即使使用带有套接字的非阻塞密码 stream，应用程序仍然会阻塞

Question

Hello I used the cipher in this post 5777105

But the decrypting code still blocks until the buffer size is reached. Do you know another way to make it non-blocking? Note the decrypting part is running on Android.

Encrypting part:

    CipherInputStream cis;
    String salt = "1234567890123456";
    String password = "abcdEFGH";

    password = password.concat(salt);
    String validpassword = password.substring(0, 16);
    SecretKeySpec secretKey = new SecretKeySpec(validpassword.getBytes(),"AES");   
    AlgorithmParameterSpec paramSpec = new IvParameterSpec(salt.getBytes());

    try  {
        // Creation of Cipher objects
        Cipher encrypt = 
         Cipher.getInstance("AES/CFB8/NoPadding");
        encrypt.init(Cipher.ENCRYPT_MODE, secretKey,paramSpec);

        // Open the file
        try {
             fis = new FileInputStream(file);
        } catch(IOException err) {
             System.out.println("Cannot open file!");
             return null;
        }
        cis = new CipherInputStream(fis, encrypt);

        // Write to the Encrypted file
        fos = new FileOutputStream(desFile);
        byte[] b = new byte[256];
        int i = cis.read(b);
        while (i != -1) {
             fos.write(b, 0, i);
             i = cis.read(b);
        }

Decrypting part:

    CipherInputStream cis;
    String salt = "1234567890123456";
    String password = "abcdEFGH";

    password = password.concat(salt);
    String validpassword = password.substring(0, 16);          
    SecretKeySpec secretKey =new SecretKeySpec(validpassword.getBytes(),"AES");        
    AlgorithmParameterSpec paramSpec = new IvParameterSpec(salt.getBytes());

     try {
         // Creation of Cipher objects
         Cipher decrypt = 
              Cipher.getInstance("AES/CFB8/NoPadding");
         decrypt.init(Cipher.DECRYPT_MODE, secretKey,paramSpec); 

         // Open the Encrypted file
         cis = new CipherInputStream(is, decrypt); 

         int bytesRead;
         int current = 0;
         byte[] b = new byte[256];
         bytesRead = cis.read(b,0,256);

Answer 1

The reason for cis.read getting blocked is simple: The Cipher stream wraps around the socket stream (you pass the socket stream to Cipher stream constructor) hence whenever you call read on Cipher stream it will cause the code in cipher stream to read data from socket so that it can decrypt the data. This is where (read from the socket stream) the code blocks.

You should not have any problem with blocking unitll you are running this code in UI thread. You can run this code on another worker thread so that your UI doesn't freeze