java - 在 Swing 中更新 JLabel 中的图像图标？使用 revalidate() 和 repaint() 但不起作用

Question

好吧，我刚刚习惯 OOP，并且正在学习 swing。我正在制作一个简单的应用程序，它是由 4 个图像(一个 X、一个 O、一个正方形和一个三角形)组成的 2x2 网格，单击任意一个图像会将颜色的形状切换为蓝色。

虽然我无法让它切换到新图像，但我认为这与我的程序的一些基本内容有关。

介意看一下吗？

JFrame 类:

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JFrame;
import javax.swing.JButton;
import javax.swing.JLabel;
import javax.swing.ImageIcon;
import java.awt.image.BufferedImage;
import javax.imageio.ImageIO;
import java.io.File;
import java.io.IOException;
import javax.swing.JPanel;

public class Frame1 {

    public JFrame frame;

        Frame1 window = new Frame1();
        window.frame.setVisible(true);

    }

    public Frame1() {
        initialize();
    }

    private void initialize() {
        frame = new JFrame();
        frame.setBounds(100, 100, 900, 900);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.getContentPane().setLayout(null);

        Squares x = new Squares("images\\black-X.png", "images\\blue-X.png", 0, 0, 450, 450, "x");
        Squares o = new Squares("images\\black-O.png", "images\\blue-O.png", 450, 0, 450, 450, "o");
        Squares sq = new Squares("images\\black-sq.png", "images\\blue-sq.png", 0, 425, 450, 450, "sq");
        Squares tri = new Squares("images\\black-tri.png", "images\\blue-tri.png", 450, 410, 450, 450, "tri");


        frame.getContentPane().add(x.getLabel());
        frame.getContentPane().add(o.getLabel());
        frame.getContentPane().add(sq.getLabel());
        frame.getContentPane().add(tri.getLabel());
    }


}

鼠标监听器类:

import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import javax.swing.JFrame;
import javax.swing.JOptionPane;
import javax.swing.JPanel;

public class clickListener implements MouseListener{

    Squares ob = new Squares();

    public clickListener(Squares newSquare) {
        ob = newSquare;
    }

    public void mouseClicked(MouseEvent e) {
        ob.changePic();
    }

}

然后我为每个图像创建一个对象类

import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;

import javax.imageio.ImageIO;
import javax.swing.ImageIcon;
import javax.swing.JLabel;
import javax.swing.JOptionPane;
import javax.swing.JPanel;

public class Squares {

    String pic1, pic2, name;
    int x, y, width, height;

    JPanel panel = new JPanel();
    JLabel label = new JLabel();

    public Squares() {
        ;
    }

    public Squares(String pic1, String pic2, int x, int y, int width, int height, String name) {
        this.pic1 = pic1;
        this.pic2 = pic2;
        this.x = x;
        this.y = y;
        this.width = width;
        this.height = height;
        this.name = name;

        BufferedImage myPic1 = null;

        try {
            myPic1 = ImageIO.read(new File(pic1));

        } catch (IOException ex) {System.out.println("error in image upload");}

        /*
        panel.setBounds(x, y, width, height);
        panel.add(new JLabel(new ImageIcon(myPic1)));   
        panel.addMouseListener(new clickListener(this));
        */

        label = new JLabel(new ImageIcon(myPic1));
        label.setBounds(x, y, width, height);
        label.addMouseListener(new clickListener(this));
    }

    public JLabel getLabel() {
        return label;
    }

    public String getName() {
        return this.name;
    }

    public void changePic() {
        JOptionPane.showMessageDialog(null, "change pic reached for " + this.name);
        BufferedImage myPic2 = null;
        try {myPic2 = ImageIO.read(new File(pic2));}
        catch(IOException ex) {System.out.println("error in image upload");}
        label = new JLabel(new ImageIcon(myPic2));
        label.setBounds(x, y, width, height);
        label.repaint();
        label.revalidate();
    }
}

我最初使用包含每个 JLabel 的 JPanel，但为了简化事情，我将它们全部删除。

所以，是的，任何建议都会受到赞赏。谢谢!

