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Exception on Draw.IsEnabled = true

egismazeika

Hi,
I have a Draw object for simple drawing on the map and a Button for enabling it:
ctrlDrawItem.IsEnabled = true;

Sometimes it works as expected but sometimes fails:

{System.NullReferenceException: Object reference not set to an instance of an object.
   at ESRI.ArcGIS.Client.LayerCanvas.PrepareAnimation()
   at ESRI.ArcGIS.Client.Map.beginZoomToExtent(Envelope targetExtent, Boolean skipAnimation)
   at ESRI.ArcGIS.Client.Map.zoomToResolution(Double resolution, MapPoint center, Boolean skipAnimation)
   at ESRI.ArcGIS.Client.Map.ZoomToResolution(Double resolution, MapPoint center)
   at ESRI.ArcGIS.Client.Map.ZoomToResolution(Double resolution)
   at ESRI.ArcGIS.Client.Map.Layers_LayersInitialized(Object sender, EventArgs args)
   at ESRI.ArcGIS.Client.LayerCollection.LayersInitializedHandler.Invoke(Object sender, EventArgs args)
   at ESRI.ArcGIS.Client.LayerCollection.calculateLevelScheme()
   at ESRI.ArcGIS.Client.LayerCollection.LayerCollection_CollectionChanged(Object sender, NotifyCollectionChangedEventArgs e)
   at System.Collections.Specialized.NotifyCollectionChangedEventHandler.Invoke(Object sender, NotifyCollectionChangedEventArgs e)
   at System.Collections.ObjectModel.ObservableCollection`1.OnCollectionChanged(NotifyCollectionChangedEventArgs e)
   at System.Collections.ObjectModel.ObservableCollection`1.InsertItem(Int32 index, T item)
   at System.Collections.ObjectModel.Collection`1.Add(T item)
   at ESRI.ArcGIS.Client.Draw.Activate()
   at ESRI.ArcGIS.Client.Draw.OnIsEnabledPropertyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
   at System.Windows.DependencyObject.RaisePropertyChangeNotifications(DependencyProperty dp, Object oldValue, Object newValue)
   at System.Windows.DependencyObject.UpdateEffectiveValue(DependencyProperty property, EffectiveValueEntry oldEntry, EffectiveValueEntry& newEntry, ValueOperation operation)
   at System.Windows.DependencyObject.SetValueInternal(DependencyProperty dp, Object value, Boolean allowReadOnlySet)
   at System.Windows.DependencyObject.SetValue(DependencyProperty dp, Object value)
   at ESRI.ArcGIS.Client.Draw.set_IsEnabled(Boolean value)
   at ViewPage.EditGeometry()
   at ViewPageXAML.cmdEditGeometry_Click(Object sender, RoutedEventArgs e)
   at System.Windows.Controls.Primitives.ButtonBase.OnClick()
   at System.Windows.Controls.Button.OnClick()
   at System.Windows.Controls.Primitives.ButtonBase.OnMouseLeftButtonUp(MouseButtonEventArgs e)
   at System.Windows.Controls.Control.OnMouseLeftButtonUp(Control ctrl, EventArgs e)
   at MS.Internal.JoltHelper.FireEvent(IntPtr unmanagedObj, IntPtr unmanagedObjArgs, Int32 argsTypeIndex, String eventName)}

Still can't find any workarounds, just restarting the app and hopping that it will work this time.

Using SL 2.0 RC. Any ideas?

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DenisT

Checked API 2.3 and 2.4, it looks like the bug still exists.

When I enable my Draw instance, the Map raises ExtentChanged event. I examined event args and noticed that the old extent and the new one are the same.
The raised event is not the problem for me. The problem is that my dynamic map layers blink.

Normally when a dynamic layer redraws, for example when you pan, the old image stay visible (with empty borders) until the new one arrives. Then the old image is replaced with the new one.
But not in this case. In this case the dynamic layer goes blank, then the web-request is made, and when response is arrived the image will appear.
Tiled layers work fine.

This happens only if Map.SnapToLevels is set to true.

