Finding the right argument for addActionListener

Question

I'm trying to make a button that toggles the state of the button (changes color and text) when pressed. But I can't get the addActionListener to work and I can't find the ToggleState method from my main class. I am new to java and would appreciate your help.

I get the errors - “The method addActionListener(ActionListener) in the type AbstractButton is not applicable for the arguments” - "ActionListener cannot be resolved to a type"

package Grafiktest;

import javax.swing.*;
import java.awt.*;

public class coolgrafik extends JFrame implements ActionListener {

private static final long serialVersionUID = 1L;
private JPanel panel;
private JLabel label;

public coolgrafik(){

    //super(title);
    setSize(400,60);
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    panel = new JPanel();
    panel.setBackground(Color.GRAY);
    label = new JLabel("test");
    panel.add(label);

    MyButton button = new MyButton(Color.green, Color.red, "RUN","STOP");
    panel.add(button);
    button.addActionListener(this);

    add(panel);
}

public static void main(String[] args){
    new coolgrafik().setVisible(true);
    //toggleState(Color.green, Color.red, "RUN","STOP");
}

public void actionPerformed(ActionEvent e) {
    toggleState(Color.green, Color.red, "RUN","STOP");
}
}

and this is the button class

package Grafiktest;

import javax.swing.*;
import java.awt.*;

public class MyButton extends JButton{

private static final long serialVersionUID = 1L;

public MyButton(Color c1, Color c2, String s1, String s2){

    setText(s1);
    setForeground(c1);
    setBackground(c1);
    setOpaque(true);

}

public void toggleState(Color c1, Color c2, String s1, String s2){

    setText(s2);
    setForeground(c2);
    setBackground(c2);
    setOpaque(true);

}

}

Answer 1

Let's just stop a second and think about what you're trying to do. You want to change the state of the button when it's pressed.

The real question is, who's actually responsible for doing that? Any ActionListener monitoring the button should be focused on carrying out the work they need to do, not managing the button as well, what happens when you have more than one ActionListener attached to the button? Who becomes responsible for it then?

What about if, instead, we made the button self managing? That is, the button monitors itself and update its state accordingly

Because you'd need to manage the selected state anyway, I've used a JToggleButton instead, as it has a "selected"/"unselected" state internally.

public class MyButton extends JToggleButton {

    private static final long serialVersionUID = 1L;

    public class State {
        public Color color;
        public String text;

        public State(Color color, String text) {
            this.color = color;
            this.text = text;
        }

    }

    private final State unselectedState;
    private final State selectedState;

    public MyButton(Color c1, Color c2, String s1, String s2) {

        selectedState = new State(c1, s1);
        unselectedState = new State(c2, s2);

        setContentAreaFilled(false);
        setBorderPainted(false);
        setFocusPainted(false);
        setOpaque(true);

        toggleState();

        getModel().addChangeListener(new ChangeListener() {
            @Override
            public void stateChanged(ChangeEvent e) {
                toggleState();
            }
        });

    }

    public void toggleState() {

        State state = !getModel().isSelected() ? selectedState : unselectedState;

        setText(state.text);
        setForeground(Color.WHITE);
        setBackground(state.color);

    }
}

Basically all this does it will configure the button based on the selected state of the ButtonModel.

You could use an ActionListener and register it directly to the button itself in similar fashion, but you'd need to manage which state it's using

Answer 2

To complete @Japu_D_Cret 's comment :

You either need to make your toggleState method static to call it like you do in your actionPerformed method, or to use your button to call it :

button.toggleState(Color.green, Color.red, "RUN","STOP");

as it is a method defined in your MyButton class and not in your coolgrafik class.

Answer 3

"The method addActionListener(ActionListener) in the type AbstractButton is not applicable for the arguments” - "ActionListener cannot be resolved to a type"

you didn't import the class ActionListener, since it's not in java.awt.* but in java.awt.event.ActionListener - for reference https://docs.oracle.com/javase/7/docs/api/java/awt/event/ActionListener.html

But I still can't use my toggleState method from the actionperformer. How come?

well in your void actionPerformed(ActionEvent) you try to call a method called void toggleState(Color,Color,String,String) - but it is not declared in the same class nor is it statically imported.

You obviously want to call the toggleState method on your object button of class MyButton, to do that you have to call the method on that object like button.toggeState(...) This will also not directly work, since your object button is only known in your constructor and you have to add an object attribute to your coolgrafik class, like you did with the panels - then it should work just fine

here are code fragments that you need to change in your coolgrafik class

attributes:

private JPanel panel;
private JLabel label;
private MyButton button;

in your coolgrafik constructor

//...
this.button = new MyButton(Color.green, Color.red, "RUN","STOP");
this.panel.add(this.button);
this.button.addActionListener(this);
//...

and your actionPerformed Method

public void actionPerformed(ActionEvent e) {
    button.toggleState(Color.green, Color.red, "RUN","STOP");
}