Fire an Event Only After Another Event Has Been Fired

Question

Hello StackOverflow,

I have a GeoExt map panel with a zoom control. I'd really like to disable some of the nodes in a tree panel when the layers on my map are "out of range" aka their setVisibility is set to false. I have my zoomend event working and I also have a checkchange event working, but the checkchange event gets evaluated more than once if the user pushes the zoombar more than one level and the other problem is that even after the zoomend event is over the checkchange still gets fired every time the user merely clicks the node's checkbox on or off. I really need a way to control this checkchange event to only run once and to stop it from firing if the user is not using the zoombar...

map.events.on({ "zoomend": function (e) {

                layerTree.on("checkchange", function (node, checked) {
                    alert(node.text + "Inside event");
                    if(checked == false)
                        node.disable();
                    else if(checked == true)
                        node.enable();

                });

                    if (this.getZoom() > 7) {
                        tib_villages.setVisibility(true);
                        tib_lakes.setVisibility(true);
                        tib_townships.setVisibility(true);


                    }
                    else {

                                    tib_villages.setVisibility(false);
                                    tib_lakes.setVisibility(false);
                                    tib_townships.setVisibility(false);

                        if (this.getZoom() > 5) {
                            infrastructure.setVisibility(true);
                            geography.setVisibility(true);
                            geography2.setVisibility(true);
                            tib_countys.setVisibility(true);

                        }
                        else{
                            infrastructure.setVisibility(false);
                            geography.setVisibility(false);
                            geography2.setVisibility(false);
                            tib_countys.setVisibility(false);
                        }
                    }//end else

                }//end function (e)

            }); //end map.events.on

Thank you for all your time and feedback :)

elshae

Answer 1

It turns out that the work has already been done for us :). There is a patch at http://trac.geoext.org/attachment/ticket/235/autoDisableLayerNode.patch which will automatically disable/enable nodes based on their minScale/maxScale properties etc. I applied the patch by putting this file in my GeoExt directory and running the following command in my GeoExt directory:

patch -p0 < autoDisableLayerNode.patch

I hope this helps! It worked wonders for me :)

elshae