I don't know why but I can't reproduce that behavior in a simple example. It looks like there are some additional conditions.

P.S. Sorry for my English.

AndyWright

Yeh sorry for the confusion there. I posted to this thread because it seemed like my issue may have been related to the original issue.

Anyway, I am currently doing the workaround you suggested. It works for the most part, but there are still some very weird things that happen from time to time that are related to this issue. I guess at this point I'll wait for version 2.2 to come out and test everything against that. Do you have any idea when that might be released or if I could get my hands on a beta version?

JenniferNery

Ahh okay. I'm sorry about misunderstanding. I guess the title of this thread no longer applies.

Anyway, I was able to repro the issue with v2.1 Final. Map ExtentChanged got fired everytime the Draw is enabled. Thank you for reporting this bug. This will be fixed in future version of the API. I'm no longer able to repro the issue with our latest source code.

Notice that when ExtentChanged is raised by enabling/disabling draw, the following is true:
e.NewExtent.Equals(e.OldExtent). For a workaround then, you can ignore cases when there is no real extent change.

AndyWright

Jennifer,

You are right there is no exception that is getting thrown. The issue here is not about errors, it's about the map extent changed event getting fired for no apparent reason. Put a breakpoint in the map extent changed event then click one of the tools in the toolbar. Why on earth would that event fire because you enabled a draw object? Now set the SnapToLevels property to false and/or remove the min/max scale thresholds. Now the map extent changed event doesn't fire when you click one of the tools in the toolbar.

Like I said in my previous post, we have issues scattered throughout our application with the map extent changed event firing for no good reason. And we're not willing to set SnapToLevels equal to false to remedy that. I'm interested to hear why this event fires when the map extent doesn't change and what possible workarounds there might be until this issue is fixed in an upcoming version of the API.

Thanks ...

JenniferNery

I am using the code you provided against assemblies from v2.1 Final. Choosing draw mode should enable/disable draw but no exception is thrown for me.

Could you be more specific with steps to reproduce?
Something like:
1. Choose Point from ToolBar.
2. Draw the point on map.
3. Choose Clear graphics from ToolBar. Exception should be thrown.

AndyWright

Sure, here you go. I'm really convinced that the SnapToLevels="true" is the real culprit here. There are cases throughout my application where map extent changed events fire for no apparent reason when that property is set to true. When I set it to false they no longer fire. I'm interested to see what you can come up with on this. It's turned into a royal pain in the arse for us.

Here's the XAML ...

<UserControl x:Class="ESRI_Test.MainPage"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" 
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" 
    xmlns:esri="http://schemas.esri.com/arcgis/client/2009">
    <Grid x:Name="LayoutRoot" Background="White">

        <Grid.Resources>
            <esri:SimpleLineSymbol x:Key="DrawLineSymbol" Color="Green" Width="4" />
            <esri:SimpleFillSymbol x:Key="DrawFillSymbol" Fill="#3300FF00" BorderBrush="Green" BorderThickness="2" />
            <esri:SimpleMarkerSymbol x:Key="DefaultMarkerSymbol" Color="Red" Size="12" Style="Circle" />
            <esri:SimpleLineSymbol x:Key="DefaultLineSymbol" Color="Red" Width="4" />
            <esri:SimpleFillSymbol x:Key="DefaultFillSymbol" Fill="#33FF0000" BorderBrush="Red" BorderThickness="2" />
        </Grid.Resources>

        <esri:Map x:Name="MyMap" Extent="-15000000,2000000,-7000000,8000000" SnapToLevels="True" MinimumResolution="0.0746126492252985" MaximumResolution="1222.99245256249">
            <esri:ArcGISTiledMapServiceLayer ID="StreetMapLayer" 
                      Url="http://services.arcgisonline.com/ArcGIS/rest/services/World_Street_Map/MapServer"/>
            <esri:GraphicsLayer ID="MyGraphicsLayer" />
        </esri:Map>

