Develop Reference

How to make a JButton that will create other buttons within a JPanel?

I am creating a user system to hold multiple details of multiple users. so i would like to create a button that would be able to create another button. when the second button is pressed a form will open for the user to fill. I have already created the form for the user to fill but i cannot manage to make the button to create more buttons to work. I have coded this but it does not show the button on the Jpanel.
I have created the following code:
private void mainButtonActionPerformed(java.awt.event.ActionEvent evt) {
JButton b=new JButton("Click Here");
b.setBounds(50,100,95,30);
jPanel3.add(b);
b.setVisible(true);
}
This doesn't seem to create a new button within jPanel3. Have I typed up the code incorrectly or is there an alternative correct way of doing this?
I would like 3 buttons in a row and then a new row of buttons.

Your code and question is missing too much information to be answered completely or well. About all I can say is
Always call jPanel3.revalidate() and jPanel3.repaint() on the container after adding or removing components from it as this tells the container's (here jPanel3) layout managers to re-layout all components and then re-draw them.
The container's layout manager is key for this to work well -- we have no idea what it is at the moment, and some layout managers will allow you to do this easily (e.g., FlowLayout, GridLayout) while others won't (e.g., GroupLayout).
There's no need for b.setVisible(true); since your newly created JComponent (JButton here) is already visible by default.
You appear to assume that it's using null layouts since you're calling setBounds(...), and this is a Bad Idea™. While null layouts and setBounds() might seem to Swing newbies like the easiest and best way to create complex GUI's, the more Swing GUI'S you create the more serious difficulties you will run into when using them. They won't resize your components when the GUI resizes, they are a royal witch to enhance or maintain, they fail completely when placed in scrollpanes, they look gawd-awful when viewed on all platforms or screen resolutions that are different from the original one.
When asking such questions, try to create and post with the question a small but complete program that we can test and run, and that illustrates your problem, a minimal example program (please click on the link).
For example, my MCVE that shows how your code can work:
import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.GridLayout;
import javax.swing.*;
#SuppressWarnings("serial")
public class AddButton extends JPanel {
private JPanel jPanel3 = new JPanel(); // panel to hold buttons
public AddButton() {
// create JButton that will add new buttons to jPanel3
JButton addMoreButtonsBtn = new JButton("Add More Buttons");
// give it an ActionListener
addMoreButtonsBtn.addActionListener(e -> {
final JButton newButton = new JButton("Click Here");
// when you click it, it removes itself (just for grins)
newButton.addActionListener(e2 -> {
jPanel3.remove(newButton);
// again revalidate and repaint
jPanel3.revalidate();
jPanel3.repaint();
});
// add to jPanel3, the "container"
jPanel3.add(newButton);
// revalidate and repaint the container
jPanel3.revalidate();
jPanel3.repaint();
});
// create a JPanel and put the add more buttons button to it
JPanel bottomPanel = new JPanel();
bottomPanel.add(addMoreButtonsBtn);
// give jPanel3 a layout that can handle new buttons
// a gridlayout with 1 column and any number of rows
jPanel3.setLayout(new GridLayout(0, 1));
// add it to the top of another JPanel that uses BorderLayout
JPanel borderLayoutPanel = new JPanel(new BorderLayout());
borderLayoutPanel.add(jPanel3, BorderLayout.PAGE_START);
// and add that to a JScrollPane, so we can add many buttons and scroll
JScrollPane scrollPane = new JScrollPane(borderLayoutPanel);
// make the vert scrollbar always visible
scrollPane.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);
// force GUI to be larger
setPreferredSize(new Dimension(400, 200));
// give the main JPanel a BorderLayout
setLayout(new BorderLayout());
// and add scrollpane to center
add(scrollPane, BorderLayout.CENTER);
// add bottom panel to the bottom
add(bottomPanel, BorderLayout.PAGE_END);
}
private static void createAndShowGui() {
AddButton mainPanel = new AddButton();
JFrame frame = new JFrame("AddButton");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().add(mainPanel);
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(() -> createAndShowGui());
}
}

