Exception in "AWT-EventQueue-0" java.lang.NullPointerException

Question

This programs take in a string for a parameter. Currently filled with:

"http://localhost/media/svu.mp4"

I have made sure the URL exists.

I am using the VLCj library to create the mediaPlayerComponent (which is placed inside the container (JPanel mainPanel) ). The component mainPanel is then placed inside the JLayeredPanel layers. On top of that, I place a clear (non-opaque) layer (JPanel glassPane). According to everything I've read, this should be working and Eclipse isn't showing any errors or warnings.

The stack trace is as follows:

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
   at client.test.Client.<init>(Client.java:62)
   at client.test.Client$1.run(Client.java:44)
   at java.awt.event.InvocationEvent.dispatch(Unknown Source)
   at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
   ....

The code is below. Line 62 is marked with a comment. The JPanels and JLayeredPanel, as well as the windowDimensions are all created as static objects above the main method in my code.

Any and all help is greatly appreciated.

static JLayeredPane layers = new JLayeredPane();
static JPanel mainPanel, glassPane = new JPanel();

public Client(String toPlay) {
    JFrame frame = new JFrame("Client");
    mediaPlayerComponent = new EmbeddedMediaPlayerComponent();
    MediaPlayer mediaPlayer= mediaPlayerComponent.getMediaPlayer();

    frame.setSize(windowDimensions[0], windowDimensions[1]);
    frame.setLayout(new BorderLayout());
    frame.setExtendedState(frame.getExtendedState() | JFrame.MAXIMIZED_BOTH);
    frame.setResizable(false);
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);       
    frame.add(layers, BorderLayout.CENTER);

    layers.setBounds(0,0,windowDimensions[0], windowDimensions[1]);
    mainPanel.setBackground(Color.black); /* This is line 62 */
    mainPanel.setBounds(0,0,windowDimensions[0], windowDimensions[1]);
    mainPanel.setOpaque(true);
    mainPanel.add(mediaPlayerComponent);

    glassPane.setBackground(Color.white);
    glassPane.setBounds(0,0,windowDimensions[0], windowDimensions[1]);
    glassPane.setOpaque(false);

    layers.add(mainPanel, new Integer(0), 0);
    layers.add(glassPane, new Integer(1), 0);

    frame.setVisible(true);
    mediaPlayer.playMedia(toPlay);
}

What is at (Client.java:62) line no?

Braj
– Braj

2014-05-30 18:08:05 +00:00
Commented May 30, 2014 at 18:08 — Braj
– Braj, Commented May 30, 2014 at 18:08
Marked by comment /*This is line 62 */

Nick
– Nick

2014-05-30 18:11:04 +00:00
Commented May 30, 2014 at 18:11 — Nick
– Nick, Commented May 30, 2014 at 18:11

BitNinja · Accepted Answer · 2014-05-30 18:18:41Z

2

mainPanel has not been intitialized, even if it looks like it has. You have this code:

static JPanel mainPanel, glassPane = new JPanel();

This only inititalzes glassPane. In order to initialize mainPanel you have to change your code to this:

static JPanel mainPanel = new JPanel(), glassPane = new JPanel();

answered May 30, 2014 at 18:18

BitNinja

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2 Comments

Nick Over a year ago

I'm gonna choose @David Xu for best answer because he called it first, but you're absolutely correct. Execution went without a hitch! Thanks a lot guys!

BitNinja Over a year ago

@NickMedovich As you should, he beat me to it :).

David Xu · Accepted Answer · 2014-05-30 18:08:29Z

1

You haven't initialized mainPanel. Try adding mainPanel = new JPanel(); above the error line.

You'll also need to call frame.add(mainPanel); after you initialize the panel.

answered May 30, 2014 at 18:08

David Xu

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4 Comments

Nick Over a year ago

I initialize each of the panels statically above the main method: JPanel mainPanel, glassPane = new JPanel();

David Xu Over a year ago

The only way that line is throwing an NPE is if mainPanel is null.

Nick Over a year ago

Well at least the form is showing now. Adding the mainPanel initialization to its own line made the form show up. Now I just have to figure out why the video isn't loading. Thank you very much!!

Nick Over a year ago

And just to throw it out there, I don't add the mainPanel to the frame at all. I add the mainPanel to the JLayeredPanel, add the glassPane on top, then add the whole JLayeredPanel to the frame.

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