我正在开发一个包含libnodave库的应用程序（与Siemens PLC连接）。我想简单地阅读一些数据并定期放入Android屏幕。应用程序正在模拟器上正常工作，但在真实设备上我得到 NullPointerException 。我认为我的问题来自Java语言的使用，但我不确定。我正在添加以下代码：
任何人都可以解释为什么会发生这种情况吗？
这是错误消息：
09-05 13:28:01.359: E/HAHAHA(16267): java.lang.NullPointerException
09-05 13:28:01.359: E/HAHAHA(16267): at nodave.DataIsoTCP.ReadMyData(DataIsoTCP.java:83)
09-05 13:28:01.359: E/HAHAHA(16267): at com.example.haus.EnglishScreen$2$1$1.run(EnglishScreen.java:95)
09-05 13:28:01.359: E/HAHAHA(16267): at android.os.Handler.handleCallback(Handler.java:587)
09-05 13:28:01.359: E/HAHAHA(16267): at android.os.Handler.dispatchMessage(Handler.java:92)
09-05 13:28:01.359: E/HAHAHA(16267): at android.os.Looper.loop(Looper.java:130)
09-05 13:28:01.359: E/HAHAHA(16267): at android.app.ActivityThread.main(ActivityThread.java:3687)
09-05 13:28:01.359: E/HAHAHA(16267): at java.lang.reflect.Method.invokeNative(Native Method)
09-05 13:28:01.359: E/HAHAHA(16267): at java.lang.reflect.Method.invoke(Method.java:507)
09-05 13:28:01.359: E/HAHAHA(16267): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:867)
09-05 13:28:01.359: E/HAHAHA(16267): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:625)
09-05 13:28:01.359: E/HAHAHA(16267): at dalvik.system.NativeStart.main(Native Method)
这是EnglishScreen.java
import nodave.DataIsoTCP;
import android.app.Activity;
import android.content.Intent;
import android.opengl.Visibility;
import android.os.Bundle;
import android.os.Handler;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
public class EnglishScreen extends Activity {
Button read;
Button back;
Button next;
TextView user;
TextView bowlValue;
TextView scrollValue;
TextView productValue;
TextView polymerValue;
TextView flushValue;
TextView automaticValue;
//Intent i=new Intent();
String logiName="admin";
Handler myHandler = new Handler();
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.english);
user=(TextView)findViewById(R.id.user);
//textviews
bowlValue=(TextView)findViewById(R.id.bowlValue);
scrollValue=(TextView)findViewById(R.id.scrollValue);
productValue=(TextView)findViewById(R.id.productValue);
polymerValue=(TextView)findViewById(R.id.polymerValue);
flushValue=(TextView)findViewById(R.id.flushValue);
automaticValue=(TextView)findViewById(R.id.automaticValue);
read=(Button)findViewById(R.id.read);
back=(Button)findViewById(R.id.back);
next=(Button)findViewById(R.id.Next);
next.setVisibility(View.INVISIBLE);
try{
Intent i = getIntent();
String login=i.getStringExtra("login");
//i.putExtra("login", login);
user.setText(login);
if(logiName.equals(login)){
next.setVisibility(View.VISIBLE);
}
}
catch(Exception e){}
try{
DataIsoTCP.ConnectIsoTcp("192.168.1.10");}
catch(Exception e){}
next.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
Intent setIntent = new Intent(getApplicationContext(),SetScreen.class);
startActivity(setIntent);
}
});
read.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
new Thread(new Runnable() {
@Override
public void run() {
// TODO Auto-generated method stub
while (true) {
try {
myHandler.post(new Runnable() {
@Override
public void run() {
try {
// TODO Auto-generated method stub
// Write your code here to update the UI.
// bowlValue.setText(String.valueOf(DataIsoTCP.ReadMyData()));
bowlValue.setText(String
.valueOf(DataIsoTCP
.ReadMyData(3,
28,4)));
// scrollValue.setText(String.valueOf(DataIsoTCP.ReadMyFloatData(4,30)));
// productValue.setText(String.valueOf(DataIsoTCP.ReadMyFloatData(5,24)));
// polymerValue.setText(String.valueOf(DataIsoTCP.ReadMyFloatData(6,10)));
// flushValue.setText(String.valueOf(DataIsoTCP.ReadMyFloatData(7,24)));
// automaticValue.setText(String.valueOf(DataIsoTCP.ReadMyFloatData(8,24)));
} catch (Exception e) {
// TODO: handle exception
Log.e("HAHAHA","exception",e);
}
}
});
Thread.sleep(5000);
} catch (Exception e) {
// TODO: handle exception
}
}
}
}).start();
}
});
//User name from main page
//Back button function
back.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
finish();
}
});
}
}
这是DataIsoTCP.java：
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.Socket;
import android.R.bool;
public class DataIsoTCP {
public static boolean Connection = false;
public static int i, j;
public static long a, b, c;
public static float d, e, f;
public static char buf[];
public static byte buf1[];
public static PLCinterface di;
public static TCPConnection dc;
public static Socket sock;
public static int slot;
