Convert String to Array or Bytes

Hi Guys,

First project here and it has been a steep learning curve. I have some code in the TwoWaySerialComm class that will write to a Com port. In my other class EBIAlarm i have my GUI. The aim of my app is the send strings out of the Com port by pressing Jbutton1-3 I can open the Com port but I don't know how to send the string. Any pointers?


Convert String to Array of Bytes.

import gnu.io.CommPort; import gnu.io.CommPortIdentifier; import gnu.io.SerialPort; import java.io.IOException; import java.io.InputStream; import java.io.OutputStream; public class TwoWaySerialComm { public TwoWaySerialComm() { super(); } void connect ( String portName ) throws Exception { CommPortIdentifier portIdentifier = CommPortIdentifier.getPortIdentifier(portName); if ( portIdentifier.isCurrentlyOwned() ) { System.out.println("Error: Port is currently in use"); } else { CommPort commPort = portIdentifier.open(this.getClass().getName(),2000); if ( commPort instanceof SerialPort ) { SerialPort serialPort = (SerialPort) commPort; serialPort.setSerialPortParams(9600,SerialPort.DATABITS_8,SerialPort.STOPBITS_1,SerialPort.PARITY_NONE); InputStream in = serialPort.getInputStream(); OutputStream out = serialPort.getOutputStream(); (new Thread(new SerialReader(in))).start(); (new Thread(new SerialWriter(out))).start(); } else { System.out.println("Error: Only serial ports are handled by this."); } } } /** */ public static class SerialReader implements Runnable { InputStream in; public SerialReader ( InputStream in ) { this.in = in; } public void run () { byte[] buffer = new byte[1024]; int len = -1; try { while ( ( len = this.in.read(buffer)) > -1 ) { System.out.print(new String(buffer,0,len)); } } catch ( IOException e ) { e.printStackTrace(); } } } /** */ public class SerialWriter implements Runnable { OutputStream out; public SerialWriter ( OutputStream out ) { this.out = out; } public void run () { try { int c = 0; while ( ( c = System.in.read()) > -1 ) { this.out.write(c); } } catch ( IOException e ) { e.printStackTrace(); } } } }

import java.io.*; import javax.swing.*; import java.io.IOException; import java.io.OutputStream; import java.io.UnsupportedEncodingException; public class EBIAlarm extends javax.swing.JFrame { public TwoWaySerialComm twoWaySerCom; public TwoWaySerialComm.SerialWriter serialWriter; public EBIAlarm() { initComponents(); twoWaySerCom = new TwoWaySerialComm(); try { twoWaySerCom.connect("COM7"); } catch (Exception e) { e.printStackTrace(); } } private void initComponents() { jTextArea1 = new javax.swing.JTextArea(); jTextArea2 = new javax.swing.JTextArea(); jScrollPane1 = new javax.swing.JScrollPane(); jButton1 = new javax.swing.JButton(); jButton2 = new javax.swing.JButton(); jButton3 = new javax.swing.JButton(); jButton4 = new javax.swing.JButton(); jTextArea1.setColumns(60); jScrollPane1.setViewportView(jTextArea2); setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE); setTitle("Alarm Generator"); jTextArea1.setText("Enter custom string here"); jTextArea2.setText("Result"); jButton1.setText("Alarm 1"); jButton2.setText("Alarm 2"); jButton3.setText("Alarm 3"); jButton4.setText("Custom Alarm"); javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane()); getContentPane().setLayout(layout); layout.setHorizontalGroup( layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING) .addGroup(layout.createSequentialGroup() .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.CENTER) .addComponent(jButton1) .addComponent(jButton2) .addComponent(jButton3) .addComponent(jButton4) .addComponent(jTextArea1) .addComponent(jTextArea2) .addComponent(jScrollPane1) ))); layout.setVerticalGroup( layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING) .addGroup(layout.createSequentialGroup() .addComponent(jButton1) .addGap(20) .addComponent(jButton2) .addGap(20) .addComponent(jButton3) .addGap(20) .addComponent(jButton4) .addGap(20) .addComponent(jTextArea1) .addGap(20) .addComponent(jTextArea2) .addContainerGap(0,0)) .addComponent(jScrollPane1) ); pack(); jButton1.addActionListener(new java.awt.event.ActionListener() { public void actionPerformed(java.awt.event.ActionEvent evt){ jButton1ActionPerformed(evt); } private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) { } }); jButton2.addActionListener(new java.awt.event.ActionListener() { public void actionPerformed(java.awt.event.ActionEvent evt) { jButton2ActionPerformed(evt); } private void jButton2ActionPerformed(java.awt.event.ActionEvent evt) { jTextArea2.setText("Alarm 2 Activated, String: "+alarm2); } }); jButton3.addActionListener(new java.awt.event.ActionListener() { public void actionPerformed(java.awt.event.ActionEvent evt) { jButton3ActionPerformed(evt); } private void jButton3ActionPerformed(java.awt.event.ActionEvent evt) { jTextArea2.setText("Alarm 3 Activated, String: "+alarm3); } }); jButton4.addActionListener(new java.awt.event.ActionListener() { public void actionPerformed(java.awt.event.ActionEvent evt) { jButton4ActionPerformed(evt); } private void jButton4ActionPerformed(java.awt.event.ActionEvent evt) { jTextArea2.setText("Custom alarm, string sent: "+jTextArea1.getText ()); } }); } public static void main(String args[]) { java.awt.EventQueue.invokeLater(new Runnable() { public void run() { new EBIAlarm().setVisible(true); } }); } private void updateTextArea(final String text) { SwingUtilities.invokeLater(new Runnable() { public void run() { jTextArea2.append(text); } }); } private void redirectSystemStreams() { OutputStream out = new OutputStream() { @Override public void write(int b) throws IOException { updateTextArea(String.valueOf((char) b)); } @Override public void write(byte[] b, int off, int len) throws IOException { updateTextArea(new String(b, off, len)); } @Override public void write(byte[] b) throws IOException { write(b, 0, b.length); } }; System.setOut(new PrintStream(out, true)); System.setErr(new PrintStream(out, true)); } // Variables declaration private static javax.swing.JButton jButton1; private javax.swing.JButton jButton2; private javax.swing.JButton jButton3; private javax.swing.JButton jButton4; private javax.swing.JTextArea jTextArea1; public javax.swing.JTextArea jTextArea2; private javax.swing.JScrollPane jScrollPane1; String alarm1 = "*995R15,67,3#"; String alarm2 = "*993R03,67,6#"; String alarm3 = "*994R14,67,1#"; // End of variables declaration }

