在我的JTextArea类中添加滚动条可扩展JFrame

Question

I have a JTextArea in my GUI (my GUI class extends JFrame), which I have added using the following code:

public static JTextArea displayOutput = new JTextArea(text, rows, columns);

displayOutput.setBounds(10, 610, 700, 450);
panel.add(displayOutput);
displayOutput.setEditable(false);

I now want to add a scroll bar to the JTextArea, and have tried doing this by adding the lines:

JScrollPane displayOutputScroll = new JScrollPane(displayOutput);
displayOutputScroll.setVericalScrollBarPolicy(ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS);

But, I get a syntax error on "setVerticalScrollBarPolicy", which says that an Identifier is expected after this token.

I have also tried adding the scrollbar with this line instead:

JScrollPane displayOutputScroll = new JScrollPane(displayOutput, JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);

But get a compile error that says: "The constructor JScrollPane(JTextArea, int) is undefined.

Can someone point out to me what I'm doing wrong here? How can I add a scroll bar to the JTextArea?

Here is the full code for my Gui class, as requested:

package openDIS;

import java.applet.*;
import java.awt.*;

import javax.swing.*;

import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
import java.io.IOException;
import java.net.UnknownHostException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

public class Gui extends JFrame{

public static String text = "";
public static int rows = 20;
public static int columns = 5;
public static JTextArea receivingNetworkInfo = new JTextArea(text, rows, columns);
public static JTextArea sendingNetworkInfo = new JTextArea(text, rows, columns);
public static JTextArea displayOutput = new JTextArea(text, rows, columns);
public static JTextArea displayFilteredOutput = new JTextArea(text, rows, columns);

/*Add scroll bars to the display areas */
JScrollPane displayOutputScroll = new JScrollPane(displayOutput);
displayOutputScroll.setVerticalScrollBarPolicy(ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS);

/*Create a JComboBox to display filter options, and JTextField to allow user to enter filter criteria */
public static String[] filterOptions = {"", "Site", "Application", "ID"};
public static JComboBox<String> filter1 = new JComboBox<String>(filterOptions); /*Adding the '<String>' parameters to JComboBox got rid of the warnings 29/04/2014 */
public static JTextField filter1Text = new JTextField();
public static JComboBox filter2 = new JComboBox(filterOptions);
public static JTextField filter2Text = new JTextField();
public static JComboBox filter3 = new JComboBox(filterOptions);
public static JTextField filter3Text = new JTextField();

public static boolean filterButtonClicked;

/*Create an ExecutorService and then call shutdown in my ActionListener for stop */
public static final ExecutorService pool = Executors.newSingleThreadExecutor();

public Gui(){
    setTitle("DIS Filter");
    setSize(1000, 1000);
    setLocation (10, 10);
    setDefaultCloseOperation(EXIT_ON_CLOSE);

    initGui();
}

private void initGui(){
    //JFrame frame = new JFrame();
    JPanel panel = new JPanel();

    this.getContentPane().add(panel);
    this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    this.setTitle("DIS Filter");
    this.setSize(1400, 1100);

    EspduSender.initSocket();
    panel.setLayout(null);

    /*Add JTextArea to display receivingNetwork info */
    receivingNetworkInfo.setBounds(10, 10,700, 60);
    panel.add(receivingNetworkInfo);
    receivingNetworkInfo.setEditable(false);
    receivingNetworkInfo.setText("Default receiving broadcast address: " + Networks.DEFAULT_BROADCAST_ADDRESS_STRING + "\n" + 
                            "Default receiving multicast group: " + Networks.DEFAULT_MULTICAST_GROUP_STRING + "\n" + 
                            "Default receiving port: " + Networks.receivePORT);

    /*Add a JTextArea to display the output DIS information */
    displayFilteredOutput.setBounds(10, 80, 700, 450);
    panel.add(displayFilteredOutput);
    displayFilteredOutput.setEditable(false);

    /*Add JTextArea to display sendingNetwork info */
    sendingNetworkInfo.setBounds(10, 540, 700, 60);
    panel.add(sendingNetworkInfo);
    sendingNetworkInfo.setEditable(false);
    sendingNetworkInfo.setText("Default sending broadcast address: " + Networks.DEFAULT_BROADCAST_ADDRESS_STRING + "\n" + 
                                "Default sending multicast group: " + Networks.DEFAULT_MULTICAST_GROUP_STRING + "\n" +
                                "Default sending PORT: " + Networks.sendPORT);


    /*Add displayFilteredOutput JTextArea */
    displayOutput.setBounds(10, 610, 700, 450);
    panel.add(displayOutput);
    displayOutput.setEditable(false);
    add(panel);
    //displayOutput.append("hello");