Centering a fixed size canvas in a JFrame

I'm in the process of creating a circuit editor (similar to any regular paint software with a basic menu and a canvas with specifiable dimensions). I am currently trying to transform the previously unscrollable canvas (JPanel) to a scrollable one.
The obvious design error at the moment is that while the scrollbars seem to correctly reflect the internal size of the canvas (which can of course be way bigger than the JFrame), due to the canvas JPanel being added in the CENTER of the BorderLayout of the master panel, it always resizes along with the JFrame.
public final class MainFrame extends JFrame
{
public MainFrame()
{
JPanel menuPanel = new JPanel(new FlowLayout(FlowLayout.LEFT));
// Populate Menu Panel
// ...
JPanel canvasPanel = new JPanel();
canvasPanel.setBackground(Color.white);
Dimension canvasDims = new Dimension(800,600);
canvasPanel.setPreferredSize(canvasDims);
canvasPanel.setMinimumSize(canvasDims);
canvasPanel.setMaximumSize(canvasDims);
JScrollPane canvasScrollPane = new JScrollPane(
canvasPanel,
JScrollPane.VERTICAL_SCROLLBAR_AS_NEEDED,
JScrollPane.HORIZONTAL_SCROLLBAR_AS_NEEDED);
JPanel masterPanel = new JPanel(new BorderLayout());
masterPanel.add(menuPanel, BorderLayout.NORTH);
masterPanel.add(canvasScrollPane, BorderLayout.CENTER);
setContentPane(masterPanel);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setSize(1200, 700);
setMinimumSize(new Dimension(500, 500));
setLocationRelativeTo(null);
setVisible(true);
}
I've read quite a few posts regarding centering JPanels and scrollbars but with both complexities added together, things might be a bit more complicated as I haven't yet found a solution.
What I'm really trying to achieve is to have the canvas' JPanel fixed in whatever size the user might have specified and centered in the middle as well as the scrollbars behaving as one would expect like in the beloved windows' paint:
How would you go about doing this/fixing my design? Any help would be greatly appreciated!
P.S. Happy new Year :)

JPanel fixed in whatever size the user might have specified and centered in the middle as well as the scrollbars behaving as one would expect
So you need to nest panels so the canvas panel can be displayed at its preferred size, while the parent panel resizes with the size of the frame.
An easy way to do this is with a JPanel that uses a GridBagLayout. Then you add the canvas panel to this panel using the default GridBagConstraints.
So the basic structure of the panels would be:
JPanel canvas = new JPanel();
canvas.setPreferredSize( new Dimension(300, 300) );
canvas.setBackground(Color.RED);
JPanel wrapper = new JPanel( new GridBagLayout() );
wrapper.add(canvas, new GridBagConstraints() );
frame.add(new JScrollPane(wrapper));
Note: there is no need for your "masterPanel". The default layout manager for the content pane of a JFrame is a BorderLayout, so you just add the "menuPanel" and "scrollPane" directly to the frame with the proper BorderLayout constraints.

Put a JLabel over two JButtons

Okay so before you ask, yes I'm not using any Layout Manager. No, that doesn't make this bad design (as I've seen people in here saying because someone simply didn't use one). The thing is i want the label to always (and I mean always) show over the two buttons (over the gap left by them which makes it impossible to put it as an Icon or a text on the JButton).
JFrame frame = new JFrame("ColorTap");
private void init() {
JButton jb1 = new JButton(""), jb2 = new JButton("-");
JLabel label = new JLabel("TEXT HERE");
label.setForeground(Color.white);
label.setFont(new Font("Arial Bold",Font.ITALIC,30));
label.setBounds(60,249,200,100);
frame.setLayout(null);
jb1.setBounds(0, 0, 300,298);
jb2.setBounds(0, 302, 300, 300);
jb1.setBackground(Color.black);
jb2.setBackground(Color.black);
jb1.setBorderPainted(false);
jb2.setBorderPainted(false);
frame.add(label);
frame.add(jb1);
frame.add(jb2);
frame.setResizable(false);
frame.setSize(300, 628);
frame.setLocation(550, 50);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
}
After this what's stranger to me is that the button on the bottom stays under the label and not the one on the top... HELP! Thanks

Swing is optimized to paint components in two dimensions. That is it assumes components will never overlap. Overlapping JButtons cause a problem because of the rollover effects which only cause the buttons to be painted, not the label, so the button is painted over the top of the label.
So you need to tell Swing that components do overlap so Swing can make sure components are painted in the proper ZOrder:
JPanel panel = new JPanel()
{
#Override
public boolean isOptimizedDrawingEnabled()
{
return false;
}
};
Now you can set the layout manager of the panel and add your components to the panel and they will be painted properly.
See: How to put a JButton with an image on top of another JButton with an image? for a working example that DOES use layout managers.

