Re: [Geotools-gt2-users] A question about displaying vehicle's position on DirectLayer

[Jody G. <jod...@gm...>]

Thanks for the description wbh, I am not sure I know enough about how
gt-swing has set things up. I assume you want to get a new background image
drawn each time pan and/or zoom occurs.

Jody

--
Jody Garnett

On 3 March 2015 at 18:41, wbh <wan...@16...> wrote:

> Jody,
> sorry for the unclear description.....
> ------------------what I want---------------------------
> App receives a serie of vehicle GPS data, each of which is drew by a
> filled circle. But only the last GPS should be displayed on the
> DirectLayer, representing the current position of the vehicle
> -----------------what I do--------------------------
> Step 1 use socket to receive and send vehicle's position (Lon, Lat)
> Step 2 extend DirectLayer to GpsDirectLayer, which have an ArrayList to
> store all of the GPS point
> Step 3 when socket receives the first GPS, get the background image of
> the GPS will cover before draw it. This background image contains the map
> which is covered by GPS
> Step 4 Draw the first GPS by a filled circle
> Step 5 When socket receives the second GPS, we need to :
> (1) erase the first GPS. Draw the background image, which is saved at step
> 3. So the first GPS is covered by this image
> (2) Draw the second GPS
> -------------------my problem------------------
> When PAN and ZOOM, all layers are redrawn (I think). So the background
> image in Step 3 is no longer available. I mean, the map GPS covers is moved
> by PAN or ZOOM.
> ------------------How I solve--------------------
> when PAN and ZOOM, set this background image to null (so it won't be
> drawn). So I have to listen the PAN and ZOOM operation, and set the
> background image (it is a member variable of GpsDirectLayer) to null there
>
> I am not sure whether I describe my problem clearly this time
>
> 在 2015-03-04 06:05:57，"Jody Garnett" <jod...@gm...> 写道：
>
> I am not quite sure what you are stuck on. I guess that setting the
> background to null asks the demo to draw it again?
>
> --
> Jody Garnett
>
> On 2 March 2015 at 18:19, wbh <wan...@16...> wrote:
>
>> Plus, after debug, my idea, that setting the background of the GPS is
>> null after PAN or ZOOM, solves my problem.
>> However, I feel this is not the best way.
>> Can anybody tell me how to solve my problem?
>>
>>
>>
>>
>> 在 2015-03-02 21:41:40，"wbh" <wan...@16...> 写道：
>>
>> Dears,
>> I have a simple app which displays the vehicle's current position.
>> -------------------my way------------------------
>> 1 use socket to receive and send vehicle's position (Lon, Lat)
>> 2 extend DirectLayer to GpsDirectLayer, which have an ArrayList to store
>> all of the GPS point
>> 3 when socket receives a GPS, add it to the ArrayList and call Draw()
>> method of GpsDirectLayer. In this method, erase the previous point and draw
>> the latest GPS. (Thanks Michael Bedward for the FlyingSaucer demo ^^)
>> 4 In eras() method, get the background of the GPS (use Raster) before
>> draw it
>> -------------------my problem------------------
>> If no PAN, ZOOM operation, all goes well. But when PAN and ZOOM, all
>> layers are redrawn (I think). So the stored raster for the background is no
>> longer available (or needed).
>> What can I do to avoid this?
>> My first idea is set the background is null when PAN or ZOOM is
>> performed, is that the correct way?
>> Thanks in advance!
>>
>>
>>
>>
>>
>>
>>
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