car/src/main/java/androidx/car/drawer/CarDrawerController.java
private boolean maybeHandleUpClick() {
        // Check if already at the root level.
        if (mAdapterStack.size() <= 1) {
            return false;
        }

        CarDrawerAdapter adapter = mAdapterStack.pop();
        adapter.setTitleChangeListener(null);
        adapter.cleanup();
        setDisplayAdapter(mAdapterStack.peek());
        runLayoutAnimation(NAVIGATE_UP_ANIM);
        return true;
    }
/**
     * Switches to the previous level in the drawer hierarchy if the current list being displayed
     * is not the root adapter. This is analogous to a navigate up.
     *
     * @return {@code true} if a navigate up was possible and executed. {@code false} otherwise.
     */
Switches to the previous level in the drawer hierarchy if the current list being displayed
is not the root adapter. This is analogous to a navigate up.

@return  true if a navigate up was possible and executed.  false otherwise.
Switches to the previous level in the drawer hierarchy if the current list being displayed is not the root adapter . This is analogous to a navigate up . @return true if a navigate up was possible and executed . false otherwise .
private boolean maybeHandleUpClick() {
        if (mAdapterStack.size() <= 1) {
            return false;
        }
        CarDrawerAdapter adapter = mAdapterStack.pop();
        adapter.setTitleChangeListener(null);
        adapter.cleanup();
        setDisplayAdapter(mAdapterStack.peek());
        runLayoutAnimation(NAVIGATE_UP_ANIM);
        return true;
    }
private boolean maybeHandleUpClick ( ) { if ( mAdapterStack . size ( ) <= 1 ) { return false ; } CarDrawerAdapter adapter = mAdapterStack . pop ( ) ; adapter . setTitleChangeListener ( null ) ; adapter . cleanup ( ) ; setDisplayAdapter ( mAdapterStack . peek ( ) ) ; runLayoutAnimation ( NAVIGATE_UP_ANIM ) ; return true ; }
Switches to the previous level in the drawer hierarchy if the current list being displayed
 is not the root adapter.
Switches to the previous level in the drawer hierarchy if the current list being displayed is not the root adapter .
// Check if already at the root level.