有没有办法在加载时调整图像大小？图像链接到 JList

Question

这是我写的代码。它唯一的问题是我无法调整图像大小。我尝试过 getScaledInstance 不起作用。关于如何解决这个问题的任何想法。另外，为什么我必须使用容器来显示图片，面板是否足以显示结果，但在添加容器之前我没有得到任何输出。

package split;

import javax.swing.event.*;
import java.awt.*;
import javax.swing.*;
import javax.swing.event.ListSelectionEvent;
import javax.swing.event.ListSelectionListener;
import java.awt.Container;

public class Split extends JFrame implements ListSelectionListener{
   
    JFrame f;
    JSplitPane s1;
    JList list1;
    JPanel listP,ImgP;
    JLabel img;
    Container contentPane;
   
   
    String a[] = {"Mercury", "Venus", "Earth", "Mars", "Jupiter", "Saturn", "Uranus", "Neptune"};
   
    Split(){
        list1 = new JList(a);
        list1.addListSelectionListener(new ListSelectionListener(){
            @Override
            public void valueChanged(ListSelectionEvent e) {
                switch(list1.getSelectedIndex()){
                case 0:
                    img.setIcon(new ImageIcon("C:\\Users\\DELL\\Desktop\\Planets\\Mercury_profile_MDIS_MESSENGER.jpg"));
                    break;
                case 1:
                    img.setIcon(new ImageIcon("C:\\Users\\DELL\\Desktop\\Planets\\Venus_from_Mariner_10.jpg"));
                    break;
                case 2:
                    img.setIcon(new ImageIcon("C:\\Users\\DELL\\Desktop\\Planets\\download.jpg"));
                    break;
                case 3:
                    img.setIcon(new ImageIcon("C:\\Users\\DELL\\Desktop\\Planets\\download (1).jpg"));
                    break;
                case 4:
                    img.setIcon(new ImageIcon("C:\\Users\\DELL\\Desktop\\Planets\\Jupiter_and_its_shrunken_Great_Red_Spot.jpg"));
                    break;
                case 5:
                    img.setIcon(new ImageIcon("C:\\Users\\DELL\\Desktop\\Planets\\download (2).jpg"));
                    break;
                case 6:
                    img.setIcon(new ImageIcon("C:\\Users\\DELL\\Desktop\\Planets\\download (3).jpg"));
                    break;
                case 7:
                    img.setIcon(new ImageIcon("C:\\Users\\DELL\\Desktop\\Planets\\Neptune_-_Voyager_2_(29347980845)_flatten_crop.jpg"));
                    break;
                }
               
            }
       
        });
        listP = new JPanel();
        listP.add(list1);
       
        img = new JLabel();
        ImgP = new JPanel();
        ImgP.add(img);
       
        s1 = new JSplitPane(JSplitPane.HORIZONTAL_SPLIT,listP, ImgP);
        s1.setOneTouchExpandable(true);
        s1.setDividerLocation(150);
        contentPane = getContentPane();
        contentPane.add(s1);
       
        setSize(500,500);
        setVisible(true);
   
       
                }

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

    @Override
    public void valueChanged(ListSelectionEvent e) {
        throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates.
    }
   
}

Answer 1

使用 JList 时，所需的任何大小调整都可以在渲染器中完成。例如，选择时左侧列表中的图像是主视图大小的 10%。

这是渲染器：

class ScaledImageListCellRenderer extends DefaultListCellRenderer {

    @Override
    public Component getListCellRendererComponent(
            JList list, Object value, int index, boolean isSelected, boolean cellHasFocus) {
        Component c = super.getListCellRendererComponent(
                list, value, index, isSelected, cellHasFocus);

        JLabel l = (JLabel)c;
        BufferedImage bi = (BufferedImage)value;
        int w = bi.getWidth();
        int h = bi.getHeight();
        String s = w + "x" + h;
        l.setText(s);
        l.setIcon(new ImageIcon(bi.getScaledInstance(w/10, h/10, BufferedImage.SCALE_FAST)));

        return l;
    }
};

这是使用渲染器的独立源代码：

import java.awt.*;
import java.awt.image.*;
import java.util.Random;
import javax.swing.*;
import javax.swing.event.*;

public class ScaleBigImages {
    int sz = 50;
    int s = 10;
    Random random = new Random();
    JLabel imageLabel = new JLabel();

    ScaleBigImages() {
        init();
    }

    protected final void init() {
        JPanel gui = new JPanel(new BorderLayout(2,2));
        JList list = new JList();
        gui.add(new JScrollPane(list), BorderLayout.LINE_START);
        DefaultListModel dlm = new DefaultListModel();
        for (int ii=0; ii<19; ii++) {
            dlm.addElement(getBigImage());
        }
        list.setModel(dlm);
        list.setCellRenderer(new ScaledImageListCellRenderer());
        imageLabel.setIcon(new ImageIcon(new BufferedImage(
                s*sz,s*sz, BufferedImage.TYPE_INT_ARGB)));
        JPanel center = new JPanel(new GridBagLayout());
        center.add(imageLabel);
        gui.add(center);
        ListSelectionListener lsl = new ListSelectionListener() {
            @Override
            public void valueChanged(ListSelectionEvent e) {
                BufferedImage bi = (BufferedImage) list.getSelectedValue();
                imageLabel.setIcon(new ImageIcon(bi));
            }
        };
        list.addListSelectionListener(lsl);
        list.getSelectionModel().setSelectionMode(ListSelectionModel.SINGLE_SELECTION);

