使用 openFileInput(Uri) 和多线程打开多个文件

Question

I'm trying to open multiple files with multiple threads using context.getContentResolver().openInputStream(Uri) but it seems that when reading, all the threads read from the same file. I've tried making the method synchronized but did not work. Here is the code:

private String getVideoData(Uri uri) {
        String res = null;
        MyActivity activity = ActivityTransferer.getInstance().getActivity();

        try { 
            InputStream fis = activity.getContentResolver().openInputStream(uri);

            if (fis != null) {
                ByteArrayOutputStream byteOutputStream = new ByteArrayOutputStream();

                byte[] bytes = new byte[4096];

                int read = fis.read(bytes);

                while (read != -1) {
                    byteOutputStream.write(bytes);
                    read = fis.read(bytes);
                }

                byte[] data = byteOutputStream.toByteArray();

                res = java.util.Base64.getEncoder().encodeToString(data);

                fis.close();
                byteOutputStream.close();
            }
        } catch (Exception e) {
            e.printStackTrace();
        }

        return res;
}

And the code that calls this method is:

private EncryptedFile encryptUri(Uri uri) {
        EncryptedFile res = null;
        MyActivity activity = ActivityTransferer.getInstance().getActivity();

        String type = activity.getContentResolver().getType(uri);

        if (type != null) {
            String data;
            System.out.println("Path: " + uri.getPath());
            System.out.println("Type: " + type);
            if (type.startsWith("video")) {

                data = getVideoData(uri);
                res = new EncryptedVideo();
                System.out.println("Data: " + data);
                res.encrypt(data, password);

            }
            else {

                data = getImageData(uri);
                res = new EncryptedPicture();
                res.encrypt(data, password);

            }
        }

        return res;
}

which is called from:

while (!toEncrypt.isEmpty()) {
        file = toEncrypt.poll();

        encrypted = encryptUri(file);

        result.add(encrypted);
}

Printing the first 100 bytes of byte[] data = byteOutputStream.toByteArray(); I get:

I/System.out: 0-0-0-24-102-116-121-112-109-112-52-50-0-0-0-0-109-112-52-50-105-115-111-109-0-0-0-24-98-101-97-109-1-0-0-0-1-0-0-0-0-0-0-0-2-0-0-0-0-0--126-6-109-111-111-118-0-0-0-108-109-118-104-100-0-0-0-0-0-0-0-0-0-0-0-0-0-0-2-88-0-0--86-30-0-1-0-0-1-0-0-0-0-0-0-0-0-0-0-0-

and on other thread:

I/System.out: 0-0-0-24-102-116-121-112-109-112-52-50-0-0-0-0-109-112-52-50-105-115-111-109-0-0-0-24-98-101-97-109-1-0-0-0-1-0-0-0-0-0-0-0-2-0-0-0-0-0--126-6-109-111-111-118-0-0-0-108-109-118-104-100-0-0-0-0-0-0-0-0-0-0-0-0-0-0-2-88-0-0--86-30-0-1-0-0-1-0-0-0-0-0-0-0-0-0-0-0-

Printing with:

for (int i = 0; i < 100; i++)
    System.out.print(data[i] + "-");

with Base64 encoding (also same o both obviously):

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

By the way, ActivityTransferer.getInstance().getActivity() returns the current Context.

Please if you could help me I'd appreciate it a lot. Thank you!

Answer 1

Fixed it!

The solution in this case is to make the method private String getVideoData(Uri uri) static and synchronized ( private static synchronized String getVideoData(Uri uri) ). I think the problem is that some operation used in the code is using an static method or variable. So by making the method static and synchronized it will wait for other threads to finish before starting the operation.

In this case, InputStream fis = activity.getContentResolver().openInputStream(uri); is probably what is causing the problem.