无法从 jpanel 中删除组件

Question

我重构了我的代码以生成一个最小的、可重现的示例。

问题 - 我无法从面板上移除卡片（我在出现问题的代码中进行了评论，请参阅 class "ClearCardEventListener"）。

完整代码如下。

在运行程序之前，您将需要一个需要下载并添加到资源文件夹的图像= https://ibb.co/MNccGS0

运行程序
单击 "Add card" 按钮（这将在面板上添加 2 of hearts 图像图标）

单击 "Clear card" 按钮（这是问题所在，我无法从面板中取出卡）

package debug.debug;

import java.awt.Insets;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;

import javax.swing.ImageIcon;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;

public class App extends JFrame {
    public static void main(String[] args) {
        App app = new App();

        Insets insets = app.getInsets();
        app.setSize(300 + insets.left + insets.right,
            300 + insets.top + insets.bottom);
    }

    JPanel panel;
    JButton clearCardButton;
    JButton addCardButton;

    List<Card> playerCards = new ArrayList<Card> ();

    Deck deck = new Deck();

    public App() {
        setTitle("BlackJack Game");
        setVisible(true);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setLocationRelativeTo(null);
        panel = new JPanel();
        add(panel);
        panel.setLayout(null);
        addCardButton = new JButton("Add card");
        clearCardButton = new JButton("Clear card");

        panel.add(addCardButton);
        panel.add(clearCardButton);

        addCardButton.addActionListener(new AddCardEventListener(this, this.deck));
        clearCardButton.addActionListener(new ClearCardEventListener(this, this.deck));

        addCardButton.setBounds(150, 50, addCardButton.getPreferredSize().width, addCardButton.getPreferredSize().height);
        clearCardButton.setBounds(150, 100, clearCardButton.getPreferredSize().width, clearCardButton.getPreferredSize().height);

    }

    public JPanel getPanel() {
        return panel;
    }

    public void addPlayerCard(Card card) {
        playerCards.add(card);
    }

    public List<Card> getPlayerCards() {
        return playerCards;
    }

    public List<JLabel> getPlayerCardLabels() {

        List<JLabel> playerCardLabels = new ArrayList<JLabel> ();

        for (int i = 0; i<this.getPlayerCards().size(); i++) {
            playerCardLabels.add(this.getPlayerCards().get(i).getCardLabel());

        }

        return playerCardLabels;
    }

}

class AddCardEventListener implements ActionListener {

    private App app;
    private Deck deck;

    AddCardEventListener(App app, Deck deck) {
        this.app = app;
        this.deck = deck;
    }

    public void actionPerformed(ActionEvent arg0) {

        // Player gets a card
        app.addPlayerCard(deck.getCard());

        // Display that player's card
        app.getPanel()
            .add(app.getPlayerCards().get(0).getCardLabel()).setBounds(0, 0, 72, 96);

    }

}

class ClearCardEventListener implements ActionListener {

    private App app;
    private Deck deck;

    ClearCardEventListener(App app, Deck deck) {
        this.app = app;
        this.deck = deck;
    }

    public void actionPerformed(ActionEvent arg0) {

        System.out.println("DEBUG: " + app.getPlayerCards().get(0).getCardLabel());

        /***
         * 
         * NOT ABLE TO REMOVE CARD, WHY ???
         * 
         */

        app.getPlayerCards().get(0).getCardLabel().setIcon(null);
        app.getPlayerCards().get(0).getCardLabel().revalidate();
        app.getPlayerCards().get(0).getCardLabel().repaint();

        app.getPanel().remove(app.getPlayerCards().get(0).getCardLabel());

    }

}

class Card {

    private String suit;
    private String rank;
    private int value;

    public void setSuit(String suit) {
        this.suit = suit;
    }
    public void setRank(String rank) {
        this.rank = rank;
    }
    public void setValue(int value) {
        this.value = value;
    }
    public String getSuit() {
        return suit;
    }
    public String getRank() {
        return rank;
    }
    public int getValue() {
        return value;
    }