        JFrame f = new JFrame("Scale Big Images");
        f.setLocationByPlatform(true);
        f.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
        f.add(gui);
        f.pack();
        f.setMinimumSize(f.getSize());
        f.setVisible(true);
    }

    class ScaledImageListCellRenderer extends DefaultListCellRenderer {

        @Override
        public Component getListCellRendererComponent(
                JList list, Object value, int index, boolean isSelected, boolean cellHasFocus) {
            Component c = super.getListCellRendererComponent(
                    list, value, index, isSelected, cellHasFocus);

            JLabel l = (JLabel)c;
            BufferedImage bi = (BufferedImage)value;
            int w = bi.getWidth();
            int h = bi.getHeight();
            String s = w + "x" + h;
            l.setText(s);
            l.setIcon(new ImageIcon(bi.getScaledInstance(w/10, h/10, BufferedImage.SCALE_FAST)));

            return l;
        }
    };

    private BufferedImage getBigImage() {
        int w = s*sz;
        int h = s*sz;
        int r = random.nextInt(s/2);
        if (random.nextBoolean()) {
            w -= r*sz;
        } else {
            h -= r*sz;
        }

        return new BufferedImage(w,h,BufferedImage.TYPE_INT_RGB);
    }

    public static void main(String[] args) {
        Runnable r = new Runnable() {
            @Override
            public void run() {
                new ScaleBigImages();
            }
        };
        SwingUtilities.invokeLater(r);
    }
}

Answer 2

我可能建议使用 JScrollPane，这将允许您的 JLabel/image 占据比窗口当前可用的空间更多的空间，例如...

< /a>

import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.io.IOException;
import javax.imageio.ImageIO;
import javax.swing.ImageIcon;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JList;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JSplitPane;
import javax.swing.event.ListSelectionEvent;
import javax.swing.event.ListSelectionListener;

public final class Main {

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

    public Main() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                JFrame frame = new Split();
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class Split extends JFrame {

        public Split() {
            String a[] = {"Mercury", "Venus", "Earth", "Mars", "Jupiter", "Saturn", "Uranus", "Neptune"};
            JList list1 = new JList(a);
            final JLabel img = new JLabel();
            list1.addListSelectionListener(new ListSelectionListener() {
                @Override
                public void valueChanged(ListSelectionEvent e) {
                    if (e.getValueIsAdjusting()) {
                        return;
                    }
                    try {
                        switch (list1.getSelectedIndex()) {
                            case 0:
                                img.setIcon(new ImageIcon(ImageIO.read(getClass().getResource("/images/Cute1.png"))));
                                break;
                            case 1:
                                img.setIcon(new ImageIcon(ImageIO.read(getClass().getResource("/images/Cute2.png"))));
                                break;
                            case 2:
                                img.setIcon(new ImageIcon(ImageIO.read(getClass().getResource("/images/Cute3.png"))));
                                break;
                            case 3:
                                img.setIcon(new ImageIcon(ImageIO.read(getClass().getResource("/images/Cute4.png"))));
                                break;
                            case 4:
                                img.setIcon(new ImageIcon(ImageIO.read(getClass().getResource("/images/Cute5.png"))));
                                break;
                            case 5:
                                img.setIcon(new ImageIcon(ImageIO.read(getClass().getResource("/images/Cute6.png"))));
                                break;
                            case 6:
                                img.setIcon(new ImageIcon(ImageIO.read(getClass().getResource("/images/Cute7.png"))));
                                break;
                            case 7:
                                img.setIcon(new ImageIcon(ImageIO.read(getClass().getResource("/images/Cute8.png"))));
                                break;
                        }
                    } catch (IOException ex) {
                        JOptionPane.showMessageDialog(img, "Could not load image", "Error", JOptionPane.ERROR_MESSAGE);
                    }

                }

            });

            JPanel basePane = new JPanel(new BorderLayout()) {
                @Override
                public Dimension getPreferredSize() {
                    return new Dimension(400, 400);
                }
            };
            basePane.add(new JScrollPane(img));

            JSplitPane s1 = new JSplitPane(JSplitPane.HORIZONTAL_SPLIT, new JScrollPane(list1), basePane);
            s1.setOneTouchExpandable(true);
            s1.setDividerLocation(150);

            add(s1);
        }

    }
}

参见如何使用滚动窗格了解更多详细信息。

您还应该学习使用 ImageIO.read，从长远来看，它会为您节省很多问题和麻烦，请参阅 读取/加载图像

如果您仍然想调整图像大小，那么您还可以看看...

• <一个href="https://stackoverflow.com/questions/13166402/drawn-image-inside-panel-seems-to-have-wrong-xy-offset/13168202#13168202">面板内绘制的图像似乎有错误的x， y 偏移量
• 怎么做当应用程序窗口大小调整时，我也调整应用程序内的图像大小吗？
• 调整大小后图像质量非常低 - Java
• <一href="https://stackoverflow.com/questions/11959758/java-maintaining-aspect-ratio-of-jpanel-background-image/11959928#11959928">Java：保持 JPanel 背景图像的宽高比
• <一个href="https://stackoverflow.com/questions/14548808/scale-the-imageicon-automatically-to-label-size/14553003#14553003">将 ImageIcon 自动缩放到标签大小

作为几个示例