using official android fab lib

FAB.java

FloatingActionButton fab = new FloatingActionButton(context);
    fab.setId(View.generateViewId());
    fab.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            Log.d("DEBUG", "onFabFoo");
        }});
    fab.setImageResource(R.drawable.btn_plus);
    fab.setElevation(2);
    fab.setSize(FloatingActionButton.SIZE_MINI);
    fab.setFocusable(true);

RelativeLayout.LayoutParams lay = new RelativeLayout.LayoutParams(ViewGroup.LayoutParams.WRAP_CONTENT, ViewGroup.LayoutParams.WRAP_CONTENT);
lay.addRule(RelativeLayout.ALIGN_PARENT_BOTTOM);
lay.addRule(RelativeLayout.ALIGN_PARENT_LEFT);
lay.setMargins(2,2,2,2);
fab.setLayoutParams(lay);