我有一个名为Main的课程。 java的。在此输出由inputLine显示,inputLine是从com端口串行获取的字符串。我希望此字符串值用于同一默认包中的其他类。我如何在其他类中调用此字符串。如何创建此类的实例并在任何其他xyz.java类中调用字符串inputLine。一个例子非常有用。
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.OutputStream;
import gnu.io.CommPortIdentifier;
import gnu.io.SerialPort;
import gnu.io.SerialPortEvent;
import gnu.io.SerialPortEventListener;
import java.util.Enumeration;
public class Main implements SerialPortEventListener
{
SerialPort serialPort;
/** The port we're normally going to use. */
private static final String PORT_NAMES[] = {
"COM30", // Windows
};
/**
* A BufferedReader which will be fed by a InputStreamReader
* converting the bytes into characters
* making the displayed results codepage independent
*/
private BufferedReader input;
/** The output stream to the port */
private OutputStream output;
/** Milliseconds to block while waiting for port open */
private static final int TIME_OUT = 2000;
/** Default bits per second for COM port. */
private static final int DATA_RATE = 9600;
public void initialize() {
CommPortIdentifier portId = null;
Enumeration portEnum = CommPortIdentifier.getPortIdentifiers();
//First, Find an instance of serial port as set in PORT_NAMES.
while (portEnum.hasMoreElements()) {
CommPortIdentifier currPortId = (CommPortIdentifier) portEnum.nextElement();
for (String portName : PORT_NAMES) {
if (currPortId.getName().equals(portName)) {
portId = currPortId;
break;
}
}
}
if (portId == null) {
System.out.println("Could not find COM port.");
return;
}
try {
// open serial port, and use class name for the appName.
serialPort = (SerialPort) portId.open(this.getClass().getName(),
TIME_OUT);
// set port parameters
serialPort.setSerialPortParams(DATA_RATE,
SerialPort.DATABITS_8,
SerialPort.STOPBITS_1,
SerialPort.PARITY_NONE);
// open the streams
input = new BufferedReader(new InputStreamReader(serialPort.getInputStream()));
output = serialPort.getOutputStream();
// add event listeners
serialPort.addEventListener(this);
serialPort.notifyOnDataAvailable(true);
} catch (Exception e) {
System.err.println(e.toString());
}
}
/**
* This should be called when you stop using the port.
* This will prevent port locking on platforms like Linux.
*/
public synchronized void close() {
if (serialPort != null) {
serialPort.removeEventListener();
serialPort.close();
}
}
/**
* Handle an event on the serial port. Read the data and print it.
*/
public synchronized void serialEvent(SerialPortEvent oEvent) {
if (oEvent.getEventType() == SerialPortEvent.DATA_AVAILABLE) {
try {
String inputLine=input.readLine();
System.out.println(inputLine);
} catch (Exception e) {
System.err.println(e.toString());
}
}
// Ignore all the other eventTypes, but you should consider the other ones.
}
public static void main(String[] args) throws Exception {
Main main = new Main();
main.initialize();
Thread t=new Thread() {
public void run() {
//the following line will keep this app alive for 1000 seconds,
//waiting for events to occur and responding to them (printing incoming messages to console).
try {Thread.sleep(1000000);} catch (InterruptedException ie) {}
}
};
t.start();
System.out.println("Started");
}
}
答案 0 :(得分:0)
首先,如果要在其他地方访问变量,变量必须是实例变量或类变量,在方法中创建的变量只能存在于该方法内部,并且一旦方法返回就会死亡。
为了从另一个类访问变量,你必须使它可用,在Java中没有像C ++那样的朋友。你有3个选择。
答案 1 :(得分:0)
在您的情况下,您应该只创建一个类变量。
只需在课堂内声明public static String inputLine;
Change String inputLine = input.readLine();到inputLine=input.readLine();
,您可以使用Main.inputLine从同一个包中的其他类访问它。
答案 2 :(得分:0)
听起来像我的观察者模式...
创建一个接口,例如。 SerialListener,每个要通知的类都实现。该接口有一个带字符串参数的方法,每次新信息到达时,您的Main类都会调用该方法。 因为主类有方法来注册新的侦听器并将它们存储在列表中
列出toBeCalled = new ArrayList()
就像Swing等其他听众一样。