change android toolbar back button shape

Each Android Activity has a toolbar or Action Bar. On the Home screen, we may not see or need a Back-Button. But, on inner activities or screens, we need to show Back-Button arrow or Up button at the top-left position. Let us know how to show the Android toolbar back button, change Color and Shape in the Android studio programmatically. We try to click it and go back to the parent activity. Eventually, we solve the problem of the Not-Showing or Not-working Android Toolbar.