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Urgent!!! A NullPointerException !!! I can't solve it.

Chrono Wren
Greenhorn

Joined: Jul 01, 2002
Posts: 12
I have complied 3 files (SerialBean.java;SerialBuffer.java;ReaderSerial.java) as my package successfully, it is named serial. The package extends javax.comm.*; I wanna do some serial work.
Then I maked an application :SerialExample1
--------------------------------------code----------------------------------
----------------------------SerialExmaple1.java-----------------------------
import serial.*;
import java.io.*;
import javax.comm.*;
public class SerialExample1
{
public static void main(String args[])
{
SerialBean sB=new SerialBean(1);
sB.Initialize();
sB.WritePort("Hi,Chrono");
sB.ClosePort();
}
}
-----------------------------------------------------------------------------
It is good enough to deliver the String "Hi,Chrono".
Then I maked another windows application :SerialExample2
------------------------------------code-------------------------------------
-----------------------------Frame1.java-------------------------------------
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import com.borland.jbcl.layout.*;
import serial.*;
import java.io.*;
import javax.comm.*;
public class Frame1 extends JFrame
{
private JPanel contentPane;
private XYLayout xYLayout1 = new XYLayout();
private Button button1 = new Button();
private TextField textField1 = new TextField();
private SerialBean sB=new SerialBean(1);
//Construct the frame
public Frame1()
{
enableEvents(AWTEvent.WINDOW_EVENT_MASK);
try
{
jbInit();
}
catch(Exception e)
{
e.printStackTrace();
}
}
//Component initialization
private void jbInit() throws Exception
{
//setIconImage(Toolkit.getDefaultToolkit().createImage(Frame1.class.getResource("[Your Icon]")));
contentPane = (JPanel) this.getContentPane();
button1.setLabel("button1");
button1.addActionListener(new Frame1_button1_actionAdapter(this));
contentPane.setLayout(xYLayout1);
this.setSize(new Dimension(400, 300));
this.setTitle("Frame Title");
textField1.setText("textField1");
contentPane.add(button1, new XYConstraints(54, 52, -1, -1));
contentPane.add(textField1, new XYConstraints(195, 57, -1, -1));
}
//Overridden so we can exit when window is closed
protected void processWindowEvent(WindowEvent e)
{
super.processWindowEvent(e);
if (e.getID() == WindowEvent.WINDOW_CLOSING)
{
System.exit(0);
}
}
void button1_actionPerformed(ActionEvent e)
{
sB.Initialize();
sB.WritePort("Hi Chrono");
sB.ClosePort();
}
}
class Frame1_button1_actionAdapter implements java.awt.event.ActionListener
{
private Frame1 adaptee;
Frame1_button1_actionAdapter(Frame1 adaptee)
{
this.adaptee = adaptee;
}
public void actionPerformed(ActionEvent e)
{
adaptee.button1_actionPerformed(e);
}
}
------------------------------------------------------------------------------
---------------------------SerialExample2.java--------------------------------
import javax.swing.UIManager;
import java.awt.*;
public class SerialExample2
{
private boolean packFrame = false;
//Construct the application
public SerialExample2()
{
Frame1 frame = new Frame1();
//Validate frames that have preset sizes
//Pack frames that have useful preferred size info, e.g. from their layout
if (packFrame)
{
frame.pack();
}
else
{
frame.validate();
}
//Center the window
Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize();
Dimension frameSize = frame.getSize();
if (frameSize.height > screenSize.height)
{
frameSize.height = screenSize.height;
}
if (frameSize.width > screenSize.width)
{
frameSize.width = screenSize.width;
}
frame.setLocation((screenSize.width - frameSize.width) / 2, (screenSize.height - frameSize.height) / 2);
frame.setVisible(true);
}
//Main method
public static void main(String[] args)
{
try
{
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
}
catch(Exception e)
{
e.printStackTrace();
}
new SerialExample2();
}
}
-----------------------------------------------------------------------------------

