Android development : realtime scrolling chart using apache CircularFifoBuffer

Scrolling chart, code fragment written using the apache commons collection CircularFifoBuffer implementation.

Each refresh redraws the whole screen, giving the illusion of a scrolling chart without having to translate the canvas.

  import org.apache.commons.collections15.buffer.CircularFifoBuffer;
  .....
    private CircularFifoBuffer<Sample> mLocalBuffer;
    
    protected Runnable serviceConsumer = new Runnable() {

        @Override
        public void run() {
            if (!isStarted)
                return;
            synchronized (mLocalBuffer) {
                // se ha raccolto almeno un valore
                if (mService != null && mService.currentSample > 0 && !isScrolled) {
                    mScrollOffset = mService.currentSample;
                    Sample sample = mService.getSampleValue(mScrollOffset);
                    mLocalBuffer.add(sample);
                    drawSamples();
                    mReqNum++;
                }
            }
            handler.postDelayed(this, mUpdateSpeed);
        }
    };    
    .....
    
    protected void drawSamples() {
        Canvas c = new Canvas(mBitmap);
        c.drawColor(Color.BLACK);

        drawAxis();

        Paint paint = new Paint();
        if (isScrolled)
            paint.setColor(Color.GRAY);
        else
            paint.setColor(Color.GREEN);
        int lastX = 0;
        synchronized (mLocalBuffer) {
            for (Sample sample : mLocalBuffer) {
                float newY = mRect.centerY() + mScaleY
                        * (sample.values[SensorManager.DATA_Z] - SensorManager.STANDARD_GRAVITY);
                int newX = (lastX + mSpeed);
                c.drawLine(lastX, (lastX == 0 ? newY : mLastY), newX, newY, paint);
                mLastY = newY;
                lastX = newX;
            }
        }
        invalidate();
    }

    protected void drawAxis() {
        Paint paint = new Paint();
        paint.setColor(Color.WHITE);
        Canvas c = new Canvas(mBitmap);
        c.drawLine(mRectF.left, mRectF.centerY(), mRectF.right, mRectF.centerY(), paint);
        c.drawLine(mRectF.centerX(), mRectF.top, mRectF.centerX(), mRectF.bottom, paint);
    }
.....