openmap-arch.sgml

OpenMap是一个基于JavaBeansTM的开发工具包。利用OpenMap你就能够快速构建用于访问legacy数据库的应用程序与applets。OpenMap提供了允许用户查看和操作地理空间信息的

</#if>
<p>
The ToolPanel is a Component that looks for components implementing
the <htmlurl url="api/com/bbn/openmap/gui/Tool.html" name="Tool">
interface.  It provides a quick interface to make tools and controls
visible and accessable.
<p>
Some of the components available are pictured above, and explained
below:
<p>
<itemize>
<item>
<sect2>OMToolSet<label id="sec-toolpanel">
<p>
The <htmlurl url="./api/com/bbn/openmap/gui/OMToolSet.html"
name="OMToolSet"> is a composite GUI JavaBean, set up to control the
view and mouse modes of the MapBean.  Any one of its parts may be
hidden from view by adjusting its properties:

<itemize>
<item>
Directional control.  Made from the <htmlurl
url="./api/com/bbn/openmap/gui/NavigatePanel.html"
name="NavigatePanel"> Bean.  This lets you pan the screen in the
direction of the button that is pressed.

<item>
Zoom buttons.  Made from the <htmlurl
url="./api/com/bbn/openmap/gui/ZoomPanel.html" name="ZoomPanel">.
This panel has two buttons - the plus (+) button zooms in (increases
scale by 2X), and the minus (-) button zooms out (decreases scale by
2X).

<item>
Scale field window. This shows the current scale setting (1:scale),
and also lets you enter a desired scale directly.
</itemize>

<item>
LayersPanel launch button.  The LayersPanel is explained <ref id="sec-layerspanel" name="here">.

<item>
Drawing Tool Launcher.  The <htmlurl
url="api/com/bbn/openmap/tools/drawing/package-summary.html"
name="Drawing Tool"> lets the users draw different graphics on the
map, and direct those graphics to layers or components that can use
them.  It uses the MapHandler to find these components.

<item>
OverviewMapHandler.  The <htmlurl
url="api/com/bbn/openmap/gui/OverviewMapHandler.html"
name="OverviewMapHandler"> is a self-contained MapBean that provides a
reference view of a source MapBean, and also provides control over the
MapBean.

<item>
MouseMode Selector.  The <htmlurl
url="api/com/bbn/openmap/gui/MouseModePanel.html"
name="MouseModePanel"> provides a way to control the <htmlurl
url="api/com/bbn/openmap/MouseDelegator.html" name="MouseDelegator">,
choosing the active <htmlurl
url="api/com/bbn/openmap/event/MapMouseMode.html"
name="MapMouseMode">.

<item>
<htmlurl url="api/com/bbn/openmap/gui/ProjectionStackTool.html"
name="Projection Stack buttons">.  The <htmlurl
url="api/com/bbn/openmap/proj/ProjectionStack.html"
name="ProjectionStack"> remembers past map projections and lets the
user go back to preious projections.  It also lets the user go forward
again.

</itemize>

<sect2>InformationDelegator<label id="sec-infodelegator">
<p>
<#if output=html>
<IMG SRC="images/whopanel.png">
</#if>
The <htmlurl url="./api/com/bbn/openmap/InformationDelegator.html"
name="InformationDelegator"> is a JavaBean used for status updates and
messages.  The <bf><ref id="sec-navmousemode"
name="NavMouseMode"></bf> uses the InformationDelegator to display the
latitude, longitude, and XY pixel location of the cursor on the
MapBean window.  Layers can use the InformationDelegator to display
one-liners, pop-up messages, and web pages.  The colored lights at the
right of the widget reflect whether particular layers are working
(red) or are finished (green).  The lights are buttons that launch the
palette for the layer it represents.

