Question

我试图从串口读取一个双。我可以在String中读取它，但是当我将String解析为Double时，结果没有意义，并且它与String不一样。

这是我的代码：

public void serialEvent(SerialPortEvent event){
        switch(event.getEventType()) {

            case SerialPortEvent.DATA_AVAILABLE:
                byte[] readBuffer = new byte[8];
                try {
                    while (inputStream.available()>0) {
                     int numBytes = inputStream.read(readBuffer);
                     String peso = new String (readBuffer, 0, numBytes, "UTF-8");
                     System.out.print(new String (readBuffer, 0, numBytes, "UTF-8"));
                    //double d = ByteBuffer.wrap(readBuffer).order(ByteOrder.LITTLE_ENDIAN ).getDouble();
                    //System.out.print(d);
                     m_dWeightBuffer = Double.parseDouble(peso);
                     System.out.print(m_dWeightBuffer);
                     }
                     //System.out.print(new String (readBuffer, 0, numBytes, "UTF-8"));
                    } catch (IOException ex) {}
                break;

        } 
    }

但现在，您知道如何将此字符串转换为Double？

System.out.print(new String (readBuffer, 0, numBytes, "UTF-8")); 输出：000.250好

m_dWeightBuffer = Double.parseDouble(peso); System.out.print(m_dWeightBuffer);输出：0.00.0250.0错误

System.out.println(new String (readBuffer, 0, numBytes, "UTF-8"));输出：

0 0 0 .250

Answer 1

前言

服务器似乎正在串行端口上写入4个块，可能是64位字：

0
0
0
0.250

你正在读取64位的最大缓冲区（readBuffer.length * 8位），所以最后一个可能是：

0011111111010000000000000000000000000000000000000000000000000000

试一试：

        String s = "0011111111010000000000000000000000000000000000000000000000000000"; 
        double d = Double.longBitsToDouble(Long.parseLong(s,2));
        System.out.println(d); //-> 0.25

至于现在没有错误。

答案

可能你想要在一个点上处理所有4个块，所以你可以尝试以下 - 当然，很大程度上取决于我忽略的协议的语义：

    public void serialEvent(SerialPortEvent event){
            switch(event.getEventType()) {

                case SerialPortEvent.DATA_AVAILABLE:
                    byte[] readBuffer = new byte[8];
                    String peso = "";
                    try {
                         while (inputStream.available()>0) {
                             int numBytes = inputStream.read(readBuffer);
                             peso += new String (readBuffer, 0, numBytes, "UTF-8");
                         }

                         m_dWeightBuffer = Double.parseDouble(peso);

                    } catch (IOException ex) {}
                    break;

            } 
    }

也就是说，在读取所有数据后创建double。

Answer 2

尝试这样做：

 public void serialEvent(SerialPortEvent event){
            switch(event.getEventType()) {

                case SerialPortEvent.DATA_AVAILABLE:
                    byte[] readBuffer = new byte[8];


                    try {
                         while (inputStream.available()>0) {
                             int numBytes = inputStream.read(readBuffer);
                             peso += new String (readBuffer, 0, numBytes, "UTF-8").replaceAll("\\s+","").replaceAll("\\n", "").replaceAll("\\r", "");

                         }
                    } catch (IOException ex) {}

                    break;

            } 
    }

Inicialize此SerialEvent方法的String peso OUTSIDE。

从串口读取双倍

2 个答案:

前言

答案