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Message:

Help me with this implementing TableModule

Posted by sam_hou on November 23, 2001 at 5:02 PM

I encounter a servere problem when I run a swing project.

The structure is:
ongoing
|->todoswing(main)
|->todoitem(
|->todolist
|->todorepository

Here are the codes of this project, when I tried to add a row into the
table, the application downed, who can tell me why? I tried to debug this
file, I found I created the row successfully, but it maybe something wrong
with the "fireTableRowsInserted(0, 0);" in the method of insertRow() in the
class of todotablemodel.

//todorepository.java
package ongoing.toDoStorage;

import ongoing.toDoComponents.*;
import java.util.Iterator;

public interface ToDoRepository {

boolean add( ToDoItem newItem );

boolean remove( ToDoItem itemToRemove );

ToDoItem find( String nameToFind );

Iterator iterator();
}

//todoitem.java
package ongoing.toDoComponents;

import java.util.GregorianCalendar;
import java.util.Calendar;

public class ToDoItem {

protected String name = null;
protected String description = null;
protected GregorianCalendar creationDate = null;
protected GregorianCalendar dueDate = null;

// START constructors -----------------------------

public ToDoItem() {
this( "", "", null );

}

public ToDoItem( String newName, String newDescription, GregorianCalendar
newDueDate ) {
name = newName;
description = newDescription;
dueDate = newDueDate;

creationDate = new GregorianCalendar();
}

// END constructors -----------------------------

// START ACCESSOR methods -----------------------------

public void setName( String newName ) {
name = newName;
}

public String getName() {
return name;
}

public void setDescription( String newDescription ) {
description = newDescription;
}

public String getDescription() {
return description;
}

public Calendar getCreationDate() {
return creationDate;
}

public void setDueDate( GregorianCalendar newDueDate ) {
dueDate = newDueDate;
}

public Calendar getDueDate() {
return dueDate;
}

// END ACCESSOR methods ------------------------------

public String toDebugString() {

return "ToDoItem: " + name + ", " + description
+ ", Created on " + creationDate.getTime()
+ ", Due Date is " + dueDate.getTime();

}

public String toString() {

return name;
}
}

//todolist.java
package ongoing.toDoStorage;

import ongoing.toDoComponents.*;
import java.util.Iterator;
import java.util.Vector;

public class ToDoList implements ToDoRepository {

private Vector theList = null;

// nothing to do in constructor, so no need to include default constructor

public boolean add( ToDoItem newItem ) {
return getTheList().add( newItem );
}

public boolean remove( ToDoItem itemToRemove ) {
return getTheList().remove( itemToRemove );

}

public ToDoItem find( String nameToFind ) {
try {

// Iterate through "theList", compare name of each with "nameToFind",
// return first matching ToDoItem
for (Iterator i = getTheList().iterator(); i.hasNext(); ) {

ToDoItem nextItem = (ToDoItem) i.next();
if ( nextItem.getName().equals( nameToFind ) ) {
return nextItem;
}

}
} catch (Throwable e) {
handleException(e);
}

// No match found, or exception caught before finding match,
// so return null
return null;
}

public Iterator iterator() {
return getTheList().iterator();
}

private Vector getTheList() {

if ( theList == null ) {
try {
theList = new Vector();
} catch (Throwable e) {
handleException(e);
}
}

return theList;
}

private void handleException(Throwable e) {
System.out.println("Error in ToDoList: " + e.getMessage() );
e.printStackTrace();
}

}

//todoswing.java
package ongoing.toDoSwing;

import java.awt.BorderLayout;

import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import java.util.Calendar;
import java.util.Date;
import java.util.GregorianCalendar;
import java.util.Iterator;

import java.text.SimpleDateFormat;

import javax.swing.ListSelectionModel;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTable;

import javax.swing.table.AbstractTableModel;

import ongoing.toDoComponents.ToDoItem;

import ongoing.toDoStorage.ToDoRepository;
import ongoing.toDoStorage.ToDoList;