<sect2>LayersPanel<label id="sec-layerspanel">
<p>
<#if output=html>
<IMG SRC="images/layers-window.png">
</#if>
<P>
The <htmlurl url="./api/com/bbn/openmap/gui/LayersPanel.html"
name="LayersPanel"> is used to manage the display and order of the
layers in the MapBean.  This panel also lets you bring up and dismiss
the GUI controls for a layer, called layer palettes.  Some of the
buttons act on a `selected' layer.  Click on the layer name to select
it.

<itemize>
<item>
<#if output=html>
<IMG SRC="images/top.png">
</#if>
Move the selected layer to the top of the map.
<item>
<#if output=html>
<IMG SRC="images/up.png">
</#if>
The selected layer exchanges position with the one above it.
<item>
<#if output=html>
<IMG SRC="images/down.png">
</#if>
The selected layer exchanges position with the one below it.
<item>
<#if output=html>
<IMG SRC="images/bottom.png">
</#if>
Move the selected layer to the bottom of the map.
<item>
<#if output=html>
<IMG SRC="images/DeleteLayer.png">
</#if>
Delete the selected layer from the application.
<item>
<#if output=html>
<IMG SRC="images/AddLayer.png">
</#if>
Add a layer to the application.
<item>
<#if output=html>
<IMG SRC="images/layerNotSelected.png">
</#if>
Click this to add the layer to the map.
<item>
<#if output=html>
<IMG SRC="images/layerSelected.png">
</#if>
Click this to remove the layer from the map.
<item>
<#if output=html>
<IMG SRC="images/palette_off.png">
</#if>
The GUI palette for the layer is not active.  Click this to display
it.
<item>
<#if output=html>
<IMG SRC="images/palette_on.png">
</#if>
The GUI palette for the layer is active.
</itemize>



<!-- Layers and PlugIn Section -->



<sect>Layers and PlugIns<label id="sec-layers">
<p>
<htmlurl url="./api/com/bbn/openmap/Layer.html" name="Layers"> are
components that get added to the MapBean in a hierarchical stacking
order.  The map is drawn by painting the graphics of each layer
starting with the bottommost one and proceeding up the hierarchy.
Successive layers render their graphics on top of the graphics of
lower ones.
<p>
<htmlurl url="./api/com/bbn/openmap/plugin/package-summary.html"
name="PlugIns"> are components that are used by the PlugInLayer to
fetch data and prepare graphics for the map.
<p>
Layers and PlugIns are responsible for aquiring, constructing, and rendering their
own graphical data.  The <bf><ref id="sec-omgraphics"
name="OMGraphics"></bf> package provides a simple way to construct
vector and raster graphics out of geo-spatial and XY data.
<p>
They can also be interactive, by registering for mouse events and
constructing their very own GUI widget controls.
<p>
When a layer is added to the MapBean, it automatically becomes a
<htmlurl url="api/com/bbn/openmap/event/ProjectionListener.html"
name="ProjectionListener"> of the MapBean.  This means that the layer
receives notification when the <bf><ref id="sec-projection"
name="Projection"></bf> (or view) of the map changes.
<p>
To reiterate, the standard capabilities of a Layer are:
<itemize>
<item>Create, manage, and render graphical objects.  
<item>Receive and respond to mouse events over the map.
<item>Create GUI controls for additional configuration.
</itemize>

<sect1>ShapeLayer<label id="sec-shapelayer">
<p>
This is a generic layer for displaying data in <htmlurl
url="http://www.esri.com/" name="ESRI"> shapefile format.  See the
<htmlurl url="api/com/bbn/openmap/layer/shape/ShapeLayer.html"
name="ShapeLayer"> class.

<sect1>ShapePlugIn<label id="sec-shapeplugin">
<p>
A different component for handling Shape data is in the 
<htmlurl url="api/com/bbn/openmap/plugin/esri/package-summary.html"
name="esri plugin"> package.

<sect1>VPFLayer<label id="sec-vpflayer">
<p>
This is a generic layer for displaying <htmlurl
url="http://www.nima.mil/" name="NIMA"> VPF data.  See the <htmlurl
url="api/com/bbn/openmap/layer/vpf/VPFLayer.html" name="VPFLayer">
class.


