show a message when updating a custom widget in wordpress backend - wordpress

Question

I'm developing a custom wordpress widget. The widget needs some data from the user and needs to check this data server-side.
I wrote the code that checks the data inside the function 'update' of the widget. When I press the button save of the widget the function update got called correctly and my validation is executed.
public function update( $new_instance, $old_instance ) {
$instance = array();
foreach ($this->fields as $field) {
$fieldName = $field['name'];
$instance[$fieldName] =
(!empty($new_instance[$fieldName]) strip_tags($new_instance[$fieldName]) : '' );
}
$check = validate($new_instance);
return $instance;
}
What I need is to display a message to the user based on the result of the validation. How can I do this? For what I've seen the function update is called through ajax so I can't use an admin notice.
Is it possible?How can I do that?

Answer 1

Try below code
add_action('admin_notices', 'misha_custom_order_status_notices');
function misha_custom_order_status_notices() {
global $pagenow, $typenow;
if( get_transient( 'fx-admin-notice-panel' )){
echo "<div class=\"updated\"><p>Custom notification comes here</p></div>";
}
}
public function update( $new_instance, $old_instance ) {
$instance = array();
foreach ($this->fields as $field) {
$fieldName = $field['name'];
$instance[$fieldName] =
(!empty($new_instance[$fieldName])?
strip_tags($new_instance[$fieldName]) :
''
);
}
$check = validate($new_instance);
set_transient( 'fx-admin-notice-panel', true, 5 );
return $instance;
}