ActionBar with arrow in a MapsActivity

If your Activity extends from AppCompatActivity you can use:

public class MainActivity extends AppCompatActivity {
...
...

      getSupportActionBar().setDisplayHomeAsUpEnabled(true);
      getSupportActionBar().setDisplayShowHomeEnabled(true);

that results in:

In the event that your Activity extends from FragmentActivity :

public class MainActivity extends FragmentActivity {

The option is to add a Toolbar:

<android.support.v7.widget.Toolbar
    android:id="@+id/toolbar"
    android:layout_width="0dp"
    android:layout_height="56dp"
    android:layout_marginLeft="8dp"
    android:layout_marginRight="8dp"
    android:background="?attr/colorPrimary"
    android:theme="@style/ThemeOverlay.AppCompat.ActionBar"
    app:layout_constraintHorizontal_bias="0.0"
    app:layout_constraintLeft_toLeftOf="parent"
    app:layout_constraintRight_toRightOf="parent"
    app:popupTheme="@style/ThemeOverlay.AppCompat.Light"
    tools:layout_editor_absoluteY="8dp"
    android:layout_marginStart="8dp"
    android:layout_marginEnd="8dp">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Fragment title" />

</android.support.v7.widget.Toolbar>

and assign the arrow:

Toolbar toolbar = (Toolbar)findViewById(R.id.toolbar);
toolbar.setNavigationIcon(R.drawable.ic_arrow_back);
toolbar.setNavigationOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View v) {
         getActivity().onBackPressed();
    }
});

and get something similar to:

I recommend this site to get "material design" icons.