我编写了一个扩展JDialog的类，当我按保存时显示(保存是一个JMenuItem对象)。但是，当我按下“保存”时，我收到一个对话框，其中显示文件名为空，并且我没有机会输入任何内容。
我在这里做错了什么？任何帮助将不胜感激。
谢谢。
这是我的 JDialog 扩展类的代码:
package ui;
import java.awt.FlowLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JDialog;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JRadioButton;
import javax.swing.JTextField;
import javax.swing.border.EmptyBorder;
public class SaveImageView extends JDialog {
private final JPanel contentPanel = new JPanel ();
private JTextField txtFilename;
public int type; // 0 -> png, 1 -> jpg, 2 -> gif
public String filename;
public SaveImageView () {
setTitle("Save Image");
setBounds(100, 100, 450, 230);
getContentPane().setLayout(null);
contentPanel.setBounds(0, 0, 434, 229);
contentPanel.setBorder(new EmptyBorder(5, 5, 5, 5));
getContentPane().add(contentPanel);
contentPanel.setLayout(null);
{
JLabel lblFilename = new JLabel("Filename: ");
lblFilename.setBounds(10, 95, 58, 20);
contentPanel.add(lblFilename);
}
{
txtFilename = new JTextField();
txtFilename.setBounds(78, 95, 123, 20);
contentPanel.add(txtFilename);
txtFilename.setColumns(10);
}
{
JRadioButton rdbtnGif = new JRadioButton("GIF");
rdbtnGif.setBounds(123, 11, 43, 23);
contentPanel.add(rdbtnGif);
rdbtnGif.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent arg0) {
type = 2;
}
});
}
{
JRadioButton rdbtnJpg = new JRadioButton("JPG");
rdbtnJpg.setBounds(123, 37, 43, 23);
contentPanel.add(rdbtnJpg);
rdbtnJpg.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
type = 1;
}
});
}
{
JRadioButton rdbtnPng = new JRadioButton("PNG");
rdbtnPng.setBounds(123, 63, 45, 23);
contentPanel.add(rdbtnPng);
rdbtnPng.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
type = 0;
}
});
}
JLabel lblImageTypeTo = new JLabel("Image type to save: ");
lblImageTypeTo.setBounds(10, 11, 144, 23);
contentPanel.add(lblImageTypeTo);
JLabel lblNote = new JLabel("NOTE: Images will be saved in \"output\" folder.");
lblNote.setBounds(10, 132, 273, 22);
contentPanel.add(lblNote);
{
JPanel buttonPane = new JPanel();
buttonPane.setBounds(0, 160, 434, 33);
contentPanel.add(buttonPane);
buttonPane.setLayout(new FlowLayout(FlowLayout.RIGHT));
{
JButton okButton = new JButton("OK");
okButton.setActionCommand("OK");
buttonPane.add(okButton);
getRootPane().setDefaultButton(okButton);
okButton.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent arg0) {
filename = txtFilename.getText();
}
});
}
{
JButton cancelButton = new JButton("Cancel");
cancelButton.setActionCommand("Cancel");
buttonPane.add(cancelButton);
}
}
}
}
这是在我的主 GUI 类中，这是我将 ActionListener 添加到项目时的情况:
//////////////////////////////////////////////////////////
// Save - Menu Item //
//////////////////////////////////////////////////////////
JMenuItem saveItem = new JMenuItem("Save");
saveItem.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
SaveImageView siv = new SaveImageView();
siv.setVisible(true);
String typeStr = (siv.type == 0) ? "png" : ((siv.type == 1) ? "jpg" : "gif");
try {
ImageIO.write(img, typeStr, new File("output/" + siv.filename + "." + typeStr));
} catch (IOException e1) {
e1.printStackTrace();
}
}
});
menu.add(saveItem);
这是我收到的错误:
java.io.FileNotFoundException: output\null.png (The system cannot find the path specified)
at java.io.RandomAccessFile.open(Native Method)
at java.io.RandomAccessFile.<init>(Unknown Source)
at javax.imageio.stream.FileImageOutputStream.<init>(Unknown Source)
at com.sun.imageio.spi.FileImageOutputStreamSpi.createOutputStreamInstance(Unknown Source)
at javax.imageio.ImageIO.createImageOutputStream(Unknown Source)
at javax.imageio.ImageIO.write(Unknown Source)
at ui.PPMViewer$1.actionPerformed(PPMViewer.java:40)
at javax.swing.AbstractButton.fireActionPerformed(Unknown Source)
at javax.swing.AbstractButton$Handler.actionPerformed(Unknown Source)
at javax.swing.DefaultButtonModel.fireActionPerformed(Unknown Source)
at javax.swing.DefaultButtonModel.setPressed(Unknown Source)
at javax.swing.AbstractButton.doClick(Unknown Source)
at javax.swing.plaf.basic.BasicMenuItemUI.doClick(Unknown Source)
at javax.swing.plaf.basic.BasicMenuItemUI$Handler.mouseReleased(Unknown Source)
at java.awt.Component.processMouseEvent(Unknown Source)
at javax.swing.JComponent.processMouseEvent(Unknown Source)
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)
at java.awt.EventQueue.access$400(Unknown Source)
at java.awt.EventQueue$2.run(Unknown Source)
at java.awt.EventQueue$2.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.AccessControlContext$1.doIntersectionPrivilege(Unknown Source)
at java.security.AccessControlContext$1.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
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)
at java.awt.EventDispatchThread.run(Unknown Source)
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at javax.imageio.ImageIO.write(Unknown Source)
at ui.PPMViewer$1.actionPerformed(PPMViewer.java:40)
at javax.swing.AbstractButton.fireActionPerformed(Unknown Source)
at javax.swing.AbstractButton$Handler.actionPerformed(Unknown Source)
at javax.swing.DefaultButtonModel.fireActionPerformed(Unknown Source)
at javax.swing.DefaultButtonModel.setPressed(Unknown Source)
at javax.swing.AbstractButton.doClick(Unknown Source)
at javax.swing.plaf.basic.BasicMenuItemUI.doClick(Unknown Source)
at javax.swing.plaf.basic.BasicMenuItemUI$Handler.mouseReleased(Unknown Source)
at java.awt.Component.processMouseEvent(Unknown Source)
at javax.swing.JComponent.processMouseEvent(Unknown Source)
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)
at java.awt.EventQueue.access$400(Unknown Source)
at java.awt.EventQueue$2.run(Unknown Source)
at java.awt.EventQueue$2.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.AccessControlContext$1.doIntersectionPrivilege(Unknown Source)
at java.security.AccessControlContext$1.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
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)
at java.awt.EventDispatchThread.run(Unknown Source)
最佳答案
看起来像代码:filename = txtFilename.getText();永远不会被调用，因为您在保存之前没有单击“确定”按钮。
这是因为你的主 GUI 类在打开 JDialog 后不会暂停，而是继续运行。
停止此行为的一种方法是将窗口模式设置为 true ，或者，如果您想避免魔法值，Dialog.ModalityType.DEFAULT_MODAL .
因此在构造函数中添加行 setModal(true) .
按下“确定”和“取消”按钮后，您将需要退出 JDialog 。
您可以通过添加以下行来完成此操作:
dispose();
到您的 ActionListener 代码。
关于java - JDialog 获取输入，而不是获取错误，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/16252472/