        <Canvas Width="370" Height="110" HorizontalAlignment="Right" VerticalAlignment="Top" Margin="0,15,15,0" >
            <Rectangle Stroke="Gray"  RadiusX="10" RadiusY="10" Fill="#77919191" Canvas.Left="0" 
                       Canvas.Top="0" Width="370" Height="110" >
                <Rectangle.Effect>
                    <DropShadowEffect/>
                </Rectangle.Effect>
            </Rectangle>
            <Rectangle Fill="#FFFFFFFF" Stroke="DarkGray" RadiusX="5" RadiusY="5" Canvas.Left="10" 
                       Canvas.Top="10" Width="350" Height="90"  />
            <TextBlock x:Name="ToolTile" Foreground="Black" Width="340" TextAlignment="Center" 
                       FontSize="9" FontWeight="Bold" Canvas.Left="20" Canvas.Top="10" 
                       Text="Use these tools to add graphics to the map." />
            <StackPanel Orientation="Vertical" Canvas.Top="5" Canvas.Left="20">
                <esri:Toolbar x:Name="MyToolbar" MaxItemHeight="80" MaxItemWidth="80"
                    Grid.Row="0" VerticalAlignment="Top" HorizontalAlignment="Center"
                    ToolbarItemClicked="MyToolbar_ToolbarItemClicked" 
                    ToolbarIndexChanged="MyToolbar_ToolbarIndexChanged"
                    Width="330" Height="80">
                    <esri:Toolbar.Items>
                        <esri:ToolbarItemCollection>
                            <esri:ToolbarItem Text="Add a point">
                                <esri:ToolbarItem.Content>
                                    <Image Source="Assets/images/i_draw_point.png" Stretch="UniformToFill" Margin="5" />
                                </esri:ToolbarItem.Content>
                            </esri:ToolbarItem>
                            <esri:ToolbarItem Text="Add a Polyline">
                                <esri:ToolbarItem.Content>
                                    <Image Source="Assets/images/i_draw_line.png" Stretch="UniformToFill" Margin="5" />
                                </esri:ToolbarItem.Content>
                            </esri:ToolbarItem>
                            <esri:ToolbarItem Text="Add a Polygon">
                                <esri:ToolbarItem.Content>
                                    <Image Source="Assets/images/i_draw_poly.png" Stretch="UniformToFill" Margin="5" />
                                </esri:ToolbarItem.Content>
                            </esri:ToolbarItem>
                        </esri:ToolbarItemCollection>
                    </esri:Toolbar.Items>
                </esri:Toolbar>
                <TextBlock x:Name="StatusTextBlock" Text="" FontWeight="Bold" HorizontalAlignment="Center"/>
            </StackPanel>
        </Canvas>

        
    </Grid>
</UserControl>

Here's the code behind ...

using System.Windows.Controls;
using ESRI.ArcGIS.Client;
using ESRI.ArcGIS.Client.Symbols;

namespace ESRI_Test
{
    public partial class MainPage : UserControl
    {
        private Draw MyDrawObject;
        private Symbol _activeSymbol = null;

        public MainPage()
        {
            InitializeComponent();

            MyDrawObject = new Draw(MyMap)
            {
                LineSymbol = LayoutRoot.Resources["DrawLineSymbol"] as LineSymbol,
                FillSymbol = LayoutRoot.Resources["DrawFillSymbol"] as FillSymbol
            };

