: if (filePath != null ) {
12: //文件路径不为空，则调用扫面当个文件的方法
13: IBinder binder = arguments.getIBinder("listener" );
14:
IMediaScannerListener listener = 15: (binder == null ? null : IMediaScannerListener.Stub.asInterface(binder));
16: Uri uri = scanFile(filePath, arguments.getString("mimetype" ));//扫描单个文件
17: if (listener != null ) {
18: //执行扫描完成方法
19:
listener.scanCompleted(filePath, uri); 20:
} 21: } else {
22: //如果文件路径为空，则获取扫面手机内存或者sdcard
23: String volume = arguments.getString("volume" );
24: String[] directories = null ;
25: //内置卡
26: if (MediaProvider.INTERNAL_VOLUME.equals(volume)) {
27: // scan internal media storage
28: directories = new String[] {
29: Environment.getRootDirectory() + "/media" ,
30:
}; 31: }//外置卡
32: else if (MediaProvider.EXTERNAL_VOLUME.equals(volume)) {
33: // scan external storage
34: directories = new String[] {
35:
Environment.getExternalStorageDirectory().getPath(), 36:
}; 37:
} 38:
39: if (directories != null ) {
40: if (Config.LOGD) Log.d(TAG, "start scanning volume " + volume);
41: //扫描
42:
scan(directories, volume); 43: if (Config.LOGD) Log.d(TAG, "done scanning volume " + volume);
44:
} 45:
} 46: } catch (Exception e) {
47: Log.e(TAG, "Exception in handleMessage" , e);
48:
} 49:
50:
stopSelf(msg.arg1); 51:
} 52:
}; 在ServiceHandler中主要根据相关参数来调用不同的扫描方法。
那是在哪里调用ServiceHandler发送消息的呢？请看如下代码：
1:
@Override 2: public void onCreate() {
3:
PowerManager pm = (PowerManager) getSystemService(Context.POWER_SERVICE); 4:
mWakeLock = pm.newWakeLock(PowerManager.PARTIAL_WAKE_LOCK, TAG); 5: //启用新线程，这样就可以避免阻塞，执行run，初始化成员变量loop和handler
6: Thread thr = new Thread(null , this , "MediaScannerService" );
7:
thr.start(); 8:
} 9:
10:
@Override 11: public int onStartCommand(Intent intent, int flags, int startId) {
12: while (mServiceHandler == null ) {
13: synchronized (this ) {
14: try {
15:
wait(100); 16: } catch (InterruptedException e) {
17:
} 18:
} 19:
} 20:
21: if (intent == null ) {
22: Log.e(TAG, "Intent is null in onStartCommand: " , new NullPointerException());
23: return Service.START_NOT_STICKY;
24:
} 25:
26:
Message msg = mServiceHandler.obtainMessage(); 27:
msg.arg1 = startId; 28:
msg.obj = intent.getExtras(); 29: //ServiceHandler发送消息
30:
mServiceHandler.sendMessage(msg); 31:
32: // Try again later if we are killed before we can finish scanning.
33: return Service.START_REDELIVER_INTENT;
34:
} 35:
36:
@Override 37: public void onDestroy() {
38: // Make sure thread has started before telling it to quit.
