Install4j: changing size of a JPanel in custom InstallerScreen

Question

I am trying to change the size of the JPanel which is to be returned in createComponent() and adjust it to the size of the Frame/ the screen using getParent() . but the panels size remains unchanged. The code for my CustomPanel follows:

    class CustomPanel extends JPanel {
        final Image backImage = getBackImage();

        @Override
        protected void paintComponent(Graphics g) {

            super.paintComponent(g);
            g.drawImage(backImage, 0, 0, null);
        }

        @Override
        public Dimension getPreferredSize() {
            Container c = this.getParent();
            Dimension d = new Dimension(c.getWidth(), c.getHeight());
            return d;
        }
    }

and the sample code inside the createComponent() method follows:

JPanel buttonPanel = new CustomPanel();
buttonPanel.add(button);    
return buttonPanel;

I have tried to do it directly when instantiating the buttonPanel which gave me error. The sample code for this is:

JPanel buttonPanel = new JPanel();
Container c = buttonPanel.getParent();
Dimension d = new Dimension(c.getWidth(), c.getHeight());
buttonPanel.setSize(d);
buttonPanel.add(button);
return buttonPanel;

and the error log is:

Caused by: java.lang.NullPointerException
    at com.test.customcode.SampleScreenNew.createComponent(SampleScreenNew.java:101)
    at com.install4j.runtime.installer.frontend.ScreenEnvelope.addScreenContent(ScreenEnvelope.java:372)
    at com.install4j.runtime.wizard.StandardScreen.createMainPanel(StandardScreen.java:136)
    at com.install4j.runtime.wizard.StandardScreen.setupComponent(StandardScreen.java:78)
    at com.install4j.runtime.wizard.StandardScreen.initScreen(StandardScreen.java:50)
    at com.install4j.runtime.installer.frontend.ScreenEnvelope.init(ScreenEnvelope.java:61)
    at com.install4j.runtime.installer.frontend.ScreenEnvelope.<init>(ScreenEnvelope.java:46)
    at com.install4j.runtime.installer.frontend.WizardScreenExecutor$1.run(WizardScreenExecutor.java:199)
    at java.awt.event.InvocationEvent.dispatch(Unknown Source)
    at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
    at java.awt.EventQueue.access$300(Unknown Source)
    at java.awt.EventQueue$3.run(Unknown Source)
    at java.awt.EventQueue$3.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
    at java.awt.EventQueue.dispatchEvent(Unknown Source)
    at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
    at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
    at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
    at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
    at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
    at java.awt.EventDispatchThread.run(Unknown Source)

Answer 1

In your screen implementation, override

@Override
public boolean isFillVertical() {
    return true;
}

@Override
public boolean isFillHorizontal() {
    return true;
}

Then the panel returned by createComponent() will fill all the available space.