copy file from /root/storage/emulated/0 fails on android

Question

I am trying to copy files from a location on the device to the app folder, and using:

public static void copyFile(final String srcAbsolutePath, final String dstAbsolutePath) throws IOException {
        FileInputStream srcFileStream = null;
        FileOutputStream dstFileStream = null;
        try {
            srcFileStream = new FileInputStream(srcAbsolutePath);
            dstFileStream = new FileOutputStream(dstAbsolutePath);
            byte[] writeBytes = new byte[1024];

            int bytesCount;
            while ((bytesCount = srcFileStream.read(writeBytes)) > 0) {
                dstFileStream.write(writeBytes, 0, bytesCount);
            }
        } catch (IOException ex) {
            Log.e(TAG, "Failed to copy the file from src="+srcAbsolutePath+" to="+dstAbsolutePath, ex);
            throw ex;
        } finally {
            // close the streams
            if (srcFileStream != null) {
                srcFileStream.close();
            }

            if (dstFileStream != null) {
                dstFileStream.close();
            }
        }
    }

and I am running into this error:

Failed to copy the file from src=/root/storage/emulated/0/TestApp/1a5e67e1-c166-4a52-abb4-3de61898e109.pdf to=/data/user/0/com.myapp.package/files/78e6a56b-3141-4024-a3a1-f3f44ccc6dfb.pdf
                                                                      java.io.FileNotFoundException: /root/storage/emulated/0/TestApp/1a5e67e1-c166-4a52-abb4-3de61898e109.pdf (Permission denied)

I have the following permissions:

<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

I am using https://github.com/spacecowboy/NoNonsense-FilePicker to pick the file (Uri).

I have the following in AndroidManifest.xml

    <provider
        android:name="android.support.v4.content.FileProvider"
        android:authorities="${applicationId}.provider"
        android:exported="false"
        android:grantUriPermissions="true">
        <meta-data
            android:name="android.support.FILE_PROVIDER_PATHS"
            android:resource="@xml/nnf_provider_paths" />
    </provider>

How to fix the error?

Answer 1

Finally found an utility in NoNonsense-FilePicker (getFileForUri):

https://github.com/spacecowboy/NoNonsense-FilePicker/blob/master/library/src/main/java/com/nononsenseapps/filepicker/Utils.java