动作侦听器Java

Question

For my class I need to use my ActionListener. I am having trouble adding my ActionListener to my buttons. I have to use the word "this" like this.buttons to add my ActionListener but Im having trouble doing that. I will get to my actionPerformed method later but my main problem is my ActionListener.

public class TextButtonsHW extends JFrame implements ActionListener {
private JButton[] buttons;  //Do not change
private JTextArea textArea; //Do not change
//Assign values for these constants in the constructor
private final int ENTER;    //Index of Enter button in buttons
private final int SPACE;    //Index of Space button in buttons
private final int CLEAR;    //Index of Clear button in buttons

/**
 * Set up this frame and its contents.
 * @param title Title to appear in JFrame title bar
 */
public TextButtonsHW(String title) {

    super(title); //call parent JFrame constructor to set the title

    buttons = new JButton[] { new JButton("A"), new JButton("B"), new JButton("C"),
                  new JButton("1"), new JButton("2"), new JButton("3"),
                  new JButton("X"), new JButton("Y"), new JButton("Z"),
                  new JButton("Enter"), new JButton("Space"), new JButton("Clear")};

    ENTER = buttons.length-3;
    SPACE = buttons.length-2;
    CLEAR = buttons.length-1;

    textArea = new JTextArea(15, 5);
    textArea.setEditable(false);

    this.buttons[0].addActionListener(I dont know what to put right here);

    //TODO: instantiate all JButtons, add them to the buttons array,
    //  and register "this" as the ActionListener for each button.
    //DONE
    //TODO: assign values to ENTER, SPACE, and CLEAR constants to
    //  indicate the indexes of those buttons in the buttons array
    //DONE
    //TODO: create the JTextArea textArea
    //TODO: set its "editable" property to false
    //DONE
    //Create a TextButtonsHWPanel to display the buttons and textArea

    TextButtonsHWPanel mainPanel = new TextButtonsHWPanel(buttons, textArea);
    this.getContentPane().add(mainPanel);
    this.pack();
}


public void actionPerformed(ActionEvent e) {


    //TODO: update the text of textArea according to which
    //  button generated the ActionEvent.

}


public static void main(String[] args) {
    final TextButtonsHW f = new TextButtonsHW("Text Buttons");
    f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    f.setLocationRelativeTo(null); //centers frame on screen
    f.setVisible(true);
}

}

Answer 1

buttons[0].addActionListener(this);

Answer 2

Since you have 12 buttons you could also go for a for-loop to add ActionListener to all your buttons ie

for(int i=0; i<12; i++)
{
    buttons[i].addActionListener(this);
}

Instead of a long code ie

buttons[0].addActionListener(this);
buttons[1].addActionListener(this);
........................

Answer 3

Though buttons[0].addActionListener(this); will work well, From design perspective I will suggest to have separate class (may be inner class) which implements ActionListner and pass its object reference to the method.

the whole point of Object Oriented programming is to delegate different responsibilities to different Objects(classes), so code becomes more maintainable and reusable.