label text auto update

[Ayy Looz]

how can i make labels "listen" to changes (in a String[] array for example) ??

i mean, i have an array that is updated whenever a change occurs to a server (that i monitor)

i want the labels to be "in sync" with the array content

can i do that ?

[Rob Spoor]

You could wrap the array in a wrapper class, and make that class fire events.

For instance:

class StringArray
{
    private final String[] array;

    private final PropertyChangeSupport changeSupport;

    public StringArray(String[] array)
    {
        this.array = array;
        changeSupport = new PropertyChangeSupport(this);
    }

    public int length()
    {
        return array.length();
    }

    public String get(int index)
    {
        return array[index];
    }

    public void set(int index, String value)
    {
        String old = array[index];
        if (!eq(old, value))
        {
            array[index] = value;
            changeSupport.firePropertyChange(String.valueOf(index), old, value);
        }
    }

    public void addPropertyChangeListener(PropertyChangeListener l)
    {
        // listen to all properties
        changeSupport.addPropertyChangeListener(l);
    }

    public void removePropertyChangeListener(PropertyChangeListener l)
    {
        changeSupport.removePropertyChangeListener(l);
    }

    private boolean eq(String s1, String s2)
    {
        return (s1 == null ? s2 == null : s1.equals(s2));
    }
}

Usage:

StringArray array = new StringArray(args);
array.addPropertyChangeListener(new PropertyChangeListener()
{
    public void propertyChange(PropertyChangeEvent e)
    {
        int index = Integer.parseInt(e.getPropertyName());
        String oldValue = e.getOldValue();
        String newValue = e.getNewValue();
    }
});

You just have to make sure that all access to the array is done through the wrapper class.

[Ayy Looz]

sorry but i'm a java newbie, i couldnt figure out how to use that code to auto update the label's text :/

[Rob Spoor]

You need to keep an association between the JLabels and the array indexes. Storing the JLabels in their own array would be easiest. After retrieving the index as I have already shown, you simply retrieve the JLabel and change its text:

public void propertyChange(PropertyChangeEvent e)   
{   
    int index = Integer.parseInt(e.getPropertyName());   
    // String oldValue = e.getOldValue();   // don't need the old value
    String newValue = e.getNewValue();   
    JLabel label = labels[index];
    label.setText(newValue);
}

[Ayy Looz]

thank you very much
i'll give it a try