    // Hardcoded for debugging, so every card image is a 2 of hearts
    public JLabel getCardLabel() {
        return new JLabel(new ImageIcon(getClass()
            .getResource("/cards/2h.png")));
    }
}

class Deck {

    private final String RANKS[] = {
        "Ace",
        "Deuce",
        "Three",
        "Four",
        "Five",
        "Six",
        "Seven",
        "Eight",
        "Nine",
        "Ten",
        "Jack",
        "Queen",
        "King"
    };
    private final String SUITS[] = {
        "Spades",
        "Hearts",
        "Diamonds",
        "Clubs"
    };

    private Card[] deck;
    static private int cardPosition = 0;

    public Deck() {
        deck(); // Create the deck
        shuffle(); // shuffle the deck
    }

    public Card[] deck() {
        deck = new Card[52];

        for (int x = 0; x<deck.length; x++) {
            String rankTemp = RANKS[x % 13];
            String suitTemp = SUITS[x / 13];
            deck[x] = new Card();
            deck[x].setRank(rankTemp);
            deck[x].setSuit(suitTemp);
            deck[x].setValue((x % 13) + 1);
            if (deck[x].getValue() > 10)
                deck[x].setValue(10);
            else if (deck[x].getValue() == 1)
                deck[x].setValue(11);
        }

        return deck;
    }

    public void shuffle() {
        Collections.shuffle(Arrays.asList(deck()));
    }

    public Card[] getDeck() {
        return deck;
    }

    public Card getCard() {
        return deck[cardPosition++];
    }

}

Answer 1

问题 #1

每次你调用 Card#getCardLabel 它都会创建一个新的 JLabel 实例...

class Card {

    // Hardcoded for debugging, so every card image is a 2 of hearts
    public JLabel getCardLabel() {
        return new JLabel(new ImageIcon(getClass()
            .getResource("/cards/2h.png")));
    }
}

这意味着当您...

app.getPanel().add(app.getPlayerCards().get(0).getCardLabel()).setBounds(0, 0, 72, 96);

和...

System.out.println("DEBUG: " + app.getPlayerCards().get(0).getCardLabel());

和...

app.getPlayerCards().get(0).getCardLabel().setIcon(null);
app.getPlayerCards().get(0).getCardLabel().revalidate();
app.getPlayerCards().get(0).getCardLabel().repaint();

app.getPanel().remove(app.getPlayerCards().get(0).getCardLabel());

每次调用实际上都是创建一个 JLabel 的新实例，因此屏幕上显示的与您要修改的那个无关。

因此，您的 Card#getCardLabel 应该只创建一个 JLabel 一次，这也称为 "lazy loading"...

class Card {

    private JLabel label;

    //...

    // Hardcoded for debugging, so every card image is a 2 of hearts
    public JLabel getCardLabel() {
        if (label == null) {
            // Simple image for demonstration purposes
            BufferedImage img = new BufferedImage(100, 150, BufferedImage.TYPE_INT_RGB);
            Graphics2D g2d = img.createGraphics();
            g2d.setColor(Color.WHITE);
            g2d.fillRect(0, 0, 100, 150);
            g2d.setColor(Color.RED);
            g2d.drawLine(0, 0, 100, 150);
            g2d.drawLine(100, 0, 0, 150);
            g2d.dispose();

            label = new JLabel(new ImageIcon(img));
        }

        return label;
    }
}

问题 #2

Swing 是惰性的（好的，它是 "optimised"），这意味着添加或删除组件本身不会触发布局或绘制过程。这样做是为了让您可以对 UI 进行大量更改，而不是让它尝试更新每个更改，这会非常慢。

这意味着当你添加或删除一个组件时，你还应该调用 repaint 来触发一个新的绘制通道（我也推荐 revalidate，但你没有使用任何布局管理器，所以它不会为你做任何事情）

app.getPanel().remove(app.getPlayerCards().get(0).getCardLabel());
app.getPanel().repaint();

无法从 jpanel 中删除组件

Unable to remove component from jpanel

java

oop

swing

jcomponent

jpanel

问题 #1

问题 #2