Develop Reference

How to store the content of a JTextArea into a class?

I'm working on a program that serves as a hypothetical email system in which users can be created and can send messages to other users that have been created.
The message will be stored in a "Message" class, and the text is typed in a JTextArea in a GUI. What I want to know is how I would go about storing the text typed into the JTextArea, in the exact same layout (indentations and all), within the Message class. I thought about text files but then there would have to be one for each message, potentially creating an infinite number of them, and I don't like the concept of having to make a system for coming up with unique names for each text file.
Can you please give me some advice?

Simply implement the DocumentListener interface, then do the following:
JTextArea someMessage = new JTextArea();
someMessage.getDocument().addDocumentListener(new MyDocumentListener());
someMessage.getDocument().putProperty("name", "Text Area");
Here, we assume the name of the listener you implement is called MyDocumentListener, and the implementation could be as simple as:
class MyDocumentListener implements DocumentListener {
String newline = "\n";
#Override
public void insertUpdate(DocumentEvent e) {
updateLog(e, "inserted into");
}
#Override
public void removeUpdate(DocumentEvent e) {
updateLog(e, "removed from");
}
#Override
public void changedUpdate(DocumentEvent e) {
//Plain text components do not fire these events
}
public void updateLog(DocumentEvent e, String action) {
Document doc = (Document)e.getDocument();
int changeLength = e.getLength();
displayArea.append(
changeLength + " character" +
((changeLength == 1) ? " " : "s ") +
action + doc.getProperty("name") + "." + newline +
" Text length = " + doc.getLength() + newline);
}
}
Examples taken from Oracle website. I recommend reading the rest of that article as it goes into much depth of how to effectively listen for updates to the internal document model.
How to get text that was inserted
insertUpdate is what notifies you when new text has been typed into the textarea. You can get the freshly inserted text by calling off to the DocumentEvent#getOffset and DocumentEvent#getLength. Using both methods, you can get the offset (index) within document where the insertion happened, as well as the length of the change.
Then to get the actual text that was inserted, you call DocumentEvent#getDocument#getText and supplying the offset and length you got from the event.
How to get all the text in the textarea
You can use this similar method to get the entire text in the document by making use of Document#getStartPosition and Document#getEndPosition, then calling Document#getText.
Or even easier, JTextArea#getText

how to display information in panel after a button is clicked?

I'm working on a application which takes pizza orders. Once the user clicks the order summary button the program would display the order summary. The application looks like this:
I would like to print out the order summary(only not the error) in a new penal with a JTextArea like such:
But I don't know how. This is what my application displays right now:
Here is the Code related to the display:
orderSummary = "Customer Name: " + name +
"\nPhone Number: " + phoneNumber +
"\nSize: " + size +
"\nToppings: " + toppings +
"\nTotal: $" + total;
if(error)
JOptionPane.showMessageDialog(null, ErrorString);
else
JOptionPane.showMessageDialog(null, orderSummary);
Error display:

I'm not 100% sure of what you are asking, but if you are looking for a dialog to popup (not just a panel), then you could try something like:
JDialog zMessageDialog = new JDialog((java.awt.Frame) null, true);
zMessageDialog.setTitle("Order summary");
zMessageDialog.setLayout(new BorderLayout());
JTextArea zTextArea = new JTextArea("Blah blah\nblah blah\nblah blah");
zTextArea.setEditable(false);
zTextArea.setColumns(40);
zTextArea.setRows(10);
zTextArea.setBackground(null);
JScrollPane zScrollPane = new JScrollPane(zTextArea);
zMessageDialog.add(zScrollPane, BorderLayout.CENTER);
zMessageDialog.revalidate();
zMessageDialog.pack();
zMessageDialog.setVisible(true);
This just puts a JTextArea in a JDialog. It makes the JTextArea non-editable, and sets its background color to null (which makes it look less editable).
Of course, this may not be the best way to go in terms of a user interface, but that is a different question. If you are using an IDE like Netbeans, you can easily create a separate class based on JDialog and add a panel at the bottom with an "OK" button, and whatever other customizations you desire.

