Android Canvas Multiple Frames

I have the following code, which I've got from an example at Github (1):

private void drawWaveform(Canvas canvas) {
    canvas.drawColor(Color.BLACK);

    float width = getWidth();
    float height = getHeight();
    float centerY = height / 2;

    // We draw the history from oldest to newest so that the older audio data is further back
    // and darker than the most recent data.
    int colorDelta = 255 / (HISTORY_SIZE + 1);
    int brightness = colorDelta;

    for (short[] buffer : mAudioData) {
        mPaint.setColor(Color.argb(brightness, 128, 255, 192));
        float lastX = -1;
        float lastY = -1;

        // For efficiency, we don't draw all of the samples in the buffer, but only the ones
        // that align with pixel boundaries.
         for (int x = 0; x < width; x++) {

                int index = (int) ((x / width) * buffer.length);
                short sample = buffer[index];
                float y = (sample / MAX_AMPLITUDE_TO_DRAW) * centerY + centerY;

                if (lastX != -1) {
                    canvas.drawLine(lastX, lastY, x, y, mPaint);
                }

                lastX = x;
                lastY = y;
            }


        brightness += colorDelta;//muda o brilho da proxima onda a ser desenhada
    }
}

So I understood that it takes the parameter HISTORY_SIZE = 6 in this examples, so it draws 6 waveforms in the screen, with different brigthness in each one, to create a fade-out effect.

I won't need this effect in my project. What I actually need is to draw the first wave until the point (width/HISTORY_SIZE) and then start drawing the second wave from the last point drawed in the first wave.

So each wave are a different short[] array in my LinkedList.

I could try to simplify and change the HISTORY_SIZE for 2, but I just don't seem to know how to edit my start and end point.

With the code I showed you, it is always starting the next wave from the point (-1,-1).

How do I change that?

It's probably very basic stuff, but I haven't really found a post related to this issue.

Sorry if this post is unnappropriate and thanks for your time.