我为“GPS蓝牙接收器”编写了一些代码它向我发送了持续数据并收到了它，但我无法在text-box中显示。
建议我如何在“while循环”未结束时改进继续数据的代码。
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.Enumeration;
import java.util.TooManyListenersException;
public class communication {
public static CommPortIdentifier portId = null;
public String com() throws UnsupportedCommOperationException, IOException,
TooManyListenersException
{
int c = 1;
String wantedPortName = "COM16";
Enumeration portIdentifiers = CommPortIdentifier.getPortIdentifiers();
while (portIdentifiers.hasMoreElements()) {
CommPortIdentifier pid = (CommPortIdentifier) portIdentifiers.nextElement();
if (pid.getPortType() == CommPortIdentifier.PORT_SERIAL
&& pid.getName().equals(wantedPortName)) {
portId = pid;
break;
}
}
if (portId == null) {
System.err.println("Could not find serial port " + wantedPortName);
System.exit(1);
} else {
System.out.println("system find gps reciever");
}
SerialPort port = null;
try {
port = (SerialPort) portId.open("RMC", 1);
System.out.println("all are ok");
} catch (PortInUseException e) {
System.err.println("Port already in use: " + e);
System.exit(1);
}
// int i=Integer.parseInt(new vps().baud_rate.getItemAt(new vps().baud_rate.getItemCount()));
port.setSerialPortParams(4800, SerialPort.DATABITS_8, SerialPort.STOPBITS_1,
SerialPort.PARITY_NONE);
BufferedReader is = null;
try {
is = new BufferedReader(new InputStreamReader(port.getInputStream()));
System.out.println("data is ok");
} catch (IOException e) {
System.err.println("Can't open input stream: write-only");
is = null;
}
while (new test().bp)// this is variable is ouside of class and define by public it work
{
String st = is.readLine();
// System.out.println(st);
// st = st.replace(st, "");
return st;
}
if (is != null)
is.close();
if (port != null)
port.close();
}
}
测试类代码......
import java.io.IOException;
import java.util.TooManyListenersException;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.comm.UnsupportedCommOperationException;
/*
* To change this template, choose Tools | Templates
* and open the template in the editor.
*/
/*
* test.java
*
* Created on Mar 11, 2013, 9:08:52 AM
*/
/**
*
* @author DJ ROCKS
*/
public class test extends javax.swing.JFrame {
public boolean bp=false;
/** Creates new form test */
public test() {
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() {
ok = new javax.swing.JButton();
a = new javax.swing.JTextField();
setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
ok.setText("ok");
ok.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
okActionPerformed(evt);
}
});
a.setText(" ");
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.LEADING)
.addGroup(layout.createSequentialGroup()
.addGap(62, 62, 62)
.addComponent(a, javax.swing.GroupLayout.PREFERRED_SIZE, 394, javax.swing.GroupLayout.PREFERRED_SIZE))
.addGroup(layout.createSequentialGroup()
.addGap(238, 238, 238)
.addComponent(ok)))
.addContainerGap(124, Short.MAX_VALUE))
);
layout.setVerticalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addContainerGap()
.addComponent(a, javax.swing.GroupLayout.PREFERRED_SIZE, 39, javax.swing.GroupLayout.PREFERRED_SIZE)
.addGap(67, 67, 67)
.addComponent(ok)
.addContainerGap(160, Short.MAX_VALUE))
);
pack();
}// </editor-fold>
private void okActionPerformed(java.awt.event.ActionEvent evt) {
// TODO add your handling code here:
bp=true;
if(evt.getSource()==ok)
{
try {
a.setText(new communication().com());
} catch (UnsupportedCommOperationException ex) {
Logger.getLogger(test.class.getName()).log(Level.SEVERE, null, ex);
} catch (IOException ex) {
Logger.getLogger(test.class.getName()).log(Level.SEVERE, null, ex);
} catch (TooManyListenersException ex) {
Logger.getLogger(test.class.getName()).log(Level.SEVERE, null, ex);
}
}
}
/**
* @param args the command line arguments
*/
public static void main(String args[]) {
java.awt.EventQueue.invokeLater(new Runnable() {
public void run() {
new test().setVisible(true);
}
});
}
// Variables declaration - do not modify
private javax.swing.JTextField a;
private javax.swing.JButton ok;
// End of variables declaration
}
当我运行此代码编译器时显示此类错误....
Exception in thread "AWT-EventQueue-0" java.lang.RuntimeException: Uncompilable source code - missing return statement
at communication.com(communication.java:14)
at test.okActionPerformed(test.java:86)
at test.access$000(test.java:22)
at test$1.actionPerformed(test.java:47)
at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2018)
at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2341)
at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:402)
at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:259)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:252)
at java.awt.Component.processMouseEvent(Component.java:6505)
at javax.swing.JComponent.processMouseEvent(JComponent.java:3321)
at java.awt.Component.processEvent(Component.java:6270)
at java.awt.Container.processEvent(Container.java:2229)
at java.awt.Component.dispatchEventImpl(Component.java:4861)
at java.awt.Container.dispatchEventImpl(Container.java:2287)
at java.awt.Component.dispatchEvent(Component.java:4687)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4832)
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4492)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4422)
at java.awt.Container.dispatchEventImpl(Container.java:2273)
at java.awt.Window.dispatchEventImpl(Window.java:2719)
at java.awt.Component.dispatchEvent(Component.java:4687)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:723)
at java.awt.EventQueue.access$200(EventQueue.java:103)
at java.awt.EventQueue$3.run(EventQueue.java:682)
at java.awt.EventQueue$3.run(EventQueue.java:680)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:87)
at java.awt.EventQueue$4.run(EventQueue.java:696)
at java.awt.EventQueue$4.run(EventQueue.java:694)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:693)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:244)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:163)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:151)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:147)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:139)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:97)
答案 0 :(得分：2)
这是你功能的结束：
while(new test().bp)//this is variable is ouside of class and define by public it work
{
st = is.readLine();
return st;
}
if (is != null) is.close();
if (port != null) port.close();
如果bp为false，则退出while循环而不返回。在这种情况下，你关闭is和port，然后......没有return语句。因此，如果发生这种情况，编译器不知道应该返回什么。
顺便说一句，那个循环逻辑毫无意义，因为它是一个美化的“如果” - 如果你回来，你就不可能再次循环。