基于Android扫描sd卡与系统文件的介绍

如果你做过多媒体应用，一定会苦恼过，怎样获取sd卡中的多媒体文件。android还是很强大的，如果你知道怎么调用android的api，万事就ok了。
当手机或模拟器开机时，会调用android的MediaScanner，扫描sd卡和内存里的文件。以下是log信息。
复制代码 代码如下:
12-13 15:39:11.062: VERBOSE/MediaPlayerService(67): Create new media retriever from pid 349

12-13 15:39:11.082: DEBUG/MediaScannerService(349): getDefaultLocale =zh_CN
12-13 15:39:11.122: DEBUG/SurfaceFlinger(102): Layer::requestBuffer(this=0x7c8c68), index=1, pid=12866, w=309, h=192 success
12-13 15:39:11.142: INFO/MediaScanner(349): mOriginalCount = 14, prune thumb flag = false

12-13 15:39:11.142: DEBUG/MediaScanner(349):  prescan time: 44ms

12-13 15:39:11.142: DEBUG/MediaScanner(349):     scan time: 13ms

12-13 15:39:11.142: DEBUG/MediaScanner(349): postscan time: 2ms

12-13 15:39:11.142: DEBUG/MediaScanner(349):    total time: 59ms

12-13 15:39:11.152: DEBUG/MediaProvider(349): un-lock thumbnail worker

12-13 15:39:11.152: DEBUG/MediaProvider(349): un-lock thumbnail worker

12-13 15:39:11.182: DEBUG/MediaScannerService(349): done scanning volume external

那么扫描后的记录它保存到哪里了呢。哈。你觉得在哪里呢？data/data/com.android.media/providers/databases/external
它存了些什么信息呢，拉出来看看吧：

那么，我们直接使用ContentProvider就可以直接获取到sd卡中多媒体的信息了，你还用去listfile么？还用去自己解析媒体文件中的信息么(时长，文件名，专辑名。。应有尽有哦)？
复制代码 代码如下:
Cursor cursor = context.getContentResolver().query(
    MediaStore.Audio.Media.EXTERNAL_CONTENT_URI,
    new String[] { MediaStore.Audio.Media._ID, MediaStore.Audio.Media.DISPLAY_NAME, MediaStore.Audio.Media.TITLE,
      MediaStore.Audio.Media.DURATION, MediaStore.Audio.Media.ARTIST, MediaStore.Audio.Media.ALBUM,
      MediaStore.Audio.Media.YEAR, MediaStore.Audio.Media.MIME_TYPE, MediaStore.Audio.Media.SIZE, MediaStore.Audio.Media.DATA}
    , "_size>?", new String[]{1024*1024+""},null);

好了，最后一个问题
当你往sd卡中添加一些多媒体文件的时候，android没有自动将它刷新到数据库中。那么我们怎么让它手动刷新呢，如下：
复制代码 代码如下:
IntentFilter intentFilter = new IntentFilter(Intent.ACTION_MEDIA_SCANNER_STARTED);
        intentFilter.addAction(Intent.ACTION_MEDIA_SCANNER_FINISHED);
        intentFilter.addDataScheme("file");
        scanReceiver = new ScanSdFilesReceiver();
        registerReceiver(scanReceiver, intentFilter);
        sendBroadcast(new Intent(Intent.ACTION_MEDIA_MOUNTED, Uri.parse("file://" + Environment.getExternalStorageDirectory())));

 
private class ScanSdFilesReceiver extends BroadcastReceiver {
        public void onReceive(Context context, Intent intent) {
            String action = intent.getAction();
            if (Intent.ACTION_MEDIA_SCANNER_STARTED.equals(action)) {
                scanHandler.sendEmptyMessage(STARTED);
            }
            if (Intent.ACTION_MEDIA_SCANNER_FINISHED.equals(action)) {
                scanHandler.sendEmptyMessage(FINISHED);
            }
        }
    }

 
private Handler scanHandler = new Handler() {
        public void handleMessage(Message msg) {
            super.handleMessage(msg);
            switch (msg.what) {
            case STARTED:
                MyDialog scanDialog = new MyDialog(LocalList.this);
                scanalertDialog = scanDialog.scanFile();
                scanalertDialog.show();
                Log.i(TAG, "showing");
                break;
            case FINISHED:
                ArrayList tempSongs = ReadFileList.readDataFromSD(LocalList.this, LOCAL);
                if (tempSongs != null && tempSongs.size()>0) {
                    if (songs != null && songs.size()>0) {
                        songs.clear();
                        songs.addAll(tempSongs);
                        songAdapter.notifyDataSetChanged();
                    }else {
                        songs = new ArrayList();
                        songs.addAll(tempSongs);
                        initSong_lv();
                    }
                }else {
                    Toast.makeText(LocalList.this, "SD卡中没有歌曲，请添加后再扫描", Toast.LENGTH_SHORT).show();
                }
                Log.i(TAG, "finish");
                if (scanalertDialog!=null && scanalertDialog.isShowing()) {
                    scanalertDialog.dismiss();
                }
                unregisterReceiver(scanReceiver);
                break;
            case DISMISS:
                Log.i(TAG, "dismiss");
                if (scanalertDialog!=null && scanalertDialog.isShowing()) {
                    scanalertDialog.dismiss();
                }
            default:
                break;
            }