/**
* ToDoSwing uses JTable to produce a Swing front-end for the
* ToDoList class. ToDoItems can be added, deleted, and editted.
*/
public class ToDoSwing extends JFrame {
public static void main(String[] args) {
ToDoSwing todo = new ToDoSwing();
todo.show();
}

private JPanel tablePane;
private JPanel buttonPane;

private JTable toDoTable;
private ToDoTableModel toDoModel;

private JButton insertRow;
private JButton deleteRow;

/**
* Constructor creates the ToDoSwing window
*/
public ToDoSwing() {
super("To-do List");

tablePane = new JPanel();
buttonPane = new JPanel();

/*
* Create the data model for the JTable
*/
toDoModel = new ToDoTableModel();

/*
* Create the JTable to display to-do items
*/
toDoTable = new JTable(toDoModel);

/*
* Only allow one row to be selected at a time
*/
toDoTable.setSelectionMode(ListSelectionModel.SINGLE_SELECTION);

/*
* Put the JTable into a JScrollPane to support automatic
* scrolling.
*/
JScrollPane scrollPane = new JScrollPane(toDoTable);
tablePane.add(scrollPane);

/*
* Insert Row button allows an item to be added
* to the end of the list of to-do items
*/
insertRow = new JButton("Insert Row");
insertRow.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent event) {
toDoModel.insertRow();
}
});

/*
* Delete Selected Row allows the selected item
* to be removed from the list of to-do items
* If no row is selected when the button is pressed,
* an error message dialog pops up.
*/
deleteRow = new JButton("Delete Selected Row");
deleteRow.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent event) {
int selectedRow = toDoTable.getSelectedRow();
if (selectedRow == -1) {
JOptionPane.showMessageDialog(
ToDoSwing.this,
"Please select a row to delete",
"Deletion Error",
JOptionPane.ERROR_MESSAGE);
return;
}

toDoModel.deleteRow(selectedRow);
}
});

/*
* Add the insert and delete buttons to the
* button pane
*/
buttonPane.add(insertRow);
buttonPane.add(deleteRow);

/*
* Add the JTable to the middle of the frame and
* the buttons to the bottom of the frame (centered)
*/
getContentPane().add(tablePane, BorderLayout.CENTER);
getContentPane().add(buttonPane, BorderLayout.SOUTH);

/*
* When the user exits the application, simply shut down
* the program. If you want to supply an 'Are you sure?'
* dialog window when the user tries to close the application
* down, this is the place to do it.
*/
addWindowListener(new WindowAdapter() {
public void windowClosing(WindowEvent event) {
System.exit(0);
}
});

pack();
}
}

/**
* This class uses ToDoList to store a list of to-do items
*/
class ToDoTableModel extends AbstractTableModel {
/*
* data represents the items in the to-do list
*/
private ToDoList data = new ToDoList();

/**
* The fields associated with items in the
* to-do list. If new attributes are
* added to ToDoItem, this code will also
* need to be updated to support these new fields
*/
private String[] fields = new String[] {
"Name",
"Description",
"Creation Date",
"Due Date"
};

/*************** TableModel interface methods implemented below ********/

/**
* Return the number of fields.
*/
public int getColumnCount() {
//fill in the code for this method!
return fields.length;
}

/**
* This method returns the name of a column associated with
* a particular index. Note that the model gives you
* the index associated with the original position of
* a column in the table even if the user manually drags it
* to a new position.
*/
public String getColumnName(int column) {
//replace existing code and fill in the code for this method!
return fields[column];
}

/**
* Returns the number of rown in the list of To-Do items.
* Since ToDoList does not have a method like 'size()',
* it is necessary to iterate through all the records and keep
* count of how many are found in total. This is not ideal,
* but it will do for now.
*/
public int getRowCount() {
//replace existing code and fill in the code for this method!
int rown=0;
while(data.iterator().hasNext()){
rown++;
data.iterator().next();
}
return rown;
}

