Using Listeners in Custom Netbeans Platform Wizards
Tuesday May 22 2018

This tutorial explains how you can add validation to your custom wizards in the Netbeans Platform. This works by setting a boolean variable to false and then throwing a WizardValidationException which will show an error message in the wizard, disabling the ability to click the Next or Finish buttons.

The problem with this is that after the above happens, there is no way to enable these buttons again. And the way to achieve this is not covered in that tutorial.

Therefore, in this blog post I will explain just how to do that.

We will be working only with the controller class of each panel. When using the wizard to generate your wizard, these classes will typically have a class suffix like WizardPanel1.

Let's begin by first implementing the DocumentListener interface and add a Set of ChangeListeners:

public class DoSomethingWizardPanel1 implements WizardDescriptor.ValidatingPanel<WizardDescriptor>, DocumentListener {

  private Set<ChangeListener> listeners = new HashSet(1);

  // ...
}

Second, in the getComponent() method we will need to add the DocumentListener to each of the fields we want to trigger the change. For this example I will use a single text field:

@Override
public DoSomethingVisualPanel1 getComponent() {
    if (component == null) {
        component = new DoSomethingVisualPanel1();
        component.getNameField().getDocument().addDocumentListener(this);
    }
    return component;
}

With the above implementation you will need to define a getter method getNameField() that returns the text field, inside the actual panel class that was also generated.

Next we will need to include some listener implementations:

@Override
public void addChangeListener(ChangeListener l) {
    synchronized (listeners) {
        listeners.add(l);
    }
}

@Override
public void removeChangeListener(ChangeListener l) {
    synchronized (listeners) {
        listeners.remove(l);
    }
}

public void fireChangeEvent() {
    Set<ChangeListener> ls;
    synchronized (listeners) {
        ls = new HashSet(listeners);
    }

    ChangeEvent ev = new ChangeEvent(this);
    for (ChangeListener l : ls) {
        l.stateChanged(ev);
    }
}

Next, the DocumentListener implementation:

@Override
public void insertUpdate(DocumentEvent de) {
    change();
}

@Override
public void removeUpdate(DocumentEvent de) {
    change();
}

@Override
public void changedUpdate(DocumentEvent de) {
    change();
}

The change() method is as follows:

private void change() {
    setValid(true);
}

And lastly the setValid method that will re-enable the buttons:

private void setValid(boolean val) {
    isValid = val;
    fireChangeEvent();
}

If the user input fails validation when the next/finish buttons are clicked again, the exception will be thrown again and the buttons will be disabled again. When the user types in the text field again, the listeners will work their magic, enabling the buttons once again.

References

  1. https://platform.netbeans.org/tutorials/nbm-wizard.html
  2. https://blogs.oracle.com/geertjan/disablingenabling-a-wizard-panels-finish-button

netbeans platform

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