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标题: 有点急的问题~请大大教我这是什么问题 [打印本页]

作者: Iceleafleave 时间: 2009-6-24 09:57 PM
标题: 有点急的问题~请大大教我这是什么问题
Exception in thread "main" java.lang.NullPointerException
at AssignmentGUI.<init>(AssignmentGUI.java:146)
at demoassignment.main(demoassignment.java:5)

作者: Super-Tomato 时间: 2009-6-24 10:18 PM

原帖由 Iceleafleave 于 2009-6-24 09:57 PM 发表
Exception in thread "main" java.lang.NullPointerException
at AssignmentGUI.(AssignmentGUI.java:146)
at demoassignment.main(demoassignment.java:5)

你没預防空值的可能性就做文字或数字处理就会出現這個错误

作者: Iceleafleave 时间: 2009-6-25 11:50 AM
标题: 回复 #2 Super-Tomato 的帖子
可以给个例子吗？我不太明白

作者: Super-Tomato 时间: 2009-6-25 12:30 PM

原帖由 Iceleafleave 于 2009-6-25 11:50 AM 发表
可以给个例子吗？我不太明白

你該把自己的 coding 貼出來吧

作者: Iceleafleave 时间: 2009-6-25 01:12 PM
标题: 回复 #4 Super-Tomato 的帖子
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class AssignmentGUI extends Frame implements ActionListener, ItemListener{
private JTabbedPane tab;
private Panel pentry=new Panel();
private Panel pdisplay=new Panel();
private Panel psearch=new Panel();
private Panel pbutton=new Panel();
private Panel pbutton2=new Panel();
private Panel pbutton3=new Panel();

private Panel ptype=new Panel();

private int counter=0;
private int counter2=0;

private Label lblblank,lblblank2,lblblank3;

private Label lbltitle,lblid,lblname,lblpriority,lbltype,lbldescribtion,lblcompanyname,lbltypecompany;

private Label lbltitled,lblidd,lblnamed,lblpriorityd,lbltyped,lbldescribtiond,lblcompanynamed,lbltypecompanyd;
private Label lblidr,lblnamer,lblpriorityr,lbltyper,lbldescribtionr,lblcompanynamer,lbltypecompanyr;

private Label lbltitle1,lblsearch,lblid1,lblname1,lblpriority1,lbltype1,lbldescribtion1,lblcompanyname1,lbltypecompany1;
private Label lblid2,lblname2,lblpriority2,lbltype2,lbldescribtion2,lblcompanyname2,lbltypecompany2;

private TextField txtid,txtname,txtdesc,txtcompany;
private TextField txtsearch;

JComboBox [] t=new JComboBox[4];
private Button btnreset,btnsave,btnnext,btnprevious,btndisplay,btnsearch;
String choice;
char [] tempt=new char[4];
private boolean flag,flag2=false,flag3=false;
productmethod [] pm =new productmethod[4];

public AssignmentGUI(){
super("Product Record");
tab=new JTabbedPane();
Color blue=new Color(50,150,255);
Color red=new Color(255,150,150);
Color yellow=new Color(255,200,100);
Color gray=new Color(230,230,230);

for(int i=0;i<4;i++){
t=new JComboBox();
t.addItem("Accounting");
t.addItem("Anti-Virus");
t.addItem("Reader");
t.addItem("Customise");
t.setSelectedItem("Accounting");
choice=t.getSelectedItem().toString();
tempt=choice.charAt(0);
t.addItemListener(this);
}

lbltitle=new Label("Product Requirement Record");
lblid=new Label(counter+1+". Product ID: ");
lblname=new Label("Product Name: ");
lblpriority=new Label("Priority: ");
lbltype=new Label("Type of Product: ");
lbldescribtion=new Label("Product Describtion: ");
lblcompanyname=new Label("Company Name: ");
lbltypecompany=new Label("Type Of Company: ");

lbltitled=new Label("Product Requirement Result");
lblidd=new Label(counter2+1+". Product ID: ");
lblnamed=new Label("Product Name: ");
lblpriorityd=new Label("Priority: ");
lbltyped=new Label("Type of Product: ");
lbldescribtiond=new Label("Product Describtion: ");
lblcompanynamed=new Label("Company Name: ");
lbltypecompanyd=new Label("Type Of Company: ");
lblidr=new Label();
lblnamer=new Label();
lblpriorityr=new Label();
lbltyper=new Label();
lbldescribtionr=new Label();
lblcompanynamer=new Label();
lbltypecompanyr=new Label();

