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Thread: Problem with swing GUI components in JPanel

  1. #1
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    Default Problem with swing GUI components in JPanel

    Hi everyone,

    I am writing a program with a login screen. That's two labels and one textfield and a passwordField.
    Now, when i want to run the program, i am seeing the JFram, the Panel and one label. The second label and two fields aren't showing up at first. Afther i resize the JFrame with dragging the mouse the other label and fields appear.

    Why it doesn't show when the program is started?

    Kind regards
    Wim


  2. #2
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    Default Re: Problem with swing GUI components in JPanel

    Probably because you did something wrong in your code.
    But we cant really tell because we dont know your code.

    When you post your code make sure to put it inside [code] brackets.

  3. #3
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    Default Re: Problem with swing GUI components in JPanel

    Ok i am sorry that i didn't include the code.

    Here it is:
    package kim.contracts.view;
     
    import java.awt.*;
    import javax.swing.*; 
    import javax.swing.border.Border;
     
    public class LoginView
    {
    	public LoginView()
    	{
    		JFrame loginFrame;
    		JLabel login, username, password;
    		JTextField usernametxt;
    		JPasswordField passwordtxt;
    		JPanel loginPanel;
    		Border border;
    		JButton loginBtn, resetBtn;
     
    		loginFrame = new JFrame("Contracts Login");
    		login = new JLabel("Log Hier In:");
    		loginPanel = new JPanel(new GridBagLayout());
    		border = BorderFactory.createLineBorder(Color.BLUE);
     
     
    		loginFrame.setSize(600,300);
    		loginFrame.setLayout(null);
    		loginFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    		loginFrame.setLocation(600,400);
    		loginFrame.setVisible(true);
     
    		login.setSize(100,20);
    		login.setVisible(true);
    		login.setLocation(50,5);
    		loginFrame.add(login, BorderLayout.NORTH);
     
    		loginPanel.setSize(500,200);
    		loginPanel.setBorder(border);
    		loginPanel.setLocation(40,30);
    		loginPanel.setVisible(true);
    		loginFrame.add(loginPanel, BorderLayout.CENTER);
     
    		GridBagConstraints gbc = new GridBagConstraints();
    		gbc.insets =  new Insets(5,15,0,0);
     
    		username = new JLabel("Gebruikersnaam: ");
    		gbc.gridx = 0;
    		gbc.gridy = 0;
    		loginPanel.add(username, gbc);
    		username.setSize(100,20);
    		username.setVisible(true);
     
    		usernametxt = new JTextField(10);
    		gbc.gridx = 1;
    		gbc.gridy = 0;
    		loginPanel.add(usernametxt, gbc);
    		usernametxt.setVisible(true);
     
    		password = new JLabel("Paswoord: ");
    		gbc.gridx = 0;
    		gbc.gridy = 1;
    		loginPanel.add(password, gbc);
    		username.setSize(100,20);
    		username.setVisible(true);
     
    		passwordtxt = new JPasswordField(10);
    		gbc.gridx = 1;
    		gbc.gridy = 1;
    		loginPanel.add(passwordtxt, gbc);
    		usernametxt.setVisible(true);
     
    		loginBtn = new JButton("Log in");
    		gbc.gridx = 0;
    		gbc.gridy = 2;
    		loginPanel.add(loginBtn, gbc);
    		loginBtn.setVisible(true);
     
    		resetBtn = new JButton("Reset velden");
    		gbc.gridx = 1;
    		gbc.gridy = 2;
    		loginPanel.add(resetBtn, gbc);
    		resetBtn.setVisible(true);
     
    	}
    }
    Last edited by Norm; September 8th, 2014 at 09:45 AM. Reason: Didn't find code tags / Added / to end tag

  4. #4
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    Default Re: Problem with swing GUI components in JPanel

    The problem is you make your frame visible and afterwards you keep adding components to it.
    Once you make a frame visible the frame will then arrange its contents and paint itself. If you change something later you need to call either the pack() method on the frame, or validate().
    Or simply, make sure that loginFrame.setVisible(true) is the last thing you do in your code.

    By the way, some of your lines are very confusing to me and I dont understand why you do it that way. For example, you set "null" as the layout of your loginFrame, but later you try to add components to the frame using constraints from other layouts, namely the BorderLayout. That just cant work and it seems you are making a mistake.

  5. #5
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    Default Re: Problem with swing GUI components in JPanel

    Ok thanks for the answer.

    Yes i tried to do it in one layoutmanager , but then i cant seem to set the panel on the right position. and to use no layout and work with setBounds would be bad practice i think?

  6. #6
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    Default Re: Problem with swing GUI components in JPanel

    A null layout is usually a very bad idea. It doesnt scale well, actually, it doesnt scale at all. And you have so much work to position all elements by hand.
    Just study the different layouts and dont be afraid to use several panels that use yet another layout to achieve what you want.

    Was your original problem solved by now?

  7. #7
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    Default Re: Problem with swing GUI components in JPanel

    yes it is surely solved, thanks to your answer

    Thank you.

    --- Update ---

    PS: thanks for the extra information too.

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