How to lock Android folder programmatically?

Question

I am making an Android application, and I want to prevent users from opening some folder. In that folder user can store image or video files. It would be great if I could protect that folder with password.

Which is the best way to do that?

Answer 1

Here is Both function for encrypt and decrypt file in Sdcard folder. we can not lock folder but we can encrypt file using AES in Android, it may help you.

static void encrypt() throws IOException, NoSuchAlgorithmException, NoSuchPaddingException, InvalidKeyException {
    // Here you read the cleartext.
    FileInputStream fis = new FileInputStream("data/cleartext");
    // This stream write the encrypted text. This stream will be wrapped by another stream.
    FileOutputStream fos = new FileOutputStream("data/encrypted");

    // Length is 16 byte
    SecretKeySpec sks = new SecretKeySpec("MyDifficultPassw".getBytes(), "AES");
    // Create cipher
    Cipher cipher = Cipher.getInstance("AES");
    cipher.init(Cipher.ENCRYPT_MODE, sks);
    // Wrap the output stream
    CipherOutputStream cos = new CipherOutputStream(fos, cipher);
    // Write bytes
    int b;
    byte[] d = new byte[8];
    while((b = fis.read(d)) != -1) {
        cos.write(d, 0, b);
    }
    // Flush and close streams.
    cos.flush();
    cos.close();
    fis.close();
}

static void decrypt() throws IOException, NoSuchAlgorithmException, NoSuchPaddingException, InvalidKeyException {
    FileInputStream fis = new FileInputStream("data/encrypted");

    FileOutputStream fos = new FileOutputStream("data/decrypted");
    SecretKeySpec sks = new SecretKeySpec("MyDifficultPassw".getBytes(), "AES");
    Cipher cipher = Cipher.getInstance("AES");
    cipher.init(Cipher.DECRYPT_MODE, sks);
    CipherInputStream cis = new CipherInputStream(fis, cipher);
    int b;
    byte[] d = new byte[8];
    while((b = cis.read(d)) != -1) {
        fos.write(d, 0, b);
    }
    fos.flush();
    fos.close();
    cis.close();
}

Answer 2

You should save this information on the internal storage. Normally other apps can't access these files. From the quideliness:

You can save files directly on the device's internal storage. By default, files saved to the internal storage are private to your application and other applications cannot access them (nor can the user). When the user uninstalls your application, these files are removed.

See the link: http://developer.android.com/guide/topics/data/data-storage.html#filesInternal

Answer 3

Insted of LOCK i will saggest you make folder with . like foldername -> .test

user cant see that folder here is code

File direct = new File(Environment.getExternalStorageDirectory() + "/.test");

   if(!direct.exists())
    {
        if(direct.mkdir()) 
          {
           //directory is created;
          }

    }

above code is create folder with name ".test" (in SD CARD) then save your data(file, video.. whatever) in this folder user cant access it.

if you create folder in internal storage then if user clear data of your app then that folder may EMPTY!