We Keep Coding

Append swing jbutton elements to array in java

I am working on a messaging application. The GUI is written in Java Swing. When the client starts, it asks my server for the chats a specific user is involved in. The server will send these in the form of an string array eg: {CHAT_PATH,CHAT_PATH}.
Once the client receives this it feeds it to my GUI class, which is supposed to display each chat name in the list (I will filter out the rest of the path) on screen listed downward. This is where my problem lies. I start by creating a JButton list:
JButton[] chat_names = {};
and then I loop through the list of chats (chat_data) and add to my chat_names list a new JButton for each chat name. Like this:
for (int x=0; x<chat_data.length-1; x++){
chat_names[x] = new JButton(chat_data[x]);
chat_names[x].setBounds(100,100,100,100);
}
for (int x=0; x<chat_names.length; x++){
frame.add(chat_names[x]);
}
When I do this I get the following syntax error:
Exception in thread "main"
java.lang.ArrayIndexOutOfBoundsException: Index 0 out of
bounds for length 0
at gui_main.menu_screen(gui_main.java:16)
at Main.main(Main.java:89)
Does anyone know if this is fixable or another way I could display a list of buttons each with a chat_name on them.

Here you created an array of JButtons with length 0
JButton[] chat_names = {};
You can either call
chat_names = new JButton[chat_data.length];
before the for-loops or create a
List<JButton> chatNames = new ArrayList<>();
to have a variable length list of buttons
As a tip use camelCase rather than snake_case for your variables and methods, as that's the convention.
And one more thing don't manually specify the bounds of each JButton, instead use a proper Layout Manager for example GridLayout or BoxLayout may work. If you insist on using setBounds and (more than surely) null-layout you may find yourself in a problem similar to this one when trying to run it on a different computer or a different monitor.
You can also merge these 2 loops:
for (int x=0; x<chat_data.length-1; x++){
chat_names[x] = new JButton(chat_data[x]);
chat_names[x].setBounds(100,100,100,100);
}
for (int x=0; x<chat_names.length; x++){
frame.add(chat_names[x]);
}
Into one, reducing one iteration over all the chats and thus improving performance:
for (int x=0; x<chat_data.length-1; x++){
chat_names[x] = new JButton(chat_data[x]);
chat_names[x].setBounds(100,100,100,100); //Use a layout manager!
frame.add(chat_names[x]);
}

Create and place JLabels on JPanel with a loop

I'm new to swing and I've been trying some new things. I'd like to create and place JLabels on a JPanel, but as many as I want, using a loop. I'm trying to make a snake game, btw.
/*Up here I set the number of parts (JLabels) I want and instantiate my ArrayList
to store them later.*/
snakeBodyParts = 3;
snakeBody = new ArrayList<>();
/*This is the part I'm struggling with. First, bodyPartIndex is going to go from 0
to my desired number of parts. On each time it's going to store an int for the X position
of the JLabel and an int for the Y position. That way I'm going to get
JLabels on a horizontal line, each time an unit farther away.*/
for (int bodyPartIndex = 0; bodyPartIndex < snakeBodyParts; bodyPartIndex++) {
snakePositionsX[bodyPartIndex] = 50 - (bodyPartIndex * UNIT_SIZE);
snakePositionsY[bodyPartIndex] = 50;
/*Then, I add a JLabel to my list, and get it back to my "bodyPart" JLabel.*/
snakeBody.add(new JLabel());
bodyPart = snakeBody.get(bodyPartIndex);
/*Here I set the location on my "bodyPart" JLabel, using the coordinates I created before,
and set its icon (it's out of the loop)*/
bodyPart.setLocation(snakePositionsX[bodyPartIndex], snakePositionsY[bodyPartIndex]);
bodyPart.setIcon(imgIconBodyPart);
/*And finally I replace the old bodyPart with the recently modified one, I then add it to my JPanel (this.add) */
snakeBody.set(bodyPartIndex, bodyPart);
this.add(bodyPart, new org.netbeans.lib.awtextra.AbsoluteConstraints(snakePositionsX[bodyPartIndex], snakePositionsY[bodyPartIndex], UNIT_SIZE, UNIT_SIZE));
}
I'm pretty sure I've done a lot of things wrong, I'm still trying to understand what I'm doing, but the end result is a blank screen, can anyone help me? I really need to know how to do this.

Refresh JPanel in Java Swing

Let's suppose I've a list of String like this
List<String> button_names={"Button1","Button2","Button3","Button4"};
I've to insert JButtons with those texts in a JPanel so I do
for (int i=0; i<button_names.length; i++)
myJPanel.add(new JButton(button_name[i]));
My question is... If my model (in this case, my List button_names) changes for any reasons, how can I refresh my JPanel in order to show that change?
Should I do
myJPanel.removeAll()
and insert again my JButtons()? Thank you in adance

Yes removeAll and then reinserting new buttons is the easiest and generally the best way to go. Otherwise, you have to start figuring out which buttons have been removed, which have been added, and where in the list these new buttons are. Also, buttons in the list should change position I guess, so you'd have to cover that case to.
You can write a method like this that you could use in initial creation, and when you want to reload the list
void addButtonsToPanel(JPanel p) {
p.removeAll();
for (int i=0; i<button_names.length; i++)
myJPanel.add(new JButton(button_name[i]));
validate();
repaint();
}