It is a bad code!!! I compiled them seccessfully but It can't work .The java system gave
some wrong messages
-----------------------------------------------------------------------------------
Exception occurred during event dispatching:java.lang.NullPointerExceptionat serial.SerialBean.WritePort(SerialBean.java:115)at Frame1.button1_actionPerformed(Frame1.java:66)at Frame1_button1_actionAdapter.actionPerformed(Frame1.java:82)at java.awt.Button.processActionEvent(Button.java:329)at java.awt.Button.processEvent(Button.java:302)at java.awt.Component.dispatchEventImpl(Component.java:2593)at java.awt.Component.dispatchEvent(Component.java:2497)at java.awt.EventQueue.dispatchEvent(EventQueue.java:339)at java.awt.EventDispatchThread.pumpOneEventForHierarchy(EventDispatchThread.java:131)at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:98)at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93)at java.awt.EventDispatchThread.run(EventDispatchThread.java:85)-----------------------------------------------------------------------------------
I tried to debug it in Frame1.java:66 and SerialBean.java:115 but I can not find any error.
How to deal with it?
Here are the code about package serial
-----------------------------------code--------------------------------------------
----------------------------SerialBean.java----------------------------------------
package serial;
import java.io.*;
import java.util.*;
import javax.comm.*;
/**
*
* This bean provides some basic functions to implement full dulplex
* information exchange through the srial port.
*
*/
public class SerialBean
{
static String PortName;
CommPortIdentifier portId;
SerialPort serialPort;
static OutputStream out;
static InputStream in;
SerialBuffer SB;
ReadSerial RT;
/**
*
* Constructor
*
* @param PortID the ID of the serial to be used. 1 for COM1,
* 2 for COM2, etc.
*
*/
public SerialBean(int PortID)
{
PortName = "COM" + PortID;
}
/**
*
* This function initialize the serial port for communication. It startss a
* thread which consistently monitors the serial port. Any signal capturred
* from the serial port is stored into a buffer area.
*
*/
public int Initialize()
{
int InitSuccess = 1;
int InitFail = -1;
try
{
portId = CommPortIdentifier.getPortIdentifier(PortName);
try
{
serialPort = (SerialPort)
portId.open("Serial_Communication", 2000);
} catch (PortInUseException e)
{
return InitFail;
}
//Use InputStream in to read from the serial port, and OutputStream
//out to write to the serial port.
try
{
in = serialPort.getInputStream();
out = serialPort.getOutputStream();
} catch (IOException e)
{
return InitFail;
}
//Initialize the communication parameters to 9600, 8, 1, none.
try
{
serialPort.setSerialPortParams(9600,
SerialPort.DATABITS_8,
SerialPort.STOPBITS_1,
SerialPort.PARITY_NONE);
} catch (UnsupportedCommOperationException e)
{
return InitFail;
}
} catch (NoSuchPortException e)
{
return InitFail;
}
// when successfully open the serial port, create a new serial buffer,
// then create a thread that consistently accepts incoming signals from
// the serial port. Incoming signals are stored in the serial buffer.
SB = new SerialBuffer();
RT = new ReadSerial(SB, in);
RT.start();
// return success information
return InitSuccess;
}
/**
*
* This function returns a string with a certain length from the incomin
* messages.
*
* @param Length The length of the string to be returned.
*
*/
public String ReadPort(int Length)
{
String Msg;
Msg = SB.GetMsg(Length);
return Msg;
}
/**
*
* This function sends a message through the serial port.
*
* @param Msg The string to be sent.
*
*/
public void WritePort(String Msg)
{
int c;
try
{
for (int i = 0; i < Msg.length(); i++)
out.write(Msg.charAt(i));
} catch (IOException e) {}
}
/**
*
* This function closes the serial port in use.
*
*/
public void ClosePort()
{
RT.stop();
serialPort.close();
}
}
---------------------------------------------------------------------------------
----------------------------ReadSerial.java--------------------------------------
package serial;
import java.io.*;
/**
*
* This class reads message from the specific serial port and save
* the message to the serial buffer.
*
*/
public class ReadSerial extends Thread
{
private SerialBuffer ComBuffer;
private InputStream ComPort;
/**
*
* Constructor
*
* @param SB The buffer to save the incoming messages.
* @param Port The InputStream from the specific serial port.
*
*/
public ReadSerial(SerialBuffer SB, InputStream Port)
{
ComBuffer = SB;
ComPort = Port;
}
public void run()
{
int c;
try
{
while (true)
{
c = ComPort.read();
ComBuffer.PutChar(c);
}
} catch (IOException e) {}
}
}
------------------------------------------------------------------------------------
------------------------------SerialBuffer.java-------------------------------------
package serial;
public class SerialBuffer
{
private String Content = "";
private String CurrentMsg, TempContent;
private boolean available = false;
private int LengthNeeded = 1;
/**
*
* This function returns a string with a certain length from the incomin
* messages.
*
* @param Length The length of the string to be returned.
*
*/
public synchronized String GetMsg(int Length)
{
LengthNeeded = Length;
notifyAll();
if (LengthNeeded > Content.length())
{
available = false;
while (available == false)
{
try
{
wait();
} catch (InterruptedException e) { }
}
}
CurrentMsg = Content.substring(0, LengthNeeded);
TempContent = Content.substring(LengthNeeded);
Content = TempContent;
LengthNeeded = 1;
notifyAll();
return CurrentMsg;
}
/**
*
* This function stores a character captured from the serial port to the
* buffer area.
*
* @param t The char value of the character to be stored.
*
*/
public synchronized void PutChar(int c)
{
Character d = new Character((char) c);
Content = Content.concat(d.toString());
if (LengthNeeded < Content.length())
{
available = true;
}
notifyAll();
}
}
-----------------------------------------------------------------------------------
Help me !!!
Mapraputa Is
Leverager of our synergies
Sheriff

Joined: Aug 26, 2000
Posts: 10065
Please, do not post the same question in multiple forums. This post should be enough to get an answer


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subject: Urgent!!! A NullPointerException !!! I can't solve it.