Agfdhyk

I'm experiencing a strange problem with the java JFrame class in one of my programs. Thankfully I'm able to duplicate this issue using the FrameDemo.java example taken from Oracle's website:

https://docs.oracle.com/javase/tutorial/displayCode.html?code=https://docs.oracle.com/javase/tutorial/uiswing/examples/components/FrameDemoProject/src/components/FrameDemo.java

I change the dimension of emptyLabel to (3005, 100) and then compile and launch the program. On my dual monitor display, I expect the frame to almost span both monitors (they're each 1920 pixels wide).

Instead, what I'm seeing is that the JFrame is sized to fit the width of a single monitor. I can't seems to get the window to come up spanning both monitors. Am I doing something wrong here? I'm running on Centos 7.5 and am using jdk 1.8.0_60.

The exact code appears below. It's mostly a copy/paste from Oracle's demo, with some comments cut to keep it short.

import java.awt.*;

import java.awt.event.*;

import javax.swing.*;



/* FrameDemo.java requires no other files. */

public class FrameDemo {

    /**

     * Create the GUI and show it.  For thread safety,

     * this method should be invoked from the

     * event-dispatching thread.

     */

    private static void createAndShowGUI() {

        //Create and set up the window.

        JFrame frame = new JFrame("FrameDemo");

        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);



        JLabel emptyLabel = new JLabel("blahblah");

        emptyLabel.setPreferredSize(new Dimension(3005, 100));

        frame.getContentPane().add(emptyLabel, BorderLayout.CENTER);



        //Display the window.

        frame.pack();

        frame.setVisible(true);

    }



    public static void main(String args) {

        //Schedule a job for the event-dispatching thread:

        //creating and showing this application's GUI.

        javax.swing.SwingUtilities.invokeLater(new Runnable() {

            public void run() {

                createAndShowGUI();

            }

        });

    }

}

Many thanks to MadProgrammer. Unfortunately, in my more complicated program, the second call to pack didn't seem to do the trick.

The workaround I eventually settled on was to compute the cumulative width of all my components (they were loaded into a JSplitPane). This is equal to the widths of the left pane, the right pane and the divider. If this cumulative width exceeds the width of a monitor, I set frame minimum size to this cumulative width. This seems to ensure that the frame can span two monitors when it appears. Then after making things visible, I reset the minimum size to a value I saved at startup time. This allows my JFrame to come up on two screens but still be resizable to something smaller.

This truly is a nasty workaround. I have reported this as a bug to http://bugs.java.com. It's listed as the following bug: http://bugs.java.com/bugdatabase/view_bug.do?bug_id=JDK-8213620