Java更改颜色JLabel

Question

I know how to change a color in java from a JLabel object if you do it like this

JLabel label = new JLabel("label text");
label.setForeground(Color.red);

but::

i create my JLabes dynamic like this

center.add(new JLabel("Antwoord Vraag"+ (i +1) +": "+antwoord.get(i),SwingConstants.LEFT));

How could i change the color of a JLabel object without giving the object a name.

Answer 1

What you are looking for is a builder pattern for JLabel , which AFAIK does not exist. You can either create your own builder class, or extend JLabel with your own class that takes color as constructor argument (which is weird since JLabel has many properties, imagine what happens if each of them ahd it's own special constructor).

JLabelBuilder example:

public class JLabelBuilder {
    private Color fColor;
    private String text;

    public void setForegroundColor(Color c) {
        fColor = c;
    }

    public void setText(String t) {
        text = t;
    }

    public JLabel build() {
        if (text != null && fColor != null) {
            JLabel label = new JLabel(text);
            label.setForeground(fColor);
            return label;
        } else {
            ...
        }
    }
}

Usage:

center.add(new JLabelBuilder()
                   .setText("Antwoord Vraag" + (i + 1) + ": " + antwoord.get(i))
                   .setForegroundColor(Color.red)
                   .build());

Anyway, I don't see the harm in two more lines of code. Explicitly declaring your object variable is also a good practice for readability reasons. This will also work inside a loop:

for(int i = 0 ; i < maxCounter ; i++) {
    String text = "Antwoord Vraag" + (i + 1) + ": " + antwoord.get(i);
    JLabel label = new JLabel(text, SwingConstants.LEFT);
    label.setForeground(Color.red);
    center.add(label);
} 

Answer 2

There are a couple of ways you can do this, but not with the standard JLabel - you'll need your own subclass or helper. For example:

public class CLabel extends JLabel
{
    public CLabel(String text)
    {
        super(text);
    }

    public CLabel(String text, Color color)
    {
        super(text);
        setForeground(color);
    }

    public CLabel withColor(Color color)
    {
        setForeground(color);
        return this;
    }
}

Then you can do either of the following:

    new CLabel("Hello", Color.RED);
    new CLabel("Hello").withColor(Color.RED);

Answer 3

You're going to have to split this up into multiple lines:

JLabel label = new JLabel("Antwoord Vraag"+ (i +1) +": "+antwoord.get(i),SwingConstants.LEFT);
label.setBackground(Color.GREEN);
label.setOpaque(true);
center.add(label);

PS- I'm going to start calling them "JLabes" too- much trendier! :p

Answer 4

This line:

center.add(new JLabel("Antwoord Vraag"+ (i +1) +": "+antwoord.get(i),SwingConstants.LEFT)); 

is in a for loop for creating more JLabels

    for(int i = 0; i<maxCounter; i++)
    {

        // Goede Antwoorden toevoegen aan de center
       center.add(new JLabel("Antwoord Vraag"+ (i +1) +": "+antwoord.get(i),SwingConstants.LEFT));                      
    } 

Because this is not working in the for loop:

    JLabel label[i] = new JLabel("Antwoord Vraag"+ (i +1) +": "+antwoord.get(i),SwingConstants.LEFT);

Is there a sollution to change the color

I have solved the problem. Before i start the loop i creat a array:

JLabel[] labels = new JLabel[maxCounter];

Then in the forloop:

           labels[i] = new JLabel("Antwoord Vraag"+ (i +1) +": "+antwoord.get(i),SwingConstants.LEFT);
           // verander de kleur van de labels
           labels[i].setForeground(rood);
           center.add(labels[i]);