lbltitle1=new Label("Product Record Search");
lblsearch=new Label("Search ID: ");
lblid1=new Label("Product ID: ");
lblname1=new Label("Product Name: ");
lblpriority1=new Label("Priority: ");
lbltype1=new Label("Type of Product: ");
lbldescribtion1=new Label("Product Describtion: ");
lblcompanyname1=new Label("Company Name: ");
lbltypecompany1=new Label("Type Of Company: ");
lblid2=new Label();
lblname2=new Label();
lblpriority2=new Label();
lbltype2=new Label();
lbldescribtion2=new Label();
lblcompanyname2=new Label();
lbltypecompany2=new Label();

txtid=new TextField("",100);
txtname=new TextField("",100);
txtdesc=new TextField("",100);
txtcompany=new TextField("",100);
txtsearch=new TextField("",100);

btnreset=new Button("Reset");
btnreset.setBackground(blue);
btnreset.setForeground(Color.white);
btnreset.addActionListener(this);

btnsave=new Button("Save");
btnsave.setBackground(blue);
btnsave.setForeground(Color.white);
btnsave.addActionListener(this);

btnnext=new Button("Next");
btnnext.setBackground(red);
btnnext.setForeground(Color.white);
btnnext.addActionListener(this);
btnnext.setEnabled(false);

btnprevious=new Button("Previous");
btnprevious.setBackground(red);
btnprevious.setForeground(Color.white);
btnprevious.addActionListener(this);
btnprevious.setEnabled(false);

btndisplay=new Button("Display");
btnprevious.setBackground(red);
btnprevious.setForeground(Color.white);
btnprevious.addActionListener(this);
btnprevious.setEnabled(false);

btnsearch=new Button("Search");
btnprevious.setBackground(yellow);
btnprevious.setForeground(Color.white);
btnprevious.addActionListener(this);
btnprevious.setEnabled(false);

for(int j=0;j<pm.length;j++)
pm[j]=new productmethod();

pentry.setLayout(new GridLayout(13,2,0,2));
lbltitle.setBackground(blue);
lbltitle.setForeground(Color.white);
lblblank.setBackground(blue);
pentry.add(lbltitle);
pentry.add(lblblank);
pentry.add(lblid);
pentry.add(txtid);
pentry.add(lblname);
pentry.add(txtname);
pentry.add(lblpriority);
//radio button priority
pentry.add(lbltype);

//add the JComboBox Component
ptype.setLayout(new GridLayout(0,4,0,2));
ptype.add(t[0]);
ptype.add(new Label());
ptype.add(new Label());
ptype.add(new Label());
pentry.add(ptype);

pentry.add(lbldescribtion);
pentry.add(txtdesc);
pentry.add(lblcompanyname);
pentry.add(txtcompany);

pentry.add(lbltypecompany);
//radio button of company type

//group the button
pbutton.setLayout(new GridLayout(0,3,2,2));
pbutton.add(new Label());
pbutton.add(btnreset);
pbutton.add(btnsave);
pentry.add(pbutton);

//panel display
lbltitled.setBackground(red);
lbltitled.setForeground(Color.white);
lblblank2.setBackground(red);

pdisplay.setLayout(new GridLayout(15,2,0,2));
pdisplay.add(lbltitled);
pdisplay.add(lblblank2);
pdisplay.add(lblidd);
pdisplay.add(lblidr);
pdisplay.add(lblnamed);
pdisplay.add(lblnamer);
pdisplay.add(lblpriorityd);
pdisplay.add(lblpriorityr);
//priority radio panel
pdisplay.add(lbltyped);
pdisplay.add(lbltyper);
pdisplay.add(lbldescribtiond);
pdisplay.add(lbldescribtionr);
pdisplay.add(lblcompanynamed);
pdisplay.add(lblcompanynamer);
pdisplay.add(lbltypecompanyd);
pdisplay.add(lbltypecompanyr);
//type radio button
pbutton2.setLayout(new GridLayout(0,3,2,2));
pbutton2.add(btndisplay);
pbutton2.add(btnprevious);
pbutton2.add(btnnext);
pdisplay.add(pbutton2);

