如果JTextField中有任何输入，则KeyListener不响应

Question

I develop a simple MVC Calculator app. I decided to add some functionality by implementing KeyListener in CalculatorView. But this KeyListener only responds when there is no input in JTextField (before any input was made by pushing GUI buttons) or it responds when I press "ESC". I know some people here advice to use KeyBindings instead of KeyListener, but then I need to have 12 KeyBindings in my code (10 for numbers, 1 for ESC and 1 for "." character). Is there any way to make KeyListener to work properly in my app?

And here is the code:

/**
 *
 * @author Kate Nezdoly
 */
public class CalculatorView implements ActionListener, KeyListener {   

private JButton[] operButtons = new JButton[13];
private JButton[] numberButtons = new JButton[12];
private String[] operators = {"C", "(", ")", "+", "-", "*", "/", "^", "cos", "sin",
    "tan", "sqrt"};
private String[] numbers = {"1", "2", "3", "4", "5", "6", "7", "8",
    "9", "0", ".", "="};

public CalculatorView() {
    try {
        UIManager.setLookAndFeel(
                UIManager.getSystemLookAndFeelClassName());
    } catch (UnsupportedLookAndFeelException | ClassNotFoundException | InstantiationException | IllegalAccessException e) {
        System.err.println(e.getMessage());
    }

    createAndShowGUI();
}
private JTextField input;
private boolean decimal = true;

private JPanel createContentPane() {
    JPanel totalGUI = new JPanel(new BorderLayout(12, 8));
    input = new JTextField("0.0", 18);
    input.addKeyListener(this);
    input.setEditable(false);
    input.setBackground(Color.white);
    input.setHorizontalAlignment(JTextField.RIGHT);

    JPanel action_buttons = new JPanel(new GridLayout(5, 2));

    operButtons[0] = new JButton(operators[0]);
    action_buttons.add(operButtons[0]);

    for (int i = 1; i < operators.length; i++) {
        operButtons[i] = new JButton(operators[i]);
        operButtons[i].addActionListener(this);
        operButtons[i].setActionCommand(operators[i]);
        action_buttons.add(operButtons[i]);
    }

    JPanel number_buttons = new JPanel(new GridLayout(5, 2));

    for (int i = 0; i < numbers.length - 1; i++) {
        numberButtons[i] = new JButton(numbers[i]);
        numberButtons[i].addActionListener(this);
        numberButtons[i].setBackground(Color.lightGray);
        numberButtons[i].setActionCommand(numbers[i]);
        number_buttons.add(numberButtons[i]);
    }

    numberButtons[11] = new JButton(numbers[11]);
    number_buttons.add(numberButtons[11]);

    totalGUI.add(input, BorderLayout.PAGE_START);
    totalGUI.add(number_buttons, BorderLayout.CENTER);
    totalGUI.add(action_buttons, BorderLayout.LINE_END);

    totalGUI.setOpaque(true);
    return totalGUI;
}

private void createAndShowGUI() {
    JFrame frame = new JFrame("Calculator");

    frame.setContentPane(createContentPane());
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.pack();
    frame.setVisible(true);
    frame.setSize(300, 190);
    frame.setResizable(false);
}

public void actionPerformed(ActionEvent ae) {
    String temp = ae.getActionCommand();

    if (input.getText().equals("0.0")) {
        input.setText("");
    }

    if (temp.equals(".")) {
        if (decimal) {
            decimal = false;
            input.setText(input.getText() + "" + temp);
        }
    } 
    else {
        input.setText(input.getText() + "" + temp);
    }
}

public void buttonActionListeners(ActionListener al) {
    //add "=" action listener
    numberButtons[11].setActionCommand(numbers[11]);
    numberButtons[11].addActionListener(al);

    //add "C" action listener
    operButtons[0].setActionCommand(operators[0]);
    operButtons[0].addActionListener(al);

}

// Gets the text from the Text Box and converts it into a Double.
public String getFieldText() {
    return input.getText();
}

// Sets the text displayed on the Text Box.
public void setFieldText(String message) {
    input.setText("" + message);
    decimal = true;
}    

@Override
public void keyTyped(KeyEvent e) {

}

@Override
public void keyPressed(KeyEvent e) {
    if (e.getKeyCode() == 27) {
        System.exit(0);
    } else if (e.getKeyCode() >= 48 && e.getKeyCode() <= 57) {
        if (input.getText().equals("0.0")) {
            setFieldText(String.valueOf(e.getKeyChar()));
        } else {
            setFieldText(input.getText() + e.getKeyChar());

        }
}
}

@Override
public void keyReleased(KeyEvent e) {

}


}

Controller class:

public class CalculatorController implements  ActionListener {

private CalculatorView view;    

public CalculatorController( CalculatorView view)   {  
    this.view = view;
    view.buttonActionListeners(this);
}

@Override
public void actionPerformed(ActionEvent e) {
    String action = e.getActionCommand();
    switch (action) {
        case "=":
            view.setFieldText(Parser.parse(view.getFieldText()));                
            break;
        case "C":
            view.setFieldText("0.0");
            break;
    }
}

public static void main(String args[]){
    CalculatorView calc = new CalculatorView();
    CalculatorController contr = new CalculatorController(calc);
  }

}

Answer 1

I think that there isn't any reason for implement KeyListener/KeyBinding ,

1) add as ActionCommand to the JButtons example here

private String[] numbers = {"1", "2", "3", "4", "5", "6", "7", "8", "9", "0", ".", "="};

2) change JTextField to the JFormattedTextField with NumberInstance/Formatter , then there are alowed only Numbers and decimal separator, and no longer there reason for listening from KeyBoard by implement KeyListener/KeyBinding s nor parsing/testing for NumberInstance

3) if is there more than one that one JFormattedTextField (value could be imputed or pasted from ClipBoard) or for example JFormattedTextField and JTextArea (for showing previous calculations) then chaining these fiedls by using DocumentListener