<sect1>EarthquakeLayer<label id="sec-earthquakelayer">
<p>
The <htmlurl url="api/com/bbn/openmap/layer/EarthquakeLayer.html"
name="EarthquakeLayer"> displays data of recent earthquake activity.
It gets its data by querying live data feeds at the <htmlurl
url="http://www.usgs.gov/" name="USGS">.


<sect1>Raster Layers<label id="sec-raster-layers">
<p>
<itemize>
<item><htmlurl url="./api/com/bbn/openmap/layer/rpf/RpfLayer.html"
name="Raster Product Format (RPF) Layer">, which displays <htmlurl
url="http://www.nima.mil/" name="NIMA's"> CADRG and CIB data.
<item><htmlurl url="./api/com/bbn/openmap/layer/dted/DTEDLayer.html"
name="DTED Layer">, which displays NIMA's Digital Terrain Elevation
Data.
</itemize>


<sect1>Writing your own Layer or PlugIn<label id="sec-write-your-own-layer">
<p>
To write your own layer, you need to extend the <htmlurl
url="api/com/bbn/openmap/Layer.html" name="Layer"> class.  The minimum
requirement is that you override the <tt/projectionChanged()/ and
<tt/paint()/ methods.  This former method is invoked when your layer
is part of the MapBean and the view changes (e.g., when someone
recenters the map).  It is up to you to fetch and prepare your
graphics (or maybe do something else), and then <tt/repaint()/
yourself.  The easiest way to write your own layer is to derive it
from another one already cooked up.  For some simple examples see the
<htmlurl url="api/com/bbn/openmap/layer/GraticuleLayer.html"
name="GraticuleLayer"> and <htmlurl
url="api/com/bbn/openmap/layer/test/TestLayer.html" name="TestLayer">
classes.
<P>
Many layers get their data from the local disk or cdrom of the machine
that they run on, but there are others that query remote sites on the
Internet.  The <bf><ref id="sec-earthquakelayer" name="Earthquake
Layer"></bf> is a good example of live layer.
<p>
To write your own PlugIn, you can extend the <htmlurl
url="api/com/bbn/openmap/plugin/AbstractPlugIn.html"
name="AbstractPlugIn"> class, which implements the <htmlurl
url="api/com/bbn/openmap/plugin/AbstractPlugIn.html"
name="PlugIn"> interface.  You only have to implement <tt/the
getRectangle()/ method, which returns an <htmlurl
url="api/com/bbn/openmap/omGraphics/OMGraphicList.html"
name="OMGraphicList"> to the PlugInLayer.  PlugIns can also receive
MouseEvents and create a GUI palette, just like layers.  The advantage
to creating a PlugIn is that you don't have to deal with the <ref
id="sec-swingworker" name="Swing Worker"> which should be used by
layers to kick off another thread to do their work, in order not to
slow the application down.  The PlugInLayer does this for the PlugIn.

