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Problems with BorderLayout() in Java

I've tried a lot of different ways, but I will explain two and what was happening (no error messages or anything, just not showing up like they should or just not showing up at all):
First, I created a JPanel called layout and set it as a BorderLayout. Here is a snippet of how I made it look:
JPanel layout = new JPanel();
layout.setLayout(new BorderLayout());
colorChoice = new JLabel("Choose your color: ");
layout.add(colorChoice, BorderLayout.NORTH);
colorBox = new JComboBox(fireworkColors);
colorBox.addActionListener(this);
layout.add(colorBox, BorderLayout.NORTH);
In this scenario what happens is they don't show up at all. It just continues on with whatever else I added.
So then I just tried setLayout(new BorderLayout()); Here is a snippet of that code:
setLayout(new BorderLayout());
colorChoice = new JLabel("Choose your color: ");
add(colorChoice, BorderLayout.NORTH);
colorBox = new JComboBox(fireworkColors);
colorBox.addActionListener(this);
add(colorBox, BorderLayout.NORTH);
In this scenario they are added, however, the width takes up the entire width of the frame and the textfield (not shown in the snippet) takes up basically everything else.
Here is what I have tried:
setPreferredSize() & setSize()
Is there something else that I am missing? Thank you.
I also should note that this is a separate class and there is no main in this class. I only say this because I've extended JPanel instead of JFrame. I've seen some people extend JFrame and use JFrame, but I haven't tried it yet.

You created a JPanel, but didn't add it to any container. It won't be visible until it is added to something (a JFrame, or another panel that is in a frame somewhere up the hierarhcy)
You added two components to the same position in the BorderLayout. The last one added is the one that will occupy that position.
Update:
You do not need to extend JFrame. I never do, instead I always extend JPanel. This makes my custom components more flexible: they can be added in another panel, or they can be added to a frame.
So, to demonstrate the problem I will make an entire, small, program:
public class BadGui
{
public static void main(String[] argv)
{
final JFrame frame = new JFrame("Hello World");
final JPanel panel = new JPanel();
panel.add(new JLabel("Hello"), BorderLayout.NORTH);
panel.add(new JLabel("World"), BorderLayout.SOUTH);
frame.setVisible(true);
}
}
In this program I created a panel, but did not add it to anything so it never becomes visible.
In the next program I will fix it by adding the panel to the frame.
public class FixedGui
{
public static void main(String[] argv)
{
final JFrame frame = new JFrame("Hello World");
final JPanel panel = new JPanel();
panel.add(new JLabel("Hello"), BorderLayout.NORTH);
panel.add(new JLabel("World"), BorderLayout.SOUTH);
frame.getContentPane().add(panel);
frame.setVisible(true);
}
}
Note that in both of these, when I added something to the panel, I chose different layout parameters (one label I put in 'North' and the other in 'South').

Here is an example of a JPanel with a BorderLayout that adds a JPanel with a button and label to the "North"
public class Frames extends JFrame
{
public Frames()
{
JPanel homePanel = new JPanel(new BorderLayout());
JPanel northContainerPanel = new JPanel(new FlowLayout());
JButton yourBtn = new JButton("I Do Nothing");
JLabel yourLabel = new JLabel("I Say Stuff");
homePanel.add(northContainerPanel, BorderLayout.NORTH);
northContainerPanel.add(yourBtn);
northContainerPanel.add(yourLabel);
add(homePanel);
setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
setLocationRelativeTo(null);
setExtendedState(JFrame.MAXIMIZED_BOTH);
setTitle("Cool Stuff");
pack();
setVisible(true);
}
public static void main(String[] args)
{
SwingUtilities.invokeLater(Frames::new);
}
}

The below suggestion is assuming that your extending JFrame.
Testing
First of all, without seeing everything, theres always a numerous amount of things you can try.
First off, after you load everything, try adding this in (Again, assuming your extending JFrame:
revalidate();
repaint();
I add this into my own Swing projects all the time, as it refreshes and checks to see that everything is on the frame.
If that doesn't work, make sure that all your JComponent's are added to your JPanel, and ONLY your JPanel is on your JFrame. Your JFrame cannot sort everything out; the JPanel does that.
JPanel window = new JPanel();
JButton button = new JButton("Press me");
add(window);
window.add(button); // Notice how it's the JPanel that holds my components.
One thing though, you still add your JMenu's and what-not through your JFrame, not your JPanel.

how to make a java swing JFrame resize correctly

I'm wondering why I can't resize my Frame below and have all of the components resize smaller and bigger as I resize frame. Thank you!!!
public class TPASimulatorGUI extends JFrame{
JPanel mainPanel = new JPanel();
BoxLayout layout = new BoxLayout(mainPanel,BoxLayout.Y_AXIS);
mainPanel.setLayout(layout);
// add things to main panel
JPanel it = new JPanel(new FlowLayout(FlowLayout.LEADING));
it.add(mainPanel);
this.getContentPane().add(it);
this.setSize(new Dimension(1190,770));
this.setVisible(true);
}

JPanel it = new JPanel(new FlowLayout(FlowLayout.LEADING));
it.add(mainPanel);
A FlowLayout always respects the preferred size of the components added to it.
Get rid of the "it" panel and try just using
//this.getContentPane().add(it);
add(mainPanel);
The default layout for a frame is a BorderLayout which will try to increase/decrease the size of all components added to it.

