I am working on developing a GUI using Java. The GUI at some point would make a connection to R using Rserve to perform some function. I first tested the connection with R using Rserve in the main method the GUI and it worked perfectly. Here is the code:
public static void main(String[] args) throws RserveException,
REXPMismatchException {
// Setting up connection to R
RConnection rc = new RConnection();
REXP x = rc.eval("R.version.string"); //example to check if connection to R is set
System.out.println(x.asString());
// Run the GUI construction in the Event-Dispatching thread for thread-safety
SwingUtilities.invokeLater(new Runnable() {
@Override
public void run() {
new GUIMain(); // Let the constructor do the job
}
});
}
Now, I want to setup the connection to R in the actionPerformed method (on performing a specific event). Which I am unable to do.
public void actionPerformed(ActionEvent e) {
//Handle open raw imaging file button and menu item action.
if ((e.getSource() == OpenImagingFileButton) || (e.getSource() == LoadRawSpectraMenuItem)) {
int returnVal = fc1.showOpenDialog(GUIMain.this);
if (returnVal == JFileChooser.APPROVE_OPTION) {
file = fc1.getSelectedFile();
System.out.println(file.getAbsolutePath());
REXP x = null; //example to check if connection to R is set
try {
x = rc.eval("R.version.string");
} catch (RserveException e1) {
e1.printStackTrace();
}
try {
System.out.println(x.asString());
} catch (REXPMismatchException e1) {
e1.printStackTrace();
}
System.out.println(" - Done ");
}
}
}
If I insert throws RserveException, REXPMismatchException in this method then I get the error that the overridden method do not throw these exceptions. On surrounding the code withtry-catch block (as shown in the code above), I get the following errors:
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at GUIMain.actionPerformed(GUIMain.java:482)
at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2018)
at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2341)
at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:402)
at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:259)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:252)
at java.awt.AWTEventMulticaster.mouseReleased(AWTEventMulticaster.java:289)
at java.awt.Component.processMouseEvent(Component.java:6516)
at javax.swing.JComponent.processMouseEvent(JComponent.java:3312)
at java.awt.Component.processEvent(Component.java:6281)
at java.awt.Container.processEvent(Container.java:2229)
at java.awt.Component.dispatchEventImpl(Component.java:4872)
at java.awt.Container.dispatchEventImpl(Container.java:2287)
at java.awt.Component.dispatchEvent(Component.java:4698)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4832)
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4492)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4422)
at java.awt.Container.dispatchEventImpl(Container.java:2273)
at java.awt.Window.dispatchEventImpl(Window.java:2719)
at java.awt.Component.dispatchEvent(Component.java:4698)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:747)
at java.awt.EventQueue.access$300(EventQueue.java:103)
at java.awt.EventQueue$3.run(EventQueue.java:706)
at java.awt.EventQueue$3.run(EventQueue.java:704)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:87)
at java.awt.EventQueue$4.run(EventQueue.java:720)
at java.awt.EventQueue$4.run(EventQueue.java:718)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:717)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:242)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:161)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:150)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:146)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:138)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:91)
How can I resolve this?
