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Mouse position - Feb 28, 2013 at 1:43PM
Robert MacKay
5 Posts

How does one access the move position (x y) shown in the yellow box of the drawing panel?  I wanted to click on the screen and use the mouse position for a trace or a new drawable circle or rectangle.  This seems way too easy but I haven't yet found an example that uses this. Any help will be appreciated


Replies to Mouse position

Re: Mouse position - Feb 28 2013 2:06PM
Francisco Esquembre
138 Posts

Hi Robert,

Suppose your drawing panel is called "myDrawingPanel", then:

double x = _view.myDrawingPanel.getMouseX();
double y = _view.myDrawingPanel.getMouseY();

give you what you want in the panel world coordinates.

While

int px = _view.myDrawingPanel.getMouseIntX();
int py = _view.myDrawingPanel.getMouseIntY();

give you the point in pixels (if that is of any use for you).

Paco



Re: Re: Mouse position - Feb 28 2013 2:24PM
Robert MacKay
5 Posts

Thank you for your quick reply.  I'll give that a try.



Re: Re: Mouse position - Feb 28 2013 4:51PM
Robert MacKay
5 Posts

Hi Paco,
I tried your suggestion.

my drawing panel is named drawingPanel for this test.  My code in the evolution panel (of model) is:

int px = _view.drawingPanel.getMouseIntX();
int py = _view.drawingPanel.getMouseIntY();
_println("x= " +px +"y= "+py);

It seems to compile okay but I get the message (in output area)

Exception in thread "Thread-2" java.lang.NullPointerException
at org.opensourcephysics.display.InteractivePanel.getMouseIntX(Unknown Source)
at ch4.tryimage_pkg.tryimage._evolution1(tryimage.java:235)
at ch4.tryimage_pkg.tryimage._stepModel(tryimage.java:190)
at org.colos.ejs.library.Animation.step(Unknown Source)
at org.colos.ejs.library.Animation.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)


I also tried
x = _view.drawingPanel.getMouseX();
y = _view.drawingPanel.getMouseY();

and got a similar error message.

Do I need to import something before running this or build a custom class?
Thank you for your patience.
Bob



Re: Re: Re: Mouse position - Feb 28 2013 5:46PM
Francisco Esquembre
138 Posts

Hi Bob,

I see that you are calling the methods in the Evolution. This will not work.

You must call the methods as response to a panel action (one of On Press, On Drag, or On Release). Only then, the methods return something sensible.

Otherwise, you get these null pointer errors.

In the attached example, the On Press action of the panel calls your code and prints the correct information.

Paco

Attached File: ejs_PanelClick.zip



Re: Re: Re: Re: Mouse position - Feb 28 2013 6:49PM
Robert MacKay
5 Posts

Thank you so much.  this should be perfect for my planned use.
Bob



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