39: while (mServiceLooper == null ) {
40: synchronized (this ) {
41: try {
42:
wait(100); 43: } catch (InterruptedException e) {
44:
} 45:
} 46:
} 47:
mServiceLooper.quit(); 48:
} 以上三个方法是属于Service的生命周期的。当我们调用startService的时候，如果对应的Service还未创建就会调用 onCreate方法===方法。每次startService的时候就调用onStartCommand，所以ServiceHandler就在此发送 消息了。
最后，稍微看一下MSS里面扫描方面。主要是调用MediaScanner对媒体文件进行扫描分析的。至于MediaScanner的实现以后在分析。
1: private void openDatabase(String volumeName) {
2: try {
3: ContentValues values = new ContentValues();
4: values.put("name" , volumeName);
5: getContentResolver().insert(Uri.parse("content://media/" ), values);
6: } catch (IllegalArgumentException ex) {
7: Log.w(TAG, "failed to open media database" );
8:
} 9:
} 10:
11: private void closeDatabase(String volumeName) {
12: try {
13:
getContentResolver().delete( 14: Uri.parse("content://media/" + volumeName), null , null );
15: } catch (Exception e) {
16: Log.w(TAG, "failed to close media database " + volumeName + " exception: " + e);
17:
} 18:
} 19: //创建扫描器
20: private MediaScanner createMediaScanner() {
21: MediaScanner scanner = new MediaScanner(this );
22:
Locale locale = getResources().getConfiguration().locale; 23: if (locale != null ) {
24:
String language = locale.getLanguage(); 25:
String country = locale.getCountry(); 26: String localeString = null ;
27: if (language != null ) {
28: if (country != null ) {
29: scanner.setLocale(language + "_" + country);
30: } else {
31:
scanner.setLocale(language); 32:
} 33:
} 34:
} 35:
36: return scanner;
37:
} 38: //扫描目录
39: private void scan(String[] directories, String volumeName) {
40: // don't sleep while scanning
41:
mWakeLock.acquire(); 42:
43: ContentValues values = new ContentValues();
44:
values.put(MediaStore.MEDIA_SCANNER_VOLUME, volumeName); 45:
Uri scanUri = getContentResolver().insert(MediaStore.getMediaScannerUri(), values); 46:
47: Uri uri = Uri.parse("file://" + directories[0]);
48: sendBroadcast(new Intent(Intent.ACTION_MEDIA_SCANNER_STARTED, uri));
49:
50: try {
51: if (volumeName.equals(MediaProvider.EXTERNAL_VOLUME)) {
52:
openDatabase(volumeName); 53:
} 54:
55:
MediaScanner scanner = createMediaScanner(); 56:
scanner.scanDirectories(directories, volumeName); 57: } catch (Exception e) {
58: Log.e(TAG, "exception in MediaScanner.scan()" , e);
59:
} 60:
61: getContentResolver().delete(scanUri, null , null );
62:
63: sendBroadcast(new Intent(Intent.ACTION_MEDIA_SCANNER_FINISHED, uri));
64:
mWakeLock.release(); 65:
} 66: //扫描文件
67: private Uri scanFile(String path, String mimeType) {
68:
String volumeName = MediaProvider.INTERNAL_VOLUME; 69:
String externalStoragePath = Environment.getExternalStorageDirectory().getPath(); 70:
71: if (path.startsWith(externalStoragePath)) {
72:
volumeName = MediaProvider.EXTERNAL_VOLUME; 73:
openDatabase(volumeName); 74:
} 75:
MediaScanner scanner = createMediaScanner(); 76: //扫描单个文件
77: return scanner.scanSingleFile(path, volumeName, mimeType);
78:
} 在MediaProvider中还有一个类：MediaThumbRequest，用来创建预览图的，比如视频的预览图，图片的预览图，音频的专辑图片…这些图片的信息也是保存在数据库的，有兴趣的同学可以自己打开数据库看看里面的表。如下图：
啰哩啰唆的写了两篇文章，希望对大家有所帮助。
其中应该有不少是错误的观点，望大家指正。
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神马是MediaScanner呢？在Android的SDK里面是看不到这个类的，因为被google隐藏了。通过Android的源码我们可以看到MediaScanner的类注解多了一个@hide的标注。所以对于一般应用开发者，此文意义不是很大，大家可以绕道。
在前两篇文章中，最后我们都了解了Android的媒体文件的扫描是在MediaScannerService中调用MediaScanner的 scanDirectories或者scanSingleFile完成最终的扫描的。那么MediaScanner是如何工作的呢？
google对MediaScanner写了一大堆的类注释，如下：
1: /* In summary:
2: * Java MediaScannerService calls
3: * Java MediaScanner scanDirectories, which calls
4: * Java MediaScanner processDirectory (native method), which calls
5: * native MediaScanner processDirectory, which calls
6: * native MyMediaScannerClient scanFile, which calls
7: * Java MyMediaScannerClient scanFile, which calls
8: * Java MediaScannerClient doScanFile, which calls
9: * Java MediaScanner processFile (native method), which calls
10: * native MediaScanner processFile, which calls
11: * native parseMP3, parseMP4, parseMidi, parseOgg or parseWMA, which calls
12: * native MyMediaScanner handleStringTag, which calls
13: * Java MyMediaScanner handleStringTag.