Eclipse Plugin - Dragging text from Java editor onto custom viewer always gets null data

I have created a custom view on Eclipse and defined a drag and drop listener for it. When I drag items from my view onto the native Java editor (using TextTransfer as the mechanism), the text successfully gets pasted on the editor.
However, when I try to do the opposite i.e. when I select a piece of text from the Java editor and drag it to my view, then the cursor shows an invalid sign and the drop doesn't work as expected. The Drop Target is also set to accept TextTransfer instances.
When I have two Java editors open and I drag text from one to the other, it works perfectly. Why does it not work when I drag the text onto my view?
I overrode the dragEnter function of the DropTargetAdapter in my view to check if the drag was being detected and it was. After printing the event.datatypes, I can also see the CF_TEXT type being supported. When I print the event.data, however it is null. Why?
Code is below:
viewDropTargetAdapter = new DropTargetAdapter()
{
#Override
public void drop(DropTargetEvent event)
{
addCodeSnippetAction.run();
}
#Override
public void dragEnter(DropTargetEvent event)
{
System.out.println("DATATYPE: " + event.currentDataType);
System.out.println("DATA: " + event.data);
System.out.println("DETAIL: " + event.detail);
TransferData[] td = event.dataTypes;
for(int i=0; i<td.length; i++)
{
System.out.println("Datatype of " + i + " is: " + td[i].type + " and " +getNameFromId(td[i].type));
}
super.dragEnter(event);
}
};
viewDropTarget = new DropTarget(viewer.getControl(), DND.DROP_COPY);
viewDropTarget.setTransfer(new Transfer[] {TextTransfer.getInstance()});
viewDropTarget.addDropListener(viewDropTargetAdapter);
Output is below:
DATATYPE: org.eclipse.swt.dnd.TransferData#77f5c2c7
DATA: null
DETAIL: 0
Datatype of 0 is: 13 and CF_UNICODETEXT
Datatype of 1 is: 1 and CF_TEXT

After some researching, I realized that it is necessary to set the event.detail variable manually in the DragEnter function. After adding the line:
event.detail = DND.DROP_COPY;
it works now.

calling a second method while one method call is still in progress causes program to crash