    /*The code underneath here will never be reached unless I specify how long to perform this method call for- */
    /*Since the receivePdu() method has no 'end' condition- it keeps looping continually until told to stop */
    /*Try using a timer to specify how long it should be called for */
    long start = System.currentTimeMillis();
    long end = start + 60*1000; /* 60 seconds * 1000 ms/sec */      

    /*Move pool ExecutorService to top of class, make it public so that it can be used in EspduReceiver.java (06/05/2014 @ 11:00) */
    /*Create an ExecutorService and then call shutdown in my ActionListener for stop */
//  final ExecutorService pool = Executors.newSingleThreadExecutor();

    /*Create 'Quit' button and add it to the panel */
    JButton quitButton = new JButton("Quit");
    panel.add(quitButton);
    quitButton.setBounds(1080, 500, 80, 30); /*Set the location of the button in the window, and its size */

    quitButton.addActionListener(new ActionListener(){
        @Override
        public void actionPerformed(ActionEvent e){
            System.exit(0);
            pool.shutdown();
        }
    });

    setLocationRelativeTo(null);
    panel.repaint();
    setDefaultCloseOperation(EXIT_ON_CLOSE);    

    /*Create 'StartCapture' button and add it to the panel */
    JButton startCaptureButton = new JButton("Start");
    panel.add(startCaptureButton);
    startCaptureButton.setBounds(1080, 350, 80, 30);

    startCaptureButton.addActionListener(new ActionListener(){
        public void actionPerformed(ActionEvent e){
            Filter.getFilterConditions();
            EspduReceiver.startCapture();
            EspduReceiver.stopCapture = false;

            EspduSender.senderThread = new Thread(){

                public void run(){
                    //FilteredPdu.displayFilteredPdu();
                    /*Need to add a call to stop Filter.retrieveFilteredPdu() before calling the Filter.filterPDUs method (14/05/2014 @ 15:00) */
            /*      EspduReceiver.stopCapture = true; /*Setting 'stopCapture' to true will cause the capture to stop when the Filter button is
                                                        pressed- use another boolean that will stop the call to Filter.retrieveFilteredPdu()*/
            /*      EspduReceiver.pauseCapture = true; 
                    Filter.pauseCaptureForFilter(); /*Don't need a call to these two lines */
                    try {
                        EspduSender.sendPdu();
                    } catch (IOException e) {
                        // TODO Auto-generated catch block
                        System.out.println("UnknownHostException in call to EspduSender.sendPdu(); from startCaptureButton ActionListener");
                        e.printStackTrace();
                    }
                /*  Filter.filterPDUs(); /* Try commenting this line since it's now been added to the invokeLater() method in the main(), at end of
     *                                      this class. It is now being called from the Filter.pauseCaptureForFilter() method (14/05/2014 @ 15:40)
     */
                }
            //  EspduSender.senderThread.start();
            };
            EspduSender.senderThread.start();
        }
    }); 


    /*Create 'StopCapture' button and add it to the panel */
    JButton stopCaptureButton = new JButton("Stop");
    panel.add(stopCaptureButton);
    stopCaptureButton.setBounds(1080, 400, 80, 30);

    stopCaptureButton.addActionListener(new ActionListener(){
        @Override
        public void actionPerformed(ActionEvent e){
            EspduReceiver.stopCapture = true;
        }
    });

    /*Add the filters to the window */
    panel.add(filter1);
    filter1.setBounds(720, 50, 100, 30);
    panel.add(filter1Text);
    filter1Text.setBounds(850, 50, 200, 30);

    panel.add(filter2);
    filter2.setBounds(720, 90, 100, 30);
    panel.add(filter2Text);
    filter2Text.setBounds(850, 90, 200, 30);

    panel.add(filter3);
    filter3.setBounds(720, 130, 100, 30);
    panel.add(filter3Text);
    filter3Text.setBounds(850, 130, 200, 30);


    /*Add buttons that will call 'retrieve' functions from Filter.java, and display only the entities that match the filtered
     *  values in the GUI. */

    /*Get entities with matching site */
    JButton filterButton = new JButton("Filter");
    panel.add (filterButton);
    filterButton.setBounds(900, 400, 80, 30);

    filterButton.addActionListener(new ActionListener(){

        boolean filterButtonClicked = true;
        @Override
        public void actionPerformed(ActionEvent e){