Layout inside Layout

I have a JPanel with a vertical BoxLayout, for one element i want to be able to use another BoxLayout which places elements horisontally.
The code will explain what i'm trying to do:
private void prepareGUI() {
setBorder(new EmptyBorder(20, 0, 20, 0));
setLayout(new BoxLayout(this, BoxLayout.Y_AXIS));
JLabel lblTitle = new JLabel("Downloading");
lblTitle.setFont(new Font("Arial", Font.PLAIN, 20));
lblTitle.setAlignmentX(Component.CENTER_ALIGNMENT);
add(lblTitle);
Component verticalStrut = Box.createVerticalStrut(20);
add(verticalStrut);
JProgressBar progressBar = new JProgressBar();
progressBar.setStringPainted(true);
progressBar.setBorder(null);
progressBar.setValue(50);
Dimension size = new Dimension(300, 25);
progressBar.setMinimumSize(size);
progressBar.setMaximumSize(size);
progressBar.setPreferredSize(size);
add(progressBar);
BoxLayout textLayout = new BoxLayout(this, BoxLayout.Y_AXIS);
JLabel lblTest_1 = new JLabel("Test 1!");
textLayout.add(lblTest_1);
JLabel lblTest_2 = new JLabel("Test 2!");
textLayout.add(lblTest_2);
add(textLayout);
}
Now obviously this isn't possible as BoxLayout isn't a Container (It even asks for the container to be linked to on construction.
My question is what is the best way to achieve what i want? Should i create another JPanel and put that inside the first JPanel? I was thinking that but it seems a little too complicated, there must be a simpler way?

BoxLayout is not a container, it's a LayoutManager, so, components can't be added to BoxLayout since box layout is not inheriting anything from abstract class Component, it's will add to some container like JPanel or frame's container....
So, it's wrong to say:
textLayout.add(lblTest_1);
Or even
add(textLayout);
Because this method addes a component to the frame's container, and BoxLayout is not a component.
Should i create another JPanel and put that inside the first JPanel?
Except what you did and avoiding null layout, you're free to do anything, as, design is upon to you, as far as I am preferring multiple panels if wanted.

Java Swing JFrame Layout

I just wrote a simple code where I want a textfield and a button to appear on the main frame, but after running all I see is the textfield.
If I write the code of the button after the textfield then only the button is displayed.
Any idea why?
JFrame mainframe=new JFrame();
mainframe.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
mainframe.setBounds(0,0,200,200);
JButton jb=new JButton();
jb.setText("Leech");
mainframe.add(jb);
JTextField link=new JTextField(50);
mainframe.add(link);
mainframe.pack();
mainframe.setVisible(true);

The default layout on a JFrame is a BorderLayout. Calling the add method on a Container with such a layout is equivalent to a call add(..., BorderLayout.CENTER). Each of the locations of the BorderLayout can contain only one element. Hence making two calls
mainframe.add(jb);
mainframe.add(link);
results in a CENTER containing the last component you added. If you want to avoid this you can either add it to different locations, or use another layout manager (for example a FlowLayout) by calling JFrame#setLayout

Instead of adding directly Components to the JFrame, use a JPanel as container with the desired LayoutManager.
Here you can find several tutorials on layout managers.
Basically in Swing the LayoutManager is responsible for laying out the children Components (establishing their position and their size), so every container component you use inside your app, should be configured with the appropiate LayoutManager.

Add your components to a JPanel and then add that panel to the ContentPane of JFrame.
JFrame window = new JFrame();
JPanel mainframe = new JPanel();
window.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
window.setBounds(0,0,200,200);
JButton jb = new JButton();
jb.setText("Leech");
mainframe.add(jb);
JTextField link = new JTextField(50);
mainframe.add(link);
window.getContentPane().add(mainframe);
window.pack();
window.setVisible(true);

You can also use something like Flow Layout which is the default layout used by JPanel. It is used to arrange components in a line or a row. For example from left to right or from right to left:
Flow layout arranges components in line and if no space left all remaining components goes to next line. Align property determines alignment of the components as left, right, center etc.
To use it you will need to set JFrame layout by using JFrame.setLayout(layout) and to pass flow layout as a parameter.
Following example shows components arranged in flow layout:
package example.com;
import java.awt.BorderLayout;
import java.awt.FlowLayout;
import javax.swing.JButton;
import javax.swing.JFrame;
public class FlowLayoutExample {
FlowLayoutExample(){
JFrame frame = new JFrame("Flow Layout");
JButton button, button1, button2, button3, button4;
button = new JButton("button 1");
button1 = new JButton("button 2");
button2 = new JButton("button 3");
button3 = new JButton("button 4");
button4 = new JButton("button 5");
frame.add(button);
frame.add(button1);
frame.add(button2);
frame.add(button3);
frame.add(button4);
frame.setLayout(new FlowLayout());
frame.setSize(300,300);
frame.setVisible(true);
}
public static void main(String[] args) {
new FlowLayoutExample();
}
}
Check out to learn more about JFrame layouts.

JFrame's default Layout Manager is BorderLayout. If you want the automatic layout, you may use the FlowLayout:
mainframe.setLayout(new FlowLayout());
If you want to specify coordinates by setBounds() method, you have to cancel the setting of layout manager on JFrame:
mainframe.setLayout(null);
jb.setBounds(10,10,100,50);
link.setBounds(10,70,180,100);

if you see BorderLayout Documentation
mainframe.add(jb); is equals to mainframe.add(jb,BorderLayout.CENTER);
mainframe.add(link); is equals to mainframe.add(jb,BorderLayout.CENTER);
so it just show the last one