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Dynamically restrict zoom?

#1

Is it possible to dynamically change the allowable zooms? I’m trying to adjust the zoom levels depending on if a particular layer is displayed. When I exceed the set zoom, the display changes to all pink, and still lets me zoom in further.

Is there something I need to do on the client side to enable this? I’ve attached a sample project so you can see what I’m trying to do. Click on Show U.S. States then zoom in twice to get the pink display.ZoomBug.zip (1.8 MB)

#2

Hi Jay,

Thanks for your sample.

Your code have some problem.

If you want to make this layer disappear for zoomlevel 6, please just set the style like this:

ShapeFileFeatureLayer worldLayer = new ShapeFileFeatureLayer(Server.MapPath("~/App_Data/USStates.shp"));
            worldLayer.ZoomLevelSet.ZoomLevel01.DefaultAreaStyle = AreaStyles.State1;                
            worldLayer.ZoomLevelSet.ZoomLevel01.ApplyUntilZoomLevel = ApplyUntilZoomLevel.Level05;

Which only make this layer visible between level 1 to 5.

The code as below shows how to make the layer render for different zoomlevel:

ShapeFileFeatureLayer worldLayer = new ShapeFileFeatureLayer(Server.MapPath("~/App_Data/USStates.shp"));
            worldLayer.ZoomLevelSet.ZoomLevel01.DefaultAreaStyle = AreaStyles.State1;
            worldLayer.ZoomLevelSet.ZoomLevel01.ApplyUntilZoomLevel = ApplyUntilZoomLevel.Level05;

            // We don't set style for 6 and 7, only show level 8

            worldLayer.ZoomLevelSet.ZoomLevel08.DefaultAreaStyle = AreaStyles.State1;

            // Ignore 9 and render 10 to 20

            worldLayer.ZoomLevelSet.ZoomLevel10.DefaultAreaStyle = AreaStyles.Grass1;
            worldLayer.ZoomLevelSet.ZoomLevel10.ApplyUntilZoomLevel = ApplyUntilZoomLevel.Level20;

If you want to control this totally in client side, please find the target overlay in JavaScript, and directly make it hide by the OpenLayer’s API.

Wish that’s helpful.

Regards,

Don

#3

Hi Don, thanks for the reply. It’s not that I want the layer to disappear for zoom level 6, it’s that I’d like it to not zoom past zoom level 6. For instance, if I change the Index() method to be

    public ActionResult Index()
    {
        Map map1 = new Map("Map1", 600, 500);
        map1.MapBackground = new BackgroundLayer(new GeoSolidBrush(GeoColor.FromHtml("#E5E3DF")));
        map1.CurrentExtent = new RectangleShape(-138, 48, -55, 28);
        map1.MapUnit = GeographyUnit.DecimalDegree;

        WorldMapKitWmsWebOverlay worldMapKitOverlay = new WorldMapKitWmsWebOverlay();
        map1.CustomOverlays.Add(worldMapKitOverlay);

        LayerOverlay overlay = new LayerOverlay("ShapeOverlay", false, TileType.MultipleTile);
        map1.CustomOverlays.Add(overlay);

        ShapeFileFeatureLayer worldLayer = new ShapeFileFeatureLayer(Server.MapPath("~/App_Data/USStates.shp"));
        worldLayer.ZoomLevelSet.ZoomLevel01.DefaultAreaStyle = AreaStyles.State1;
        worldLayer.ZoomLevelSet.ZoomLevel01.ApplyUntilZoomLevel = ApplyUntilZoomLevel.Level05;
        worldLayer.ZoomLevelSet.ZoomLevel06.Scale = 0;
        worldLayer.ZoomLevelSet.ZoomLevel06.ApplyUntilZoomLevel = ApplyUntilZoomLevel.Level20;

        overlay.Layers.Add(worldLayer);

        map1.ZoomLevelSet = worldLayer.ZoomLevelSet;

        return View(map1);
    }

then the states display initially, the pan zoom bar shrinks, and I can’t zoom past level 6. Is there a way to do this same thing dynamically?