lbltitle1.setBackground(yellow);
lbltitle1.setForeground(Color.white);
lblblank3.setBackground(yellow);

psearch.setLayout(new GridLayout(15,2,0,2));
psearch.add(lbltitle1);
psearch.add(lblblank3);
psearch.add(lblsearch);
pbutton3.setLayout(new GridLayout(0,2,2,2));
pbutton3.add(txtsearch);
pbutton3.add(btnsearch);
psearch.add(pbutton3);
psearch.add(lblid1);
psearch.add(lblid2);
psearch.add(lblname1);
psearch.add(lblname2);
psearch.add(lblpriority1);
psearch.add(lblpriority2);
psearch.add(lbltype1);
psearch.add(lbltype2);
psearch.add(lbldescribtion1);
psearch.add(lbldescribtion2);
psearch.add(lblcompanyname1);
psearch.add(lblcompanyname2);
psearch.add(lblcompanyname1);
psearch.add(lblcompanyname2);
psearch.add(lbltypecompany1);
psearch.add(lbltypecompany2);
tab.addTab("Record",null,pentry,"Entry Record");
tab.addTab("Display",null,pdisplay,"Display Record");
tab.addTab("Search",null,psearch,"Search Record");
tab.setBackgroundAt(0,blue);
tab.setBackgroundAt(1,red);
tab.setBackgroundAt(2,yellow);
tab.setBackground(gray);
add(tab);
setSize(800,600);
setVisible(true);
}
作者: Iceleafleave 时间: 2009-6-25 01:12 PM
public static void main(String []args) throws AWTException{
assignment assi=new assignment();
assi.addWindowListener(
new WindowAdapter(){
public void windowClosing(WindowEvent e){
System.exit(0);
}
});
}

public void itemStateChanged(ItemEvent event){
for(int i=0;i<4;i++)
if(event.getSource()==t)
{
choice=t.getSelectedItem().toString();
tempt=choice.charAt(0);
}
}

public void actionPerformed(ActionEvent ae){
if(ae.getSource()==btnreset)
reset();
if(ae.getSource()==btnsave)
{
if(flag==false)
{
validate();
}
if(flag==true)
{
save();
reset();
if(counter==0)
btnnext.setEnabled(false);
else if(flag3==true)
btnnext.setEnabled(true);
counter++;
if(counter==1)
{
btndisplay.setEnabled(true);
btnsearch.setEnabled(true);
}
lblid.setText(counter+1+". product ID: ");
if(counter>=5)
{
counter=0;
lblid.setText(counter+1+". Product ID: ");
}
flag=false;
}
}
if(ae.getSource()==btndisplay)
{
display();
flag3=true;
btndisplay.setEnabled(false);
if(counter==1)
btnnext.setEnabled(false);
if(counter!=1)
btnnext.setEnabled(true);
}

if(ae.getSource()==btnnext)
{
counter2++;
if(counter2==(counter-1))
{
btnnext.setEnabled(false);
}
else
btnnext.setEnabled(true);
if(counter2==4)
btnnext.setEnabled(false);
btnprevious.setEnabled(true);
lblidd.setText(counter2+1+". Product ID: ");
display();
}
if(ae.getSource()==btnprevious)
{
counter2--;
if(counter2==0)
btnprevious.setEnabled(true);
btnnext.setEnabled(true);
lblidd.setText(counter2+1+". Product ID: ");
display();
}
if(ae.getSource()==btnsearch)
{
validate2();
search();
}
}

public void reset(){
txtid.setText("");
txtname.setText("");
//priority
for(int i=0;i<4;i++)
{
t.setSelectedItem("Accounting");
choice=t.getSelectedItem().toString();
tempt=choice.charAt(0);
}

