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Thread: Use of GraphView apenddata

  1. #1
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    Default Use of GraphView apenddata

    I am using GraphView appenddata to plot incoming data in real-time in Android.

    Android GraphView - official Project Homepage

    However, my program crashes when loading it onto my device (Jellybean 4.2.2) upon reaching the line with appenddata. In my logcat at the line with appenddata, I am getting "java.lang.NullPointerException", however I don't see anything that is being returned as NULL. I have added GraphView-3.1.1.jar to my libs folder in Eclipse.

    This is my OnCreate

     
    GraphViewSeries data;
    GraphView graph;
    double X = 0;  //initial graph x value
    double d1;
     
    @Override
    public void onCreate(Bundle savedInstanceState)
    {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
     
    Button openButton = (Button)findViewById(R.id.open);
    Button closeButton = (Button)findViewById(R.id.close);
    myLabel = (TextView)findViewById(R.id.myLabel);
    textView1 = (TextView)findViewById(R.id.textView1);
     
    LinearLayout layout = (LinearLayout) findViewById(R.id.graph1);
    graph = new LineGraphView(this, "Frequency");
     
    GraphViewSeries data =  new GraphViewSeries(new GraphView.GraphViewData[] { 
            new GraphView.GraphViewData(X, d1)
    });
     
    graph.addSeries(data); // data
    layout.addView(graph);
     
    //Open Button
    openButton.setOnClickListener(new View.OnClickListener()
    {
        public void onClick(View v)
        {
             try {
                  TimeUnit.MILLISECONDS.sleep(500); //delay added to ensure bytes come in the correct order
             }  catch (InterruptedException ie) {
                 //Handle exception
             }
            try 
            {
                findBT();
                openBT();
            }
            catch (IOException ex) { }
        }
    });
     
    //Close button
    closeButton.setOnClickListener(new View.OnClickListener()
    {
        public void onClick(View v)
        {
            try 
            {
                closeBT();
            }
            catch (IOException ex) { }
        }
    });
    }


    This is where I read data and append it to the graph.

     
    void beginListenForData()
    {   
    final Handler handler = new Handler(); 
    stopWorker = false;
    readBuffer = new byte[2];   //insert # of bytes to read
    workerThread = new Thread(new Runnable()
     
    {
        public void run()
        {                
     
            while(!Thread.currentThread().isInterrupted() && !stopWorker)
           {
                 try 
                {
                    try {
                      TimeUnit.MILLISECONDS.sleep(100); //delay added to ensure bytes come in the correct order
                }   catch (InterruptedException ie) {
                    //Handle exception
                }
     
                    int bytesAvailable = mmInputStream.available(); 
                    System.out.println("Bytes available =" +bytesAvailable);
                    if(bytesAvailable > 0){
     
                        System.out.println("Bytes available =" +bytesAvailable);    
                        byte[] packetBytes = new byte[bytesAvailable];
                        mmInputStream.read(packetBytes);
                        readBuffer = packetBytes;
                        System.out.println("packetBytes = "+ java.util.Arrays.toString(packetBytes));   
     
                        BigInteger bi = new BigInteger(readBuffer);
                        System.out.println(bi);
                        d1 = bi.doubleValue(); //format to double for GraphView
                        System.out.println(d1);
     
                                final String s = bi.toString(); // Format to string for TextView 
                                System.out.println(s);              
                                     handler.post(new Runnable()
                                        {
                                         public void run()
                                            {
                                                textView1.setText(s); 
                                                System.out.println(s);
                                                X += 1;  //0+1+1, etc.
                                                System.out.println(d1);
                                                System.out.println(X);
                                                data.appendData(new         GraphViewData(X, d1), true, 10); //crashing here
                                            }
                                        });
                                   }
                             }
     
                catch (IOException ex) 
                {
                    stopWorker = true;
                }
           }
        }
    });
     
