Java BufferedImage 在 appletviewer 中工作，但在浏览器中不起作用

Question

我是 Java 新手，我有一个小程序项目要为学校做，现在已经全部完成了。当我通过 appletviewer 命令行运行它时它工作正常，但是当我通过浏览器预览它时，图像不显示。

简而言之，我的应用程序必须显示加拿大 map ，并为每个省份提供一个按钮。每当点击一个省份时，必须显示在 map 中选择了该省份，并显示省份名称和首都名称。我在 JPanel 中绘制 map 图像。就像我说的，当我通过 appletviewer 命令行预览小程序时，它工作正常，但当我通过浏览器加载它时，图像不会显示。

该小程序会播放背景音乐，效果很好，并且在按下鼠标时会发出咔嗒声，也能正常工作。我真的很困惑为什么图像没有显示。

任何帮助将不胜感激。提前致谢。

这是主类的代码: 封装applet加拿大；

import java.applet.AudioClip;
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Container;
import java.awt.Dimension;
import java.awt.Font;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.Image;
import java.awt.Insets;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.image.BufferedImage;
import java.io.File;
import javax.imageio.ImageIO;
import javax.swing.BorderFactory;
import javax.swing.JApplet;
import javax.swing.JButton;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.SwingConstants;
import javax.swing.border.Border;
import javax.swing.border.CompoundBorder;
import javax.swing.border.EmptyBorder;
import javax.swing.border.LineBorder;

public class AppletCanada extends JApplet implements Runnable, ActionListener {
private BufferedImage[] img_map;
private BufferedImage[] img_flags;
private JPanel panelMap;

public void init() {

            //Initializing the buffered image array to be used for the map
            File[] file_images = new File[11];
    img_map = new BufferedImage[11];
    String[] str_img = new String[11];

    try {

        for(int i = 0; i < img_map.length; i++) {
            str_img[i] = this.getParameter("image" + i);
            file_images[i] = new File(str_img[i]);
            img_map[i] = ImageIO.read(file_images[i]);
        }

    }
    catch(Exception e) {}

    //Initializing the buffered images to be used as flags
    img_flags = new BufferedImage[10];
    try {
        for(int i = 0; i < img_flags.length; i++) {
            str_img[i] = this.getParameter("flag" + i);
            file_images[i] = new File(str_img[i]);
            img_flags[i] = ImageIO.read(file_images[i]);
        }
    }catch(Exception e) {}

            //Initializing the container
    iWindow = getContentPane();

    //Initializing the JPanels
    panelMap = new PanelMap(img_map, img_flags, str_prov, str_caps);

//Initializing the panel's layouts
    iWindow.setLayout(new GridBagLayout());

    //Initializing the GridBagConstraints object
    c = new GridBagConstraints();

defineC(0, 3, GridBagConstraints.CENTER, 5, 10, 15, 10, 15);
    iWindow.add(panelMap, c);

}

public void actionPerformed(ActionEvent e) {

    //When the button is clicked, the click sound is played and all button font goes to blue
    if(e != null) {
        click.play();
        btn_prov_01.setForeground(light_blue);
        btn_prov_02.setForeground(light_blue);              
        btn_prov_03.setForeground(light_blue);              
        btn_prov_04.setForeground(light_blue);              
        btn_prov_05.setForeground(light_blue);
        btn_prov_06.setForeground(light_blue);              
        btn_prov_07.setForeground(light_blue);
        btn_prov_08.setForeground(light_blue);              
        btn_prov_09.setForeground(light_blue);              
        btn_prov_10.setForeground(light_blue);
    }

//The province integer is assigned a value depending on the button that is clicked
    if(e.getSource() == btn_prov_00) {
        province = 0;
        panelMap.repaint();
    }
    else if(e.getSource() == btn_prov_01) {
        province = 1;
        panelMap.repaint();
        clickThread = new AnimButton(btn_prov_01);
        clickThread.start();
    }
    else if(e.getSource() == btn_prov_02) {
        province = 2;
        panelMap.repaint();
        clickThread = new AnimButton(btn_prov_02);
        clickThread.start();
    }
    //Goes on with the rest of the buttons
}

