srchdlph.txt

mapx + delphi 实现SEARCH

Note: This sample application and corresponding sample code is provided 
for example purposes only.  It has not undergone rigorous testing
and as such should not be shipped as part of a final application
without extensive testing on the part of the organization releasing
the end-user product.

This Delphi 4.0 example uses the MapX Ver 4 OCX Control.  The main goal 
of this example is to show the use of the new Search capabilities in MapX 
Ver 3.51.  The program shows how to use all the new search functions that 
have been added as methods of the layer object.  This shows the use of 
SearchWithinDistance, SearchWithinRectangle, SearchWithinFeature and SearchAtPoint.

Files:

searchUnit.dfm
searchUnit.pas
searchEx.dpr
searchEx.res

Overview:

There are 3 Menu Item choices, the Map Control, 2 Combo boxes and a list box.

Under the File menu option is the "exit" option to end the program.  Also there 
is a choice for Layer Control, which displays the Layer Control Stock MapX Dialog.  

Tools Menu option: The first three zoomIn, zoomOut, and pan all set the active tool 
to be the respective MapX default tool.

Search Tools: The First four menu items set the active tool to be a custom tool 
type used for performing the searches.

All Tools perform the search on the layer specified in the search layer combo box.  
The SearchWithingFeature uses the FeatureSearchLayer to determine the layer the 
feature to be used is in, and the uses the searchLayer to perform the search for 
all objects that fall within the feature clicked in.  

While performing the search, if the control key is held down, the search results 
will include all those objects that are entirely in the specified region.  If the 
shift key is down, the search results will include all those objects partially in 
specified region.  If neither are down, the search results will include all those 
objects whose centroid fall within specified region.

Programmers Note: Due to the curvature of the earth, the search for items in a 
rectangle will not return everything that would fall under the dashed line that 
gets drawn.  Instead, the rectangle will be calculated to reflect it as if it 
were drawn above the earth, so the item in the result may not be exactly as 
you expect, but this is the desired effect.

The results of the search will be populated into the listbox.

SearchWithinDistance - This tool will allow the user to draw a circle and then 
will perform a distance search using the diameter value.

SearchWithingRectangle - This tool will allow the user to draw a rectangle and 
then will perform a search within this rectangel. See programmers note above.

SearchWithingFeature - This tool will allow the user to click on a layer that 
is specified as the featureSearchLayer.  The object that the user clicks on 
will then be used as the feature to search, from the searchLayer, all the 
objects that fall within that Feature.

SearchAtPoint - This tool will search for features at the specific X, Y location 
that the user clicked.

The fifth menu item is used as an on and off menu item.  If the menu item is 
checked, the search results for the layer will become the selection for that 
layer and the objects searched will become highlighted.  If the menu is not 
checked, search results are not added as the current selection.