Skip to main content

OpenLayers - fixing "element is null" error

I've had a hard time trying to debug a problem on a Vector layer that had tooltips as well as regular popups. It worked fine but from time to time Firebug would log an error message like the following:


I'm running OpenLayers 2.8. This error messed up javascript - zooming and panning were broken, the current popup would remain un-close-able, but other markers seemed to work just fine.

I managed to track this problem to a null element in Element.js. I'm not sure why the element is null at that point, but it may be a safe thing to do to check if the element exists before trying to change its style...

I attached a patch that should solve this (adds an if before setting the style):


--- lib/OpenLayers/BaseTypes/Element.js.original 2009-08-04 15:42:45.000000000 +0300
+++ lib/OpenLayers/BaseTypes/Element.js 2009-08-04 15:40:43.000000000 +0300
@@ -47,7 +47,9 @@
hide: function() {
for (var i=0, len=arguments.length; i<len; i++) {
var element = OpenLayers.Util.getElement(arguments[i]);
- element.style.display = 'none';
+ if(element){
+ element.style.display = 'none';
+ }
}
},

@@ -61,7 +63,9 @@
show: function() {
for (var i=0, len=arguments.length; i<len; i++) {
var element = OpenLayers.Util.getElement(arguments[i]);
- element.style.display = '';
+ if(element){
+ element.style.display = '';
+ }
}
},


Of course, after applying the patch you need to re-build OpenLayers.js for this to work

Comments

Popular posts from this blog

Home Assistant + Android TV = fun

Here's a quick setup guide for controlling your Android TV from within Home Assistant. I've used it to control a genuine Android TV (Philips 7304) and an Odroid N2 running Android TV. For this to work you need ADB access. It can usually be enabled from within Developer Settings. The great part is - you don't need root access! The most important things are described in the androidtv component for Home Assistant: https://www.home-assistant.io/integrations/androidtv/ Make sure you go through the adb setup. My configuration is simple (inside configuration.yaml): media_player:   - platform: androidtv     name: TV Bedroom ATV     host: 192.168.1.61     device_class: androidtv Once Home Assistant restarts, your TV might require you to accept the connection (adb authentication). This happens only once (or until you reset your ATV to factory settings). Once running the integration will show you the current ATV state (on or off) and allows you to turn it on or off.

SmokePing + InfluxDB export + docker + slaves + Grafana = fun

I've been working for a while on this project - with the purpose of getting SmokePing measurements from different hosts (slaves) into InfluxDB so that we can better graph them with Grafana. The slaves run multiple Smokeping instances inside Docker so that they have separate networking (measure through different uplinks, independently). This will not be a comprehensive configuration guide, but a quick "how to" to handle setup and basic troubleshooting. It assumes you already know how to set up and operate a regular Smokeping install with or without slaves and that you are fluent in Smokeping configuration syntax, know your way around Docker and aren't a stranger from InfluxDB and Grafana (sorry, there's a lot of information to take in). 1. Getting Smokeping with InfluxDB support - you can get it either from the official page (most changes have been merged) - https://github.com/oetiker/SmokePing (PR discussion here: https://github.com/oetiker/SmokePing/issues/

Installing Home Assistant Supervised on an old 32bit HP laptop

 I've received a challenge from my former boss: an old HP laptop that was born in 2005:  an HP-Compaq NC6220 ( https://www.pocket-lint.com/laptops/reviews/hp/68181-hp-compaq-nc6220-notebook-laptop/ ). The specs are abysmal: So, i386, 1.7GHz single-core CPU (remember those?), 1G of DDR2 RAM (2x512M) and a 40GB ATA (not SATA!) drive. But hey, at least it has a serial port!  The challenge is to install HomeAssistant ( https://www.home-assistant.io/ ) on it so that he can monitor some Zigbee temperature sensors and relays (via a gateway). The first hurdle was to remove the BIOS password - following this nice guide: https://www.youtube.com/watch?v=ZaGKyb0ntSg Next-up - install HASSOS. Unfortunately, it doesn't support i386, but only x86_64... So, I went the Home Assistant Supervised route, and installed Debian 11 i386 edition from a netinstall USB ( https://cdimage.debian.org/debian-cd/current/i386/iso-cd/debian-11.6.0-i386-netinst.iso ).   Once Debian was up and running (didn't