SwingPropertyChangeSupport to Dynamically Update JTextArea
SwingPropertyChangeSupport is a class that can be used to monitor changes in the properties of an object. This allows other objects to be notified when a property changes, which can be useful for updating the GUI accordingly.
In this example, we are using SwingPropertyChangeSupport to allow an array displayed in a JTextArea to be updated when changes are entered via an input dialog. The array is updated OK, but the GUI is not refreshed.
Here is the modified code:
import java.awt.BorderLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.FocusListener;
import java.beans.PropertyChangeEvent;
import java.beans.PropertyChangeListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JTextArea;
import javax.swing.event.SwingPropertyChangeSupport;
public class Main {
public static void main(String[] arg) {
GuiForUpdate display = new GuiForUpdate();
display.setVisible(true);
}
}
class GuiForUpdate extends JFrame implements ActionListener {
/**
*
*/
private static final long serialVersionUID = 1L;
private FocusListener focusListener;
private String mList;
private JButton changeArrayButton;
private JTextArea codeIn, displayOutput;
private int arrayIndex;
private JPanel displayPanel;
private ArrayForUpdating arrayForUpdate = new ArrayForUpdating();
public GuiForUpdate() {
setSize(224, 180);
layoutLeft();
layoutDisplay();
layoutBottom();
}
/**
* adds a display area for array
*/
public void layoutDisplay() {
displayPanel = new JPanel();
add(displayPanel, BorderLayout.CENTER);
displayOutput = new JTextArea();
displayPanel.add(displayOutput);
displayOutput.addFocusListener(focusListener);
mList = arrayForUpdate.getBoundProperty();
arrayForUpdate.addPropertyChangeListener(new PropertyChangeListener() {
@Override
public void propertyChange(PropertyChangeEvent pcEvt) {
if (pcEvt.getPropertyName().equals(
ArrayForUpdating.BOUND_PROPERTY)) {
mList = (pcEvt.getNewValue().toString());
updateDisplay();
}
}
});
displayOutput.setText(mList);
}
/**
* adds left hand side elements to left of GUI
*/
public void layoutLeft() {
JPanel left = new JPanel();
add(left, BorderLayout.WEST);
codeIn = new JTextArea(2, 2);
left.add(codeIn);
codeIn.addFocusListener(focusListener);
}
/**
* adds bottom elements to bottom of GUI
*/
public void layoutBottom() {
JPanel bottom = new JPanel();
changeArrayButton = new JButton("Modify array");
changeArrayButton.addActionListener(this);
bottom.add(changeArrayButton);
add(bottom, BorderLayout.SOUTH);
}
/**
* Process button clicks
*/
public void actionPerformed(ActionEvent ae) {
if (ae.getSource() == changeArrayButton) {
// first check if any code entered
if (codeIn.getText().trim().length() != 0) {
// call modifyMemory() method
modifyArray();
} else
JOptionPane.showMessageDialog(null,
"Please enter something first.");
}
}
/**
* method to process modify array
*/
public void modifyArray() {
// show dialog to retrieve entered address
String addressToModify = (String) JOptionPane
.showInputDialog("At which location?");
// confirm if a string was entered
if ((addressToModify != null) && (addressToModify.length() > 0)) {
// convert to integer if decimal address entered
arrayIndex = Integer.parseInt(addressToModify);
}
// pass as integer
processInput(arrayIndex);
}
public void processInput(int a) {
String newValue = codeIn.getText();
arrayForUpdate.instructionsIn(newValue, a);
}
public void updateDisplay() {
displayOutput.setText(mList);
}
}
class ArrayForUpdating {
public static final String BOUND_PROPERTY = "bound property";
private String boundProperty = "";
private SwingPropertyChangeSupport spcSupport = new SwingPropertyChangeSupport(
this);
private StringBuilder mList;
private int[] myArray;
public ArrayForUpdating() {
myArray = new int[5];
for (int i = 0; i < myArray.length; i ) {
myArray[i] = 0;
}
setArrayyDisplayString();
}
/**
* method to create formatted string of array
*/
public void setArrayyDisplayString() {
// create StringBuilder for display in memory tab
mList = new StringBuilder();
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