How to remove item inside JPanel which is designated by an ArrayList

问题

There is a JPanel with GridLayout which is randomly populated by JButtons created using an ArrayList. Each element of the array (a Tile) contains a character. It's supposed to be a tile removing game. However, I realised that the code I wrote didn't work, because once a tile is removed, the others' indexes change.

A KeyListener is applied to the JPanel. This method is in my Model class, where the ArrayList is first created. getChar, in the Tile class, simply returns its character.

public void removeChar(char typedChar) {
    for(Tile t: _al){
            if(t.getChar() == typedChar) {
                System.out.println(typedChar + " is in the game, at index " + _al.indexOf(t) + " of the array.");
                _p.remove(_al.indexOf(t));
            }

With my code, I basically just want to remove the corresponding tile when its character key is typed. Can anyone help me see a better (well, working) way to do this? My code seems to become much more complicated because the ArrayList is full of objects, but I will need the objects later.

回答1:

Don't use a KeyListener. Swing was designed to be used with Key Bindings.

Add a Key Binding to each button. Then when the letter is typed the button will be the source of the event so you can just remove the button from the panel.

For an example of how key bindings work see below:

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

public class CalculatorPanel extends JPanel
{
    private JTextField display;

    public CalculatorPanel()
    {
        Action numberAction = new AbstractAction()
        {
            @Override
            public void actionPerformed(ActionEvent e)
            {
//              display.setCaretPosition( display.getDocument().getLength() );
                display.replaceSelection(e.getActionCommand());
            }
        };

        setLayout( new BorderLayout() );

        display = new JTextField();
        display.setEditable( false );
        display.setHorizontalAlignment(JTextField.RIGHT);
        add(display, BorderLayout.NORTH);

        JPanel buttonPanel = new JPanel();
        buttonPanel.setLayout( new GridLayout(0, 5) );
        add(buttonPanel, BorderLayout.CENTER);

        for (int i = 0; i < 10; i++)
        {
            String text = String.valueOf(i);
            JButton button = new JButton( text );
            button.addActionListener( numberAction );
            button.setBorder( new LineBorder(Color.BLACK) );
            button.setPreferredSize( new Dimension(30, 30) );
            buttonPanel.add( button );

            InputMap inputMap = button.getInputMap(JComponent.WHEN_IN_FOCUSED_WINDOW);
            inputMap.put(KeyStroke.getKeyStroke(text), text);
            inputMap.put(KeyStroke.getKeyStroke("NUMPAD" + text), text);
            button.getActionMap().put(text, numberAction);
        }
    }

    private static void createAndShowUI()
    {
        JFrame frame = new JFrame("Calculator Panel");
        frame.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );
        frame.add( new CalculatorPanel() );
        frame.pack();
        frame.setLocationRelativeTo( null );
        frame.setVisible(true);
    }

    public static void main(String[] args)
    {
        EventQueue.invokeLater(new Runnable()
        {
            public void run()
            {
                createAndShowUI();
            }
        });
    }
}

So in your case the code in the actionPerformed() method of the Action would be something like:

JButton button = (JButton)e.getSource();
JPanel parent = (JPanel)button.getParent();
parent.remove(button);
parent.revalidate();
parent.repaint();

Edit:

When using a KeyListener you might use HashMap to bind the character to the related button:

HashMap<Character, JButton> buttons = new HashMap<Character, JButton>();
...
buttons.put('a', aButton);
buttons.put('b', bButton);

Then the keyTyped() code in the KeyListener code would be something like:

JButton button = buttons.get( e.getKeyChar() );
panel.remove( button );
panel.revalidate();
panel.repaint();

来源：https://stackoverflow.com/questions/33808876/how-to-remove-item-inside-jpanel-which-is-designated-by-an-arraylist

标签

java

swing

arraylist

keylistener

indexof