Custom bottom navigation bar

BaseBottomNavActivity.java

abstract class BaseBottomNavActivity extends BaseActivity { // you can directly extend AppCompatActivity

    @Override
    @CallSuper
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        initOnCreate(savedInstanceState);
        getBottomNavigationBar().setOnTabSelectionListener(
                new CustomBottomNavigationBar.OnTabSelectionListener() {
                    @Override
                    public void onTabSelected(int position) { // start your various top-level activites from here
                        if (position != getCurrentBottomNavPosition()) {
                            switch (position) {
                                case CustomBottomNavigationBar.POSITION_HOME_TAB:
                                    HomeActivity.start(BaseBottomNavActivity.this);
                                    break;
                                case CustomBottomNavigationBar.POSITION_UPDATES_TAB:
                                    UpdatesActivity.start(BaseBottomNavActivity.this);
                                    break;
                                case CustomBottomNavigationBar.POSITION_BOOKMARKS_TAB:
                                    BookmarksActivity.start(BaseBottomNavActivity.this);
                                    break;
                                case CustomBottomNavigationBar.POSITION_PROFILE_TAB:
                                    ProfileActivity.start(BaseBottomNavActivity.this);
                                    break;
                                case CustomBottomNavigationBar.POSITION_FINISHED_STORIES_TAB:
                                    FinishedStoriesActivity.start(BaseBottomNavActivity.this);
                                    break;
                            }
                        } else {
                            onNavBarReselect();
                        }
                    }
                });
    }

    protected abstract void onNavBarReselect(); // child activity should implement how re-selecting the same (current) tab will be handled.

    @Override
    protected void onResume() {
        super.onResume();
        getBottomNavigationBar().setSelectedTab(getCurrentBottomNavPosition());
    }

//    TODO: uncomment if backstack behavior needs to change
//    @Override
//    public void onBackPressed() {
//        ActivityManager activityManager = (ActivityManager) getSystemService(ACTIVITY_SERVICE);
//        List<ActivityManager.AppTask> appTasks = activityManager.getAppTasks();
//        for (ActivityManager.AppTask task : appTasks) {
//            task.finishAndRemoveTask();
//        }
//    }

    protected abstract int getCurrentBottomNavPosition(); // e.g. for the switch case above HomeActivity returns CustomBottomNavigationBar.POSITION_HOME_TAB here

    protected abstract CustomBottomNavigationBar getBottomNavigationBar(); //e.g. get the bottom nav bar from the child's layout

    protected abstract void initOnCreate(Bundle savedInstanceState); //e.g. child activities to call this, initialize layout in this so that bottom nav bar is available when line 8 is called

    @NonNull
    protected Snackbar showSnackbar(Snackbar snackbar, boolean hasAction) { // used to show the snackbar above the bottom nav bar. This assumes that the parent of each child activity is a coordinator layout.
        Typeface font = Typeface.createFromAsset(getAssets(), AppTextView.APP_TEXT_FONT);
        TextView tv = (TextView) (snackbar.getView()).findViewById(android.support.design.R.id.snackbar_text);
        tv.setTypeface(font);
        Button button = (Button) (snackbar.getView()).findViewById(android.support.design.R.id.snackbar_action);
        button.setTypeface(font);
        CoordinatorLayout.LayoutParams params
                = (CoordinatorLayout.LayoutParams) snackbar.getView().getLayoutParams();
        params.setMargins(params.leftMargin, params.topMargin, params.rightMargin,
                getBottomNavigationBar().getBottomBarHeight());
        snackbar.getView().setLayoutParams(params);
        snackbar.show();
        return snackbar;
    }
}