            MyDrawObject.DrawComplete += MyDrawObject_DrawComplete;
        }

        private void MyToolbar_ToolbarItemClicked(object sender, ESRI.ArcGIS.Client.Toolkit.SelectedToolbarItemArgs e)
        {
            switch (e.Index)
            {
                case 0: // Point
                    MyDrawObject.DrawMode = DrawMode.Point;
                    _activeSymbol = LayoutRoot.Resources["DefaultMarkerSymbol"] as Symbol;
                    break;
                case 1: // Polyline
                    MyDrawObject.DrawMode = DrawMode.Polyline;
                    _activeSymbol = LayoutRoot.Resources["DefaultLineSymbol"] as Symbol;
                    break;
                case 2: // Polygon
                    MyDrawObject.DrawMode = DrawMode.Polygon;
                    _activeSymbol = LayoutRoot.Resources["DefaultFillSymbol"] as Symbol;
                    break;
                case 3: // Rectangle
                    MyDrawObject.DrawMode = DrawMode.Rectangle;
                    _activeSymbol = LayoutRoot.Resources["DefaultFillSymbol"] as Symbol;
                    break;
                case 4: // Freehand
                    MyDrawObject.DrawMode = DrawMode.Freehand;
                    _activeSymbol = LayoutRoot.Resources["DefaultLineSymbol"] as Symbol;
                    break;
                default: // Clear Graphics
                    MyDrawObject.DrawMode = DrawMode.None;
                    GraphicsLayer graphicsLayer = MyMap.Layers["MyGraphicsLayer"] as GraphicsLayer;
                    graphicsLayer.ClearGraphics();
                    break;
            }
            MyDrawObject.IsEnabled = (MyDrawObject.DrawMode != DrawMode.None);
        }

        private void MyToolbar_ToolbarIndexChanged(object sender, ESRI.ArcGIS.Client.Toolkit.SelectedToolbarItemArgs e)
        {
            StatusTextBlock.Text = e.Item.Text;
        }


        private void MyDrawObject_DrawComplete(object sender, ESRI.ArcGIS.Client.DrawEventArgs args)
        {
            GraphicsLayer graphicsLayer = MyMap.Layers["MyGraphicsLayer"] as GraphicsLayer;
            ESRI.ArcGIS.Client.Graphic graphic = new ESRI.ArcGIS.Client.Graphic()
            {
                Geometry = args.Geometry,
                Symbol = _activeSymbol,
            };
            graphicsLayer.Graphics.Add(graphic);
        }
    }
}

JenniferNery

And yes, I am able to replicate the problem in the sample by adding SnapToLevels and Min/Max resolution.

Oh cool then you can just copy-paste relevant code so I can replicate the issue with this same sample: http://help.arcgis.com/en/webapi/silverlight/samples/start.htm#DrawGraphics.

AndyWright

I did a clean and I'm still not able to upload. The zip file is 1.6MB, so I'm not sure why it's not letting me upload it. Can I put it on the ESRI FTP site for you?

And yes, I am able to replicate the problem in the sample by adding SnapToLevels and Min/Max resolution.

JenniferNery

Before you zip the file can you Clean Solution first? Maybe that will reduce the file size.

Are you able to reproduce the issue using this sample: http://help.arcgis.com/en/webapi/silverlight/samples/start.htm#DrawGraphics just by adding SnapToLevels, Minimum and MaximumResolution?

AndyWright

Jennifer,

I have stripped out just about everything in my application so that I can zip it all up and send it to you so you can replicate the issue I've described in here. I also now know exactly what is causing it, but I'm not sure why. I was hoping you could shed some light on that for me.

Basically when you have SnapToLevels set to true and a min/max resolution set for your map this weird map extent changed behavior happens when you click one of the three buttons at the top left of the app window. My min/max resolutions are set to exactly match the resolutions of our first and last scale level in our map caches so our users cannot zoom in or out beyond those resolutions when using ESRI services as their basemaps.

If you run the app and click on any of the buttons you will see the map blur slightly. If you put a break point in the map extent changed event you will see that those button clicks do in fact cause the map extent to change when basically all I am doing is setting a draw object to enabled. If you take the min/max resolution properties off of the map and run it again, the map extent changed event does not fire. It also does not fire either way if SnapToLevels is set to false.

So now my only issue is being able to upload my zipped up project file to you. It is only 1.6MB which is below the allowable threshold for zip files, but then I get this error ...

Request Entity Too Large
The requested resource
/newattachment.php
does not allow request data with POST requests, or the amount of data provided in the request exceeds the capacity limit.

Any ideas on how I can get this file to you? Can I send you an e-mail?

