Develop Reference

Refresh data in a JLabel

I have a program which calculates an integer and then uses the value within a JLabel. On intital creation everything is fine with the initialized value, but when I change the value of the int within the label I can't seem to find a way to update the JLabel. The relevant code is as follows:
JLabel carbLbl;
int totCarbs = 0;
public Main() {
carbLbl = new JLabel("Total Carbs: " + totCarbs);
carbLbl.setFont(new Font("KidSans", Font.PLAIN, 38));
carbLbl.setAlignmentX(Component.RIGHT_ALIGNMENT);
void addFoodToTable() {
String[] s = new String[3];
s = (String[]) foodData.get(foodChoice.getSelectedIndex());
foodList.addRow(s);
totCarbs += Integer.parseInt(s[2]);
carbLbl.repaint();
}
}
There's obviously much more code, but it's too long to include the entire script. Is there a way I can have the label update whenever I invoke the addFoodToTable() method?

The JLabel is not "bound" to your integer variable. When you change the integer you need to update the JLabel using carbLbl.setText(String.valueOf(totCarbs))

Is there not a way to simply update the JLabel using the initial constructor parameters?
carbLbl = new JLabel("Total Carbs: " + totCarbs);
What parameters? There is only a single parameter, the String to be displayed.
The compiler concatenates the hard coded String with the value of your "totCarbs" variable to create a single String.
The compiler will essentially treat the above code like:
String text = "Total Carbs" + totCarbs;
carbLbl = new JLabel( text );
The JLabel has no idea how the String was created (ie. that a variable was used to build the string).
I understand the concept of concatenation, but I just feel like that's a workaround
It is not a work around. The API of the setText(...) method states you provide a single String. So, if you want to update the label you need to provide the entire String.

How do I set the color of a JLabel using Java?

I will be creating multiple Jlabel components upon a JButton click. I know how to create a label and set text inside but I want this label to have a color.
I only know how to change the color of a label if it has a name but an important part of my program is when I declare the labels, I don't have names for them as shown in the code below:
newPanel.add(new JLabel("jlabel text"), g);
How can I set the color of the label?

I don't have names for them as shown in the code below:
newPanel.add(new JLabel("jlabel text"), g);
So give the label a name:
JLabel label = new JLabel("label text");
label.setOpaque( true );
label.setBackground( Color.RED );
newPanel.add(label, g);

You should assign the label to a variable so that you can perform additional operations on it:
JLabel myLabel = new JLabel("jlabel text");
myLabel.setForeground(new java.awt.Color.RED);
newPanel.add(myLabel);
Now place this code in a function, such as an event handler for your button. Each time you click the button it creates a new JLabel. The name myLabel only refers to the current one that is being created. So yes, you can reuse the same name to refer to a different JLabel object. At a given moment, the name can only refer to one JLabel at a time.

yourLabel.setForeground(new java.awt.Color(r,g,b);

Accessing GUI JTextField objects that are dynamically generated

I am writing a program that contains a JButton. Every time the button is clicked, a new JTextField is added to a JPanel.
My problem is that, after the user has created all the JTextFields and filled them with information, I need to get the text of each field. How can I get access to the JTextFields when they are dynamically generated, as they don't have instance names? Is there a better way to get the text of each one, without knowing their instance name.
Here is the code of the actionPerformed event of the JButton...
private void jButton4ActionPerformed(java.awt.event.ActionEvent evt) {
JTextField x = new JTextField();
x.setColumns(12);
p.add(x);
validate();
}

You say you want to get the text from each field. So, when you create the new instances x, why don't you keep a collection of them, such as adding the JTextFields to an ArrayList?
Alternatively, assuming that p is a JPanel, you should be able to get all the children, which would be the JTextFields that you're adding. Try using getComponents() like so...
Component[] children = p.getComponents();
for (int i=0;i<children.length;i++){
if (children[i] instanceof JTextField){
String text = ((JTextField)children[i]).getText():
}
}

You can find them all by looping through the components of the panel (or whatever "p" is). If necessary, check if each is a text box. That is, do p.getComponents and then loop through the returned array. Like:
Component[] components=p.getComponents();
for (Component c : components)
{
if (c instanceof JTextField)
{
String value=((JTextField)c).getText();
... do whatever ...
}
}
If they are interchangeable, that should be all you need. If you need to distinguish them, I think the cleanest thing to do would be to create your own class that extends JTextField and that has a field for a name or sequence number or whatever you need.

How do I underline text "text" when text is a field?

public class Text extends JPanel {
private String text;
public Text()
{
this.setPreferredSize(new Dimension(20,20));
setFont (new Font(text, Font.PLAIN, 24));
text = "";
}
public void showUnderline()
{
Hashtable<TextAttribute, Object> map = new Hashtable
<TextAttribute, Object>();
map.put(TextAttribute.UNDERLINE, TextAttribute.UNDERLINE_ON);
}
the text object will be created within another class. in that class I will need to underline it with the showUnderline method. The method seems incomplete.I'm shooting for the java exclusive approach, meaning no HTML.
How do I link the text to the showUnderline method?

What do you mean 'java exclusive approach, meaning no HTML' ? You probably are looking for a JLabel, and you can put very simple html in it. Here's the first result on google:
http://www.apl.jhu.edu/~hall/java/Swing-Tutorial/Swing-Tutorial-JLabel.html
It has an example of making text different colors, fonts, and bold or italicized. You could probably just do something like:
JLabel label = new JLabel("<u>MY TEXT</u>",JLabel.CENTER);
From there, you can place it like you would place any other JComponent.
If you really don't want HTML, you could use a JTextPane. Here's an example:
http://www.exampledepot.com/egs/javax.swing.text/style_hilitewords2.html

How to print to a J text box the entire contents of a tree map?

Hi Everyone thanks for taking the time to look at my question.
I would like to use the JText field I have created to display the values of a tree map which contains all the employees: ID numbers (as the key in the map)as well as an Employee object which contains a to string method of all the employee details.
the system seems to be working fine because when I print to the console (CMD) it works fine and prints out all the values in the MAP but when I try print it to a JText box it only prints one object (one employee) from the entire list.
I believe the issue lies with my for loop i am using to access all the details.
the issue lies with this line of code:
writeStrings.setText(writeStrings.getText()+" "+dEmp);
This is the code in its entirety:
public void chooseEmpToAdd()
{
JFrame frameAllEmps = new JFrame();
frameAllEmps.setSize( 450, 140 );
frameAllEmps.pack();
frameAllEmps.setVisible(true);
int x = 0;
System.out.println("ALL Emps from the tree map");
for(int key:employeeMap.keySet())
{
JTextField writeStrings;
writeStrings = new JTextField(20);
Employee dEmp = employeeMap.get(key);
System.out.println("Employe no :" +x+": "+dEmp);
writeStrings.setText(writeStrings.getText()+" "+dEmp);
frameAllEmps.add(writeStrings);
x++;
}
}

writeStrings = new JTextField(20);
You create new JTextField component on every iteration and add it to container.
JFrame uses BorderLayout as a default layout.
This layout puts your JTextField component in the center (frameAllEmps.add(writeStrings)). So you lost previous added JTextField and see only last JTextField component.