topic Re: Invalid viewpoint value in onViewpointChanged event in Qt Maps SDK Questions

Invalid viewpoint value in onViewpointChanged event

Anonymous User — Fri, 01 Sep 2023 12:28:34 GMT

Hi,

My application MapView catches onViewpointChanged event and makes some calculations. Simplified code looks like below:

MapView { id: mapView onViewpointChanged: { updateSomeInfo() } function updateSomeInfo() { if(typeof mapView.currentViewpointCenter === "undefined" || mapView.currentViewpointCenter == null) { return } if(!mapView.currentViewpointCenter) { return } // error here var centerPoint = mapView.currentViewpointCenter.center } }

Application sometimes returns error on line #17: TypeError: Cannot read property 'center' of null

I don't know how I need to check availability of mapView.currentViewpointCenter property value and don't get error. It looks like that mapView.currentViewpointCenter content changes in my event processing time.

Can someone help me?

Re: Invalid viewpoint value in onViewpointChanged event

JamesBallard1 — Fri, 01 Sep 2023 23:47:26 GMT

Hi @Anonymous User. I gave your code a spin on macOS with Qt 5.15.2 using our 100.15.0 release. It looks ok for me. I modified one of our out-of-the-box templates with your code and it prints fine. Are there any additional details you can share so we can help troubleshoot?

Here's what I tried. I also applied an API key locally for testing.

import QtQuick 2.12 import QtQuick.Controls 2.12 import Esri.ArcGISRuntime 100.15 ApplicationWindow { id: appWindow width: 800 height: 600 title: "Untitled445" MapView { id: mapView anchors.fill: parent focus: true onViewpointChanged: { updateSomeInfo() } function updateSomeInfo() { if (!mapView.currentViewpointCenter) { console.log("it's null"); return; } var centerPoint = mapView.currentViewpointCenter.center; console.log(JSON.stringify(centerPoint.json)); } Map { initBasemapStyle: Enums.BasemapStyleArcGISStreets } } }

As soon as it starts and I begin interacting the map, I see the logging:

Initializing application
Esri.ArcGISRuntime.Plugin: virtual void ArcGISRuntimePlugin::registerTypes(const char *) Esri.ArcGISRuntime
Esri.ArcGISRuntime.Plugin: static void QmlUtils::registerTypes(const char *) Esri.ArcGISRuntime
qml: {"spatialReference":{"latestWkid":3857,"wkid":102100},"x":0,"y":0}
qml: {"spatialReference":{"latestWkid":3857,"wkid":102100},"x":0,"y":0}
qml: {"spatialReference":{"latestWkid":3857,"wkid":102100},"x":-1740.0984933674335,"y":509.2080693356693}
qml: {"spatialReference":{"latestWkid":3857,"wkid":102100},"x":-697460.4504242502,"y":204099.07298399135}
qml: {"spatialReference":{"latestWkid":3857,"wkid":102100},"x":-701574.0835914724,"y":205318.75499369204}
qml: {"spatialReference":{"latestWkid":3857,"wkid":102100},"x":-704368.3717440777,"y":206153.8160307184}
qml: {"spatialReference":{"latestWkid":3857,"wkid":102100},"x":-1326097.7183212154,"y":391954.96628710814}
qml: {"spatialReference":{"latestWkid":3857,"wkid":102100},"x":-1327220.7128490992,"y":392293.60304021835}

Re: Invalid viewpoint value in onViewpointChanged event

GKmieliauskas — Sat, 02 Sep 2023 19:12:53 GMT

I have found that error only on different Android devices. It happens very rarely. Application is used for river navigation so that event fires many times during navigation time.

I have added different types of checking for validity of mapView.currentViewpointCenter. But error still happens. In one of ArcGIS AppStudio samples I have found code where mapView.currentViewpointCenter assigns to const:

const viewpointCenter = mapView.currentViewpointCenter

Then uses assigned value in code.

I am not expert in QT but maybe it could be way to avoid error.

Re: Invalid viewpoint value in onViewpointChanged event

JamesBallard1 — Tue, 05 Sep 2023 15:40:56 GMT

I would not think that var vs const would make a difference, but as I am not able to reproduce the problem I'd suggest going with that if it works for you. I recommend reaching out to Esri support if you are still hitting problems related to specific Android devices.