QML based app crashing with drag/drop

JeremyRoberts2

Hello.  We are seeing an issue with a QML based app crashing.  When we allow for dragging and dropping of a feature, if you drag the feature around long enough, eventually the app completely crashes.  We are using runtimes 100.5.  This happens on both Mac and Win PCs.  We are using the basic ArcGIS template when creating a new application and slightly modifying it to allow for drag and drop.  Please see the attached project.  Any suggestions as to why this is happening?  It takes me about 50 seconds of dragging to get it to crash but our other developers have it happen much sooner.

DragDropCrash.zip

IMG_2109.JPG

LucasDanzinger

Hi Jeremy-

I think I know what is going on here. Can you try switching out your onIdentifyLayerStatusChanged signal handler to this and see if it works?

onIdentifyLayerStatusChanged<SPAN class="punctuation token">:</SPAN> <SPAN class="punctuation token">{</SPAN>
    <SPAN class="keyword token">if</SPAN> <SPAN class="punctuation token">(</SPAN>identifyLayerStatus <SPAN class="operator token">===</SPAN> Enums<SPAN class="punctuation token">.</SPAN>TaskStatusCompleted<SPAN class="punctuation token">)</SPAN> <SPAN class="punctuation token">{</SPAN>
        featureLayer<SPAN class="punctuation token">.</SPAN><SPAN class="token function">clearSelection</SPAN><SPAN class="punctuation token">(</SPAN><SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">;</SPAN>

        <SPAN class="keyword token">for</SPAN> <SPAN class="punctuation token">(</SPAN><SPAN class="keyword token">var</SPAN> i <SPAN class="operator token">=</SPAN> <SPAN class="number token">0</SPAN><SPAN class="punctuation token">;</SPAN> i <SPAN class="operator token"><</SPAN> identifyLayerResult<SPAN class="punctuation token">.</SPAN>geoElements<SPAN class="punctuation token">.</SPAN>length<SPAN class="punctuation token">;</SPAN> i<SPAN class="operator token">++</SPAN><SPAN class="punctuation token">)</SPAN> <SPAN class="punctuation token">{</SPAN>
            selectedFeatures<SPAN class="punctuation token">.</SPAN><SPAN class="token function">push</SPAN><SPAN class="punctuation token">(</SPAN>identifyLayerResult<SPAN class="punctuation token">.</SPAN>geoElements<SPAN class="punctuation token">[</SPAN>i<SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">;</SPAN>
        <SPAN class="punctuation token">}</SPAN>
        
        featureLayer<SPAN class="punctuation token">.</SPAN><SPAN class="token function">selectFeatures</SPAN><SPAN class="punctuation token">(</SPAN>selectedFeatures<SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">;</SPAN>
    <SPAN class="punctuation token">}</SPAN>
<SPAN class="punctuation token">}</SPAN><SPAN class="line-numbers-rows"><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN></SPAN>

I think your direct assigning of `selectedFeatures = identifyLayerResult.geoElements;` is the problem. This is now assigning selectedFeatures to the list of GeoElements, but nothing is specifically holding on a reference to the GeoElements in that list, so they go out of scope and get garbage collected after a random amount of time. On Windows, for me it was between 15-20 seconds. Whenever things randomly stop working, garbage collection is a likely culprit. I ran the below code to force garbage collection, and reliably, the selectedfeatures.length is 0.

onMousePositionChanged<SPAN class="punctuation token">:</SPAN> <SPAN class="punctuation token">{</SPAN>
   <SPAN class="keyword token">if</SPAN> <SPAN class="punctuation token">(</SPAN>selectedFeatures<SPAN class="punctuation token">.</SPAN>length <SPAN class="operator token">></SPAN> <SPAN class="number token">0</SPAN><SPAN class="punctuation token">)</SPAN> <SPAN class="punctuation token">{</SPAN>
       mouse<SPAN class="punctuation token">.</SPAN>accepted <SPAN class="operator token">=</SPAN> <SPAN class="keyword token">true</SPAN><SPAN class="punctuation token">;</SPAN>
       <SPAN class="comment token">// force garbage collection</SPAN>
       <SPAN class="token function">gc</SPAN><SPAN class="punctuation token">(</SPAN><SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">;</SPAN>
       <SPAN class="keyword token">for</SPAN> <SPAN class="punctuation token">(</SPAN><SPAN class="keyword token">var</SPAN> i <SPAN class="operator token">=</SPAN> <SPAN class="number token">0</SPAN><SPAN class="punctuation token">;</SPAN> i <SPAN class="operator token"><</SPAN> selectedFeatures<SPAN class="punctuation token">.</SPAN>length<SPAN class="punctuation token">;</SPAN> i<SPAN class="operator token">++</SPAN><SPAN class="punctuation token">)</SPAN> <SPAN class="punctuation token">{</SPAN>
           selectedFeatures<SPAN class="punctuation token">[</SPAN>i<SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">.</SPAN>geometry <SPAN class="operator token">=</SPAN> mouse<SPAN class="punctuation token">.</SPAN>mapPoint<SPAN class="punctuation token">;</SPAN>
       <SPAN class="punctuation token">}</SPAN>
       <SPAN class="keyword token">if</SPAN> <SPAN class="punctuation token">(</SPAN>featureLayer<SPAN class="punctuation token">.</SPAN>featureTable<SPAN class="punctuation token">.</SPAN>updateFeaturesStatus <SPAN class="operator token">!==</SPAN> Enums<SPAN class="punctuation token">.</SPAN>TaskStatusInProgress<SPAN class="punctuation token">)</SPAN> <SPAN class="punctuation token">{</SPAN>
           featureLayer<SPAN class="punctuation token">.</SPAN>featureTable<SPAN class="punctuation token">.</SPAN><SPAN class="token function">updateFeatures</SPAN><SPAN class="punctuation token">(</SPAN>selectedFeatures<SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">;</SPAN>
       <SPAN class="punctuation token">}</SPAN>
   <SPAN class="punctuation token">}</SPAN> <SPAN class="keyword token">else</SPAN> <SPAN class="punctuation token">{</SPAN>
       <SPAN class="comment token">// this prints out right away</SPAN>
       console<SPAN class="punctuation token">.</SPAN><SPAN class="token function">log</SPAN><SPAN class="punctuation token">(</SPAN><SPAN class="string token">"no features in selectedFeatures list"</SPAN><SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">;</SPAN>
       mouse<SPAN class="punctuation token">.</SPAN>accepted <SPAN class="operator token">=</SPAN> <SPAN class="keyword token">false</SPAN><SPAN class="punctuation token">;</SPAN>
   <SPAN class="punctuation token">}</SPAN>
<SPAN class="punctuation token">}</SPAN>‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍<SPAN class="line-numbers-rows"><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN></SPAN>

If you can confirm that this matches with your findings, then please proceed with changing your code to directly store references to the Feature(s) you want. One way to do that is how I have it in the first snippet.