Re: Basic question -- I am missing the "big picture" ...

I just wanted to mention a couple of things:

The doPrepare() isn't a standard Layer method - it only exists on
certain layers. Ed, you may want to check out different OpenMap layers
to see how it is used, usually to kick off a SwingWorker to tell a layer
to re-gather graphics, project them and call repaint(). But, if your
OMGraphics are pretty set, you can create a method (if you don't have
one) to just project your graphics and call repaint().

How you manage your OMGraphics is completely up to you - you may want to
create them in the constructor, you may want to provide a method in your
layer so that other objects can create them. You may even want an
object in the MapHandler to hold on to them instead of your layer. It
all depends on how you want to organize and display your data. All a
layer is *really* responsible for, when you get right down to it, is
painting the OMGraphics in the right spot on the map relative to other
layers (depth). You just need to try to make sure that the only thing
that gets done in the paint() method of a layer is rendering. Doing
more makes the application feel slower.

I don't think you want the MapHandler to be doing more than it already
does, which is enabling objects to find each other. If anything, I
would let a different object create your layer's OMGraphics, and then
use the MapHandler to let the layer find that object to get the graphics
(or vice versa). This requires that there some design coordination
between the layer and the object, but that's cool.

- Don

On Tuesday, April 30, 2002, at 12:04 PM, Jeff Mathis wrote:

> Hi Ed,
>
> Glad to see you still hacking away.
>
> We do this all the time, as you might know. The key is when an object
> has been changed, you need to render the graphic and then repaint the
> layer.
>
> The doPrepare() method on Layer does most of this for you. What you
> have to realize here is that each layer is repainted in its own thread,
> but if you don't care then no extra handling is needed.
>
> Here is a snippet. This method is executed after the user is done
> dragging a map object to a new location:
>
> /**
> * Specified by the DrawingToolRequestor interface. This method is
> called after
> * the edit has been performed on a given location.
> * @param omg the OMGraphic object, which should be a MapEntity
> * @param oma the OMAction
> */
> public void drawingComplete(OMGraphic omg, OMAction oma) {
> Debug.message("entitylocationlayer","EntityLocationLayer:
> called drawingComplete");
> // reset the text label based on the circles coordinates
> MapEntity ent = (MapEntity)omg;
> OMGraphic g = ent.getLocationMarker();
> com.biosgroup.alac.model.general.Location newloc = null;
> if (g instanceof OMRect) {
> OMRect rect = (OMRect)g;
> ent.setLocation(rect.getNorthLat(), rect.getWestLon());
> newloc = new
> com.biosgroup.alac.model.general.Location((float)rect.getNorthLat(),
> (float)rect.getWestLon());
> } else if (g instanceof OMCircle) {
> OMCircle circ = (OMCircle)g;
> LatLonPoint l = circ.getLatLon();
> ent.setLocation(l.getLatitude(), l.getLongitude());
> newloc = new
> com.biosgroup.alac.model.general.Location((float)l.getLatitude(),
> (float)l.getLongitude());
> }
> ((Locatable)ent.getAppObject()).setLocation(newloc);
> g.setVisible(true);
> ApplicationState.fireApplicationChangeEvent(
> new ApplicationChangeEvent(this,
>
> ApplicationChangeEvent.LOCATION_EDITED));
> }
>
> then, when the ApplicationChangeEvent is received by my layer manager,
> it calls doPrepare() on the layer to repaint itself.
>
> At 09:40 PM 4/29/2002 -0600, Ed MacKerrow wrote:
>
>> Dear OpenMappers,
>>
>> I am still on the steep end of the OM learning curve and I think I
>> missing out on the "bigger picture".
>>
>> I have built a few layers that I have been able to display my objects
>> on, however, I did this by instantiating the objects, which are
>> displayed by association with a OMGraphic that has the same (lat,lon)
>> as the App objs. The mistake that I believe I have done, is to
>> instantiate these objects and OMGraphics by calling a "buildObjs()"
>> method from inside the constructor for the layer. The layer
>> constructor is invoked from the properties file call (i.e. like in the
>> OpenMap app). Should I be instantiating these objects from a
>> mapHandler instead?
>>
>> The reason I am asking is that I don't know how to update the
>> positions of those objects on the layer, since I do not have an
>> instantiated object that represents my layer class. I guess my basic
>> question is:
>>
>> How do I update the position values of objects that are displayed on a
>> layer? ( are there any simple examples of updating the positions of
>> objects that are displayed on a layer out there?)
>>
>> Thanks for your help,
>>
>> ed
>
> Jeff Mathis
> Senior Scientist / Group Leader
> BiosGroup, Inc.
> 317 Paseo de Peralta
> Santa Fe, NM 87501
> direct: 505-992-6737
> fax: 505-988-2229
> jeff.mathis@biosgroup.com
> http://www.biosgroup.com
>
> --
> [To unsubscribe to this list send an email to "majdart@bbn.com"
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>
>

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Don Dietrick, BBN Technologies, dietrick@bbn.com
10 Moulton Street, Cambridge, MA 02138
617-873-3031 [fax]-2794
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