14: * Once MediaScanner processFile returns, an entry is inserted in to the database.
15: *
16: * {@hide}
17: */
下面为调用时序图，如下：
这时序图好像不是很规范！点击看大图 ！请见谅。
开始看代码把……
1，scanDirectories。
初始化数据并调用processDirectory 处理扫描。
1: public void scanDirectories(String[] directories, String volumeName) {
2: try {
3: long start = System.currentTimeMillis();
4: //初始化
5:
initialize(volumeName); 6: //将数据库中的数据缓存到mFileCache
7: /*
8: * mFileCache.put(key, new FileCacheEntry(uri, rowId, path, lastModified));
9: */
10: prescan(null );
11: long prescan = System.currentTimeMillis();
12:
13: for (int i = 0; i < directories.length; i++) {
14: //扫描处理
15:
processDirectory(directories[i], MediaFile.sFileExtensions, mClient); 16:
} 17: long scan = System.currentTimeMillis();
18: //处理后续数据
19:
postscan(directories); 20: long end = System.currentTimeMillis();
2，processDirectory
这是一个native方法，所以我们直接转向jni，代码如下：
1: static void
2:
android_media_MediaScanner_processDirectory(JNIEnv *env, jobject thiz, jstring path, jstring extensions, jobject client) 3: { //获取MediaScanner
4:
MediaScanner *mp = (MediaScanner *)env->GetIntField(thiz, fields.context); 5: //参数判断，并抛出异常
6: if (path == NULL) {
7: jniThrowException(env, "java/lang/IllegalArgumentException" , NULL);
8: return ;
9:
} 10: if (extensions == NULL) {
11: jniThrowException(env, "java/lang/IllegalArgumentException" , NULL);
12: return ;
13:
} 14:
15: const char *pathStr = env->GetStringUTFChars(path, NULL);
16: if (pathStr == NULL) { // Out of memory
17: jniThrowException(env, "java/lang/RuntimeException" , "Out of memory" );
18: return ;
19:
} 20: const char *extensionsStr = env->GetStringUTFChars(extensions, NULL);
21: if (extensionsStr == NULL) { // Out of memory
22:
env->ReleaseStringUTFChars(path, pathStr); 23: jniThrowException(env, "java/lang/RuntimeException" , "Out of memory" );
24: return ;
25:
} 26: //初始化client实例
27:
MyMediaScannerClient myClient(env, client); 28: //mp调用processDirectory
29:
mp->processDirectory(pathStr, extensionsStr, myClient, ExceptionCheck, env); 30: //gc
31:
env->ReleaseStringUTFChars(path, pathStr); 32:
env->ReleaseStringUTFChars(extensions, extensionsStr); 33:
} 3，mp->processDirectory(pathStr, extensionsStr, myClient, ExceptionCheck, env);
1: status_t MediaScanner::processDirectory(const char *path, const char * extensions,
2: MediaScannerClient& client, ExceptionCheck exceptionCheck, void * exceptionEnv)
3: {//这方法不知道干吗的，估计跟线程有关
4:
InitializeForThread(); 5:
6: int pathLength = strlen(path);
7: if (pathLength >= PATH_MAX) {
8: return PVMFFailure;
9:
} 10: char * pathBuffer = (char *)malloc(PATH_MAX + 1);
11: if (!pathBuffer) {
12: return PVMFFailure;
13:
} 14:
15: int pathRemaining = PATH_MAX - pathLength;
16:
strcpy(pathBuffer, path); 17: if (pathBuffer[pathLength - 1] != '/' ) {
18: pathBuffer[pathLength] = '/' ;
19:
pathBuffer[pathLength + 1] = 0; 20:
--pathRemaining; 21:
} 22:
23:
client.setLocale(mLocale); 24: //有是一个关键点
25:
status_t result = doProcessDirectory(pathBuffer, pathRemaining, extensions, client, exceptionCheck, exceptionEnv); 26: //释放内存
27:
free(pathBuffer); 28: return result;
29:
} 4，doProcessDirectory
1: status_t MediaScanner::doProcessDirectory(char *path, int pathRemaining, const char * extensions,
2: MediaScannerClient& client, ExceptionCheck exceptionCheck, void * exceptionEnv)
3:
{ 4:
…… 5:
…… 6: if (type == DT_REG || type == DT_DIR) {
7: int nameLength = strlen(name);
8: bool isDirectory = (type == DT_DIR);
9:
10: if (nameLength > pathRemaining || (isDirectory && nameLength + 1 > pathRemaining)) {
11: // path too long!
