Question

我在nokia N95上调试J2ME（用eclipse编写）代码（不是我写的）试图找到错误并打印出stacktrace给了我这个：

  03:08:479 TSKR. Error:
  java.lang.NullPointerException:   0
 - java.lang.String.<init>(), bci=6
  - v.b(), bci=9
 - v.e(), bci=805
 - v.e(), bci=3

有人可以帮我理解吗？哪条线，在哪里寻找，是否有办法理解它或至少获得一些有价值和有用的信息。谢谢

更新

抱歉..这是抛出错误的函数：

public void     bluetoothFileProcessBytes(){//--------tracing out of memory error
    try{

    partCurrentLoop++;          
    fileCurrentLoop++;

    debug("Loop " + fileCurrentLoop + " of " + fileTotalLoops);

    bluetoothUpdateBytes(fileDataString.length());  
    guiUpdateProgressBar(true, partCurrentLoop, partTotalLoops);

    // LOOP Step 2: If there is no byte[] created for storing the bytes, create it. 

    if (fileBytesIsEmpty) {

        if (partCurrentNumber == partTotalNumber)
        {
            fileBytes = new byte[fileSize % (loopsPerHttpComm * BYTES_PER_LOOP)];
        }
        else    fileBytes = new byte[loopsPerHttpComm * BYTES_PER_LOOP];                    


    }   
    fileBytesIsEmpty = false;


    //LOOP Step 3: fill in the byte array with data from StringBuffer


    for (int i = 0; i < fileDataString.length(); i++) 
    {
         j = i + (partCurrentLoop - 1) * BYTES_PER_LOOP;
         c = fileDataString.charAt(i);              
         fileBytes[j] = (byte) c;   
    }
    c=0;
    j=0;
    i=0;

    //LOOP Step 4: Send the email if the byte array is full with a new HttpComm Thread

    if ((fileCurrentLoop % loopsPerHttpComm == 0
            || fileCurrentLoop == fileTotalLoops) && checkHttpCommStatus()) {


        // update partName and httpCommStatus
        String partName = fileName + " .part " + partCurrentNumber;             

        httpCommStatus = HTTP_RUNNING;

        if (fileCurrentLoop == fileTotalLoops) {        // FILE_END                 
            debug("New HttpComm Thread: FILE END"); 

            httpCommUpdateBytes(fileBytes.length);//<===================remove
            httpCommSucceeded();//<====================================remove



    /*new Thread(new HttpFileEnd(this, fileBytes, toAddress, fromAddress, fromName, digidownMAC,    partName, fileName, fileSize, digidownSoftwareVersion, partCurrentNumber, //<===============uncomment
                    partTotalNumber, DigidownApp.textObject.getActiveLanguage())).start();*/


        } else {                                    // FILE_PART


            //debug("Step 5");//<--------------------------------------------------------------------------------<-remove
        debug("New HttpComm Thread: FILE PART: " + partName);
        debug(">>>>>SEEEENDIIIING!<<<<<<<<");//<===========remove
        httpCommUpdateBytes(fileBytes.length);//<================remove
        httpCommSucceeded();//<==============================remove

/*new Thread(new HttpFilePart(this, fileBytes, toAddress, fromAddress, fromName,//<===============uncomment
                    digidownMAC, partName, fileSize, digidownSoftwareVersion,
                    partCurrentNumber, DigidownApp.textObject.getActiveLanguage())).start();*/  


    // Updating the new partTotalLoops
    if (partCurrentNumber == partTotalNumber){
partTotalLoops = fileTotalLoops - (loopsPerHttpComm * (partCurrentNumber - 1));             
            } else partTotalLoops = loopsPerHttpComm;


            partCurrentNumber++;
            partCurrentLoop = 0;
        }
        fileBytesIsEmpty = true;
        }

    // Leave the loop if failed 
    if (!errorHandlerActivated) {

        if (fileCurrentLoop < fileTotalLoops)
        {

        try{
        bluetoothIOStream.getFileBytes();//-throws null pointer exception !
        }catch(RuntimeException  ea){debug("Wammaaa!!! " + ea.toString());
                      ea.printStackTrace();}

        }
        else if(fileCurrentLoop == fileTotalLoops && checkHttpCommStatus())
                    {   bluetoothIOStream.getFileEnd(); }
    }
    }



    catch(RuntimeException e1)
    {
    Alert alert = new Alert("Fckn error!", e1.toString(), null, null);
    alert.setTimeout(Alert.FOREVER);
    debug("Error:");
    System.err.println();
    e1.printStackTrace();
    //throw e1;