这是 PanelMap 类的代码: 封装applet加拿大；

import java.awt.Color;
import java.awt.Dimension;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.Image;
import java.awt.image.BufferedImage;
import javax.swing.BorderFactory;
import javax.swing.JPanel;

public class PanelMap extends JPanel {

//Defining objects
private Image[] img_map;
private Image[] img_flags;
private String[] str_prov;
private String[] str_caps;
private Color light_blue = new Color(70, 158, 255);

//Class constructor
public PanelMap(BufferedImage[] image, BufferedImage[] img_flags, String[] str_prov, String[] str_caps) {
    this.setBorder(BorderFactory.createLineBorder(light_blue, 2));
    this.setPreferredSize(new Dimension(680, 580));
    this.setMaximumSize(new Dimension(680, 580));
    this.setMinimumSize(new Dimension(680, 580));
    this.setVisible(true);
    this.img_map = image;
    this.img_flags = img_flags;
    this.str_prov = str_prov;
    this.str_caps = str_caps;


}

//Method that paints the right map and province info depending on the province integer value from the AppletCanada class
public void paintComponent(Graphics g) {

    super.paintComponent(g);

    Font font_prov = new Font("arial", Font.BOLD, 16);
    Font font_cap  = new Font("arial", Font.PLAIN, 12);
    Color orange   = new Color(255, 128, 0);

    //If no province is selected
    if(AppletCanada.province == 0) {
        g.drawImage(img_map[0], 0, 0, this);
        g.setColor(orange);
        g.fillOval(470, 500, 10, 10);
        g.fillRect(428, 408, 154, 54);

        g.setColor(Color.white);
        g.fillRect(430, 410, 150, 40);

        g.setColor(orange);
        g.drawLine(475, 505, 505, 460);
        g.setFont(font_prov);

        g.setColor(light_blue);
        g.drawString("Capitale Nationale", 435, 425);
        g.setFont(font_cap);

        g.setColor(Color.black);
        g.drawString("Ottawa", 435, 440);
    }
    //If BC is selected
    else if(AppletCanada.province == 1) {
        g.drawImage(img_map[1], 0, 0, this);
        g.setColor(orange);
        g.fillOval(50, 430, 10, 10);
        g.fillRect(20, 350, 184, 50);

        g.setColor(Color.white);
        g.fillRect(22, 352, 180, 40);

        g.setColor(light_blue);
        g.setFont(font_prov);
        g.drawString(str_prov[0], 27, 367);

        g.setColor(Color.black);
        g.setFont(font_cap);
        g.drawString(str_caps[0], 27, 382);
        g.drawImage(img_flags[0], 170, 373, this);

        g.setColor(orange);
        g.drawLine(55, 435, 70, 400);
    }
//Goes one and does the same for the rest of the provinces

这是html代码:

<head> 
<title>Map du Canada</title> 
</head> 

<body> 

<applet code="appletCanada.AppletCanada.class" width=800 height=800> 
<param name="image0" value="image0.png">
<param name="image1" value="image1.png">
<param name="image2" value="image2.png">
<param name="image3" value="image3.png">
<param name="image4" value="image4.png">
<param name="image5" value="image5.png">
<param name="image6" value="image6.png">
<param name="image7" value="image7.png">
<param name="image8" value="image8.png">
<param name="image9" value="image9.png">
<param name="image10" value="image10.png">
<param name="flag0" value="flag_01.gif">
<param name="flag1" value="flag_02.gif">
<param name="flag2" value="flag_03.gif">
<param name="flag3" value="flag_04.gif">
<param name="flag4" value="flag_05.gif">
<param name="flag5" value="flag_06.gif">
<param name="flag6" value="flag_07.gif">
<param name="flag7" value="flag_08.gif">
<param name="flag8" value="flag_09.gif">
<param name="flag9" value="flag_10.gif">
<param name="audio" value="canadian_anthem.wav">
<param name="click" value="click.aif">
</applet> 

</body> 

</html> 

Answer 1

您正在从当前文件夹加载图像。如果您从包含图像的“bin”文件夹运行它，那么在使用 appletviewer 时，这将起作用，但不是在实际的 Applet 中，因为它不知道该“bin”文件夹的路径。

正确的方法是:

• 使用文件系统 API 访问硬盘驱动器上的特定位置，这需要正确的权限/权限，
• 将图像打包到包含您的小程序的 JAR 中(这里您只引用一个类，这看起来很奇怪)并将它们作为资源访问，
• 或者从网络服务器正确提供小程序(即使是本地测试)并远程查询服务器以获取图像。