Android sd卡读取数据库

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.MOUNT_UNMOUNT_FILESYSTEMS" />

SQLiteDatabase db;
    private final String DATABASE_PATH = android.os.Environment
            .getExternalStorageDirectory().getAbsolutePath() + "/vote";
    private String DATABASE_FILENAME = "db_vote.db";


// 初始化数据库
    private SQLiteDatabase openDatabase() {
        try {
            String databaseFilename = DATABASE_PATH + "/" + DATABASE_FILENAME;
            File dir = new File(DATABASE_PATH);
            if (!dir.exists())
                dir.mkdir();
            if (!(new File(databaseFilename)).exists()) {
                InputStream is = getResources().openRawResource(R.raw.db_vote);
                FileOutputStream fos = new FileOutputStream(databaseFilename);
                byte[] buffer = new byte[8192];
                int count = 0;
                while ((count = is.read(buffer)) > 0) {
                    fos.write(buffer, 0, count);
                }
                fos.close();
                is.close();
            }
            db = SQLiteDatabase.openOrCreateDatabase(databaseFilename, null);
            return db;
        } catch (Exception e) {
            e.printStackTrace();
        }
        return null;
    }