    workerThread.start();
    }

    Logcat

     
    03-19 17:04:05.232: D/BluetoothSocket(9590): connect(), SocketState: INIT, mPfd:     {ParcelFileDescriptor: FileDescriptor[52]}
    03-19 17:04:08.132: I/Choreographer(9590): Skipped 203 frames!  The application may be     doing too much work on its main thread.
    03-19 17:04:08.232: I/System.out(9590): Bytes available =0
    03-19 17:04:08.332: I/System.out(9590): Bytes available =0
    03-19 17:04:08.432: I/System.out(9590): Bytes available =2
    03-19 17:04:08.432: I/System.out(9590): Bytes available =2
    03-19 17:04:08.432: I/System.out(9590): packetBytes = [47, 42]
    03-19 17:04:08.432: I/System.out(9590): 12074
    03-19 17:04:08.432: I/System.out(9590): 12074.0
    03-19 17:04:08.432: I/System.out(9590): 12074
    03-19 17:04:08.432: I/System.out(9590): 12074
    03-19 17:04:08.432: I/System.out(9590): 12074.0
    03-19 17:04:08.442: I/System.out(9590): 1.0
    03-19 17:04:08.442: D/AndroidRuntime(9590): Shutting down VM
    03-19 17:04:08.442: W/dalvikvm(9590): threadid=1: thread exiting with uncaught exception (group=0x41dfe930)
    03-19 17:04:08.452: E/AndroidRuntime(9590): FATAL EXCEPTION: main
    03-19 17:04:08.452: E/AndroidRuntime(9590): java.lang.NullPointerException
    03-19 17:04:08.452: E/AndroidRuntime(9590):     at     com.example.test.MainActivity$3$1.run(MainActivity.java:208)
    03-19 17:04:08.452: E/AndroidRuntime(9590):     at android.os.Handler.handleCallback(Handler.java:725)
    03-19 17:04:08.452: E/AndroidRuntime(9590):     at android.os.Handler.dispatchMessage(Handler.java:92)
    03-19 17:04:08.452: E/AndroidRuntime(9590):     at android.os.Looper.loop(Looper.java:137)
    03-19 17:04:08.452: E/AndroidRuntime(9590):     at android.app.ActivityThread.main(ActivityThread.java:5041)
    03-19 17:04:08.452: E/AndroidRuntime(9590):     at java.lang.reflect.Method.invokeNative(Native Method)
    03-19 17:04:08.452: E/AndroidRuntime(9590):     at java.lang.reflect.Method.invoke(Method.java:511)
    03-19 17:04:08.452: E/AndroidRuntime(9590):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
    03-19 17:04:08.452: E/AndroidRuntime(9590):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
    03-19 17:04:08.452: E/AndroidRuntime(9590):     at dalvik.system.NativeStart.main03-19 17:04:05.232: D/BluetoothSocket(9590): connect(), SocketState: INIT, mPfd:     {ParcelFileDescriptor: FileDescriptor[52]}
    03-19 17:04:08.132: I/Choreographer(9590): Skipped 203 frames!  The application may be     doing too much work on its main thread.
    03-19 17:04:08.232: I/System.out(9590): Bytes available =0
    03-19 17:04:08.332: I/System.out(9590): Bytes available =0
    03-19 17:04:08.432: I/System.out(9590): Bytes available =2
    03-19 17:04:08.432: I/System.out(9590): Bytes available =2
    03-19 17:04:08.432: I/System.out(9590): packetBytes = [47, 42]
    03-19 17:04:08.432: I/System.out(9590): 12074
    03-19 17:04:08.432: I/System.out(9590): 12074.0
    03-19 17:04:08.432: I/System.out(9590): 12074
    03-19 17:04:08.432: I/System.out(9590): 12074
    03-19 17:04:08.432: I/System.out(9590): 12074.0
    03-19 17:04:08.442: I/System.out(9590): 1.0
    03-19 17:04:08.442: D/AndroidRuntime(9590): Shutting down VM
    03-19 17:04:08.442: W/dalvikvm(9590): threadid=1: thread exiting with uncaught exception (group=0x41dfe930)
    03-19 17:04:08.452: E/AndroidRuntime(9590): FATAL EXCEPTION: main
    03-19 17:04:08.452: E/AndroidRuntime(9590): java.lang.NullPointerException
    03-19 17:04:08.452: E/AndroidRuntime(9590):     at     com.example.test.MainActivity$3$1.run(MainActivity.java:208)
    03-19 17:04:08.452: E/AndroidRuntime(9590):     at android.os.Handler.handleCallback(Handler.java:725)
    03-19 17:04:08.452: E/AndroidRuntime(9590):     at android.os.Handler.dispatchMessage(Handler.java:92)
    03-19 17:04:08.452: E/AndroidRuntime(9590):     at android.os.Looper.loop(Looper.java:137)
    03-19 17:04:08.452: E/AndroidRuntime(9590):     at android.app.ActivityThread.main(ActivityThread.java:5041)
    03-19 17:04:08.452: E/AndroidRuntime(9590):     at java.lang.reflect.Method.invokeNative(Native Method)
    03-19 17:04:08.452: E/AndroidRuntime(9590):     at java.lang.reflect.Method.invoke(Method.java:511)
    03-19 17:04:08.452: E/AndroidRuntime(9590):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
    03-19 17:04:08.452: E/AndroidRuntime(9590):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
    03-19 17:04:08.452: E/AndroidRuntime(9590):     at dalvik.system.NativeStart.main(Native Method)

  2. #2
    Super Moderator Norm's Avatar
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    Default Re: Use of GraphView apenddata

    java.lang.NullPointerException
    at com.example.test.MainActivity$3$1.run(MainActivity .java:208)
    What variable is null on line 208?
    If you don't understand my answer, don't ignore it, ask a question.

  3. The Following User Says Thank You to Norm For This Useful Post:

    baseball07 (March 21st, 2014)

  4. #3
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    Default Re: Use of GraphView apenddata

    I'm not sure what is null, the values of X and d1 are defined. True is boolean. I even tried defining int numx = 10, so that it now becomes

    data.appendData(new GraphViewData(X, d1), true, numx);

    but it is still giving me the same error.

  5. #4
    Super Moderator Norm's Avatar
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    Default Re: Use of GraphView apenddata

    What is the value in the variable: data?
    If you don't understand my answer, don't ignore it, ask a question.