I am having some trouble with a couple of methods in my program: I have a method that is called when the user clicks a start button on the GUI. This method will receive all of the network traffic currently being sent/ received over the network, and display information about it to the user. The user can stop this method being called by clicking the stop button.
This method currently looks like this:
public static void retrieveFilteredPdu(){
/*Try/Catch block copied from 'receivePdu()' method in EspduReceiver.java on 07/05/2014
* Now edit it so that it will receive all PDUs, but only display the ones matching the filter values in the top JTextArea */
try{
/*Specify the socket to receive the data */
EspduReceiver.socket = new MulticastSocket(EspduSender.PORT);
EspduReceiver.address = InetAddress.getByName(EspduSender.DEFAULT_MULTICAST_GROUP);
EspduReceiver.socket.joinGroup(EspduReceiver.address);
//stopCapture = false;
/*Loop infinitely, receiving datagrams */
while(true){
/*First, set the value of the 'stopCapture' boolean to 'false', in case it has previously been set to true during the life of
* the program */
/*stopCapture = false; /*For some reason, if I do this here, clicking the 'Get site' button causes the program to start receiving
PDUs again, and you are not able to stop it without manually shutting down the program. Possibly because I am infinitely
setting the value of 'stopCapture' to false?*/
byte buffer[] = new byte[EspduReceiver.MAX_PDU_SIZE];
EspduReceiver.packet = new DatagramPacket(buffer, buffer.length);
EspduReceiver.socket.receive(EspduReceiver.packet);
Pdu pdu = EspduReceiver.pduFactory.createPdu(EspduReceiver.packet.getData()); /*Moved this line to the top of the class to declare as global variable (29/04/2014) */
if(pdu != null){
System.out.print("Got PDU of type: " + pdu.getClass().getName());
if(pdu instanceof EntityStatePdu){
EntityID eid = ((EntityStatePdu)pdu).getEntityID();
Vector3Double position = ((EntityStatePdu)pdu).getEntityLocation();
System.out.println(" EID:[" + eid.getSite() + ", " + eid.getApplication() + ", " + eid.getEntity() + "] ");
System.out.println("Location in DIS coordinates: [" + position.getX() + ", " + position.getY() + ", " + position.getZ() + "] ");
/*Add PDU to ArrayList of PDUs */
EspduReceiver.espdu.add(pdu);
/* System.out.println(" PDU added to arrayList. ");
System.out.println(espdu); /*This is printing out the actual DIS messages (i.e. edu.nps.moves.dis.EntityState...),
maybe try adding the 'eid.getSite()', etc to an ArrayList instead. Use Associative arrays/ map/ hashmap */
EspduReceiver.entitySite.add(eid.getSite());
System.out.println("Entity Site added to ArrayList from Filter.retrieveFilteredPdu() ");
EspduReceiver.entityApplication.add(eid.getApplication());
System.out.println("Entity Application added to ArrayLIst. ");
EspduReceiver.entity.add(eid.getEntity());
System.out.println("Entity ID added to ArrayList");
/*Check that everything is actually in the ArrayLists
for(int i : entity){ /*Substituted 'entity' with 'entitySite' and 'entityApplication'- values are all printed correctly.
System.out.println(i);
} */
/*07/05/2014
* Write a method that will only append the PDUs that match the filter values to the text area,
* call that method here. */
/*Now append each PDU to the text area */
Gui.displayFilteredOutput.append("\n");
Gui.displayFilteredOutput.append("EID: [" + eid.getSite() + ", " + eid.getApplication() + ", " + eid.getEntity() + "]. ");
Gui.displayFilteredOutput.append("Location in DIS coordinates: [" + position.getX() + ", " + position.getY() + ", " + position.getZ() + "] ");
/*Append every PDU that matches the filter criteria to the displayFilteredOutput JTextArea
Gui.displayFilteredOutput.append("\n");
Gui.displayFilteredOutput.append("EID: [" + eid.getSite() + ", " + eid.getApplication() + ", " + eid.getEntity() + "]. ");
Gui.displayFilteredOutput.append("Location in DIS coordinates: [" + position.getX() + ", " + position.getY() + ", " + position.getZ() + "] "); */
} else if(!(pdu instanceof EntityStatePdu)){
System.out.println("There are no PDUs currently being received.");
}
System.out.println();
}
Thread.sleep(1000);
/*Try adding a boolean to allow me to stop the capture by clicking 'stop' button- Look on stackoverflow */
boolean queryStopCapture = EspduReceiver.stopCapture;
if(queryStopCapture == true){
System.out.println("Break clause in 'queryStopCapture' if statement in EspduReceiver.java has been called. ");
break; /*Use a call to receivePdu() to populate the second JTextArea, but don't let it call a 'break' clause at all.
* Find some other way of adding a 'break' to the output displayed in the first JTextArea (01/05/2014)
* Maybe add this code to receivePdu() call in ActionListener instead of here.
*/
}
} /*end while */
} /*end try */
catch(Exception e){
System.out.println(e);
e.printStackTrace();
System.out.println("Error in retrieveFilteredPdu() method. ");
/*09/04/2014 # 17:100
* If this exception gets called, presumably it either means that pdu is not an instance of EntityStatePdu, or
* that pdu does not actually hold a packet. */
}
}
I have another method, which, in theory, should display information about only the network traffic which has attributes matching some values set by the user. This method is called when the user clicks the 'Filter' button on the GUI. The method currently looks like this:
public static void filterPDUs(){
// if(EspduReceiver.startCapture == true){
/*If EspduReceiver.startCapture is true, then the program is already receiving PDUs, so now I need to set it to only display the ones that
* match the filter criteria. Do this by checking the PDU attributes against the filter values before printing- if they match, then print,
* if not, don't. */
if((EspduReceiver.startCapture == true) && (EspduReceiver.stopCapture == false)){
/*Get the size of the sitesToBeFiltered ArrayList, and store in a variable. Will need to update the variable with every iteration
* of the loop, because the ArrayList will keep growing as long as the capture is running. */
int sitesToBeFilteredSize = sitesToBeFiltered.size();
int matchingSitesIterator = 0;
/*First, check if site filter value matches the PDU's site, if it does, then check Application, if it matches again, then check ID.
* If at any point it doesn't match, exit the while loop. */
while(matchingSitesIterator < sitesToBeFilteredSize){
System.out.println("SitesToBeFiltered.size() = " + sitesToBeFilteredSize);
if(sitesToBeFiltered.get(matchingSitesIterator) == Filter.filter1Value){
if(applicationsToBeFiltered.get(matchingSitesIterator) == Filter.filter2Value){
if(IDsToBeFiltered.get(matchingSitesIterator) == Filter.filter3Value){
Gui.displayFilteredOutput.append("Matching PDU found: [" + sitesToBeFiltered.get(matchingSitesIterator) + ", " + applicationsToBeFiltered.get(matchingSitesIterator) + ", " + IDsToBeFiltered.get(matchingSitesIterator) + "] ");
} else {Gui.displayFilteredOutput.append("Sorry, there were no PDUs found with the specified ID value.");}
Gui.displayFilteredOutput.append("Need to display every PDU that had a matching Site & Application here. ");
}else {Gui.displayFilteredOutput.append("Sorry, there were no PDUs found with the specified Application value.");}
Gui.displayFilteredOutput.append("need to display every PDU that had a matching Site here. ");
}else {Gui.displayOutput.append("Sorry, there were no PDUs found with the specified Site value.");}
}
} else {
Gui.displayFilteredOutput.append("Do something if EspduReceiver.startCapture is not true, and EspduReceiver.stopCapture is not false");
}
// }else if(EspduReceiver.startCapture == false){
/*If EspduReceiver.startCapture is false, then the program is not receiving PDUs, so I now need to call the method that will receive PDUs,
* and display only the ones that match the filter criteria. */
// }
}
The problem I'm having is that for some reason, if the user clicks the 'Filter' button to display only the PDUs with matching filter criteria, after clicking 'Start' (to call the first method), then the program crashes completely... (i.e. it appears to stop performing the function that it was carrying out, and will not respond to clicks on any buttons or even the 'Close window' button)
If they click 'Filter' after having clicked 'Start' & 'Stop' (i.e. when the first method is not running, then the second method performs its tasks as expected.
It seems that for some reason, calling the second method while the first method is still running causes the program to crash- and I can't work out why this is... can anyone point out what's going wrong here?
Edit
I have the following code in my main method:
public static void main(String[] args){
SwingUtilities.invokeLater(new Runnable(){
#Override
public void run(){
Gui gui = new Gui();
gui.setVisible(true);
}
});
}

