JFrame turns blue when adding tabs

Question

I currently have a Jframe that I want to add to a tab instead. (I used a frame just for testing purposes, to make sure the look and feel is correct, but when trying to add it to a JTabbedPane, the frame starts to look blue (weird top aswell).

I tried copying my settings from my original frame to the new frame but that did not help.

JTabbedPane tabs = new JTabbedPane();
tabs.addTab("1", frame.getContentPane());
JFrame FinalFrame = new JFrame();
FinalFrame.setDefaultLookAndFeelDecorated(true);
FinalFrame.setSize(WIDTH, HEIGTH);
FinalFrame.setLocation(100, 150);
FinalFrame.setTitle("Primal-Pvm Notification center");
FinalFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
FinalFrame.add(tabs);

Side by side view of the problem and the frame before adding it to the tab:

Edit: Answer by George Z. helped me out a lot.

Like he said to solve the problem: Don't add things to your main frame but add them to a Jpanel and add that to a JTabbedPane. If you have a Jpanel that you are adding to a tab that contains an override in the paintComponent, you have to create that class as the Jpanel so:

JPanel panel = new LineDrawer([Enter parameters]);
panel.setLayout([Enter Layout]);

have you explicitly set your LaF somewhere else? if not, I would try that and see if it changes... — JoSSte, Aug 10 '19 at 09:08

George Z. · Accepted Answer · 2019-08-10T09:49:34.110

The way you are approaching this seems to be pretty complex hence this weird behavior. (Looks like a look and feel problem? - show the part of the code that sets it)

However, I suggest you to create only one JFrame (this question explains why you should do that), set the layout of its content pane to BorderLayout and keep it like this. Its a rare situation to mess up with content panes. After that create independent JPanels representing the tab(s) you would like to have. Finally create a JTabbedPane with these panels and add it to the content frame of the JFrame.

A small example would be:

public class TabbedPanelExample extends JFrame {
    public TabbedPanelExample() {
        super("test");
        setDefaultCloseOperation(EXIT_ON_CLOSE);
        setLayout(new BorderLayout());

        JTabbedPane pane = new JTabbedPane();
        pane.addTab("FirstTab", createFirstTab());
        pane.addTab("SecondTab", createSecondTab());

        add(pane);
        setSize(400, 400);
        setLocationRelativeTo(null);
    }

    private Component createFirstTab() {
        JPanel panel = new JPanel(new FlowLayout());
        panel.add(new JLabel("Some Component"));
        panel.add(new JTextField("Some Other Component"));
        return panel;
    }

    private Component createSecondTab() {
        JPanel panel = new JPanel(new FlowLayout());
        panel.add(new JLabel("Some Component"));
        panel.add(new JButton("Some Other Component"));
        return panel;
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(() -> {
            new TabbedPanelExample().setVisible(true);
        });
    }

}

Post edit based on this comment:

Well I do have a Jframe with a lot of elements added to it so it kinda is a hassle to switch it all to panels;

A JFrame cannot have a lot of elements. You take a look on how to use root panes. The container that "has a lot of elements" of a JFrame is its rootpane which is mostly completed by its contentpane. When you frame.add(component), you add the component to its content pane. Guess what? A JFrame's content pane is a JPanel. So are a already to panels.

Now in order to make this work, try to do as i said and frame.setLayout(new BorderLayout(); //changes layout to contentpane. Assuming you have a bunch of components (lets say comp1,comp2) and you are adding them like:

frame.add(comp1);
frame.add(comp2);

You must do the following in order to make it clear. Create a JPanel and instead of frame.add(comp1), do panel.add(comp1). So this JPanel has all the components you added in JFrame. After that create your JTabbedPane:

JTabbedPane pane = new JTabbedPane();
pane.addTab("tab", panel);

and finally add this pane to the content pane of your JFrame:

frame.add(pane);

In conclusion, you will move all the components you have added to your frame into a JPanel, add this JPanel to a JTabbedPane, and finally add this JTabbedPane to the frame (contentpane). Frame has only one component.

Well I do have a Jframe with a lot of elements added to it so it kinda is a hassle to switch it all to panels; although that would fix the background color, how does it explain why the top part is like that? I expect it to be the regular java thing like in the other one. — Gerben Banaan, Aug 10 '19 at 09:34
After fiddling around with why the lines did not appear I did found a solution, I edited it on my question so future users can see that too; Thanks a lot :) — Gerben Banaan, Aug 10 '19 at 11:25

JFrame turns blue when adding tabs

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