12: continue ;
13:
} 14:
15:
strcpy(fileSpot, name); 16: if (isDirectory) {
17: // ignore directories with a name that starts with '.'
18: // for example, the Mac ".Trashes" directory
19: if (name[0] == '.' ) continue ;
20:
21: strcat(fileSpot, "/" );
22: //文件夹，递归调用
23: int err = doProcessDirectory(path, pathRemaining - nameLength - 1, extensions, client, exceptionCheck, exceptionEnv);
24: if (err) {
25: // pass exceptions up - ignore other errors
26: if (exceptionCheck && exceptionCheck(exceptionEnv)) goto failure;
27: LOGE("Error processing '%s' - skipping/n" , path);
28: continue ;
29:
} 30: } else if (fileMatchesExtension(path, extensions)) {
31: //文件，扩展名符合
32: struct stat statbuf;
33:
stat(path, &statbuf); 34: if (statbuf.st_size > 0) {
35: //调用client的scanFile方法
36:
client.scanFile(path, statbuf.st_mtime, statbuf.st_size); 37:
} 38: if (exceptionCheck && exceptionCheck(exceptionEnv)) goto failure;
39:
} 40:
} 41:
…… 42:
…… 5，client.scanFile
1: // returns true if it succeeded, false if an exception occured in the Java code
2: virtual bool scanFile(const char * path, long long lastModified, long long fileSize)
3:
{ 4:
jstring pathStr; 5: if ((pathStr = mEnv->NewStringUTF(path)) == NULL) return false ;
6: //有点反射的感觉，调用java里面mClient中的scanFile方法
7:
mEnv->CallVoidMethod(mClient, mScanFileMethodID, pathStr, lastModified, fileSize); 8:
9:
mEnv->DeleteLocalRef(pathStr); 10: return (!mEnv->ExceptionCheck());
11:
} 6，mEnv->CallVoidMethod(mClient, mScanFileMethodID, pathStr, lastModified, fileSize); 让我们回到Java
在android.media.MediaScanner.MyMediaScannerClient中的scanFile方法是直接调用doScanFile的，来看看doScanFile
1:
2: public Uri doScanFile(String path, String mimeType, long lastModified, long fileSize,
3:
boolean scanAlways) { 4: Uri result = null ;
5: // long t1 = System.currentTimeMillis();
6: try {
7:
FileCacheEntry entry = beginFile(path, mimeType, lastModified, fileSize); 8: // rescan for metadata if file was modified since last scan
9: if (entry != null && (entry.mLastModifiedChanged || scanAlways)) {
10:
String lowpath = path.toLowerCase(); 11:
boolean ringtones = (lowpath.indexOf(RINGTONES_DIR) > 0); 12:
boolean notifications = (lowpath.indexOf(NOTIFICATIONS_DIR) > 0); 13:
boolean alarms = (lowpath.indexOf(ALARMS_DIR) > 0); 14:
boolean podcasts = (lowpath.indexOf(PODCAST_DIR) > 0); 15:
boolean music = (lowpath.indexOf(MUSIC_DIR) > 0) 16:
|| (!ringtones && !notifications && !alarms && !podcasts); 17:
18: if (isMetadataSupported(mFileType)) {
19: // 调用jni方法
20: processFile(path, mimeType, this );
21: } else if (MediaFile.isImageFileType(mFileType)) {
22: // we used to compute the width and height but it's not
23: // worth it
24:
} 25:
26:
result = endFile(entry, ringtones, notifications, alarms, music, podcasts); 27:
} 28: } catch (RemoteException e) {
