JFileChooser
无法工作我在网上收到了错误:
btnNewButton.setIcon(new ImageIcon(ImageIO.read(file)));
请帮帮我,我是初学者。它给了我这个错误:
线程中的异常" AWT-EventQueue-0" java.lang.IllegalArgumentException:input == null! 在javax.imageio.ImageIO.read(未知来源) 在RecordManagementSystem.addRecord $ 1.actionPerformed(addRecord.java:185) 在javax.swing.AbstractButton.fireActionPerformed(未知来源) at javax.swing.AbstractButton $ Handler.actionPerformed(Unknown Source) 在javax.swing.DefaultButtonModel.fireActionPerformed(未知来源) 在javax.swing.DefaultButtonModel.setPressed(未知来源) 在javax.swing.plaf.basic.BasicButtonListener.mouseReleased(未知来源) at java.awt.Component.processMouseEvent(Unknown Source) 在javax.swing.JComponent.processMouseEvent(未知来源) at java.awt.Component.processEvent(Unknown Source) at java.awt.Container.processEvent(Unknown Source) at java.awt.Component.dispatchEventImpl(Unknown Source) at java.awt.Container.dispatchEventImpl(Unknown Source) at java.awt.Component.dispatchEvent(Unknown Source) at java.awt.LightweightDispatcher.retargetMouseEvent(Unknown Source) at java.awt.LightweightDispatcher.processMouseEvent(Unknown Source) at java.awt.LightweightDispatcher.dispatchEvent(Unknown Source) at java.awt.Container.dispatchEventImpl(Unknown Source) at java.awt.Window.dispatchEventImpl(Unknown Source) at java.awt.Component.dispatchEvent(Unknown Source) at java.awt.EventQueue.dispatchEventImpl(Unknown Source) 在java.awt.EventQueue.access $ 000(未知来源) 在java.awt.EventQueue $ 1.run(未知来源) 在java.awt.EventQueue $ 1.run(未知来源) at java.security.AccessController.doPrivileged(Native Method) at java.security.AccessControlContext $ 1.doIntersectionPrivilege(Unknown Source) at java.security.AccessControlContext $ 1.doIntersectionPrivilege(Unknown Source) 在java.awt.EventQueue $ 2.run(未知来源) 在java.awt.EventQueue $ 2.run(未知来源) at java.security.AccessController.doPrivileged(Native Method) at java.security.AccessControlContext $ 1.doIntersectionPrivilege(Unknown Source) at java.awt.EventQueue.dispatchEvent(Unknown Source) at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source) at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source) at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source) at java.awt.EventDispatchThread.pumpEvents(Unknown Source) at java.awt.EventDispatchThread.pumpEvents(Unknown Source) 在java.awt.EventDispatchThread.run(未知来源)
代码:
btnNewButton.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent ae) {
JFileChooser fc = new JFileChooser();
File file = fc.getSelectedFile();
int result = fc.showOpenDialog(null);
if (result == JFileChooser.APPROVE_OPTION) {
try {
btnNewButton.setIcon(new ImageIcon(ImageIO.read(file)));
} catch (IOException e) {
JOptionPane.showMessageDialog(null, e);
}
}
}
});
答案 0 :(得分:3)
您在选择之前从JFileChooser 获取该文件,因此fc.getSelectedFile()
将返回null
。
解决方案:在显示JFileChooser后,在if块中获取文件。
if (result == JFileChooser.APPROVE_OPTION) {
try {
File file = fc.getSelectedFile(); // **** line added ****
btnNewButton.setIcon(new ImageIcon(ImageIO.read(file)));
} catch (IOException e) {
JOptionPane.showMessageDialog(null, e);
}
}
另外,我喜欢避免过度压缩我的代码,以便在发生任何错误时轻松查找错误。所以我会这样做:
if (result == JFileChooser.APPROVE_OPTION) {
try {
File file = fc.getSelectedFile();
Image image = ImageIO.read(file);
Icon icon = new ImageIcon(image);
btnNewButton.setIcon(icon);
} catch (IOException e) {
// log error
}
}