使用 openFileInput(Uri) 和多線程打開多個文件

Question

我正在嘗試使用context.getContentResolver().openInputStream(Uri)打開具有多個線程的多個文件，但似乎在讀取時，所有線程都從同一個文件中讀取。 我試過使方法synchronized但沒有奏效。 這是代碼：

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;
}

而調用這個方法的代碼是：

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;
}

這是從以下調用的：

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

        encrypted = encryptUri(file);

        result.add(encrypted);
}

打印byte[] data = byteOutputStream.toByteArray();的前 100 個byte[] data = byteOutputStream.toByteArray(); 我得到：

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-

並在其他線程上：

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-

打印：

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

使用 Base64 編碼（顯然也相同）：

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

順便說一下， ActivityTransferer.getInstance().getActivity()返回當前的上下文。

請如果你能幫助我，我將不勝感激。 謝謝！

Answer 1

修復！

這種情況下的解決方案是使方法private String getVideoData(Uri uri)靜態和同步（ private static synchronized String getVideoData(Uri uri) ）。 我認為問題在於代碼中使用的某些操作使用了靜態方法或變量。 因此，通過使方法靜態和同步，它將在開始操作之前等待其他線程完成。

在這種情況下， InputStream fis = activity.getContentResolver().openInputStream(uri); 可能是導致問題的原因。