29: Log.e(TAG, "RemoteException in MediaScanner.scanFile()" , e);
30:
} 31: // long t2 = System.currentTimeMillis();
32: // Log.v(TAG, "scanFile: " + path + " took " + (t2-t1));
33: return result;
34:
} 补充：result = endFile(entry, ringtones, notifications, alarms, music, podcasts);就是在这里将媒体数据信息存放到数据库的
7，接着是native的 processFile
1: static void
2:
android_media_MediaScanner_processFile(JNIEnv *env, jobject thiz, jstring path, jstring mimeType, jobject client) 3:
{ 4:
MediaScanner *mp = (MediaScanner *)env->GetIntField(thiz, fields.context); 5:
6: if (path == NULL) {
7: jniThrowException(env, "java/lang/IllegalArgumentException" , NULL);
8: return ;
9:
} 10:
11: const char *pathStr = env->GetStringUTFChars(path, NULL);
12: if (pathStr == NULL) { // Out of memory
13: jniThrowException(env, "java/lang/RuntimeException" , "Out of memory" );
14: return ;
15:
} 16: const char *mimeTypeStr = (mimeType ? env->GetStringUTFChars(mimeType, NULL) : NULL);
17: if (mimeType && mimeTypeStr == NULL) { // Out of memory
18:
env->ReleaseStringUTFChars(path, pathStr); 19: jniThrowException(env, "java/lang/RuntimeException" , "Out of memory" );
20: return ;
21:
} 22:
23:
MyMediaScannerClient myClient(env, client); 24: //调用MediaScanner的processFile
25:
mp->processFile(pathStr, mimeTypeStr, myClient); 26:
env->ReleaseStringUTFChars(path, pathStr); 27: if (mimeType) {
28:
env->ReleaseStringUTFChars(mimeType, mimeTypeStr); 29:
} 30:
} 8，mp->processFile(pathStr, mimeTypeStr, myClient);
在此方法中根据不同的文件扩展名调用更加底层的解析方法，我想主要是ID3信息解析
1: status_t MediaScanner::processFile(const char *path, const char * mimeType, MediaScannerClient& client)
2:
{ 3:
status_t result; 4:
InitializeForThread(); 5: //初始化client
6:
client.setLocale(mLocale); 7:
client.beginFile(); 8:
9: //LOGD("processFile %s mimeType: %s/n", path, mimeType);
10: const char * extension = strrchr(path, '.' );
11: //根据扩展名调用不同的解析方法
12: if (extension && strcasecmp(extension, ".mp3" ) == 0) {
13:
result = parseMP3(path, client); 14: } else if (extension &&
15: (strcasecmp(extension, ".mp4" ) == 0 || strcasecmp(extension, ".m4a" ) == 0 ||
16: strcasecmp(extension, ".3gp" ) == 0 || strcasecmp(extension, ".3gpp" ) == 0 ||
17: strcasecmp(extension, ".3g2" ) == 0 || strcasecmp(extension, ".3gpp2" ) == 0)) {
18:
result = parseMP4(path, client); 19: } else if (extension && strcasecmp(extension, ".ogg" ) == 0) {
20:
result = parseOgg(path, client); 21: } else if (extension &&
22: ( strcasecmp(extension, ".mid" ) == 0 || strcasecmp(extension, ".smf" ) == 0
23: || strcasecmp(extension, ".imy" ) == 0)) {
24:
result = parseMidi(path, client); 25: } else if (extension &&
26: (strcasecmp(extension, ".wma" ) == 0 || strcasecmp(extension, ".aac" ) == 0)) {
27: //TODO: parseWMA needs to be renamed to reflect what it is really doing,
28: //ie. using OpenCORE frame metadata utility(FMU) to retrieve metadata.
