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Adding JButtons in for loop

JAVA Swing Problem
I want to create a list of JButtons based on a list of strings, which represents the button text.
In my first step, I collect my data for the button texts from an external text file. This data is stored in the data variable.
List<String> data = ReadFile("texts.txt")
Now I want to create the list of JButtons, named buttons. There I set their text and their Bounds. The Bounds are relative to the index, so the buttons are placed below each other. Finally, I add the button to the frame and to the buttons list.
List<JButton> buttons = new ArrayList<>();
for (int index = 0; index < data.size(); index++) {
JButton button = new JButton();
button.setText(data.get(index));
button.setBounds(0, index*50, 100, 50);
add(button);
buttons.add(button);
But when I execute this, the last Button ends big, the first ones also disappear when I don't hover over them, but that's based on the fact, that the last button ist placed above:
Picture of the executed script
The last button has the size of the frame, doesn't matter, if I resize the frame:
Picture of the resized screen
I hope someone can help me or tell me where I can find help. Thanks.

the last Button ends big, the first ones also disappear when I don't hover over them,
That is because by default the content pane of the JFrame uses a BorderLayout. When you add a component to the BorderLayout the button is added to the CENTER. However, only a single component can be added to the CENTER, so only the size/location of the last component added is managed by the BorderLayout.
Don't attempt to set the size/location of your components manually. It is the job of a layout manager to do this. In your case you can use a couple of panels with different layout so align your button in a column on the left. Something like:
JPanel buttonPanel = new JPanel( new GridLayout(0, 1) );
for (int index = 0; index < data.size(); index++) {
JButton button = new JButton();
button.setText(data.get(index));
button.setBounds(0, index*50, 100, 50);
//add(button);
buttonPanel.add( button );
buttons.add(button);
}
add(buttonPanel, BorderLayout.LINE_START);
Try the above code and you will notice that the buttons are all the same size, but the size keeps changing as the height of the frame changes.
So to prevent this resizing we need to allow the button to be displayed at their preferred height by using an additional layout manager:
//add(buttonPanel, BorderLayout.LINE_START);
JPanel wrapper = new JPanel( new BorderLayout() );
wrapper.add(buttonPanel, BorderLayout.PAGE_START);
add(wrapper, BorderLayout.LINE_START);
Read the Swing tutorial on Layout Manager for more information and examples.

JComboBox showing only if it has a single item

I have a JPanel with a CardLayout and a JComboBox inside it. They are dinamically filled with data taken from a JTable. If the JComboBox has a single item it shows just fine, but if I fill it with more than one it doesn't show.
JPanel intervalPanel = new JPanel;
CardLayout intervalLayout = new CardLayout();
intervalPanel.setLayout(intervalLayout);
JComboBox intervalComboBox = new JComboBox();
for (int i = 0; i < table.getRowCount(); i++) {
String name = (String) table.getValueAt(i, 0);
intervalComboBox.addItem(name);
JPanel p = new JPanel();
p.setName(name);
p.add(intervalComboBox);
p.add(new JLabel(name));
intervalPanel.add(p, name);
}

A Swing component can only have a single parent.
p.add(intervalComboBox);
The above statement keeps removing the combo box from the previous panel and adds it to the current panel.
but if I fill it with more than one it doesn't show.
So the reason it doesn't show is because it is only visible on the last card, but you current see the first card.
The better solution is to NOT add the combo box to the panel in the CardLayout. Instead your main panel should use a BorderLayout. Then the basic logic would be something like:
JPanel main = new JPanel( new BorderLayout() );
JComboBox comboBox = new JComboBox(...);
main.add(comboBox, BorderLayout.PAGE_START);
JPanel card = new JPanel( intervalLayout );
main.add(card, BorderLayout.CENTER);
frame.add( main );
Then you just add child panels to the "card" panel as required.
Read the section from the Swing tutorial on How to Use CardLayout for a complete working demo that uses the above design concept.

Grid layout not working?

I am trying to make a 2x2 grid layout that has a JLabel on the top left, and three buttons on the other three spaces. When I do this, I get the unexpected result of one big button (filling up the entire JDialog) that says "Do you want to push me". I don't know why this result shows up, please help, Thanks!
public void sinceyoupressedthecoolbutton() {
JDialog replacementwindow = new JDialog(); //Like a window
JButton best = new JButton("best");
JButton first = new JButton("FIRST");
JButton second = new JButton("Second");
replacementwindow.setLayout(new GridLayout(2,3,0,0)); //Row, column, distance horizontally, distance vertical
JPanel panel = new JPanel();
replacementwindow.add(panel); //adding the JPanel itself
replacementwindow.add(first);
replacementwindow.add(second);
replacementwindow.add(best);
replacementwindow.setSize(500, 500);
replacementwindow.setTitle("NEW WINDOW!");
replacementwindow.setVisible(true);
}

It's because you set the layout of your JButton, and not of your JDialog
Change
label.setLayout(new GridLayout(2,2,0,0));
to
YES.setLayout(new GridLayout(2,2,0,0));
Also, your variable called label is a JButton, you probably want to change that.

