Decode a JSON geometry

Question

Hi,

I'm looking for a way to store the Graphics of the DrawWidget in a database and load them in a next session.

I thing that I need to save the geometry and the symbol for each Graphic, and probably the best way is use JSON.encode and JSON.decode
http://help.arcgis.com/en/webapi/flex/apiref/com/esri/ags/utils/JSON.html

I can transform a geometry to JSON and the JSON string to a Object type but, How can I create a Geometry type from JSON string? I'm sure that there is something in the API (probably geometryService wrapper use that) but I can't find it.

And if you know how to create a Symbol (SimpleMarkerSymbol, SimpleLineSymbol....) or a Graphic from JSON using API or if you have a code snippet it could be very useful for me 🙂 Any help is welcome.

Thank you in advance.

Regards
Esther

PaulHastings1 · Answer

if fidelity is important maybe ByteArray?

in the app init, register the ESRI classes you're using, eg:

registerClassAlias("com.esri.ags.Graphic", Graphic);
registerClassAlias("com.esri.ags.SpatialReference", SpatialReference);
registerClassAlias("com.esri.ags.geometry.MapPoint", MapPoint);
registerClassAlias("com.esri.ags.geometry.Extent", Extent);
registerClassAlias("com.esri.ags.symbols.SimpleFillSymbol",SimpleFillSymbol);

then to serialize, for example:
protected function addBM(event:MouseEvent):void {    
 var thisBookmark:Object={};    
 var bookmark:ByteArray = new ByteArray();
 thisBookmark.extent=theMap.extent;
        // gets array of redline graphics in current map extent
 thisBookmark.redlines=redlineInExtent();
 bookmark.writeObject(thisBookmark);
        // send back to coldfusion for storage
 psService.addBM(userID,bookmarksWindow.bmName.text,
          bookmarksWindow.shareBM.selected,new Date().getTime(),bookmarkl);
}
 
ByteArray readObject() will deserialize this back to the original data, symbolization & all.

IvanBespalov · Answer

Hi. Reading reference: fromJSON () method public static function fromJSON(json:String):FeatureSet Convert from JSON to FeatureSet. Parameters json:String â?? ArcGIS JSON String Returns FeatureSet â?? a new FeatureSet See also Input JSON should match this REST response syntax Try this: 0) { var fsToExport:FeatureSet = new FeatureSet(arrGraphics.toArray()); fsToExport.geometryType = Geometry.MAPPOINT; if (fsToExport != null) { jsonFeatureSet = fsToExport.toJSON(); trace(jsonFeatureSet); } } } /** * Listen import button click handler */ protected function btnImportClick(event:MouseEvent):void { if (jsonFeatureSet != null && jsonFeatureSet.length > 0) { var fsImported:FeatureSet = FeatureSet.fromJSON(jsonFeatureSet); if (fsImported != null) { var arrImported:Array = fsImported.features as Array; myGraphicsLayer.graphicProvider = arrImported; } } } /** * Listen clear all button click handler */ protected function btnClearClick(event:MouseEvent):void { myGraphicsLayer.clear(); } ]]> In this sample: 1 - Add graphics clicking on Map 2 - Click export to JSON button 3 - Click clear graphics button 4 - Click import fromJSON button Symbols 😞 The 1 of the ways, to hold information about symbols = save it in one of the attributes in your graphic object. Parse this attribute when "FeatureSet.fromJSON" complete (create own classes, methods). Create symbol based on parsed data on fly. Good luck.

EstherColero · Answer

Thank you Ivan,

I have try this previuosly, but when I rebuild the FeatureSet there are all Graphics but there is not any geometry or symbol (all them are null)
var pFeatureSet:FeatureSet = null;
var pFeatureSet2:FeatureSet = null;
var arrGraphics:Array = new Array();
var pGraphic:Graphic;

//Store all Graphics in an Array
for (var i:int = 0; i < graphicsLayer.numGraphics; i++)
{
    pGraphic = Graphic(graphicsLayer.getChildAt(i));
    arrGraphics.push(pGraphic);
}

//Create FeatureSet
pFeatureSet = new FeatureSet(arrGraphics);

//to JSON
var strJSON:String = pFeatureSet.toJSON();

//toFeatureSet
pFeatureSet2 = FeatureSet.fromJSON(strJSON); //All graphics, but no geometries or symbols

//Now with your example
strJSON = '{"features" : [{"geometry" : {"x" : -178.24479999999991,"y" : 50.012500000000045},"attributes" : {"objectid" : 3745682,"datetime" : 1272210710000,"depth" : 31.100000000000001,"eqid" : "2010vma5","latitude" : 50.012500000000003,"longitude" : -178.2448,"magnitude" : 4.7999999999999998,"numstations" : 112,"region" : "Andreanof Islands, Aleutian Islands, Alaska","source" : "us","version" : "Q"}},{"geometry" : {"x" : -72.865099999999927,"y" : -37.486599999999953},"attributes" : {"objectid" : 3745685,"datetime" : 1272210142999,"depth" : 40.600000000000001,"eqid" : "2010vma4","latitude" : -37.486600000000003,"longitude" : -72.865099999999998,"magnitude" : 4.9000000000000004,"numstations" : 58,"region" : "Bio-Bio, Chile","source" : "us","version" : "7"}}] }';
pFeatureSet2 = FeatureSet.fromJSON(strJSON); //All graphics, but no geometries or symbols

I am using Flex viewer 2.4. does it work for you?

Regards
Esther