            FilteredPdu.thread = new Thread(){

                public void run(){
                    //FilteredPdu.displayFilteredPdu();
                    /*Need to add a call to stop Filter.retrieveFilteredPdu() before calling the Filter.filterPDUs method (14/05/2014 @ 15:00) */
            /*      EspduReceiver.stopCapture = true; /*Setting 'stopCapture' to true will cause the capture to stop when the Filter button is
                                                        pressed- use another boolean that will stop the call to Filter.retrieveFilteredPdu()*/
                    EspduReceiver.pauseCapture = true;
                    Filter.pauseCaptureForFilter();
                /*  Filter.filterPDUs(); /* Try commenting this line since it's now been added to the invokeLater() method in the main(), at end of
     *                                      this class. It is now being called from the Filter.pauseCaptureForFilter() method (14/05/2014 @ 15:40)
     */
                }
            };
            FilteredPdu.thread.start();
        //  EspduReceiver.receiveFilteredPdu();
            /*Need to check if there are any PDUs stored in 'entity' arrays first- if there aren't, then add a call to receivePdu() at
             *  the start of this method; if there are, then get the value entered into the text box, and search through the array for 
             *  a matching value.  */

            Filter.numMatchingAppsFound = 0; /*Reset this variable to 0 every time the button is clicked, so that the count doesn't carry over. */
            Filter.numMatchingSitesFound = 0; /*Reset this variable to 0 every time the button is clicked, so that the count doesn't carry over. */
                                                /*Reseting these values to 0 here doesn't seem to work for some reason. */
            //displayOutput.setText(null); /*Clear the display, so that the user only sees the results from the most recent button press. */

            /*Call 'displayFilteredPdu()' method here */
        //  FilteredPdu.displayFilteredPdu();

            /*Get matching site values from Sites ArrayList */
            try{
                //EspduReceiver.receivePdu(); /*I don't necessarily want to call receivePdu() here */
                if(EspduReceiver.entitySite.get(0) == null){
                //  EspduReceiver.receivePdu();
                //  Filter.retrieveFilteredSite(Integer.parseInt(filter1Text.getText()));
                    System.out.println("Please enter a Site value. ");
                } else {
                    /*Need to add code to retrieve value of 'filter1Text */
                    Filter.retrieveFilteredSite(Integer.parseInt(filter1Text.getText()));
                    //Filter.numMatchingSitesFound++;
                }

                if((EspduReceiver.entityApplication.get(0) == null) || (filter2Text.getText() == null)){
                //  Filter.retrieveFilteredApplication(Integer.parseInt(filter2Text.getText()));
                    System.out.println("Please enter an Application value. ");
                } else {
                    Filter.retrieveFilteredApplication(Integer.parseInt(filter2Text.getText()));
                    //Filter.numMatchingAppsFound++;
                }

                if((EspduReceiver.entity.get(0) == null) || filter3Text.getText() == null){
                    System.out.println("Please enter an ID value. ");
                } else {
                    Filter.retrieveFilteredID(Integer.parseInt(filter3Text.getText()));
                }

            }catch(Exception ex){
                System.out.println("No PDUs have yet been received. You must receive at least one PDU before you can search for a matching site entity. " + ex.toString() + "\n" +
            "or, you have selected a filter, but not entered a filter value. ");
            }

            /*Get matching applications from Application ArrayList. This code doesn't work- try adding it to the existing try/catch block instead 30/04/2014 @ 15:10 
            try{
                if(EspduReceiver.entityApplication.get(0) == null){
                    EspduReceiver.receivePdu();
                    Filter.retrieveFilteredApplication(Integer.parseInt(filter2Text.getText()));
                } else {
                    Filter.retrieveFilteredApplication(Integer.parseInt(filter2Text.getText()));
                }
            }catch(Exception ex2){
                System.out.println("No PDUs have yet been received. You must receive at least one PDU before you can search for a matching application entity. ");
            } */
            displayFilteredOutput.setText("Total number of entities with matching Site value: " + /* Filter.matchingSite.length */ Filter.numMatchingSitesFound  + "\n" +
                    " Total number of entities with matching Application value: " + /* Filter.matchingApplication.length */ Filter.numMatchingAppsFound  + "\n" +
                    " Total number of entities with matching ID value: " + /* Filter.matchingID.length */ Filter.numMatchingIDsFound );

            /*Write a method that will only add the filtered PDUs to 'displayFilteredOutput' here, and call that method within these
             * parenthesis. 01/05/2014 */
            //displayFilteredOutput.setText("");
        }
    });

}

public static void main(String[] args){ /* I also have a main in EspduSender.java- probably need to get rid of that one (14/05/2014) */
    SwingUtilities.invokeLater(new Runnable(){
        @Override
        public void run(){
            Gui gui = new Gui();
            gui.setVisible(true);
        /*  if(filterButtonClicked == true){
                Filter.filterPDUs();
            } */

        }
    });
}




}

Answer 1

you can not put statements like this out of any methods:

displayOutputScroll.setVerticalScrollBarPolicy(ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS);

Move this inside initGUI() that will resolve your problem.

EDIT

instead adding displayOutput to your panel

displayOutput.setBounds(10, 610, 700, 450);
panel.add(displayOutput);

add displayOutputScroll to the panel.

displayOutputScroll.setBounds(10, 610, 700, 450);
panel.add(displayOutputScroll);