Help with application not loading occasionally

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January 30th, 2013, 07:54 PM

CraigR15

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Solved: Help with application not loading occasionally

I really need help with an error I've been trying to fix for the past 2 days. I'm using a CardLayout and switching between different JPanels. I'm Pulling the JPanel into the Main JPanel which is shown to the user.

I'm having an issue because occasionally my application will load but no GUI components will be shown. Other times when I load the application, it loads perfectly. I really can't figure it out.

I'm using Tomcat Juno IDE to develop the application, when the app loads and doesn't show anything I see a quick glimpse of an error occurring in the console, but it disappears immediately after and I don't know any way to reveal it.

I have created a quick code example if anyone can provide any help. I don't understand why it's working occasionally.

Code:


public class TestClass { 	 	

JFrame MainScreenFrame; // Declare main JFrame
JPanel MainPanel = new JPanel(); // Panel used to set the current layout of the frame to new 

JPanel 	CardLayout cards = new CardLayout(); 

JPanel AddEmployeePanel = new JPanel(newGridBagLayout());
JPanel ShowEmployeePanel = new JPanel(newGridBagLayout());

public TestClass(){  		
MainScreenFrame = new JFrame("TestApplication"); // Create new MainFrame Panel used when opening up the application and set the title 		

MainScreenFrame.setVisible(true);
MainScreenFrame.setSize(900, 650);
MainScreenFrame.setLocationRelativeTo(null);
MainScreenFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

JFrame MainScreenFrame.setResizable(false); // Dont allow user to resize frame.

MainPanel.setLayout(cards); // actually set the current layout of MainPanel // E.g. of how im adding components

JLabel enterEmployeeInfo = new JLabel("Hmmm?");
enterEmployeeInfo.setFont(new Font("Arial", Font.BOLD, 16)); 

// SetLayout method used to set gridbagconstraints
AddEmployeePanel.add(enterEmployeeInfo, c); // c defines gridbagconstraints
JLabel lolol = new JLabel("whatever");
lolol.setFont(new Font("Arial", Font.BOLD, 16)); 
// SetLayout method used to set gridbagconstraints
ShowEmployeePanel.add(lolol, c); // c defines gridbagconstraint 

MainPanel.add(AddEmployeePanel, "ADD");
MainPanel.add(ShowEmployeePanel, "SHOW");
MainScreenFrame.add(MainPanel);
cards.show(MainPanel, "ADD"); 	} 	 	

public static void main(String[] args) { 		
new TestClass(); // Call this class  	
}}

[Sorry about indentation Is there no Java Syntax Tag?

I'm sure it's really easy, but I haven't been learning Java too long. Thank you.

Last edited by CraigR15 : January 31st, 2013 at 12:59 PM. Reason: Now solved

January 31st, 2013, 01:49 AM

MrFujin

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How do you start you program? if you dont see the console, it sounds you are stating it from your editor.
have you tried to open a command prompt and start you program that way?

When posting code, the indention will be how you make it, code tags only preserve your format.
For syntax highlighting, you can use [highlight=java] my code [/highlight] instead of the code tags.

January 31st, 2013, 05:36 AM

NormR

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One possible problem is calling setVisible() BEFORE adding any components to the frame.
Try calling it AFTER the components that you want to see have been added.

January 31st, 2013, 11:25 AM

CraigR15

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Join Date: Jan 2013

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Quote:

Originally Posted by NormR

One possible problem is calling setVisible() BEFORE adding any components to the frame.
Try calling it AFTER the components that you want to see have been added.

I havn't used the setVisible at all throughout the application. All components are visible all the time. Is this bad? Any more strain on memory resources?

Thank you, I will use Java code tags from now on.

How do you start the program from the command line?

I have managed to solve the problem and it turned out to be very easy. I was adding the JPanels add & show to the mainpanel before adding the mainpanel to the frame. I solved it by doing this:

E.g.

java Code:

Original - java Code
MainScreenFrame.add(MainPanel); // Add before JPanels MainPanel.add(AddEmployeePanel, "ADD"); MainPanel.add(ShowEmployeePanel, "SHOW"); cards.show(MainPanel, "ADD"); // then show the main panel

 
MainScreenFrame.add(MainPanel); // Add before JPanels 
 
MainPanel.add(AddEmployeePanel, "ADD");
MainPanel.add(ShowEmployeePanel, "SHOW");
 
cards.show(MainPanel, "ADD"); // then show the main panel