Basic GUI help

[Adam P.]

I'm working on a big GUI, using NetBeans since it simplified the initial container design... but now I need to link all the components to actions and events... which I'm not very experienced with.

I made a dummy GUI that does similar, but far fewer functions like my real project. Can someone help me design the actions/events for this little dummy gui, and explain how they work, so I can use that as a guide...?

The dummy project has two java files. A Scan class (Scan.java) will be used to parse a 'patient' text file, and create a String with info from that file (Scan.patient), as well as store the original pathname (Scan.path).
http://deviantone.com/javagui/Scan.java

You can create a Scan object by giving the constructor a File or String (file path) argument. You can then call the patient or path vars. The dummy 3 line patient file:
http://deviantone.com/javagui/dummy.txt

Now the hard part, the GUI from NetBeans... the syntax is a little bloated since it's machine generated, but shouldn't be too hard to figure out.
http://deviantone.com/javagui/dummyGui.java

The GUI is meant to parse whatever text file opened (for the purposes of this dummy gui, only dummy.txt will ever be browsed to, since the program can handle only 3 lines) into C:\output.txt (which you can create and leave blank beforehand).

What I need:

(1) The Open button (JButton openButton) needs to call a file chooser, where a user can browse to our dummy text file. dummyGui.java should then make a Scan object using this file.

(2) Once opened, the file path should appear in the JLabel pathLabel (you can use another gui component instead of a JLabel if you want, I just didn't know what would be the appropriate one for this sort of operation)

(3) You can select Yes/No or input some text into the combo box (JComboBox statusCombo) as well as input stuff into a text field, let's say a date (JTextField dateField). This information will also be written into output.txt

(4) Once you hit the Write button, Scan.patient, and the contents of statusCombo and dateField should be written into output.txt (it doesn't matter what line contains what, for simplicity maybe make statusCombo first, then dateField, then Scan.patient which is 2 lines)... I just need to see how to make a button do such an operation using another Object (Scan) as well as user input...

So far, I have looked through the API and File Chooser examples, and I've added the following to my code:

- instance variable to the dummyGui.java: File file; for the file that file chooser will get.
- also added openButton.addActionListener(this); to the initComponents() method.
- and another method:

public void actionPerformed(ActionEvent e) {
if(e.getSource() == openButton){
JFileChooser chooser = new JFileChooser();
int returnVal = chooser.showOpenDialog(dummyGui.this);
if(returnVal == JFileChooser.APPROVE_OPTION) {
file = chooser.getSelectedFile();
}
}
}

But when I run the GUI, and hit Open, the button gets pressed in and then the window freezes while no file browser shows ... =/

[Craig Wood]

Some of the fun in java is in how you put things together. There are many ways to do what you are wanting to do. This is one way, a suggestion, a place to start exploring possibilities.

Here I'm using another class, ButtonListener, to handle the button events. This isolates the event code from the gui code and (is an attempt to) make what we're doing easier to read, understand and maintain (in the future). Instantiate a single instance of ButtonListener and register its reference as the listener for the two buttons in dummyGui. Send back a reference to the dummyGui class in the ButtonListener constructor so we can access variables in dummyGui from within ButtonListener. To acces statusCombo and pathLabel I demoted them from their private status. You can use get methods to avoid this demotion.

Inside ButtonListener we do all the activity of opening a file dialog, updating pathLabel, gathering data and writing to the output file.

Back in dummyGui note the setActionCommand calls for each JButton. This is a way of avoiding the need to obtain a reference to the buttons within ButtonListener. Obtaining a reference would be easy enough to do:

public void actionPerformed(ActionEvent e)
JButton button = (JButton)e.getSource();
if(button == gui.openButton)

anyway and of course would require get methods or the demotion (from private access) as before.