Don't add components to a button. You add components to a panel.
So the basic code should be:
JDialog dialog = new JDialog(...);
JPanel panel = new JPanel( new GridLayout(...) );
panel.add(label);
panel.add(button1);
...
dialog.add(panel);
Also, variable names should NOT start with an upper case character! "Yes" does not follow Java standards. The other variables do. Be consistent!

Using a function to create multiple components and change line automatically [Java]

So i lost some hours already with this and i can't seem to find a solution.
Basically i have a Jframe and inside, i have a Scrollpane and a panel
I have 1 Jlabel, 1 JTextField and 1 JButton inside that panel in a single line.
The JButton can add a new JLabel, a new JTextField and a new JButton, but i can't get them to be positioned in the next line.
I have been messing around with the layouts, but none of them fits my needs, and unfortunaly i never understand or learned how the GUI of java Works.
How's the best way to just keep adding those componentes (Jlabel, Jtextfields and Jbuttons) on a next line for every click i made?
This is my code:
private void BtnaddvariableActionPerformed(java.awt.event.ActionEvent evt) {
JLabel Lblvariablextra = new JLabel("Testing");
PanelVariable.add(Lblvariablextra);
ScrollPaneVariable.setViewportView(PanelVariable);
}
The code only contains an exemple of the label tough.

Create a main panel that is added to the scroll pane when the GUI is created:
Box main = Box.createVerticalBox();
scrollPane.setViewportView( main );
Then in the ActionListener you create a child panel contain the 3 components every time the button is pressed:
JPanel child = new JPanel();
child.add( new JLabel("I'm a label") );
child.add( new JTextField(10) );
child.add( new JButton("Click Me") );
main.add(child);
Read the section from the Swing tutorial on Layout Manager to understand how layout management works.

JTextField becomes HUGE in a HorizontalBox

Please consider this Java code fragment:
Box buttonBox = Box.createHorizontalBox();
buttonBox.add(new JCheckBox("Select all"));
buttonBox.add(Box.createHorizontalGlue());
buttonBox.add(new JLabel("Filter: "));
buttonBox.add(new JTextField());
Box paneBox = Box.createVerticalBox();
paneBox.add(buttonBox);
paneBox.add(new JScrollPane(jList));
For some reason i don't get, the JTextField takes up most of the screen. The jList isn't even visible anymore. I would like to know why and how to fix it.
When i comment the line with the JTextField, it looks fine (except no JTextField, of course). Why does the JCheckBox and the JLabel not get ridiculously big? What is the purpose of a one-line JTextField being able to take up almost the whole screen?
Most people suggest to set the size of the JTextField field to my needs. However, i read that i should not call these methods, but let the LayoutManager take care of it. Now what is the most elegant solution to prevent the JTextField from becoming so big?

Try using the setPreferredSize method like this:
textFieldName.setPreferredSize(new Dimension(x, y));
Obviously input the values for x and y that you wish the JTextField size to be

You can avoid this problem by using a simple JPanel() instead of a Box for the horinzontal one. And after just set the prefered size to your JTextField.
//Box buttonBox = Box.createHorizontalBox();
JPanel buttonBox = new JPanel();
buttonBox.add(new JCheckBox("Select all"));
buttonBox.add(Box.createHorizontalGlue());
buttonBox.add(new JLabel("Filter: "));
JTextField jt = new JTextField();
jt.setPreferredSize(new Dimension(100,25));
buttonBox.add(jt);
EDIT
Btw the defaut Layout of a JPanel is the FlowLayout which place components from left to right and with centered alignement by default. You can still change the alignement.
For example:
JPanel buttonBox = new JPanel(new FlowLayout(FlowLayout.LEFT));
You can also change the gap between each components. There is some other Layout like the BorderLayout or GridLayout / GridBagLayout. I let you search on Google for more information about them.
See in yellow the JPanel, in red the VerticalBox

Box box = Box.CreateVerticalBox();
Use box.setMaximumSize(Dimension(160,80))
and box.setMinimumSize(Dimension(160,80))
then it will work :D
If you need a strut for your layout, put it in between boxes.