Two Panels in one JFrame?

i have two Panels and want them to be shown in my JFrame, but when i try it like this, i can only see the second one. Can someone please help me? :(
import javax.swing.JFrame;
public class MainWindow {
CardLayout layout;
JFrame frame;
Player panel1;
Block panel2;
public MainWindow() {
frame = new JFrame("Rechteck");
panel1 = new Player();
panel2 = new Block();
panel1.addKeyListener(new KeyListen(panel1));
frame.add(panel1);
frame.add(panel2);
frame.setSize(500,500);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}}

You have added both your panels to the BorderLayout.CENTER of your JFrame—only one can occupy that location,. This will be the last one added, panel2 in this case.
To allow the panels occupy the space evenly, you could use GridLayout:
frame.setLayout(new GridLayout(2, 1));
Aside: Better to use Key Bindings when registering key events for components in Swing.

Create a JPanel add that to the JFrame. Add panel1 and panel2 to the new panel. JFrame can only have one child, usually set by calling JFrame.setContentPane().

Java setBounds not working with JPanel

i am doing a small Gui in java. i am using setBounds methods to set the position of buttons etc on my JFrame , but problem is that when i use it with JPanel button is not visible on JFrame , and without JPanel its quite ok ,, see both the codes and please help me as i am beginner and facing these foolish problems .
This one is working fine
JFrame jframe = new JFrame("Working Fine");
jframe.setLayout(null);
JButton jbutton = new JButton("Position Test");
jbutton.setBounds(0, 0, 100, 100);
jframe.add(jbutton);
jframe.setSize(300,300);
jframe.setVisible(true);
Same code when i add Button to Jpanel then it does not work so whats wrong , please guide me
JFrame jframe = new JFrame("causing problem ");
jframe.setSize(300,300);
JPanel p = new JPanel();
jframe.setLayout(null);
JButton jbutton = new JButton("Position Test");
jbutton.setBounds(0, 0, 100, 100);
jframe.add(p);
p.add(jbutton);
p.setVisible(true);
//jframe.add(jbutton);
jframe.setVisible(true);
please help me in this small problem

You must get rid of the JPanel's layout, in order to set absolute positions:
p.setLayout(null);

The problem is that when you use absolute positioning, the JPanel component has no default size so does not appear. To get it to appear you could do
JFrame frame = new JFrame("No Problem");
JPanel panel = new JPanel() {
#Override
public Dimension getPreferredSize() {
return new Dimension(300, 300);
};
};
panel.setLayout(new FlowLayout(FlowLayout.CENTER));
JButton button = new JButton("Position Test");
panel.add(button);
frame.add(panel);
frame.pack();
frame.setVisible(true);
From Doing Without a Layout Manager
Although it is possible to do without a layout manager, you should use a layout manager if at all possible. A layout manager makes it easier to adjust to look-and-feel-dependent component appearances, to different font sizes, to a container's changing size, and to different locales.
The choice of layout manager will depend on how you wish to lay out the components.
See A Visual Guide to Layout Managers.

Automatically size JPanel inside JFrame

I have a JPanel subclass on which I add buttons, labels, tables, etc. To show on screen it I use JFrame:
MainPanel mainPanel = new MainPanel(); //JPanel subclass
JFrame mainFrame = new JFrame();
mainFrame.setTitle("main window title");
mainFrame.getContentPane().add(mainPanel);
mainFrame.setLocation(100, 100);
mainFrame.pack();
mainFrame.setVisible(true);
mainFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
But when I size the window, size of panel don't change. How to make size of panel to be the same as the size of window even if it was resized?

You can set a layout manager like BorderLayout and then define more specifically, where your panel should go:
MainPanel mainPanel = new MainPanel();
JFrame mainFrame = new JFrame();
mainFrame.setLayout(new BorderLayout());
mainFrame.add(mainPanel, BorderLayout.CENTER);
mainFrame.pack();
mainFrame.setVisible(true);
This puts the panel into the center area of the frame and lets it grow automatically when resizing the frame.

You need to set a layout manager for the JFrame to use - This deals with how components are positioned. A useful one is the BorderLayout manager.
Simply adding the following line of code should fix your problems:
mainFrame.setLayout(new BorderLayout());
(Do this before adding components to the JFrame)

If the BorderLayout option provided by our friends doesnot work, try adding ComponentListerner to the JFrame and implement the componentResized(event) method. When the JFrame object will be resized, this method will be called. So if you write the the code to set the size of the JPanel in this method, you will achieve the intended result.
Ya, I know this 'solution' is not good but use it as a safety net.
;)

From my experience, I used GridLayout.
thePanel.setLayout(new GridLayout(a,b,c,d));
a = row number, b = column number, c = horizontal gap, d = vertical gap.
For example, if I want to create panel with:
unlimited row (set a = 0)
1 column (set b = 1)
vertical gap= 3 (set d = 3)
The code is below:
thePanel.setLayout(new GridLayout(0,1,0,3));
This method is useful when you want to add JScrollPane to your JPanel. Size of the JPanel inside JScrollPane will automatically changes when you add some components on it, so the JScrollPane will automatically reset the scroll bar.

As other posters have said, you need to change the LayoutManager being used. I always preferred using a GridLayout so your code would become:
MainPanel mainPanel = new MainPanel();
JFrame mainFrame = new JFrame();
mainFrame.setLayout(new GridLayout());
mainFrame.pack();
mainFrame.setVisible(true);
GridLayout seems more conceptually correct to me when you want your panel to take up the entire screen.