Moodle development error in new plugin module with file manager - plugins

Question

Please if you can help me in my problem, I'm developing a new module in Moodle (v. 2.4) (mod_problem), as part of my master thesis.
In the mod_form I included a file manager element as follows:
//** file
//-------------------------------------------------------
$mform->addElement('header', 'content', get_string('problemfile', 'problem'));
$mform->addElement('filemanager', 'problemfile', get_string('files'), null, array('subdirs'=>1, 'accepted_types'=>'*'));
//-------------------------------------------------------
In the preprocessing method I added this:
function data_preprocessing(&$default_values) {
if ($this->current->instance) {
// editing existing instance - copy existing files into draft area
$draftitemid = file_get_submitted_draft_itemid('problemfile');
file_prepare_draft_area($draftitemid, $this->context->id, 'mod_problem', 'content', 0, array('subdirs'=>1, 'accepted_types'=>'*'));
$default_values['problemfile'] = $draftitemid;
}
}
Then in the lib.php file of my module I added the following:
$draftitemid = $problem->problemfile;
$problem->id = $DB->insert_record('problem', $problem);
$cmid = $problem->coursemodule;
$context = context_module::instance($cmid);
if (!empty($problem->problemfile)) {
$draftitemid = $problem->problemfile;
file_save_draft_area_files($draftitemid, $context->id, 'mod_problem', 'content', 0, array('subdirs'=>1, 'accepted_types'=>'*'));
}
I also created the (mod_problem_pluginfile()) function that include:
$fs = get_file_storage();
$filename = array_pop($args);
$filepath = $args ? '/'.implode('/', $args).'/' : '/';
if (!$file = $fs->get_file($context->id, 'mod_problem', 'content', 0, $filepath, $filename) or $file->is_directory()) {
send_file_not_found();
}
send_stored_file($file, 0, 0, true, array('preview' => $preview));
Then when I want to print the file list for students in view.php:
require_once($CFG->libdir.'/filelib.php');
require_once($CFG->dirroot.'/repository/lib.php');
$fs = get_file_storage();
$files = $fs->get_area_files($context->id, 'mod_problem', 'content', 0);
//try 2
foreach ($files as $file) {
$filename = $file->get_filename();
$url = moodle_url::make_pluginfile_url($file->get_contextid(), $file->get_component(),
$file->get_filearea(),$file->get_itemid(), $file->get_filepath(), $filename, false);
$out[] = html_writer::link($url, $filename);
}
$br = html_writer::empty_tag('br');
echo implode($br, $out);
when I view the module I got the list of files with the links but when I click in the link it gives me this error: Sorry, the requested file could not be found. It stop in the mod_problem_pluginfile() function when I read the files it is not found
This is the error I got:
//---------------------------------
Debug info:
Error code: filenotfound
Stack trace:
line 476 of \lib\setuplib.php: moodle_exception thrown
line 1977 of \lib\filelib.php: call to print_error()
line 412 of \mod\problem\lib.php: call to send_file_not_found()
line 4314 of \lib\filelib.php: call to mod_problem_pluginfile()
line 38 of \pluginfile.php: call to file_pluginfile()
//------------------------------------------
I'm not sure why it's not reading the files, even though they are stored.
Please any help with this is very appreciated as I'm running out of time in fixing such problem.

Answer 1

Seems you didn't post the full mod_problem_pluginfile() function.
if (!$file = $fs->get_file($context->id, 'mod_problem', 'content', 0, $filepath, $filename) or $file->is_directory()) {
send_file_not_found();
}
It could be your $context->id, make sure it's the same you as you called file_save_draft_area_files()