AndyWright

Jennifer,

I don't believe this problem is related to having multiple draw objects in the same application. I've commented out all references to every draw object in my app except for one and I can still get the map extent changed event to fire. Like you, I haven't been able to replicate this behavior in the sample on ESRI's SL API website. At this point it feels like one of those needle in a haystack type things. My app is huge and a lot of things are happening independent of these draw objects that could be contributing to this problem. Right now I can't say with any certainty that this is an issue with the draw object itself.

Thanks for your help with this Jennifer ...

AndyWright

Jennifer,

Thanks for the reply. Yeh, we are definitely using multiple draw objects. Each one of our tools that needs draw object functionality has its own draw object. I don't know how else we would do it. When one tool is active it's draw object is enabled and the others are disabled. Then we can react to the draw object completed event properly for that particular tool. It is Monday morning so I'm probably not thinking too clearly yet, but I can't see how you could make one draw object work for multiple tools within the same application. Each of them need to do different things in the draw object completed event, and if that one draw object is always enabled for the different tools then all of their draw object completed events will fire at the same time. It doesn't seem like that's a valid way to proceed here. I suppose we could constantly un-subscribe and re-subscribe to the draw object completed events over and over as each tool becomes active and inactive, but that doesn't seem too elegant either.

Are you able to replicate my issue with multiple draw objects in one application?

JenniferNery

When Draw is enabled, map navigation is disabled - you cannot pan or zoom - this is by design since mouse events now are used for drawing not for navigating the map.
You can see that behavior in this sample
http://help.arcgis.com/en/webapi/silverlight/samples/start.htm#DrawGraphics

I cannot replicate the issue by using the sample above and adding a button to disable Draw, ExtentChanged is not fired even when SnapToLevels is True. The difference is this sample works with only one Draw object. I wonder if maybe the issue is with having multiple Draw objects. Can you share some code? Do you mean each button is a different Draw object?

AndyWright

I've found a workaround that works about 90% of the time. Hopefully someone at ESRI can explain why the ExtentChanged event is getting fired when you set the IsEnabled property on a draw object and also why this workaround does not work 100% of the time.

Inside of my map's ExtentChanged event I am now testing to see if the OldExtent is equal to the NewExtent. If they are equal I don't add the new extent to the extent collection. There are still times when I set a draw object IsEnabled where this doesn't work, but most of the time it does. here's my code ...

if (e.OldExtent.Equals(e.NewExtent))
{
    return;
}

Here are the values for an OldExtent and a NewExtent that didn't work. Where I come from these are absolutely equal. What is going on here?

e.OldExtent = {-12460952.8600617,3948499.37002462,-12460530.6649134,3948805.71530195}
e.NewExtent = {-12460952.8600617,3948499.37002462,-12460530.6649134,3948805.71530195}

AndyWright

I think I've stumbled on to an issue very closely related to the one in this post. I have an application that has various tools that have their own draw objects. I created a draw object manager that handles enabling/disabling these draw objects whenever necessary. It all works great except for the fact that every time I enable/disable a draw object the map's ExtentChanged event fires and the map gets blurry for a split second. That blurriness is the only indicator you have that the map extent changed - the map doesn't actually move at all. So now when I use my zoom next/previous tools they appear to not work, unless you click them multiple times so it can go through all the map extents created when the IsEnabled property on the draw objects gets set.

I do have SnapToLevels set to true and it does not happen when SnapToLevels is set to false. We need SnapToLevels to be true though. Our maps just look a hell of a lot better that way. The false setting kind of blurs things a little bit.

Is anyone seeing this same behavior? We are using the 2.1 API by the way.

egismazeika

You are right, it is the same issue.

For the moment, the best workaround is to unset SnapToLevels bu it should be fixed for final.

Thanks, eagerly waiting for the final

DominiqueBroux

You are right, it is the same issue.

For the moment, the best workaround is to unset SnapToLevels bu it should be fixed for final.

egismazeika

It seems that my issue is related to
http://forums.arcgis.com/threads/7332-navigation-issues

and Draw object often fails when Map.SnapToLevels == true.

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