所以我有这个代码。我正在尝试实施点击以保存JMenuBar，然后点击加载。我无法序列化JPanel。
如何保存当前的情节视图？布局设置为AbsoluteLayout，因此GroupLayout问题不是问题。我已阅读Google搜索，我知道不建议这样做但我还能保存并加载它吗？
package tester;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Shape;
import java.awt.geom.Line2D;
import java.awt.image.BufferedImage;
import javax.swing.*;
import static tester.Plot.XMAX;
import static tester.Plot.XMIN;
import static tester.Plot.YMAX;
import static tester.Plot.YMIN;
import java.io.*;
/**
*
* @author Sana
*/
public class NewJFrame2 extends javax.swing.JFrame{
public class Plot extends JPanel implements java.io.Serializable {
public double xmin=0;
public double xmax=0;
public double ymin=0;
public double ymax=0;
public static final int XMIN = 45;
public static final int XMAX = 420;
public static final int YMIN = 300;
public static final int YMAX = 25;
Plottable2D plotFunction;
Shape myShape;
double[]xS;
double[]yS;
Graphics2D g2d;
public void setAxis(double[] a){
xmin=a[0];
xmax=a[1];
ymin=a[2];
ymax=a[3];
}
public void setFunction(Plottable2D plotFunction){
this.plotFunction = plotFunction;
xS = new double[100];
for (int i=0;i<99;i++)
xS=HW6ArrayMath.linspace(xmin, xmax, 99);
yS = plotFunction.evaluate(xS);
//repaint();
}
@Override
public void paintComponent(Graphics g){
Plot myPlot = (Plot) jPanel1;
g.setColor(Color.white);
g.fillRect(0, 0, getWidth(), getHeight());
myPlot.setAxis(new double[] {0,1,0,1});
myPlot.setFunction(new MyFunction());
Graphics2D g2d = (Graphics2D) g;
String xminString = "" + xmin;
String xmaxString = "" + xmax;
String yminString = "" + ymin;
String ymaxString = "" + ymax;
g2d.setColor(Color.BLUE);
g2d.drawLine(XMIN,YMIN,XMAX,YMIN);
g2d.drawString(xminString,XMIN, YMIN+10);
g2d.drawString(xmaxString,XMAX, YMIN+10);
g2d.drawLine(XMIN,YMIN, XMIN, YMAX);
g2d.drawString(yminString,XMIN-15,YMIN);
g2d.drawString(ymaxString,XMIN-15,YMAX);
for (int i=0;i<99-1;i++){
double a = (xS[i]*(XMAX-XMIN))+XMIN;
double b = (YMIN-(yS[i]*(YMIN-YMAX)));
double c = (xS[i+1]*(XMAX-XMIN))+XMIN;
double d = (YMIN-((yS[i+1]*(YMIN-YMAX))));
g2d.draw(new Line2D.Double(a, b, c,d));
}
}
}
/**
* Creates new form NewJFrame2
*/
public NewJFrame2() {
initComponents();
}
/**
* This method is called from within the constructor to initialize the form.
* WARNING: Do NOT modify this code. The content of this method is always
* regenerated by the Form Editor.
*/
@SuppressWarnings("unchecked")
// <editor-fold defaultstate="collapsed" desc="Generated Code">
private void initComponents() {
jPanel1 = new Plot();
jLabel2 = new javax.swing.JLabel();
jLabel3 = new javax.swing.JLabel();
jLabel1 = new javax.swing.JLabel();
jMenuBar2 = new javax.swing.JMenuBar();
jMenu3 = new javax.swing.JMenu();
jMenuItem2 = new javax.swing.JMenuItem();
jMenuItem3 = new javax.swing.JMenuItem();
setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
getContentPane().setLayout(new org.netbeans.lib.awtextra.AbsoluteLayout());
jPanel1.setBackground(new java.awt.Color(255, 240, 240));
jPanel1.setLayout(new org.netbeans.lib.awtextra.AbsoluteLayout());
jLabel2.setText("X Axis");
jPanel1.add(jLabel2, new org.netbeans.lib.awtextra.AbsoluteConstraints(250, 330, -1, -1));
jLabel3.setText("Y Axis");
jPanel1.add(jLabel3, new org.netbeans.lib.awtextra.AbsoluteConstraints(10, 151, -1, -1));
getContentPane().add(jPanel1, new org.netbeans.lib.awtextra.AbsoluteConstraints(57, 46, 520, 360));
jLabel1.setText("My Plot");
getContentPane().add(jLabel1, new org.netbeans.lib.awtextra.AbsoluteConstraints(300, 30, 40, -1));
jMenu3.setText("File");
jMenuItem2.setLabel("Save");
jMenuItem2.addMouseListener(new java.awt.event.MouseAdapter() {
public void mouseClicked(java.awt.event.MouseEvent evt) {
jMenuItem2MouseClicked(evt);
}
});
jMenuItem2.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
jMenuItem2ActionPerformed(evt);
}