CustomBottomNavigationBar.java

public class CustomBottomNavigationBar extends FrameLayout {
// These would be names and associated positions of the tabs specific to your app
    public static final int POSITION_HOME_TAB = 0;
    public static final int POSITION_UPDATES_TAB = 2;
    public static final int POSITION_FINISHED_STORIES_TAB = 1;
    public static final int POSITION_BOOKMARKS_TAB = 3;
    public static final int POSITION_PROFILE_TAB = 4;
// Passed in from the activities using this, in the setter below
    private OnTabSelectionListener mTabSelectionListener;
// For some first-time arrangements of the layout    
    private boolean drawn;
    private LayoutBottomBarBinding binding;
// To store resource ids of the drawable for the icons, the order of tabs above should be the same
    private Integer[] tabResId;
// Used in initial layout
    private boolean shadowDrawn;

    public CustomBottomNavigationBar(Context context) {
        super(context);
        initLayout(context);
    }

    public CustomBottomNavigationBar(Context context, AttributeSet attrs) {
        super(context, attrs);
        initLayout(context);
    }

    public CustomBottomNavigationBar(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        initLayout(context);
    }

    public CustomBottomNavigationBar(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) {
        super(context, attrs, defStyleAttr, defStyleRes);
        initLayout(context);
    }

    private void initLayout(Context context) {
        LayoutInflater layoutInflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        binding = DataBindingUtil.inflate(layoutInflater, R.layout.layout_bottom_bar, this, true);

        tabResId = new Integer[]{R.id.home_tab_btn, R.id.leaderboard_tab_btn, R.id.activity_tab_btn,
                R.id.bookmarks_tab_btn, R.id.profile_tab_btn};
        binding.homeTabBtn.setOnClickListener(new InternalTabSelectionListener(POSITION_HOME_TAB));
        binding.activityTabBtn.setOnClickListener(new InternalTabSelectionListener(POSITION_UPDATES_TAB));
        binding.leaderboardTabBtn.setOnClickListener(new InternalTabSelectionListener(POSITION_FINISHED_STORIES_TAB));
        binding.bookmarksTabBtn.setOnClickListener(new InternalTabSelectionListener(POSITION_BOOKMARKS_TAB));
        binding.profileTabBtn.setOnClickListener(new InternalTabSelectionListener(POSITION_PROFILE_TAB));

        setWillNotDraw(false);

        setClipToPadding(false);
        setClipToOutline(false);
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        if (!drawn) {
            drawn = true;
            Rect rect = new Rect();
            ((View) getParent()).getGlobalVisibleRect(rect);
            setY(rect.bottom - rect.top - getContext().getResources().getDimension(R.dimen.bottom_bar_with_shadow_height));
            invalidate();
        } else if (!shadowDrawn) {
            shadowDrawn = true;
            binding.shadowGradient.draw(canvas);
        }
    }

    public int getBottomBarHeight() {
        return binding.bottomBarLayout.getHeight();
    }

    public void setOnTabSelectionListener(OnTabSelectionListener tabSelectionListener) {
        this.mTabSelectionListener = tabSelectionListener;
    }

    public void setSelectedTab(int position) {
        binding.bottomBarLayout.check(tabResId[position]);
    }

    public interface OnTabSelectionListener {
        void onTabSelected(int position);
    }

    private class InternalTabSelectionListener implements OnClickListener {
        private final int mCurrentPosition;

        public InternalTabSelectionListener(int currentTabPosition) {
            mCurrentPosition = currentTabPosition;
        }

        @Override
        public void onClick(View view) {
            if (mTabSelectionListener != null) {
                mTabSelectionListener.onTabSelected(mCurrentPosition);
            }
        }
    }
}

HomeActivity.java

public class HomeActivity extends BaseBottomNavActivity { //thinned down sample implementation of the BaseBottomNavActivity above

    private ActivityHomeBinding binding;

    public static void start(Activity activity) {
        Intent intent = new Intent(activity.getApplicationContext(), HomeActivity.class);
        intent.setFlags(Intent.FLAG_ACTIVITY_REORDER_TO_FRONT);
        activity.startActivity(intent);
    }
  
    public static Intent getStartIntent(Context context) { // if required in a service etc
        Intent intent = new Intent(context, HomeActivity.class);
        intent.setFlags(Intent.FLAG_ACTIVITY_REORDER_TO_FRONT);
        return intent;
    }

