Can READ_EXTERNAL_STORAGE block pdfs from being displayed in an Android Studio app?

First of all, never use the file API for fetching the media from device storage except you have a special requirement. It’s slow as hell when you have so many files stored on the device and memory consumption is a thing to consider when making an app.

Here, you can read all the media files using Mediastore API which is memory efficient and provides many customizations while loading media files.

So, all you have to do is get the storage permission and then load PDFs using mediastore like this,

Load all PDFs from device storage including SD card :

public ArrayList<MediaModel> getAllPDFFromStorage(Context ctx) {
        ArrayList<MediaModel> pdfList = new ArrayList<>();

        String[] projection = {
                MediaStore.Files.FileColumns._ID,
                MediaStore.Files.FileColumns.DISPLAY_NAME,
                MediaStore.Files.FileColumns.DATA,
                MediaStore.Files.FileColumns.DISPLAY_NAME,
                MediaStore.Files.FileColumns.DATE_MODIFIED,
                MediaStore.Files.FileColumns.MIME_TYPE,
                MediaStore.Files.FileColumns.SIZE
        };

        String sortOrder = MediaStore.Files.FileColumns.DATE_MODIFIED + " DESC";

        String selection = MediaStore.Files.FileColumns.MIME_TYPE + " = ?";

        String mimeTypePdf = MimeTypeMap.getSingleton().getMimeTypeFromExtension("pdf");
        String[] selectionArgs = {mimeTypePdf};

        Uri collection;
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q) {
            collection = MediaStore.Files.getContentUri(MediaStore.VOLUME_EXTERNAL);
        } else {
            collection = MediaStore.Files.getContentUri("external");
        }

        Cursor cursor = ctx.getContentResolver().query(collection, projection, selection, selectionArgs, sortOrder);
        if (cursor != null && cursor.moveToFirst()) {

            do {
                long id = cursor.getLong(cursor.getColumnIndexOrThrow(MediaStore.Files.FileColumns._ID));
                String path = cursor.getString(cursor.getColumnIndexOrThrow(MediaStore.Files.FileColumns.DATA));
                String dirName = "";
                String parent = new File(path).getParent();
                if (!parent.isEmpty()) {
                    dirName = new File(parent.toString()).getName();
                }
                String name = cursor.getString(cursor.getColumnIndexOrThrow(MediaStore.Files.FileColumns.DISPLAY_NAME));
                long date = cursor.getLong(cursor.getColumnIndexOrThrow(MediaStore.Files.FileColumns.DATE_MODIFIED));
                String size = cursor.getString(cursor.getColumnIndexOrThrow(MediaStore.Files.FileColumns.SIZE));
                Uri contentUri;
                if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q) {
                    contentUri = ContentUris.withAppendedId(
                            MediaStore.Files.getContentUri(MediaStore.VOLUME_EXTERNAL), id
                    );
                } else {
                    contentUri = ContentUris.withAppendedId(
                            MediaStore.Files.getContentUri("external"), id
                    );
                }

                if (size != null && new File(path).exists()) {
                    MediaModel mediaModel = new MediaModel();
                    mediaModel.setFileName(name);
                    mediaModel.setFilePath(path);
                    mediaModel.setUri(contentUri);
                    mediaModel.setDateAdded(date);
                    mediaModel.setFileSize(Long.parseLong(size));
                    mediaModel.setDirName(dirName);
                    pdfList.add(mediaModel);
                }
            } while (cursor.moveToNext());

            cursor.close();
        }

        return pdfList;
    }

Here is the MediaModel model class for better access of file details:

class MediaModel {
    String fileName;
    String filePath;
    Uri uri;
    long dateAdded;
    long fileSize;
    String dirName;

    public String getFileName() {
        return fileName;
    }

    public void setFileName(String fileName) {
        this.fileName = fileName;
    }

    public String getFilePath() {
        return filePath;
    }

    public void setFilePath(String filePath) {
        this.filePath = filePath;
    }

    public Uri getUri() {
        return uri;
    }

    public void setUri(Uri uri) {
        this.uri = uri;
    }

    public long getDateAdded() {
        return dateAdded;
    }

    public void setDateAdded(long dateAdded) {
        this.dateAdded = dateAdded;
    }

    public long getFileSize() {
        return fileSize;
    }

    public void setFileSize(long fileSize) {
        this.fileSize = fileSize;
    }

    public String getDirName() {
        return dirName;
    }

    public void setDirName(String dirName) {
        this.dirName = dirName;
    }
}

Check your permission code and try this method and you’ll get it.

And yes, make sure you load the PDFs on background thread for better performance and populate the recyclerview on main thread.