Question

package demo;

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

/*`enter code here`
 * ComboBoxDemo.java uses these additional files:`enter code here`
 *   images/Bird.gif
 *   images/Cat.gif
 *   images/Dog.gif
 *   images/Rabbit.gif
 *   images/Pig.gif
 */
public class Demo extends JPanel
implements ActionListener {
    JLabel picture;

    @SuppressWarnings({ "rawtypes", "unchecked" })
    public Demo() {
        super(new BorderLayout());

        String[] petStrings = { "Bird", "Cat", "Dog", "Rabbit", "Pig" };

        //Create the combo box, select the item at index 4.
        //Indices start at 0, so 4 specifies the pig.
        JComboBox petList = new JComboBox(petStrings);
        petList.setSelectedIndex(4);
        petList.addActionListener(this);

        //Set up the picture.
        picture = new JLabel();
        picture.setFont(picture.getFont().deriveFont(Font.ITALIC));
        picture.setHorizontalAlignment(JLabel.CENTER);
        updateLabel(petStrings[petList.getSelectedIndex()]);
        picture.setBorder(BorderFactory.createEmptyBorder(10,0,0,0));

        //The preferred size is hard-coded to be the width of the
        //widest image and the height of the tallest image + the border.
        //A real program would compute this.
        picture.setPreferredSize(new Dimension(177, 122+10));

        //Lay out the demo.
        add(petList, BorderLayout.PAGE_START);
        add(picture, BorderLayout.PAGE_END);
        setBorder(BorderFactory.createEmptyBorder(20,20,20,20));
    }

    /** Listens to the combo box. */
    public void actionPerformed(ActionEvent e) {
        JComboBox cb = (JComboBox)e.getSource();
        String petName = (String)cb.getSelectedItem();                                                          
        updateLabel(petName);
    }

    protected void updateLabel(String name) {
        ImageIcon icon = createImageIcon("images/" + name + ".png");
        picture.setIcon(icon);
        picture.setToolTipText("A drawing of a " + name.toLowerCase());
        if (icon != null) {
            picture.setText(null);
        } else {
            picture.setText("Image not found");
        }
    }

    /** Returns an ImageIcon, or null if the path was invalid. */
    protected static ImageIcon createImageIcon(String path) {
        java.net.URL imgURL = Demo.class.getResource(path);
        if (imgURL != null) {
            return new ImageIcon(imgURL);
        } else {
            System.err.println("Couldn't find file: " + path);
            return null;
        }
    }

    /**
     * Create the GUI and show it.  For thread safety,
     * this method should be invoked from the
     * event-dispatching thread.
     */
    private static void createAndShowGUI() {
        //Create and set up the window.
        JFrame frame = new JFrame("ComboBoxDemo");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);


        JComponent newContentPane = new Demo();
        newContentPane.setOpaque(true);
        frame.setContentPane(newContentPane);


        frame.pack();
        frame.setVisible(true);
    }

    public static void main(String[] args) {
        //Schedule a job for the event-dispatching thread:
        //creating and showing this application's GUI.
        javax.swing.SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                createAndShowGUI();
            }
        });
    }
}

这是我从oracle获得的代码，但我不知道从哪里选择图像需要，因为每次我创建一个带有图像的源文件夹时，它仍然不会提取它。或者，如果你能告诉我哪部分代码正在挑选图片？我需要为我的工作使用相同的代码。

Screenshot

Answer 1

在demo src └───demo │ Demo.java └───images Bird.png Cat.png Dog.png Rabbit.png Pig.png所在的同一文件夹中创建名为(intOption = 0)的文件夹。并将您的图像放在那里。根据您的代码，图像名称为“Bird.png”，“Cat.png”，“Dog.png”，“Rabbit.png”，“Pig.png”。

所以你的项目结构是这样的：

intOption

Answer 2

ImageIcon icon = createImageIcon("images/" + name + ".png");

此行提供images/name.png的图片路径，name的值可能属于{"Bird", "Cat", "Dog", "Rabbit", "Pig"}

picture.setIcon(icon);

以上一行是将icon设置为JLabel picture。

在项目的根目录中创建名为images的文件夹，并将所有.png图像放在images文件夹中。

Answer 3

请参阅：http://www.thinkplexx.com/learn/howto/java/system/java-resource-loading-explained-absolute-and-relative-names-difference-between-classloader-and-class-resource-loading

我终于找到了问题所在，但我无法理解为什么Oracle会让代码无法正常工作。

回到发布的原始代码 https://www.codetantra.com/java/jdk6.0/tutorial/uiswing/examples/components/ComboBoxDemoProject/src/components/ComboBoxDemo.java

您需要转到项目所在的文件夹。你会看见：箱子图片 SRC

images文件夹中可能包含所有预期的图像文件，但程序无法以某种方式访问它们。将gif文件复制到包含bin，images和src的文件夹中。

您现在将看到：箱子图片 SRC Bird.gif Cat.gif 等等。

现在返回并更改Oracle的代码：

// ImageIcon icon = createImageIcon（＆＃34; images /＆＃34; + name +＆＃34; .gif＆＃34;）; //这种方式不起作用。

到

    ImageIcon icon = createImageIcon(name + ".gif");

有人能告诉我从哪里采摘图像？

3 个答案: