http://imagej.273.s1.nabble.com/How-to-construct-the-ROI-manager-tp5014113p5014129.html
> Hello,
>
> That nullpointer seems to stem from the fact that the Roi Manager might be
> emptz or uninitialized
>
> I'd suggest you add this at the beginning to make sure that this is not
> the problem
>
> If(returnedRM == null) {
> IJ.error("No RoiManager!");
> // Or you could instantiate a new RoiManager
> returnedRM = new RoiManager();
> }
>
> But your script seems to be run after the RoiManager is populated so this
> should not happen.
>
> Best
>
> Oli
>
> > -----Original Message-----
> > From: ImageJ Interest Group [mailto:
[hidden email]] On Behalf Of
> > Jan Eglinger
> > Sent: Sunday, August 23, 2015 18:34
> > To:
[hidden email]
> > Subject: Re: How to construct the ROI manager
> >
> > Hi Avital,
> >
> > > rm = RoiManager();
> > > returnedRm = rm.getInstance();
> >
> > getInstance is a _static_ method of the RoiManager class, i.e. you don't
> need
> > to create an instance of RoiManager, just call the method like this:
> >
> > rm = RoiManager.getInstance()
> >
> > See also here:
> >
http://fiji.sc/Scripting_toolbox#Select_multiple_ROIs_from_ROI_manager_a> > nd_combine_them
> >
> > Hope that helps,
> > Jan
> >
> >
> > On 23.08.15 11:04, Avital Steinberg wrote:
> > > Hi,
> > > I'm trying to count the number of objects in the roi manager in
> Javascript.
> > > I wrote the following code:
> > >
> > > importClass(Packages.ij.IJ);
> > > importClass(Packages.ij.plugin.frame.RoiManager);
> > > importClass(Packages.ij.io.OpenDialog);
> > > importClass(Packages.ij.io.DirectoryChooser);
> > > importClass(Packages.java.io.File);
> > > importClass(Packages.ij.gui.GenericDialog);
> > > importClass(Packages.ij.util.Tools);
> > > importClass(Packages.ij.plugin.Duplicator);
> > >
> > > IJ = IJ();
> > > rm = RoiManager();
> > > returnedRm = rm.getInstance();
> > > print("The returned rm is: " + returnedRm); var nObjects =
> > > rm.getCount(); print("nObjects is: " + nObjects);
> > >
> > > And I get the following error message:
> > >
> > > javax.script.ScriptException:
> > > sun.org.mozilla.javascript.internal.WrappedException: Wrapped
> > > java.lang.NullPointerException
> > >
> > > When I comment out the problematic line (var nObjects =
> > > rm.getCount();) I get the following Roi Manager type for the rm:
> > > (getInstance returned this)
> > >
> > > The returned rm is:
> > > ij.plugin.frame.RoiManager[frame61,884,327,240x330,invalid,layout=java
> > > .awt.BorderLayout,title=ROI
> > > Manager,resizable,normal]
> > >
> > > How would I count the number of ROIs in the Roi manager? And how can I
> > > use the RoiManager class methods?
> > >
> > > Thanks,
> > > Avital
> >
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