    }
}

..和未经混淆的应用程序的堆栈跟踪;这次是空指针异常之后 // Leave the loop if failed：

02:57:382 TSKR. Loop 972 of 1349
02:57:383 BIOS. Rec 978
02:57:588 TSKR. Loop 973 of 1349
02:57:590 BIOS. Rec 979
02:57:815 TSKR. Wammaaa!!! java.lang.NullPointerException:   0
java.lang.NullPointerException:   0
 - java.lang.String.<init>(), bci=6
 - net.digidown.m.digidown.bluetooth.BluetoothIOStream.readLineAsString(), bci=9
 - net.digidown.m.digidown.bluetooth.BluetoothIOStream.getVariable(), bci=844
 - net.digidown.m.digidown.bluetooth.BluetoothIOStream.getFileBytes(), bci=3
 - net.digidown.m.digidown.TaskRunner.bluetoothFileProcessBytes(), bci=430
 - net.digidown.m.digidown.bluetooth.BluetoothIOStream.getVariable(), bci=857
 - net.digidown.m.digidown.bluetooth.BluetoothIOStream.getFileBytes(), bci=3
 - net.digidown.m.digidown.TaskRunner.bluetoothFileProcessBytes(), bci=430
 - net.digidown.m.digidown.bluetooth.BluetoothIOStream.getVariable(), bci=857
 - net.digidown.m.digidown.bluetooth.BluetoothIOStream.getFileBytes(), bci=3
 - net.digidown.m.digidown.TaskRunner.bluetoothFileProcessBytes(), bci=430
 - net.digidown.m.digidown.bluetooth.BluetoothIOStream.getVariable(), bci=857
 - net.digidown.m.digidown.bluetooth.BluetoothIOStream.getFileBytes(), bci=3
 - net.digidown.m.digidown.TaskRunner.bluetoothFileProcessBytes(), bci=430
 - net.digidown.m.digidown.bluetooth.BluetoothIOStream.getVariable(), bci=857

这样做了一段时间然后......：

 - net.digidown.m.digidown.TaskRunner.bluetoothDoCommand_file(), bci=227
 - net.digidown.m.digidown.bluetooth.BluetoothIOStream.getVariable(), bci=829
 - net.digidown.m.digidown.bluetooth.BluetoothIOStream.getFileSettings(), bci=9
 - net.digidown.m.digidown.TaskRunner.bluetoothTask(), bci=90
 - net.digidown.m.digidown.bluetooth.BluetoothIOStream.getVariable(), bci=513
 - net.digidown.m.digidown.bluetooth.BluetoothIOStream.getTask(), bci=2
 - net.digidown.m.digidown.TaskRunner.bluetoothTask(), bci=172
 - net.digidown.m.digidown.bluetooth.BluetoothIOStream.getVariable(), bci=513
 - net.digidown.m.digidown.bluetooth.BluetoothIOStream.getTask(), bci=2
 - net.digidown.m.digidown.TaskRunner.bluetoothConnected(), bci=89
 - net.digidown.m.digidown.bluetooth.BluetoothIOStream.getVariable(), bci=444
 - net.digidown.m.digidown.bluetooth.BluetoothIOStream.getVariable(), bci=426
 - net.digidown.m.digidown.bluetooth.BluetoothIOStream.run(), bci=366
 - java.lang.Thread.run(), bci=11
03:01:211 TSKR. Finished Task
03:01:212 BIOS. Rec 6
03:01:356 BIOS. task = >
03:01:357 TSKR. :: Got Task: (0x3e)
03:01:358 TSKR.  
03:01:359 TSKR. ERROR HANDLER: 116 - Bluetooth communication error
03:01:389 BIOS. Initiated
03:01:389 BIOS. About to read
03:01:394 BIOS. Phone(InitiateDigidownError) received: '0x3e 0xea Data CK'
03:01:397 BIOS. About to writeLine 'error' 
03:01:468 BIOS. quitStatus = QUIT_STATUS

Answer 1

你的问题似乎是混淆。

eclipse应用程序的构建过程可能使用像proguard这样的工具来提高性能并减小将在现场部署的应用程序.jar文件的大小。

混淆的一个方法是将类和方法名称重写为更小的名称，因此堆栈跟踪的最后3行完全无法理解。

当您要调试应用程序时，需要生成一个未经模糊处理的.jar文件（至少在您发现问题仅发生在应用程序的混淆版本上之前。它会发生）

Eclipse应该允许您通过修改项目属性来关闭混淆（或将其降低到最低级别）。如果做不到这一点，手动和暂时黑客攻击用于构建.jar文件的ant .xml文件就可以了。

模糊处理参数应包含MIDlet类的名称，以便不重命名其startApp（）方法。

Answer 2

您的问题可以通过两种方式解决：

运行您的应用无需模糊处理。因此输出显示了确切的方法名称。
将System.out.println('method_name::sample_tag')放入您的方法中并排除问题可能来自他们。然后在输出中，您可以跟踪执行情况，您可以找到问题发生的点。

J2ME混淆了app stacktrace

2 个答案: