image.getWidth(null) 报错-1,图片未加载入内存

本文介绍了使用Java加载图片的两种常见方法。第一种是利用ImageIO类读取文件流,可以获取图片的详细信息;第二种是通过Toolkit获取图片资源,但初次加载可能会遇到getWidth方法报错的问题。

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java 加载图片的两种方式:

1

String imgPath = "C://demo.jpg";
BufferedImage image = ImageIO.read(new FileInputStream(imgPath));
此方法加载图片到内存,得到图片详细信息


2

String imgPath = "C://demo.jpg";
Image imageToolkit.getDefaultToolkit().getImage(imgPath);
此方法初次引用,会出现image.getWidth(null)报错
抱歉,我在之前的代码中犯了一个错误。请尝试将`origin`变量的声明移动到`CustomWindow`类的顶部,如下所示: java import java.awt.*; import javax.swing.*; import java.awt.event.*; public class CustomWindow extends JFrame { private JPanel titleBarPanel; private JButton minimizeButton; private JButton maximizeButton; private JButton closeButton; private Point origin; public CustomWindow() { // 设置窗口大小和背景色 this.setSize(1100, 700); this.getContentPane().setBackground(new Color(204, 204, 204)); // 去除窗口边框默认样式 this.setUndecorated(true); // 禁用窗口缩放 this.setResizable(false); // 居中显示窗口 Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize(); int screenWidth = screenSize.width; int screenHeight = screenSize.height; int windowWidth = this.getWidth(); int windowHeight = this.getHeight(); int x = (screenWidth - windowWidth) / 2; int y = (screenHeight - windowHeight) / 2; this.setLocation(x, y); // 鼠标可以移动窗口 titleBarPanel = new JPanel(); titleBarPanel.setBackground(Color.WHITE); titleBarPanel.addMouseListener(new MouseAdapter() { @Override public void mousePressed(MouseEvent e) { origin = new Point(e.getX(), e.getY()); } @Override public void mouseReleased(MouseEvent e) { origin = null; } }); titleBarPanel.addMouseMotionListener(new MouseMotionAdapter() { @Override public void mouseDragged(MouseEvent e) { Point p = getLocation(); setLocation(p.x + e.getX() - origin.x, p.y + e.getY() - origin.y); } }); // 添加最小化、最大化和关闭按钮 minimizeButton = new JButton(new ImageIcon("minimize.png")); maximizeButton = new JButton(new ImageIcon("maximize.png")); closeButton = new JButton(new ImageIcon("close.png")); minimizeButton.setBorderPainted(false); maximizeButton.setBorderPainted(false); closeButton.setBorderPainted(false); minimizeButton.setOpaque(false); maximizeButton.setOpaque(false); closeButton.setOpaque(false); minimizeButton.setContentAreaFilled(false); maximizeButton.setContentAreaFilled(false); closeButton.setContentAreaFilled(false); // 添加按钮功能 minimizeButton.addActionListener(new ActionListener() { public void actionPerformed(ActionEvent e) { setExtendedState(JFrame.ICONIFIED); } }); maximizeButton.addActionListener(new ActionListener() { public void actionPerformed(ActionEvent e) { if (getExtendedState() != JFrame.MAXIMIZED_BOTH) { setExtendedState(JFrame.MAXIMIZED_BOTH); } else { setExtendedState(JFrame.NORMAL); } } }); closeButton.addActionListener(new ActionListener() { public void actionPerformed(ActionEvent e) { System.exit(0); } }); // 亮按钮 minimizeButton.addMouseListener(new MouseAdapter() { @Override public void mouseEntered(MouseEvent e) { minimizeButton.setIcon(new ImageIcon("minimize_highlight.png")); } @Override public void mouseExited(MouseEvent e) { minimizeButton.setIcon(new ImageIcon("minimize.png")); } }); maximizeButton.addMouseListener(new MouseAdapter() { @Override public void mouseEntered(MouseEvent e) { maximizeButton.setIcon(new ImageIcon("maximize_highlight.png")); } @Override public void mouseExited(MouseEvent e) { maximizeButton.setIcon(new ImageIcon("maximize.png")); } }); closeButton.addMouseListener(new MouseAdapter() { @Override public void mouseEntered(MouseEvent e) { closeButton.setIcon(new ImageIcon("close_highlight.png")); } @Override public void mouseExited(MouseEvent e) { closeButton.setIcon(new ImageIcon("close.png")); } }); // 将按钮添加到标题栏 titleBarPanel.add(minimizeButton); titleBarPanel.add(maximizeButton); titleBarPanel.add(closeButton); // 将标题栏添加到窗口 this.add(titleBarPanel, BorderLayout.NORTH); // 设置窗口关闭操作 this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); this.setVisible(true); } public static void main(String[] args) { SwingUtilities.invokeLater(new Runnable() { public void run() { new CustomWindow(); } }); } } ``` 这样,`origin`变量就能在窗口移动的方法中正确地使用了。希望这次能帮到你!如果还有其他问题,请随时提问。
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