JFrame strange white stripe on top of background image

Question

I have a strange white stripe (see below) appearing on top of my background image. The code is quite simple. How to get rid of the white stripe?

//Graphics side of the game
public class GUI extends JFrame {

    private final int larghezza = 1280;
    private final int altezza = 720;
    private final String name = "Sette e Mezzo";

    private final ImageIcon backgroundImage;
    private JLabel bgImageLabel;
    private JPanel backgroundPanel, borderLayoutPanel, topGridLayout, botGridLayout;

    public GUI () {
        backgroundImage = new ImageIcon ("assets/background.png");

        bgImageLabel = new JLabel (backgroundImage);

        //Panels
        borderLayoutPanel = new JPanel (new BorderLayout ());
        topGridLayout = new JPanel (new GridLayout (1, 3));
        botGridLayout = new JPanel (new GridLayout (1, 3));
        backgroundPanel = new JPanel ();
        backgroundPanel.add (bgImageLabel);

        //Frame
        this.setName (name);
        this.setPreferredSize (new Dimension(larghezza, altezza));
        this.setDefaultCloseOperation (JFrame.EXIT_ON_CLOSE);

        //Adding to frame and panels
        borderLayoutPanel.add (topGridLayout, BorderLayout.NORTH);
        borderLayoutPanel.add (botGridLayout, BorderLayout.SOUTH);

        this.add (borderLayoutPanel);
        this.add (backgroundPanel);

        this.pack ();
        this.setLocationRelativeTo (null);  
        this.setVisible (true);
    } 
}

1) For better help sooner, post a [MCVE] or [Short, Self Contained, Correct Example](http://www.sscce.org/). (For example, to make it complete the code above needs imports and a main method) 2) *"`new ImageIcon ("assets/background.png");`"* One way to get image(s) for an example is to hot link to images seen in [this Q&A](http://stackoverflow.com/q/19209650/418556). — Andrew Thompson, May 13 '17 at 09:38

score 1 · Answer 1 · edited May 23 '17 at 12:26

Don't use setPreferredSize() when you really mean to override getPreferredSize(). In this case, the specified Dimension probably doesn't quite match the size of "assets/background.png". This allows some portion of another panel to show, perhaps backgroundPanel.

In the example below,

The default layout of JPanel is FlowLayout, which has a "default 5-unit horizontal and vertical gap." A touch of Color.blue makes the gap stand out; resize the enclosing frame to see the behavior.
As the default layout of JFrame is BorderLayout, you may not need borderLayoutPanel at all.
Because the two GridLayout panels have no content, they remain invisible. Add content to each or override getPreferredSize() in each to see the effect.
Construct and manipulate Swing GUI objects only on the event dispatch thread.

import java.awt.*;
import java.net.URL;
import javax.swing.*;

public class GUI {

    private static final String TITLE = "Title";
    private static ImageIcon IMAGE_ICON;

    private void display() {
        //Panels
        JPanel topGridLayout = new JPanel(new GridLayout(1, 3));
        JPanel botGridLayout = new JPanel(new GridLayout(1, 3));
        JPanel backgroundPanel = new JPanel();
        backgroundPanel.setBackground(Color.blue);
        backgroundPanel.add(new JLabel(IMAGE_ICON));

        //Frame
        JFrame f = new JFrame(TITLE);
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        //Add components
        f.add(topGridLayout, BorderLayout.NORTH);
        f.add(backgroundPanel);
        f.add(botGridLayout, BorderLayout.SOUTH);

        f.pack();
        f.setLocationRelativeTo(null);
        f.setVisible(true);
    }

    public static void main(String[] args) throws Exception {
        IMAGE_ICON = new ImageIcon(new URL("http://i.imgur.com/mowekvC.jpg"));
        EventQueue.invokeLater(new GUI()::display);
    }
}

I can almost see a cup floating above the beans. – trashgod May 13 '17 at 12:12 — trashgod, May 13 '17 at 12:12

JFrame strange white stripe on top of background image

1 Answers1