I'm using Qt6.5.2 with ArcGIS Maps SDK for Qt 200.2.0 with an offline application that displays 2D maps.
Two basemaps (one .tpk and one .vtpk) plus operational layers (tpk's) are being loaded and can be made visible/not visible as required with no issues at all.
I want to be able to unload and delete individual base maps or operational layers so that the offline file associated can be deleted (and possibly another file copied to the same location/name to replace it and then be loaded and displayed). The reason for this is the base map .vtpk file is over 50GB in size so I don't want unused files of that size hanging around.
The .tpk base map is loaded first and appended to the collection of base map base layers, so it will have an index of zero in the LayerListModel. The .vtpk base map is loaded second so will have an index of 1.
An illustration of the code to load the .vtpk base map within a class derived from Esri::ArcGISRuntime::MapGraphicsView is shown here:
ArcGISVectorTiledLayer* basemapLayer_p = new ArcGISVectorTiledLayer(new VectorTileCache(basemapFilename, this), this);
basemapLayer_p->setName(basemapFilename);
basemapLayer_p->setMaxScale(MapScaleFromZoomLevel(MaximumZoomLevel));
basemapLayer_p->setMinScale(MapScaleFromZoomLevel(MinimumZoomLevel));
connect(basemapLayer_p, &Layer::doneLoading, this, &MyMapView::layerFinishedLoading, Qt::QueuedConnection);
basemapLayer_p->load();
basemapLayer_p->setVisible(true);
map()->basemap()->baseLayers()->append(basemapLayer_p);
Code for the .tpk base map and operational layers are similar (but using different ArcGIS classes for the TiledLayer and TilesCache). All works fine and the application is notified when the loading of each of the layers is completed.
Later when the user selects a file to use in place of an existing base map or operational layer, everything seems to work OK for the .tpk base map and operational layers but there is a problem with the .vtpk base map.
An illustration of the code to remove and delete the layer (and cache) and then the disk file is shown below:
ArcGISVectorTiledLayer* basemapLayerToDelete_p = map()->basemap()->baseLayers()->at(1);
map()->basemap()->baseLayers()->removeAt(1);
VectorTileCache* cache_p = basemapLayerToDelete_p->vectorTileCache();
delete basemapLayerToDelete_p;
delete cache_p;
if (!QFile::remove(basemapFilename))
{
// remove fails and other investigations shows it is a
// "The process cannot access the file because it is being used by another process"
// type of error situation
}
As indicated by the comment towards the end of the code fragment, the operation to remove the file fails and when using std C++ rather than Qt methods to try and remove it the error information available indicated that the file was still being used.
Initially, I tried just removing and deleting the base map layer but thinking that the VectorTileCache might not be being deleted by the ArcGISVectorTiledLayer I am now getting the pointer for the cache and deleting that too - with no different result.
I cannot see the internals of the ArcGIS Maps SDK for Qt so I do not know when/what opens the .vtpk file and when it is closed. I don't see any methods/signals related to unloading a layer of any type.
I've looked for other inspiration on how to fix this and the closest thing I found was a post in the .NET area from over 4 years ago (https://community.esri.com/t5/net-maps-sdk-questions/can-t-delete-vtpk-file-after-loading/m-p/195154...) but that did not have anyone reporting a successful fix.
Am I missing something? I would be grateful if someone is able to advise how to make a (large) .vtpk file close and know when it has been closed so the physical file can be deleted from the disk.