txtdesc.setText("");
txtcompany.setText("");
//tyofcp
}

public void save(){
String id,name,type,describ,cn;
char[] pgr=new char[5];
id=txtid.getText();
pm[counter].setproductid(id);
name=txtname.getText();
pm[counter].setproductname(name);
//priority
for(int i=0;i<4;i++)
{
pgr=tempt;
}
pm[counter].setaccounting(pgr[0]);
pm[counter].setantivirus(pgr[1]);
pm[counter].setcomecial(pgr[2]);
pm[counter].setreader(pgr[3]);
pm[counter].setother(pgr[4]);
describ=txtdesc.getText();
pm[counter].setproductdescribtion(describ);
cn=txtcompany.getText();
pm[counter].setcompanyname(cn);
//tpofcp
}

public void display(){
char temp2;
String temp3;
lblidr.setText(pm[counter2].getproductid());
lblnamer.setText(pm[counter2].getproductname());
//proirity
temp2=pm[counter2].getaccounting();
temp3=Character.toString(temp2);

temp2=pm[counter2].getantivirus();
temp3=Character.toString(temp2);
lbltyper.setText(temp3);
temp2=pm[counter2].getcomecial();
temp3=Character.toString(temp2);
lbltyper.setText(temp3);
temp2=pm[counter2].getreader();
temp3=Character.toString(temp2);
lbltyper.setText(temp3);
temp2=pm[counter2].getother();
temp3=Character.toString(temp2);

lbltyper.setText(temp3);

lbldescribtionr.setText(pm[counter2].getproductdescribtion());
lbldescribtionr.setText(pm[counter2].getcompanyname());
//tyofcp
}

public void search(){
String str,temp6;
char temp7;
flag2=true;
String [] idarray=new String [counter];
str=txtsearch.getText();
for(int k=0;k<counter;k++)
{
idarray[k]=pm[k].getproductid();
if(idarray[k].equals(str))
{
flag2=true;
lblid2.setText(pm[k].getproductid());
lblname2.setText(pm[k].getproductname());
temp7=pm[k].getaccounting();
temp6=Character.toString(temp7);
lbltype2.setText(temp6);

temp7=pm[k].getantivirus();
temp6=Character.toString(temp7);
lbltype2.setText(temp6);

temp7=pm[k].getcomecial();
temp6=Character.toString(temp7);
lbltype2.setText(temp6);

temp7=pm[k].getreader();
temp6=Character.toString(temp7);
lbltype2.setText(temp6);

temp7=pm[k].getother();
temp6=Character.toString(temp7);
lbltype2.setText(temp6);
break;

}
else if (!(idarray[k].equals(str)))
flag2=false;
}
if(flag2==false)
JOptionPane.showMessageDialog(this,"Record not found.");
}

public void validate() throws ArithmeticException{
flag=false;
if(txtid.getText().equals("")||txtname.getText().equals("")||txtdesc.getText().equals("")||txtcompany.getText().equals(""))
{
JOptionPane.showMessageDialog(this,"Please fill in all fields.");
}
else if(txtid.getText().matches("\\d{3}-\\d{1}"))
{
JOptionPane.showMessageDialog(this,"Invalide ID format.(eg.000-1)");
txtid.requestFocus();
}
else
{
flag=true;
}
}

public void validate2(){
if(txtsearch.getText().equals(""))
{
JOptionPane.showMessageDialog(this,"Please enter search ID.");
txtsearch.requestFocus();
}
else if(!txtsearch.getText().matches("\\d{3}-\\d{1}"))
{
JOptionPane.showMessageDialog(this,"Invalid ID format. (eg.000-1");
txtsearch.requestFocus();
}
}

}
作者: Super-Tomato 时间: 2009-6-25 01:36 PM
從你的編輯器中 AssignmentGUI 第 146 行是哪一行??
是 new productmethod 這行嗎??
作者: Iceleafleave 时间: 2009-6-25 01:46 PM
标题: 回复 #7 Super-Tomato 的帖子
lblblank.setBackground(blue);
是这个~
作者: Super-Tomato 时间: 2009-6-25 03:53 PM

原帖由 Iceleafleave 于 2009-6-25 01:46 PM 发表
lblblank.setBackground(blue);
是这个~

如果是這個 lblblank 的話就代表你沒有 new Label 指定對象
作者: Iceleafleave 时间: 2009-6-25 04:32 PM
标题: 回复 #9 Super-Tomato 的帖子
o~谢谢Super-Tomato

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