Answer 1

所以“核心”问题在于您的 changePic 方法

public void changePic() {
    JOptionPane.showMessageDialog(null, "change pic reached for " + this.name);
    BufferedImage myPic2 = null;
    try {
        myPic2 = ImageIO.read(new File(pic2));
    } catch (IOException ex) {
        System.out.println("error in image upload");
    }
    label = new JLabel(new ImageIcon(myPic2));
    label.setBounds(x, y, width, height);
    label.repaint();
    label.revalidate();
}

在此方法中，您创建了一个 JLabel 的新实例，但它永远不会添加到附加到屏幕的任何容器中，因此它永远不会显示。

简单的解决方案是简单地更改 JLabel 现有实例的 icon 属性

public void changePic() {
    JOptionPane.showMessageDialog(null, "change pic reached for " + this.name);
    BufferedImage myPic2 = null;
    try {
        myPic2 = ImageIO.read(new File(pic2));
    } catch (IOException ex) {
        System.out.println("error in image upload");
    }
    label.setIcon(new ImageIcon(pic2));
}

观察结果...

在检查代码时，我发现了一些可以做得更好的事情。

• (尽管它的名字如此)管理主框架确实不是 Frame1 的责任。通过不同的容器可以更好地管理核心功能，这可以解耦组件，并使其在长期错误中更加灵活和可重用 - 您也不需要在组件中包含框架管理的复杂性和其他职责。
• 您应该避免 null 布局。更简单的解决方案是使用 GridLayout，因为您提供的实现存在布局问题
• Squares 不需要知道父容器想要的位置或大小 - 这实际上并不是父容器应该直接做出的决定。相反，Squares 应该向父容器提供大小调整提示，以便它可以就如何布局所有子组件做出更好的决策。 JLabel 本身能够提供此信息。
• 可以说，Squares 应该从 JLabel 扩展 - 这纯粹是为了简单起见。 JLabel 是显示图像的首选位置，因此它是这项工作的不错选择，但围绕它包装一个类只会使其管理变得更加麻烦，在这种情况下，增加的值(value)非常小。对于组合优于继承达成了一项协议(protocol)，但在这种情况下，我不确定它会增加任何更多的值(value)
• ClickListener 不需要创建 Squares 的实例，它只是构造函数要求任何调用者将 Squares 的实例传递给它不管怎样
• 由于它的核心功能，如果无法加载任一图像，Squares 就会失败，这将使诊断这些问题变得更加容易，而不是让程序继续在“ splinter ”状态

恕我直言

示例

import java.awt.EventQueue;
import java.awt.GridLayout;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import javax.imageio.ImageIO;
import javax.swing.ImageIcon;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;

public class Game {

    public static void main(String[] args) {
        new Game();
    }

    public Game() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    try {
                        UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                    } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                        ex.printStackTrace();
                    }

                    JFrame frame = new JFrame("Testing");
                    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                    frame.add(new GamePane());
                    frame.pack();
                    frame.setLocationRelativeTo(null);
                    frame.setVisible(true);
                } catch (IOException ex) {
                    ex.printStackTrace();
                }
            }
        });
    }

    public class GamePane extends JPanel {

        public GamePane() throws IOException {
            initialize();

        }

        private void initialize() throws IOException {
            Square x = new Square("images\\black-X.png", "images\\blue-X.png", "x");
            Square o = new Square("images\\black-O.png", "images\\blue-O.png", "o");
            Square sq = new Square("images\\black-sq.png", "images\\blue-sq.png", "sq");
            Square tri = new Square("images\\black-tri.png", "images\\blue-tri.png", "tri");

            setLayout(new GridLayout(2, 2));

            add(x);
            add(o);
            add(sq);
            add(tri);
        }

    }

    public class ClickListener extends MouseAdapter {

        private Square ob;

        public ClickListener(Square newSquare) {
            ob = newSquare;
        }

        public void mouseClicked(MouseEvent e) {
            ob.changePic();
        }

    }

    public class Square extends JLabel {

        String name;
        private BufferedImage myPic1, myPic2;

        public Square(String pic1, String pic2, String name) throws IOException {
            this.name = name;

            myPic1 = ImageIO.read(new File(pic1));
            myPic2 = ImageIO.read(new File(pic2));

            setIcon(new ImageIcon(myPic1));
            addMouseListener(new ClickListener(this));
        }

        public String getName() {
            return this.name;
        }

        public void changePic() {
            setIcon(new ImageIcon(myPic2));
        }
    }
}