/**
* Return the object in the cell of the table
* specified by the row and column index that's
* passed in. First iterate through the
* items in the the to-do list until you
* reach the item at the specified row,
* then use getColumnByName to get the
* attribute for the specified column
* of the desired item. Determine if
* the object is a Calendar using the
* 'instanceof' operator and use the
* following code to format date
* information for display:
* Date date = ((Calendar) obj).getTime();
*
* return new SimpleDateFormat("MM/dd/yyyy").format(date);
*
*/
public Object getValueAt(int row, int column) {
//replace existing code and fill in the code for this method!
Object obj;
obj=getColumnByName(fields[column],getItem(row));
if(column<2)
return obj;
else
{
Date date=((GregorianCalendar) obj).getTime();
return new SimpleDateFormat("MM/dd/yyyy").format(date);
}
}

/**
* When an item is editted, this method puts the changed
* item back into the ToDoList. Find the appropriate
* item as in the getValueAt method, then use
* the setColumnByName method to store the value
* in the selected cell in ToDoList. See
* fireTableCellUpdated method to make sure
* the change is properly displayed by the table.
*/
public void setValueAt(Object newVal, int row, int column) {
//replace existing code and fill in the code for this method!
getValueAt(row,column);
String column_name=getColumnName(column);
setColumnByName(column_name,getItem(row),newVal);
fireTableCellUpdated(row, column);
}

/**
* The item create date should not be editable,
* all other cells should be editable.
*/
public boolean isCellEditable(int row, int column) {
//replace existing code and fill in the code for this method!
if(column!=2)
return true;
else
return false;
}

/*************** Utility methods below ********/

/**
* Append a new, blank, row to the list of
* items in ToDoList
*/
public void insertRow() {
//replace existing code and fill in the code for this method!
ToDoItem new_Item=new ToDoItem();
data.add(new_Item);
for(int i=0;i<4&&i!=2;i++)
setColumnByName(fields,new_Item,"");
fireTableRowsInserted(0, 0);
}

/**
* Find the item located in the specified row
* and remove it from ToDoList. See
* fireTableDataChanged method to refresh the
* display of the table.
*/
public void deleteRow(int row) {
//replace existing code and fill in the code for this method!
data.remove(getItem(row));
fireTableRowsDeleted(row, row);
}

/**
* For a given ToDoItem, return the object
* in the item associated with the specified
* column name.
*/
private Object getColumnByName(String columnName, ToDoItem item) {
if (columnName.equals("Name")) {
return item.getName();
}

if (columnName.equals("Description")) {
return item.getDescription();
}

if (columnName.equals("Creation Date")) {
return item.getCreationDate();
}

if (columnName.equals("Due Date")) {
return item.getDueDate();
}

return null;
}

/**
* Set the object for the specified column name in the
* DoToItem that is passed in to the new value
* specified by newVal. The date must be entered in
* MM/dd/yyyy (e.g. 12/04/2001) format.
*/
private void setColumnByName(String columnName, ToDoItem item,
Object newVal) {
if (columnName.equals("Name")) {
item.setName((String) newVal);
}

if (columnName.equals("Description")) {
item.setDescription((String) newVal);
}

if (columnName.equals("Due Date")) {
SimpleDateFormat dateFormat = new SimpleDateFormat("MM/dd/yyyy");
dateFormat.setLenient(true);
try {
Date date = dateFormat.parse((String) newVal);
Calendar calendar = Calendar.getInstance();
calendar.setTime(date);

item.setDueDate((GregorianCalendar) calendar);
}
catch (Exception e) {
/*
* For now just ignore an eror that occurs due
* to a bad date format being passed in
*/
e.printStackTrace();
}
}
}

/**
* Return the ToDoItem associated with a particular row
*/
private ToDoItem getItem(int row) {
int i=0;
Iterator iter = data.iterator();

ToDoItem item = null;
while (iter.hasNext()) {
item = (ToDoItem) iter.next();
if (i == row) {
break;
}

i++;
}

return item;
}
}