clear = (Button)findViewById(R.id.button2);
    clear.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View arg0) {
            coords = TouchEventView.getFloats(TouchEventView.points);
            if (coords.length < 4) {
                Toast.makeText(MainActivity.this,"You must have at least one line",Toast.LENGTH_LONG).show();
            }
            else if ( coords.length < 6) {
                SendData(length(coords[0],coords[1],coords[2],coords[3]));
                SendData("s");
            }
            else {
                for (int i = 0; i<coords.length-4; i=i+4) {
                    SendData(length(coords[i],coords[i+1],coords[i+2],coords[i+3]));
                    SendData(turn(coords[i],coords[i+1],coords[i+2],coords[i+3],coords[i+6],coords[i+7]));
                }
                int i = coords.length-4;
                SendData(length(coords[i],coords[i+1],coords[i+2],coords[i+3]));
                SendData("s");
            }
        }
    });

@Override
public boolean onTouchEvent(MotionEvent event) {
    float eventX = event.getX();
    float eventY = event.getY();

    gestureDetector.onTouchEvent(event);
        switch (event.getAction()) {
            case MotionEvent.ACTION_DOWN:
                if (! canvas_cleared) {
                    if (x < 0) {
                        x = eventX;
                        y = eventY;
                        startx = x;
                        starty = y;
                    }
                    else {
                        x = x1;
                        y = y1;
                    }
                    points.add(x);
                    points.add(y);
                    x1 = eventX;
                    y1 = eventY;
                }
                return true;
            case MotionEvent.ACTION_MOVE:
                x1 = eventX;
                y1 = eventY;
                break;
            case MotionEvent.ACTION_UP:
                if (canvas_cleared) {
                    x = -1;
                    y = -1;
                    canvas_cleared = false;
                }
                else {
                    points.add(eventX);
                    points.add(eventY);
                }
                break;
            default:
                return false;
    }
    invalidate();
    return true;
}