When you start new Android project, with SDK version 23, you will notice e-mail icon, like on picture:
Open activity_main.xml, in my case it is located in app\src\main\res\layout\activity_main.xml, and delete code:
<android.support.design.widget.FloatingActionButton android:id="@+id/fab" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_gravity="bottom|end" android:layout_margin="@dimen/fab_margin" android:src="@android:drawable/ic_dialog_email" />
Then in MainActivity.java, in my case it is located in app\src\main\java\com\example\smi\myapplication\MainActivity.java delete code:
FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab); fab.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View view) { Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG) .setAction("Action", null).show(); } });