Java GUI - Getting random value from array

So I have this 2d array of buttons and I have an array of images. I want to get the images on the buttons but I want the images to be on random buttons every time the program starts. Like this:What I want it to look like. Right now I can only get one color to be on all of the buttons by changing the value of icons when I make the new JButton. What I think I need to do is have Math.Random() set to a variable and to get a random value from the array of images and then put the variable in icons[] when i declare the new JButton but I don't know if this is right and don't know how to do it. I did some searching and tried using this:
var randomValue = icons[Math.floor(Math.random() * icons.length)];
but I get an error saying
possible loss of precision, required int, found double.
Help would be greatly appreciated. If you want me to post the entire code let me know.
// 2D Array of buttons
buttons = new JButton[8][8];
for(int row=0; row<8; row++)
{
for (int col=0; col<8; col++)
{
buttons[row][col] = new JButton(icons[0]);
buttons[row][col].setLocation(6+col*70, 6+row*70);
buttons[row][col].setSize(69,69);
getContentPane().add(buttons[row][col]);
}
}
// Array of images
public static ImageIcon[] icons = {new ImageIcon("RedButton.png"),
new ImageIcon("OrangeButton.png"),
new ImageIcon("YellowButton.png"),
new ImageIcon("GreenButton.png"),
new ImageIcon("BlueButton.png"),
new ImageIcon("LightGrayButton.png"),
new ImageIcon("DarkGrayButton.png")};

I'd simplify this greatly by putting all my ImageIcons in an ArrayList, calling java.util.Collections.shuffle(...) on the ArrayList, and then passing out the ImageIcons from the shuffled ArrayList in order. Or if your buttons allow for repeated icons, then use a java.util.Random variable, say called random and simply call random.nextInt(icons.length) to get a random index for my array.
As an aside, please for your own sake, don't use null layout and absolute positioning. Your grid of JButtons is begging to be held in a GridLayout-using JPanel. Begging.
As an aside, why are you posting questions on the same project but using different names? You've similar posts but different user names in both of your other posts here:
JButtons won't update on button click
My New Game JButton is not working?

Before you set the icons on the JButton use this shuffle function...
public ImageIcon[] shuffle(ImageIcon[] icons)
{
int index = 0;
ImageIcon temp = 0;
for(int i = icons.length -1; i > 0; i--)
{
index = r.nextInt(i + 1);
temp = icons[index];
icons[index] = icons[i];
icons[i] = temp;
}
return icons;
}

Collecting data from a large number of Swing text fields

I am currently writing a sudoku solver in Java. What I need now is some kind of Swing GUI to input the known numbers. I created a JFrame, but manually adding 81 text fields from the toolbox seems like a bad solution. I am also able to add with code like this:
this.setLayout(new GridLayout(9, 9));
for (int i = 0; i < 81; i++)
{
this.add(new JTextField("Field"));
}
However, I do not know how to address these text fields afterwards to collect the user input into a two-dimensional array. How can I do that?

A different solution would be to use a JTable. You could allow for the TableModel to maintain the full data solution, as well as a copy of the user's attempts. The CellRenderers and CellEditors could handle the user experience. See this tutorial.

Struggled a bit with this for my own sudoku solver, but ended up going for painting on a JPanel, and adding a mouse listener to that.. Than determine the current field using mouse position with his function:
addMouseListener(new MouseAdapter() {
private int t(int z) {
return Math.min(z / factor, 8);
};
#Override
public void mouseMoved(MouseEvent e) {
setToolTipPossibilities(t(e.getX()), t(e.getY()));
}
#Override
public void mousePressed(MouseEvent e) {
clickColumn = t(e.getX());
clickRow = t(e.getY());
}
});

First you need to declare array of JTextFields.
So just like your array to store user input you do:
private JTextField[] textFields;
After that you can use some math to map your one-dimensional array to your two dimensions.
something like this should work:
floor(index / 9), index % 9
for x,y

Yes that will work to display the array. To read from the array you just need to call the getText method for each element.

JTable is your friend. Use a DefaultTableModel with editable String values.
String[] columnNames = new String[9];
for(int i=0; i<9; i++){columnNames[i]="";}
String[][] data = new String[9][9];
JTable tab = new JTable(columnNames,data);
When they fill it in, check that each string is an appropriate number and prompt for error.

1st way:
You could put the text fields into an array that mirrors the array that your cell values are in.
The problem with this method tho is that when you need to bind a mouseListener or ActionListener to the TextField you will have a hard time figuring out which cell number it corrisponds to.
2nd way:
You could extend the JTextField into a custom class with new instance variables that store cell number in it.
Using this method you can also implement MouseListener or ActionListener on the extended class too and get whatever information about the field you need, without searching through your array. And combining with the first to put them into an array organizes them for quick access.

Just want to post a little update.
I added an array of textfields as a field on my form:
private JTextField[] fields;
Initialized it:
fields = new JTextField[81];
And finally I am adding the fields to my form like this:
private void addComponents()
{
this.setLayout(new GridLayout(9, 9));
for (int i = 0; i < fields.length; i++)
{
fields[i] = new JTextField("" + i);
this.add(fields[i]);
}
}
The result as of now can be seen here:
Image of my textfields