Change Map Extent with CallBack
#4

Hi Jay,

Please try following code:
Client:

function UpdateDynamicOverlay(layerName) {
    Map1.ajaxCallAction("Home", "UpdateOverlay", { layer: layerName }, function (result) {
        Map1.baseLayer.numZoomLevels = (layerName == 'US' ? 5 : 20);

        var zoom = Map1.getZoom();
        if (Map1.getZoom() > Map1.baseLayer.numZoomLevels) {
            zoom = Map1.baseLayer.numZoomLevels - 1;
        }
        Map1.zoomTo(zoom);
        // Refresh overlay after callback
        Map1.redrawLayer("ShapeOverlay");
        
     
    })
}

Server:

[MapActionFilter]
    public void UpdateOverlay(Map map, GeoCollection<object> args)
    {

        var layerName = args["layer"].ToString();

        LayerOverlay overlay = map.CustomOverlays["ShapeOverlay"] as LayerOverlay;
        overlay.Layers.Clear();
        if (layerName.ToLowerInvariant() == "us")
        {
            // States layer
            ShapeFileFeatureLayer worldLayer = new ShapeFileFeatureLayer(Server.MapPath("~/App_Data/USStates.shp"));
            worldLayer.ZoomLevelSet.ZoomLevel01.DefaultAreaStyle = AreaStyles.State1;
            // worldLayer.ZoomLevelSet.ZoomLevel01.ApplyUntilZoomLevel = ApplyUntilZoomLevel.Level20;
            worldLayer.ZoomLevelSet.ZoomLevel01.ApplyUntilZoomLevel = ApplyUntilZoomLevel.Level05;
           // worldLayer.ZoomLevelSet.ZoomLevel06.Scale = 0;
            //worldLayer.ZoomLevelSet.ZoomLevel06.ApplyUntilZoomLevel = ApplyUntilZoomLevel.Level20;

            overlay.Layers.Add(worldLayer);

            map.ZoomLevelSet = worldLayer.ZoomLevelSet;
        }
        else
        {
            // Cities layer
            ShapeFileFeatureLayer countyLayer = new ShapeFileFeatureLayer(Server.MapPath("~/App_Data/cities_a.shp"));
            countyLayer.ZoomLevelSet.ZoomLevel01.DefaultPointStyle = PointStyles.Capital3;
            countyLayer.ZoomLevelSet.ZoomLevel01.DefaultTextStyle = TextStyles.Capital3("AREANAME");
            countyLayer.ZoomLevelSet.ZoomLevel01.ApplyUntilZoomLevel = ApplyUntilZoomLevel.Level20;

            overlay.Layers.Add(countyLayer);

            map.ZoomLevelSet = countyLayer.ZoomLevelSet;

        }
    }

Thanks,
Peter

#5

Thanks, Peter. That’s just what I needed. I tweaked the client side slightly to adjust the slider position and redraw it:

function UpdateDynamicOverlay(layerName) {
    Map1.ajaxCallAction("Home", "UpdateOverlay", { layer: layerName }, function (result) {
        Map1.baseLayer.numZoomLevels = (layerName == 'US' ? 5 : 20);

        var zoom = Map1.getZoom();
        if (Map1.getZoom() > Map1.baseLayer.numZoomLevels) {
            zoom = Map1.baseLayer.numZoomLevels - 1;
        }
        Map1.zoomTo(zoom);

        var zoomBar = Map1.getMapTools().panZoomBar;
        zoomBar.moveZoomBar();
        zoomBar.redraw();

        // Refresh overlay after callback
        Map1.redrawLayer("ShapeOverlay");
    })
}
#6

Hi Jay,

I am glad to hear that’s helpful.

Any question please let us know.

Regards,

Don