基於Android掃描sd卡與系統文件的介紹

如果你做過多媒體應用，一定會苦惱過，怎樣獲取sd卡中的多媒體文件。android還是很強大的，如果你知道怎麼調用android的api，萬事就ok了。
當手機或模擬器開機時，會調用android的MediaScanner，掃描sd卡和內存裡的文件。以下是log信息。
復制代碼 代碼如下:
12-13 15:39:11.062: VERBOSE/MediaPlayerService(67): Create new media retriever from pid 349<BR>
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<BR>
12-13 15:39:11.142: DEBUG/MediaScanner(349):  prescan time: 44ms<BR>
12-13 15:39:11.142: DEBUG/MediaScanner(349):     scan time: 13ms<BR>
12-13 15:39:11.142: DEBUG/MediaScanner(349): postscan time: 2ms<BR>
12-13 15:39:11.142: DEBUG/MediaScanner(349):    total time: 59ms<BR>
12-13 15:39:11.152: DEBUG/MediaProvider(349): un-lock thumbnail worker<BR>
12-13 15:39:11.152: DEBUG/MediaProvider(349): un-lock thumbnail worker<BR>
12-13 15:39:11.182: DEBUG/MediaScannerService(349): done scanning volume external

那麼掃描後的記錄它保存到哪裡了呢。哈。你覺得在哪裡呢？data/data/com.android.media/providers/databases/external
它存了些什麼信息呢，拉出來看看吧：

那麼，我們直接使用ContentProvider就可以直接獲取到sd卡中多媒體的信息了，你還用去listfile麼？還用去自己解析媒體文件中的信息麼(時長，文件名，專輯名。。應有盡有哦)？
復制代碼 代碼如下:
Cursor cursor = context.getContentResolver().query(<BR>    MediaStore.Audio.Media.EXTERNAL_CONTENT_URI,<BR>    new String[] { MediaStore.Audio.Media._ID, MediaStore.Audio.Media.DISPLAY_NAME, MediaStore.Audio.Media.TITLE,<BR>      MediaStore.Audio.Media.DURATION, MediaStore.Audio.Media.ARTIST, MediaStore.Audio.Media.ALBUM,<BR>      MediaStore.Audio.Media.YEAR, MediaStore.Audio.Media.MIME_TYPE, MediaStore.Audio.Media.SIZE, MediaStore.Audio.Media.DATA}<BR>    , "_size>?", new String[]{1024*1024+""},null);

好了，最後一個問題<BR> 當你往sd卡中添加一些多媒體文件的時候，android沒有自動將它刷新到數據庫中。那麼我們怎麼讓它手動刷新呢，如下：
復制代碼 代碼如下:
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<Song> 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<Song>();
                        songs.addAll(tempSongs);
                        initSong_lv();
                    }
                }else {
                    Toast.makeText(LocalList.this, "SD卡中沒有歌曲，請添加後再掃描", 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;
            }