29:
result = parseWMA(path, client); 30: } else {
31:
result = PVMFFailure; 32:
} 33: //调用client
34:
client.endFile(); 35:
36: return result;
37:
} 9，client.endFile()
1: void MediaScannerClient::endFile()
2:
{ 3: if (mLocaleEncoding != kEncodingNone) {
4: int size = mNames->size();
5:
uint32_t encoding = kEncodingAll; 6:
7: // compute a bit mask containing all possible encodings
8: for (int i = 0; i < mNames->size(); i++)
9:
encoding &= possibleEncodings(mValues->getEntry(i)); 10:
11: // if the locale encoding matches, then assume we have a native encoding.
12: if (encoding & mLocaleEncoding)
13:
convertValues(mLocaleEncoding); 14:
15: // finally, push all name/value pairs to the client
16: for (int i = 0; i < mNames->size(); i++) {
17: //在handleStringTag中是通过类反射的方法调用java中的handleStringTag
18: if (!handleStringTag(mNames->getEntry(i), mValues->getEntry(i)))
19: break ;
20:
} 21:
} 22: // else addStringTag() has done all the work so we have nothing to do
23:
24:
delete mNames; 25:
delete mValues; 26:
mNames = NULL; 27:
mValues = NULL; 28:
} 10，java中的handleStringTag ，这个方法主要处理那些在底层解析后的数据返回到java层
1: public void handleStringTag(String name, String value ) {
2: if (name.equalsIgnoreCase("title" ) || name.startsWith("title;" )) {
3: // Don't trim() here, to preserve the special /001 character
4: // used to force sorting. The media provider will trim() before
5: // inserting the title in to the database.
6: mTitle = value ;
7: } else if (name.equalsIgnoreCase("artist" ) || name.startsWith("artist;" )) {
8: mArtist = value .trim();
9: } else if (name.equalsIgnoreCase("albumartist" ) || name.startsWith("albumartist;" )) {
10: mAlbumArtist = value .trim();
11: } else if (name.equalsIgnoreCase("album" ) || name.startsWith("album;" )) {
12: mAlbum = value .trim();
13: } else if (name.equalsIgnoreCase("composer" ) || name.startsWith("composer;" )) {
14: mComposer = value .trim();
15: } else if (name.equalsIgnoreCase("genre" ) || name.startsWith("genre;" )) {
16: // handle numeric genres, which PV sometimes encodes like "(20)"
17: if (value .length() > 0) {
18: int genreCode = -1;
19: char ch = value .charAt(0);
20: if (ch == '(' ) {
21: genreCode = parseSubstring(value , 1, -1);
22: } else if (ch >= '0' && ch <= '9' ) {
23: genreCode = parseSubstring(value , 0, -1);
24:
} 25: if (genreCode >= 0 && genreCode < ID3_GENRES.length) {
26: value = ID3_GENRES[genreCode];
27:
} 28:
} 29: mGenre = value ;
30: } else if (name.equalsIgnoreCase("year" ) || name.startsWith("year;" )) {
31: mYear = parseSubstring(value , 0, 0);
32: } else if (name.equalsIgnoreCase("tracknumber" ) || name.startsWith("tracknumber;" )) {
33: // track number might be of the form "2/12"
34: // we just read the number before the slash
35: int num = parseSubstring(value , 0, 0);
36:
mTrack = (mTrack / 1000) * 1000 + num; 37: } else if (name.equalsIgnoreCase("discnumber" ) ||
38: name.equals("set" ) || name.startsWith("set;" )) {
39: // set number might be of the form "1/3"
40: // we just read the number before the slash
41: int num = parseSubstring(value , 0, 0);
42:
mTrack = (num * 1000) + (mTrack % 1000); 43: } else if (name.equalsIgnoreCase("duration" )) {
44: mDuration = parseSubstring(value , 0, 0);
45: } else if (name.equalsIgnoreCase("writer" ) || name.startsWith("writer;" )) {
46: mWriter = value .trim();
47:
} 48:
} 此致，此文结束，累。
三篇有关MediaScanner的文章，希望对大家有所帮助。
对C/C++不是很熟悉，如发现分析有误，请告知。