Hi Patrick ,
Can you explain where you are getting the problem

Satya

Hi Satya,

The problem lies in jButton1

I cant work out how to have jButton1 send the string called 'alarm1'

I tried

byte[] c = string.getBytes();
byte[] c = string.getBytes(Charset.forName("UTF-8"));

TwoWaySerialComm.SerialWriter.this.out.write(c);

And various other iterations with no joy

What exactly do you mean with "no joy"? Do you get a compiler error, or an error at runtime? Or does the program do something else than what you expect? If so, then what exactly did you expect and what does the program actually do - and how does it differ from what you expect?

If you get any error messages, then please copy and paste the exact error message - error messages contain important information that tell you what's wrong.

Well the error changes depending on what i write. Currently in my Jbutton1ActionPerformed I have written TwoWaySerialComm.SerialWriter.this.out.write(c); The errors produced are:

Multiple markers at this line
- c cannot be resolved to a variable
- No enclosing instance of the type TwoWaySerialComm.SerialWriter is accessible
in scope

Thanks.

The error happens when I press the jButton1 I tried to get the error to print to jTextFiels 2 but i shall ask about that in another question.

Patrick Evans wrote:- c cannot be resolved to a variable

This means that you are trying to use a variable named c, but that variable is not defined at the point you are trying to use it.

Patrick Evans wrote:- No enclosing instance of the type TwoWaySerialComm.SerialWriter is accessible

This probably is because your nested class SerialWriter is not static.

Note that your nested class SerialReader is static (line 55), but SerialWriter is not (line 85).

Thanks for your reply.

I remember changing that whilst trying to get it working. I have changed it back to: public static class SerialWriter implements Runnable but i get the same error.

With the local variable, Eclipse suggests adding byte[] c; but then the error remains for that also?

Alternatively, I tried private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) { jTextArea1.setText("Alarm 1 Activated, String: "+alarm1); byte[] c = alarm1.getBytes(); serialWriter.out.write(c, ALLBITS, ALLBITS); }

But then the error is Exception in thread "AWT-EventQueue-0" java.lang.Error: Unresolved compilation problem:
Unhandled exception type IOException

How were you able to compile that last bit of code? You should have gotten a compiler error. The write method might throw IOException, and since it's a checked exception you are required to handle it with a try-catch block.
try { serialWriter.out.write(c, ALLBITS, ALLBITS); } catch (IOException e) { // Do something to handle the exception e.printStackTrace(); }

You can only get that sort of code to compile on Eclipse. That is what we have an FAQ about.

I think i am making progress. The below suggestion threw an error about using a string where it should be an integer. I have since changed the code to:

private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) { jTextArea1.setText("Alarm 1 Activated, String: "+alarm1); try { alarm1.getBytes("utf-8"); serialWriter.out.write(alarm1.getBytes()); } catch (IOException e) { // Do something to handle the exception e.printStackTrace(); } }

I now get a null pointer. Can anyone shed some light on to why?

Thanks

Stable Library
=========================================
Native lib Version = RXTX-2.1-7
Java lib Version = RXTX-2.1-7
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at EBIAlarm$1.jButton1ActionPerformed(EBIAlarm.java:109)
at EBIAlarm$1.actionPerformed(EBIAlarm.java:102)
at javax.swing.AbstractButton.fireActionPerformed(Unknown Source)
at javax.swing.AbstractButton$Handler.actionPerformed(Unknown Source)
at javax.swing.DefaultButtonModel.fireActionPerformed(Unknown Source)
at javax.swing.DefaultButtonModel.setPressed(Unknown Source)
at javax.swing.plaf.basic.BasicButtonListener.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$3.run(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue$4.run(Unknown Source)
at java.awt.EventQueue$4.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$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)