Question

The basic idea is that: I’m downloading encrypted image file from internet and start decrypting it.

After it’s done I want to save it to the cache (if this is the best way to do what I need) and than load it in a lazy loading listview.

But for now I just want to test the showing image after decryption in an ImageView.

Here is the code I’m using :

package com.android.basetableview;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;
import javax.crypto.Cipher;
import javax.crypto.CipherInputStream;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;
import android.app.Activity;
import android.graphics.Bitmap;
import android.os.Bundle;
import android.os.Environment;
import android.util.Log;
import android.widget.ImageView;

public class BaseTableViewActivity extends Activity {
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);


        ImageView imgView = (ImageView) findViewById(R.id.imgView);

        Bitmap myBitmap = getBitmapFromURL("http://pu-twitter.netau.net/card1.png");
        imgView.setImageBitmap(myBitmap);
    }


    public static Bitmap getBitmapFromURL(String src) {
        Bitmap myBitmap = null;
            try {

                URL url = new URL(src);
                HttpURLConnection connection = (HttpURLConnection) url.openConnection();
                connection.setDoInput(true);
                connection.connect();

                //Decryption
                try {
                Cipher cipher = Cipher.getInstance("AES/CBC/NoPadding");
                SecretKeySpec keySpec = new SecretKeySpec("01234567890abcde".getBytes(), "AES");
                IvParameterSpec ivSpec = new IvParameterSpec("fedcba9876543210".getBytes());
                cipher.init(Cipher.DECRYPT_MODE, keySpec, ivSpec);

                InputStream input = connection.getInputStream();
                CipherInputStream cis = new CipherInputStream(input, cipher);
                FileOutputStream fos  = new FileOutputStream(
                           new File(Environment.getExternalStorageDirectory(), "card2_decrypted.jpg"));
                byte[] b = new byte[8];
                int i;

                while ((i = cis.read(b)) != -1) {
                  fos.write(b, 0, i);
                }
                fos.flush(); fos.close();
                cis.close(); input.close();


                //myBitmap = BitmapFactory.decodeStream(input);

                }
                catch(Exception e){
                    e.fillInStackTrace();
                    Log.v("ERROR","Errorchence : "+e);
                }

                return myBitmap;


            } catch (IOException e) {
                e.printStackTrace();
                return null;
            }
        }
}

As you can see, I’m saving the decrypted image in sdcard, but the images that I’m using are small and maybe the cache will be better option. So if you guys can give me some advice how can I do that and which is the best way to save the images and then show them as a content in a ImageView.

Answer 1

OK you don’t need to save the images:

    public static Bitmap getBitmapFromURL(String src) {
        Bitmap myBitmap = null;
            try {

                URL url = new URL(src);
                HttpURLConnection connection = (HttpURLConnection) url.openConnection();
                connection.setDoInput(true);
                connection.connect();

                //Decryption
                try {
                Cipher cipher = Cipher.getInstance("AES/CBC/NoPadding");
                SecretKeySpec keySpec = new SecretKeySpec("01234567890abcde".getBytes(), "AES");
                IvParameterSpec ivSpec = new IvParameterSpec("fedcba9876543210".getBytes());
                cipher.init(Cipher.DECRYPT_MODE, keySpec, ivSpec);

                InputStream input = connection.getInputStream();
                CipherInputStream cis = new CipherInputStream(input, cipher);


                myBitmap = BitmapFactory.decodeStream(cis);

                }
                catch(Exception e){
                    e.fillInStackTrace();
                    Log.v("ERROR","Errorchence : "+e);
                }

                return myBitmap;


            } catch (IOException e) {
                e.printStackTrace();
                return null;
            }
        }
}