CODEWITHSUNDEEP
javaandroidandroid-studio
Mukesh Kumar
Mukesh Kumar

Reputation: 133

Premission denied when write file in Sd Card

I'm developing a video player app. It downloads some video onto an sd card using Storage Access Framework. I downloaded the video successfully but I want it to be encrypted after downloading so I'm using the code below:-

import java.io.RandomAccessFile;

public class VideoCrypt {
    public static final int REVERSE_BYTE_COUNT = 1024;

    public static boolean decrypt(String path) {
        try {
            if (path == null) return false;
            File source = new File(path);
            int byteToReverse = source.length() < REVERSE_BYTE_COUNT ? ((int) source.length()) : REVERSE_BYTE_COUNT;
            RandomAccessFile f = new RandomAccessFile(source, "rw");
            f.seek(0);
            byte b[] = new byte[byteToReverse];
            f.read(b);
            f.seek(0);
            reverseBytes(b);
            f.write(b);
            f.seek(0);
            b = new byte[byteToReverse];
            f.read(b);
            f.close();
            return true;
        } catch (Exception e) {
            return false;
        }
    }

    public static boolean encrypt(String path) {
        try {
            if (path == null) return false;
            File source = new File(path);
            RandomAccessFile f = new RandomAccessFile(source, "rw");
            f.seek(0);
            int byteToReverse = source.length() < REVERSE_BYTE_COUNT ? ((int) source.length()) : REVERSE_BYTE_COUNT;
            byte b[] = new byte[byteToReverse];
            f.read(b);
            f.seek(0);
            reverseBytes(b);
            f.write(b);
            f.seek(0);
            b = new byte[byteToReverse];
            f.read(b);
            f.close();
            return true;
        } catch (Exception e) {
            return false;
        }
    }

    private static void reverseBytes(byte[] array) {
        if (array == null) return;
        int i = 0;
        int j = array.length - 1;
        byte tmp;
        while (j > i) {
            tmp = array[j];
            array[j] = array[i];
            array[i] = tmp;
            j--;
            i++;
        }
    }

Code is working fine with internal storage but in the case of theSD Card I'm getting this permission error:

ava.io.FileNotFoundException: /storage/0C69-1809/Android/tersjwafuh/ALongWa Down.@7&259: open failed: EACCES (Permission denied)

Upvotes: 0

Views: 70

Answers (1)

blackapps
blackapps

Reputation: 9292

So your encryption is just reversing all bytes of the file?

For that you do not need a RandomAccessFile especially because you load all bytes (the complete file) in a bytearray.

You can as well use the saf uri to load all bytes in a byte array. Then reverse them and then write the byte array back to saf uri.

What you did not tell us is that you converted a nice saf uri to a file path. Dont do such nasty and dirty things. Not needed. Use the uri!

A removable micro sd card is read only with classic file means since Android 4 KitKat.

Only with SAF you have write access. (Well not completely true.. on an Android 11 device you have classic file write access if you obtain 'all files access'.)

Upvotes: 1

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