});
jMenu3.add(jMenuItem2);
jMenuItem3.setLabel("Load");
jMenuItem3.addMouseListener(new java.awt.event.MouseAdapter() {
public void mouseClicked(java.awt.event.MouseEvent evt) {
jMenuItem3MouseClicked(evt);
}
});
jMenuItem3.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
jMenuItem3ActionPerformed(evt);
}
});
jMenu3.add(jMenuItem3);
jMenuBar2.add(jMenu3);
setJMenuBar(jMenuBar2);
pack();
}// </editor-fold>
private void jMenuItem2ActionPerformed(java.awt.event.ActionEvent evt) {
try {
ObjectOutputStream out = new ObjectOutputStream(new FileOutputStream("C:\\Users\\Sana\\Documents\\NetBeansProjects\\MyPlot.ser"));
out.writeObject(jLabel1);
out.writeObject(jLabel2);
out.writeObject(jLabel3);
out.close();
}
catch(Exception e) {
e.printStackTrace();
}
}
private void jMenuItem3ActionPerformed(java.awt.event.ActionEvent evt) {
// TODO add your handling code here:
}
private void jMenuItem2MouseClicked(java.awt.event.MouseEvent evt) {
}
private void jMenuItem3MouseClicked(java.awt.event.MouseEvent evt) {
try {
FileInputStream saveFile = new FileInputStream("MyPlot.ser");
ObjectInputStream restore = new ObjectInputStream(saveFile);
jPanel1 = (Plot) restore.readObject();
restore.close();
}catch (Exception exc){
exc.printStackTrace();
}
repaint();
}
/**
* @param args the command line arguments
*/
public static void main(String args[]) {
/* Set the Nimbus look and feel */
//<editor-fold defaultstate="collapsed" desc=" Look and feel setting code (optional) ">
/* If Nimbus (introduced in Java SE 6) is not available, stay with the default look and feel.
* For details see http://download.oracle.com/javase/tutorial/uiswing/lookandfeel/plaf.html
*/
try {
for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
if ("Nimbus".equals(info.getName())) {
javax.swing.UIManager.setLookAndFeel(info.getClassName());
break;
}
}
} catch (ClassNotFoundException ex) {
java.util.logging.Logger.getLogger(NewJFrame2.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (InstantiationException ex) {
java.util.logging.Logger.getLogger(NewJFrame2.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (IllegalAccessException ex) {
java.util.logging.Logger.getLogger(NewJFrame2.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (javax.swing.UnsupportedLookAndFeelException ex) {
java.util.logging.Logger.getLogger(NewJFrame2.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
}
//</editor-fold>
/* Create and display the form */
java.awt.EventQueue.invokeLater(new Runnable() {
public void run() {
new NewJFrame2().setVisible(true);
}
});
}
// Variables declaration - do not modify
private javax.swing.JLabel jLabel1;
private javax.swing.JLabel jLabel2;
private javax.swing.JLabel jLabel3;
private javax.swing.JMenu jMenu3;
private javax.swing.JMenuBar jMenuBar2;
private javax.swing.JMenuItem jMenuItem2;
private javax.swing.JMenuItem jMenuItem3;
private javax.swing.JPanel jPanel1;
// End of variables declaration
}
现在它给出了这个错误：
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at javax.swing.plaf.synth.SynthLookAndFeel.paintRegion(SynthLookAndFeel.java:371)
at javax.swing.plaf.synth.SynthLookAndFeel.update(SynthLookAndFeel.java:335)
at javax.swing.plaf.synth.SynthRootPaneUI.update(SynthRootPaneUI.java:119)
at javax.swing.JComponent.paintComponent(JComponent.java:780)
at javax.swing.JComponent.paint(JComponent.java:1056) etc.
答案 0 :(得分：7)
你这是错误的方式。您应该序列化plotview读取的数据，而不是plotview本身。
创建一个包含数据的对象：
public class PlotViewData implements Serializable {
public double xmin=0; //Should be private
public double xmax=0;
public double ymin=0;
public double ymax=0;
public static final int XMIN = 45;
public static final int XMAX = 420;
public static final int YMIN = 300;
public static final int YMAX = 25;
//Extra data with getters and setters goes here.
}
然后序列化并从该对象读取，组件应由应用程序重新创建。