動作偵聽器Java

Question

對於我的班級，我需要使用ActionListener。 我在將ActionListener添加到按鈕時遇到麻煩。 我必須像this.buttons這樣使用“ this”一詞來添加我的ActionListener，但是Im很難做到這一點。 稍后將介紹我的actionPerformed方法，但是我的主要問題是我的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

由於您有12個按鈕，因此您還可以進行for循環以將ActionListener添加到所有按鈕，即

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

代替長代碼，即

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

Answer 3

雖然buttons[0].addActionListener(this); 從設計的角度來看，我會工作的很好。我建議有一個單獨的類（可能是內部類），該類實現ActionListner並將其對象引用傳遞給該方法。

面向對象編程的重點是將不同的職責委派給不同的對象（類），因此代碼變得更加可維護和可重用。