MainActivity.java

FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
fab.setOnClickListener(new View.OnClickListener() {
  @Override
  public void onClick(View view) {
    if(mText.getText().length() > 0){
      insertNote(mText.getText().toString());
      mText.setText("");
      Snackbar.make(view, "Note added!", Snackbar.LENGTH_LONG)
     .setAction("Action", null).show();
    }
  }
});