Rserve 无法在 Java GUI 代码中的 actionPerformed 方法中设置连接

Question

我正在使用 Java 开发 GUI。 GUI 在某些时候会使用 Rserve 连接到 R 以执行某些功能。我首先在 GUI 的主要方法中使用 Rserve 测试了与 R 的连接，它运行良好。代码如下：

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
            }
        });
    }

现在，我想在 actionPerformed 方法中设置与 R 的连接（在执行特定事件时）。这是我做不到的。

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 ");
            }
        }
}

如果我在此方法中插入 throws RserveException, REXPMismatchException，则会收到错误，即被覆盖的方法不会抛出这些异常。在用try-catch 块包围代码时（如上面的代码所示），我收到以下错误：

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)

我该如何解决这个问题？

Answer 1

我通过在 actionPerformed 方法中添加一个新的 Rconnection 得到了解决方案。

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 {
                    rc = new RConnection();
                    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 ");
            }
        }
}