    @Override
    protected void initOnCreate(Bundle savedInstanceState) {
        binding = DataBindingUtil.setContentView(this, R.layout.activity_home);
    }

    @Override
    protected void onNavBarReselect() {
        removeProfileFragmentIfAdded(); // sample method call
    }

    private boolean removeProfileFragmentIfAdded() {
        boolean wasAdded = getSupportFragmentManager().popBackStackImmediate();
        if (wasAdded) {
            mIsDataFetched.setValue(true);
            setupActionBar(binding.layoutToolbar, getString(R.string.title_home), false);
            binding.contentSwipeRl.setEnabled(true);
            showToolbarIconFor(null);
            removeViewProfileFragment();
            updateAddStoryFabVisibility(false);
        }
        return wasAdded;
    }

    @Override
    protected int getCurrentBottomNavPosition() {
        return CustomBottomNavigationBar.POSITION_HOME_TAB;
    }

    @Override
    protected CustomBottomNavigationBar getBottomNavigationBar() {
        return binding.bottomNavBar;
    }

    @Override
    public void onBackPressed() {
        boolean wasAdded = removeProfileFragmentIfAdded();
        if (!wasAdded) {
            super.onBackPressed();
        }
    }
}

layout_bottom_bar.xml

<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android">

    <FrameLayout
        android:layout_width="match_parent"
        android:layout_height="@dimen/bottom_bar_with_shadow_height">

        <View
            android:id="@+id/shadow_gradient"
            android:layout_width="match_parent"
            android:layout_height="@dimen/bottom_bar_with_shadow_height"
            android:background="@drawable/shadow_gradient" />

        <RelativeLayout
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:orientation="vertical">

            <RadioGroup
                android:id="@+id/bottom_bar_layout"
                android:layout_width="match_parent"
                android:layout_height="@dimen/bottom_bar_height"
                android:layout_alignParentBottom="true"
                android:background="@color/colorPrimaryDark"
                android:elevation="4dp"
                android:gravity="center"
                android:orientation="horizontal">

                <com.adroitandroid.stitchastory.ui.RadioButtonPlus
                    android:id="@+id/home_tab_btn"
                    android:layout_width="0dp"
                    android:layout_height="match_parent"
                    android:layout_weight="1"
                    android:background="@null"
                    android:button="@drawable/ic_home" />

                <com.adroitandroid.stitchastory.ui.RadioButtonPlus
                    android:id="@+id/leaderboard_tab_btn"
                    android:layout_width="0dp"
                    android:layout_height="match_parent"
                    android:layout_weight="1"
                    android:background="@null"
                    android:button="@drawable/ic_leaderboard" />

                <com.adroitandroid.stitchastory.ui.RadioButtonPlus
                    android:id="@+id/activity_tab_btn"
                    android:layout_width="0dp"
                    android:layout_height="match_parent"
                    android:layout_weight="1"
                    android:background="@null"
                    android:button="@drawable/ic_activity" />

                <com.adroitandroid.stitchastory.ui.RadioButtonPlus
                    android:id="@+id/bookmarks_tab_btn"
                    android:layout_width="0dp"
                    android:layout_height="match_parent"
                    android:layout_weight="1"
                    android:background="@null"
                    android:button="@drawable/ic_collection_bookmarks" />

                <com.adroitandroid.stitchastory.ui.RadioButtonPlus
                    android:id="@+id/profile_tab_btn"
                    android:layout_width="0dp"
                    android:layout_height="match_parent"
                    android:layout_weight="1"
                    android:background="@null"
                    android:button="@drawable/ic_profile" />
            </RadioGroup>
        </RelativeLayout>
    </FrameLayout>
</layout>