如何在Button上使用ActionListener来更改其他类中的JLabel？

Question

I am currently doing a group assignment.One of my tasks is to use an ActionListener to add "data" to JLabels in a different class.

Another person in my group was responsible for coding the GUI, however he did a very bad job with it making my task a bit more difficult. We were taught to practice MVC standards. However I don't think I could do that properly now. The code for the GUI is a single huge chunk of code over a thousand lines long all contained in 1 method making it hard to tidy up without wasting too much time.

I have used ActionListeners before, but only in practice and when they are all in one class.

What I am trying to achieve is when a button is clicked (from the GUI class), the actionPerformed method will call methods from an external JAR file and change the JLabels from showing the text Default to the "data" obtained from the called methods.

At the moment I have 6 JLabels created with a for loop,

    int totalLbls = 6;

    JLabel lbl[] = new JLabel[totalLbls];

    for (int j = 0; j <totalLbls;j++){

         lbl[j] = new JLabel("default");
         pa2.add(lbl[j]);

Firstly, how would I change each label? Initially I thought about doing it manually and mapping it individually 6 times like so,

JLabel lb1 = new JLabel(jarname.getData());
JLabel lb2 = new JLabel(jarname.getMoreData());
.
.
.
JLabel lb6 = new JLabel(jarname.getOtherData());

The methods that are called return String values. The methods and jar file name used are just placeholder names.

Secondly, how would I go about implementing the ActionListener? I've seen examples but they often ask that we apply the MVC standards. Which means the the Controller calling both the View and Model. And in my case there is only a really messy View.

Answer 1

One way to go about doing it if you are not implementing ActionListener to the main class is to make one specific for that button.

yourButton.addActionListener(new ActionListener(){
    public void actionPerformed(ActionEvent arg0) {
        /* Set your labels here.
        OtherClass.lb1.setText(jarname.getData());
        OtherClass.lb2.setText(jarname.getMoreData());
        .
        .
        .
        OtherClass.lb6.setText(jarname.getOtherData());
        */
    }
});

Answer 2

Pass the instance of the class that knows about the JLabels into the class that has the action listener. For example (simplified access for example):

public class LabelContainer { // May well extend JPanel or JFrame
  public JLabel label1 = new JLabel("First");
 // Plus five more..
}

public class LabelChanger implements ActionListener { // May well extend JButton
  private LabelContainer labels;
  public LabelChanger(LabelContainer labels) {
    this.labels = labels;
    someWidget.addActionListener(this);
  }

  public void actionPerformed(ActionEvent e)
  {
    labels.label1.setText("Changed");
    // five more...
  } 
}