<sect2>OMGraphics<label id="sec-omgraphics">
<p>
<htmlurl url="./api/com/bbn/openmap/omGraphics/package-tree.html"
name="OMGraphics"> help you to turn your vector or raster data into
interactive graphics that can be rendered on the map canvas.
Each OMGraphic provides a simple interface to manage projecting,
rendering, and gesturing.
<p>
In general, there are three steps needed to get your data to appear on
the screen.  The OMGraphic needs to be created.  Then call
<tt/generate()/ on the OMGraphic with the current <bf><ref
id="sec-projection" name="Projection"></bf> to prepare for rendering.
Then call <tt/render()/ on the OMGraphic with the java.awt.Graphics
context.  This final step is usually performed when the <tt/paint()/
method is invoked on your layer.  To trigger the AWT painting, call
<tt/repaint()/, instead of <tt/paint()/ directly.  Note that even if
the graphic is already in XY, it still needs to be `generated' before
it is `rendered', or it will not show up on the map.
<P>
<itemize>
<item>Vector graphics
	<itemize>
	<item><htmlurl url="./api/com/bbn/openmap/omGraphics/OMCircle.html" name="Circle">
	<item><htmlurl url="./api/com/bbn/openmap/omGraphics/OMLine.html" name="Line">
	<item><htmlurl url="./api/com/bbn/openmap/omGraphics/OMPoly.html" name="Polygon and Polyline">
	<item><htmlurl url="./api/com/bbn/openmap/omGraphics/OMRect.html" name="Rectangle">
	</itemize>
<item>Raster Graphics
	<itemize>
	<item><htmlurl url="./api/com/bbn/openmap/omGraphics/OMBitmap.html" name="Bitmap">
	<item><htmlurl url="./api/com/bbn/openmap/omGraphics/OMRaster.html" name="Raster (image)">
	</itemize>
<item>Other
	<itemize>
	<item><htmlurl url="./api/com/bbn/openmap/omGraphics/OMGraphic.html" name="Parent Graphic">
	<item><htmlurl url="./api/com/bbn/openmap/omGraphics/OMText.html" name="Text">
	<item><htmlurl url="./api/com/bbn/openmap/omGraphics/OMGraphicList.html" name="Graphic List">
	</itemize>
</itemize>
<p>
The <htmlurl url="./api/com/bbn/openmap/omGraphics/OMGraphicList.html"
name="OMGraphicList"> is a unique OMGraphic: it can be used to manage
a vector of OMGraphics.  It can also contain other OMGraphicLists, so
you can create nested groupings of graphics.
<p>
And of course you can extend any of the OMGraphic classes to create
your own specific graphic or extended functionality.


<sect2>Layer GUI Palettes
<P>
Palettes are layer-specific GUI components that provide another means
to configure and interact with the layer.  The Layer interface
provides a <tt/getGUI()/ method which can be used by the layer to
return its GUI.  The OpenMap Viewer application presents a layer's
palette in an InternalFrame.  This is accessible from the <ref
id="sec-layerspanel" name="LayersPanel"> component.


<sect2>Multi-threading and the SwingWorker<label id="sec-multithreading">
<p>
When developing your own layer you should be aware of how it could
potentially affect the overall performance of OpenMap.  Specifically,
a layer should not block too long on <tt/paint()/,
<tt/projectionChanged()/, or other interface methods.  If, for
instance, your layer needs to do a lot of computation each time
<tt/projectionChanged()/ is invoked, then you should consider spawning
a thread to do the work.  This way you won't block the propagation of
<tt/projectionChanged()/ to other layers and components.  Since all
layers are Swing components, they can call <tt/repaint()/ anytime when
they've got something new to show.  So once your thread finishes doing
work, and you've got new data, you can initiate a <tt/repaint()/.
<P>
<label id="sec-swingworker">
The <htmlurl url="./api/com/bbn/openmap/util/SwingWorker.html"
name="SwingWorker"> is a class which supports spawning and managing
worker threads; Sun has a <htmlurl
url="http://java.sun.com/docs/books/tutorial/ui/swingMisc/threads.html#SwingWorker"
name="tutorial"> on the SwingWorker.  Several of our main Layers use
this service, including the <bf><ref id="sec-shapelayer"
name="ShapeLayer"></bf>.

<!--       -->

<sect>Projection<label id="sec-projection">
<p>
The <htmlurl url="api/com/bbn/openmap/proj/Projection.html"
name="Projection"> interface allows you read-only access to the
current MapBean projection.  The MapBean updates all the Layers and
other <htmlurl
url="./api/com/bbn/openmap/event/ProjectionListener.html"
name="ProjectionListeners"> when the view changes.
<p>
A Projection object is defined with:
<itemize>
<item>Latitude and longitude of the center point of the MapBean canvas
<item>Scale,
<item>Height and width of the MapBean canvas
<item>Projection type (Mercator, Orthographic, etc)
</itemize>



</article>