Implementing cursortools

To implement a new cursortool, the best way is to study and subclass existant cursortools with a similar behaviour:

• for example cursortool #DragTool if your tool needs a mouse drag;
• or cursortool#NClickTool if your tool uses several clicks

(see Jump Developer's Guide chapter 6. for more informations on cursortool classes)

Let's create a simple cursortool that displays cursor coordinates in a java console, each time we click once in the layerViewPanel (not a very useful tool...):

public class CoordinateCursorTool extends AbstractCursorTool{
     private Coordinate actualCoord = new Coordinate(); 
     public RasterQueryCursorTool() //constructor does nothing special here
     

     public Icon getIcon() {
     return IconLoader.icon("My_toolbar_Icon.gif");
     //specify here the toolbar icon file (button image) to use%
    }

     public Cursor getCursor() {
     return createCursor(IconLoader.icon("My_Cursor.gif")
            .getImage()); //specify here the cursor image file to use
    }


   
    public void deactivate() {
    }

    public boolean isRightMouseButtonUsed() {
        return false;
    }


    public void mouseClicked(MouseEvent e) {
        try {//add here the code to    execute when the mouse is clicked%
            actualCoord = getPanel().getViewport().toModelCoordinate(
                    e.getPoint());
	system.out.println(actualCoord); //Display coordinates as a string
        } catch (NoninvertibleTransformException e1) {
                  e1.printStackTrace();
        }
	fireGestureFinished();  //Notify that mouse gesture is finished 
        }

     public boolean isGestureInProgress() {
        return false;
    }

    public void cancelGesture() {
    }

    public String getName() {
        return "CoordinateTool";
    }

    protected Shape getShape() throws Exception {
        return null; //because nothing should be drawn here
    }

    protected void gestureFinished() throws Exception {
        reportNothingToUndoYet();

        }}

Then we add our cursortool to the workbench toolbar. This can be done in the initialize() method of a new plugin:

     public void initialize(PlugInContext context){
      WorkbenchFrame frame = context.getWorkbenchContext()
      .getWorkbench().getFrame();

         frame.getToolBar().addCursorTool(new CoordinateCursorTool());

      //etc...

In the workbench, you have now a new button. Press it and the CoordinateCursortool becomes active (the #activate method is called). Have fun!

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Thanks to Paul Plouy for writing up the tutorial above. Note that there are some subclasses of AbstractCursorTool that you can subclass to get additional power for free; for example: MultiClickTool, SpecifyFeaturesTool, etc. For examples of their use, see the classes in com.vividsolutions.jump.workbench.ui.cursortool [Jon Aquino 2005-09-22]

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There are several good examples of CursorTools in the OpenJUMP source code. Check out the cursortools folder. [Jon Aquino 2005-11-04]