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我调用了这个程序Main.java，它从手机获取串行输入。问题是数字显示正确，但函数BGMusicmaindc()是在if条件下给出的（IE if inputLineis 1 play BGMusicmaindc()）。但它正在为所有按下的键播放音乐。如果找到，该else语句也给出错误说不。

注意：代码在public synchronized void serialEvent(SerialPortEvent oEvent).

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.io.File;
import java.io.FileInputStream;
import java.lang.String;
import java.util.Enumeration;
import javax.swing.JOptionPane;
import sun.audio.AudioData;
import sun.audio.AudioDataStream;
import sun.audio.AudioPlayer;
import sun.audio.AudioStream;


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 code page independent
    */
    public BufferedReader input;
    /** The output stream to the port */
    public 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 static String inputLine;
    public synchronized void serialEvent(SerialPortEvent oEvent) {
        if (oEvent.getEventType() == SerialPortEvent.DATA_AVAILABLE) {
            try {
                inputLine=input.readLine();
                                System.out.println(inputLine);

                                if (Main.inputLine.equals("1"));
                        {
                           BGMusicmaindc();
                        }
else
    System.out.println("");
            }
                        catch (Exception e) {
            //  System.err.println(e.toString());

            }
        }
        // Ignore all the other eventTypes, but you should consider the other ones.
    }

        public void BGMusicmaindc() { //Plays the background music
            //make a new AudioPlayer.
              AudioPlayer mynewBackgroundPlayer = AudioPlayer.player;

              AudioDataStream myLooop = null;
            //use a try block in case the file doesn't exist.
              try {
              AudioStream mynewBackgroundMusic = new AudioStream(new FileInputStream(new File(getClass().getResource(
                      "welcome.wav").toURI())));
              AudioData mynewData = mynewBackgroundMusic.getData();
              myLooop = new AudioDataStream(mynewData);
              }
              catch(Exception error) {JOptionPane.showMessageDialog(null, "Invalid file!");}

              // play background music.
              mynewBackgroundPlayer.start(myLooop);
        }

    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");
    }
}
4

1 回答 1

5

if这是我在语句不起作用时看到的常见错误。删除;此条件语句中的，它应该按预期工作：

if (Main.inputLine.equals("1"));  // <---- remove that ;
{
    BGMusicmaindc();
}

注意：您也可以使用简单的if陈述（我个人的喜好）：

if (Main.inputLine.equals("1")) BGMusicmaindc();
于 2013-03-30T15:20:04.473 回答