You need to show more of the code, as others have said, but if you're using Swingworkers or other threads to run these methods, then either the methods have to be thread-safe or they need to be synchronized to prevent their execution from being interleaved. If you're directly accessing Swing components outside the event-dispatching thread, then Swing will make demons come out of your nose, so don't do that (there are some special exceptions for some text components, but generally it's prohibited). If you're not sure, stick assert java.awt.EventQueue.isDispatchThread() before every statement that constructs or uses a Swing object, and enable assertions in the runtime system.

I assume Gui is built on Swing. Read the Swing tutorial, and pay attention to the Event Dispatch Thread. I can't see how the Swing portion of you code works, but I'm guessing you are locking up the EDT somehow. A long-running process needs to run in its own thread and use SwingUtilities.invokeLater() to update Swing components, like your text area.

Making a JFrame act like a dialog box

I have a form for the user to fill out in a JFrame which then writes the collected data to a JTable in a different class.
I'm trying to configure it that when the user selects "Submit" that the JFrame will close, but not close down the program. What would be the command I need to achieve this?
The code for the submit button is as follows is as follows:
JButton bMark = new JButton("Submit");
bMark.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
String start = tbStart.getText();
String end = tbEnd.getText();
String[] marking = {start, end, active, body, dysk, trem, brady};
//This is just for me to ensure the collected data is correct
System.out.println(marking[0] + " " +marking[1] + " " +marking[2] + " " +
marking[3] + " " + marking[4] + " " + marking[5] + " " + marking[6]);
//This is is the class the form data is being sent to
markTable.main(marking);
//This is where I would like the close the current window
}
});
bMark.setBounds(308, 191, 86, 23);
The class name is createMark and the method is public createMark
Thanks to anyone who replies,
Jared.

//This is where I would like the close the current window
there are these ways
JFrame#setVisible(false), but not terminating current JVM, this session exist until PC restarted,
JFrame#dispose() terminating current JVM,
System#exit(int); terminating current JVM,
better would be to JFrame#setDefaultCloseOperation
don't suplly JOptionPane, maybe will be better use that directly

You need to set the default close operation on the JFrame as such:
frame.setDefaultCloseOperation(JFrame.HIDE_ON_CLOSE);
This will take care of the case where the user closes the window using the title bar or hits something like Alt+F4.
Next, simply call setVisible(false) when the submit button is pressed.