[android help] Android Fast and Precise Canvas Graphing?

I am developing an android application which gets graph values over tcp and draws the graph realtime and continuously.The application has to draw 100 pixels/values per second, finishing a 1000 pixel width graph in 10 seconds.

I am developing on a Samsung Galaxy Tab 10.1 Tablet.

Below is the main activity code.I just pasted necessary parts.

public class MainActivity extends Activity {

private MyGraph graph;
private Handler mHandler;
private Handler mHandler2;
private boolean running;

public static int counter=1;
private int limit=1000;

private class MyGraph extends View {

  private Paint       paintecg     = new Paint();
  private Paint       paintdel  = new Paint();
  private Canvas      canvas     = new Canvas();

  private Bitmap cache = Bitmap.createBitmap(1000,800, Bitmap.Config.ARGB_8888);

    private float nextX;        //next point in x axis
    private float lastX=0;
    private float nextY;        // next point in y axis
    private float lastY=150;

    public MyGraph(Context context){
        super(context);

        paintecg.setStyle(Paint.Style.STROKE);
        paintecg.setColor(Color.GREEN);
        paintecg.setAntiAlias(true); paintecg.setStrokeWidth(2f);

        paintdel.setStyle(Paint.Style.FILL_AND_STROKE);
        paintdel.setColor(Color.BLACK);

    }

    public void onDraw(Canvas canvas) {
        if (cache != null)
            canvas.drawBitmap(cache, 0, 0, paintecg);

    }

    public void drawNext() {
        canvas = new Canvas(cache);

        nextX=lastX+1;
            //adding new points to the graph
            canvas.drawLine(lastX,valuearray_ecg[counter-1],nextX,valuearray_ecg[counter], paintecg);
            //emptying next 25 pixels
            canvas.drawRect(nextX, 0, nextX+25, 800, paintdel);

            lastX=nextX;

               if (nextX                    counter++;
                 }
               else {
                    counter=1;
                    lastX=0;
                 }
             postInvalidate();
          }

 }

}

This is the handler created inside oncreate() method :

    LinearLayout graphView=(LinearLayout) findViewById(R.id.layout_graph);
graph = new MyGraph(this);
        mHandler = new Handler(new Handler.Callback() {
            @Override
            public boolean handleMessage(Message msg) {
                graph.drawNext();
             if (running)
                    mHandler.sendMessageDelayed(new Message(), 10);
                return true;
            }
        });
graphView.addView(graph);

Graph is drawed inside a layout in main.xml

This way, when i set handler to 20 ms and my x-axis steps to 2 pixels, it draws 1000 pix in around 15 seconds.Weird thing is, if i lock and unlock the device while app is running, timing becomes normal and draws 1000 pixels in 10 seconds.

when i set handler's delay to 10 miliseconds and x-axis steps to 1 pixel, at first it draws 1000 pixels in 25+ seconds.After locking and unlocking it drops 20- seconds.

I see i'm probably doing it wrong.My question is, is there any way to draw a graph that fast using android's native canvas drawing? Or what is the best way to handle an app like this?

.

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