That is not a back button. It is sometimes called a "hamburger icon", and it is specifically used for indicating the presence of DrawerLayout
navigation. You can find more information in the Android documentation. You can see more about the icon's functionality here.
Non-standard back button in Action Bar Android
No hay solución correcta
Otros consejos
Licenciado bajo: CC-BY-SA con atribución
No afiliado a StackOverflow