public static byte[] by;
public static String IP;
// IP 192.168.1.10
DataIsoTCP(String host) {
IP = host;
// Nodave.Debug=Nodave.DEBUG_ALL;
buf = new char[Nodave.OrderCodeSize];
buf1 = new byte[Nodave.PartnerListSize];
try {
sock = new Socket(host, 102);
} catch (IOException e) {
System.out.println(e);
}
}
public static void StartConnection() {
Connection = false;
OutputStream oStream = null;
InputStream iStream = null;
slot = 2;
if (sock != null) {
try {
oStream = sock.getOutputStream();
} catch (IOException e) {
}
try {
iStream = sock.getInputStream();
} catch (IOException e) {
}
di = new PLCinterface(oStream, iStream, "IF1", 0,
Nodave.PROTOCOL_ISOTCP);
dc = new TCPConnection(di, 0, slot);
int res = dc.connectPLC();
if (0 == res) {
Connection = true;
System.out.println("Connection OK ");
} else {
System.out.println("No connection");
}
}
}
public static void StopConnection() {
if (Connection == true) {
Connection = false;
dc.disconnectPLC();
di.disconnectAdapter();
}
}
// read 4 bytes from MD 100
public static long ReadData() {
dc.readBytes(Nodave.FLAGS, 0, 100, 4, null);
a = dc.getU32();
return (long) a;
}
public static int ReadMyData(int db,int bol,int lenght){
//dc = new TCPConnection(di, 0, slot);
dc.readBytes(Nodave.DB, db, bol, lenght,null);
a=dc.getU32();
return (int)a;
}
public static float ReadMyFloatData(int db,int bol){
dc = new TCPConnection(di, 0, slot);
dc.readBytes(Nodave.DB, db, bol, 4, null);
d = dc.getFloat();
return (float) d;
}
// write 4 bytes to MD 100
public static void WriteData(long a) {
by = Nodave.bswap_32(a);
dc.writeBytes(Nodave.FLAGS, 0, 100, 4, by);
}
public static void WriteMyData(long a){
by=Nodave.bswap_32(a);
dc.writeBytes(Nodave.DB, 4, 0, 100, by);
}
public static void WriteMyFloatData(float deger,int db,int bol){
try {
by = Nodave.toPLCfloat(deger);
dc.writeBytes(Nodave.DB, db, bol, 4, by);
} catch (Exception e) {
// TODO: handle exception
}
}
public static void WriteThat(int onOff){
byte x=0;
if(onOff==1){
x=(byte) (x | (1<<1));
}
else
{
x=(byte)(x & ~(1<<1));
}
dc.writeBytes(Nodave.FLAGS, 0, 1, 1, by);
}
public static void ConnectIsoTcp(String adres) {
Nodave.Debug = Nodave.DEBUG_ALL
^ (Nodave.DEBUG_IFACE | Nodave.DEBUG_SPECIALCHARS);
DataIsoTCP tp = new DataIsoTCP(adres);
tp.StartConnection();
}
}
在Manifest文件中我放
<uses-permission android:name="android.permission.INTERNET"/>
<activity android:name="com.example.haus.EnglishScreen"></activity>
TCPConnection.java：
package nodave;
public class TCPConnection extends S7Connection {
int rack;
int slot;
public TCPConnection(PLCinterface ifa, int rack, int slot) {
super(ifa);
this.rack = rack;
this.slot = slot;
PDUstartIn = 7;
PDUstartOut = 7;
}
protected int readISOPacket() {
int res = iface.read(msgIn, 0, 4);
if (res == 4) {
int len = 0x100 * msgIn[2] + msgIn[3];
res += iface.read(msgIn, 4, len);
} else {
return 0;
}
return res;
}
protected int sendISOPacket(int size) {
size += 4;
msgOut[0] = (byte) 0x03;
msgOut[1] = (byte) 0x0;
msgOut[2] = (byte) (size / 0x100);
msgOut[3] = (byte) (size % 0x100);
if ((Nodave.Debug & Nodave.DEBUG_EXCHANGE) != 0) {
Nodave.dump(" send packet", msgOut, 0, size);
}
// iface = new PLCinterface(); // i put it there
iface.write(msgOut, 0, size);
return 0;
}
public int exchange(PDU p1) {
int res;
PDU p2;
if ((Nodave.Debug & Nodave.DEBUG_EXCHANGE) != 0) {
System.out.println(" enter TCP.Exchange");
}
msgOut[4] = (byte) 0x02;
msgOut[5] = (byte) 0xf0;
msgOut[6] = (byte) 0x80;
sendISOPacket(3 + p1.hlen + p1.plen + p1.dlen);
res = readISOPacket();
return 0;
}
/**
* We have our own connectPLC(), but no disconnect() Open connection to a
* PLC. This assumes that dc is initialized by daveNewConnection and is not
* yet used. (or reused for the same PLC ?)
*/
public int connectPLC() {
byte[] b4 = {
(byte) 0x11,
(byte) 0xE0,
(byte) 0x00,
(byte) 0x00,
(byte) 0x00,
(byte) 0x01,
(byte) 0x00,
(byte) 0xC1,
(byte) 0x02,
(byte) 0x01,
(byte) 0x00,
(byte) 0xC2,
(byte) 0x02,
(byte) 0x01,
(byte) 0x02,
(byte) 0xC0,
(byte) 0x01,
(byte) 0x09};
if ((Nodave.Debug & Nodave.DEBUG_CONNECT) != 0) {
System.out.println("daveConnectPLC() step 1. rack:" + rack + " slot:" + slot);
}
System.arraycopy(b4, 0, msgOut, 4, b4.length);
msgOut[17] = (byte) (rack + 1);
msgOut[18] = (byte) slot;
sendISOPacket(b4.length);
readISOPacket();
if ((Nodave.Debug & Nodave.DEBUG_CONNECT) != 0) {
System.out.println("daveConnectPLC() step 1.");
}
return negPDUlengthRequest();
}
}