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import java.io.*;
public class dummyGui extends javax.swing.JFrame {
/** Creates new form dummyGui */
public dummyGui() {
initComponents();
}
/** This method is called from within the constructor to
* initialize the form.
* WARNING: Do NOT modify this code. The content of this method is
* always regenerated by the Form Editor.
*/
private void initComponents() {//GEN-BEGIN:initComponents
java.awt.GridBagConstraints gridBagConstraints;
jPanel1 = new javax.swing.JPanel();
openButton = new javax.swing.JButton();
statusCombo = new javax.swing.JComboBox();
dateField = new javax.swing.JTextField();
pathLabel = new javax.swing.JLabel();
writeButton = new javax.swing.JButton();
addWindowListener(new java.awt.event.WindowAdapter() {
public void windowClosing(java.awt.event.WindowEvent evt) {
exitForm(evt);
}
});
jPanel1.setLayout(new java.awt.GridBagLayout());
jPanel1.setPreferredSize(new java.awt.Dimension(300, 100));
openButton.setText("Open");
openButton.setActionCommand("Open");
ButtonListener buttonListener = new ButtonListener(this);
openButton.addActionListener(buttonListener);
jPanel1.add(openButton, new java.awt.GridBagConstraints());
statusCombo.setEditable(true);
statusCombo.setModel(new javax.swing.DefaultComboBoxModel(
new String[] { "", "Yes", "No" }));
gridBagConstraints = new java.awt.GridBagConstraints();
gridBagConstraints.gridx = 0;
gridBagConstraints.gridy = 2;
jPanel1.add(statusCombo, gridBagConstraints);
dateField.setToolTipText("Date goes here");
dateField.setPreferredSize(new java.awt.Dimension(100, 20));
gridBagConstraints = new java.awt.GridBagConstraints();
gridBagConstraints.gridx = 1;
gridBagConstraints.gridy = 2;
jPanel1.add(dateField, gridBagConstraints);
gridBagConstraints = new java.awt.GridBagConstraints();
gridBagConstraints.gridx = 0;
gridBagConstraints.gridy = 1;
gridBagConstraints.gridwidth = 2;
jPanel1.add(pathLabel, gridBagConstraints);
writeButton.setText("Write");
writeButton.setActionCommand("Write");
writeButton.addActionListener(buttonListener);
jPanel1.add(writeButton, new java.awt.GridBagConstraints());
getContentPane().add(jPanel1, java.awt.BorderLayout.CENTER);
setLocation(200,200);
pack();
setVisible(true);
}//GEN-END:initComponents
/** Exit the Application */
private void exitForm(java.awt.event.WindowEvent evt) {//GEN-FIRST:event_exitForm
System.exit(0);
}//GEN-LAST:event_exitForm
/**
* @param args the command line arguments
*/
public static void main(String args[]) {
new dummyGui().show();
}
// Variables declaration - do not modify//GEN-BEGIN:variables
javax.swing.JTextField dateField;
private javax.swing.JPanel jPanel1;
private javax.swing.JButton openButton;
javax.swing.JLabel pathLabel;
javax.swing.JComboBox statusCombo;
private javax.swing.JButton writeButton;
// End of variables declaration//GEN-END:variables
}
class ButtonListener implements ActionListener {
dummyGui gui;
JFileChooser fc;
String[] data;
public ButtonListener(dummyGui dgui) {
gui = dgui;
fc = new JFileChooser(".");
}
public void actionPerformed(ActionEvent e) {
JButton button = (JButton)e.getSource();
String ac = button.getActionCommand();
if(ac.equals("Open"))
showDialog();
if(ac.equals("Write"))
writeToFile();
}
private void showDialog() {
int retVal = fc.showOpenDialog(gui);
if(retVal == JFileChooser.APPROVE_OPTION)
{
File file = fc.getSelectedFile();
gui.pathLabel.setText(file.getPath());
try {
data = new Scan(file).parse();
}
catch(IOException ioe) {
System.out.println("file dialog ioe: " + ioe.getMessage());
}
}
}
private void writeToFile() {
String status = (String)gui.statusCombo.getSelectedItem();
String dateEntry = gui.dateField.getText();
String newLine = System.getProperty("line.separator");
BufferedWriter bw = null;
try {
bw = new BufferedWriter(
new FileWriter("output.txt"));
bw.write(status + newLine);
bw.write(dateEntry + newLine);
for(int j = 0; j < data.length; j++)
bw.write(data[j] + newLine);
bw.close();
}
catch(IOException ioe) {
System.out.println("write help: " + ioe.getMessage());
}
}
}