Develop Reference

How to show interstitial ad when navigating back to the main fragment in bottom navigation

i have four fragments Home, Warning, Donate, and About, Home is the first one shown on launch, what i need is that when users are on any of these fragments (Donate, About, and Caution), and when they go back to the Home fragment using backstack only, I want to show an interstitial ad before showing the home fragment.
I don't want to show the ad when the home fragment launch for first time
Main Activity
public class MainActivity extends AppCompatActivity {
public BottomNavigationView bottomNavigationView;
Deque<Integer> integerDeque = new ArrayDeque<>(3);
boolean flag = true;
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Window window = this.getWindow();
window.setStatusBarColor(this.getResources().getColor(R.color.black));
bottomNavigationView = findViewById(R.id.bottomNavigationView);
bottomNavigationView.setItemIconTintList(null);
integerDeque.push(R.id.home_icon);
loadFragments(new Home_Fragment());
bottomNavigationView.setSelectedItemId(R.id.home_icon);
bottomNavigationView.setOnNavigationItemSelectedListener(
item -> {
int id = item.getItemId();
if (integerDeque.contains(id)) {
if (id == R.id.home_icon) {
integerDeque.size();
if (flag) {
integerDeque.addFirst(R.id.home_icon);
flag = false;
}
}
integerDeque.remove(id);
}
integerDeque.push(id);
loadFragments(getFragment(item.getItemId()));
return true;
}
);
}
#SuppressLint("NonConstantResourceId")
private Fragment getFragment(int itemId) {
switch (itemId) {
case R.id.home_icon:
bottomNavigationView.getMenu().getItem(0).setChecked(true);
return new Home_Fragment();
case R.id.guide_icon:
bottomNavigationView.getMenu().getItem(1).setChecked(true);
return new Cuation_Fragment();
case R.id.donate_icon:
bottomNavigationView.getMenu().getItem(2).setChecked(true);
return new Donate_Fragment();
case R.id.about_icon:
bottomNavigationView.getMenu().getItem(3).setChecked(true);
return new About_Fragment();
}
bottomNavigationView.getMenu().getItem(0).setChecked(true);
return new Home_Fragment();
}
public void loadFragments(Fragment fragment) {
if (fragment != null) {
getSupportFragmentManager().beginTransaction()
.replace(R.id.fragment_container, fragment, fragment.getClass().getSimpleName())
.commit();
}
}
#Override
public void onBackPressed() {
integerDeque.pop();
if (!integerDeque.isEmpty()) {
bottomNavigationView.setSelectedItemId(integerDeque.peek());
} else {
finish();
}
}
}

getBackStackEntryCount return 0 when Activity is recreated

I know this has to be simple and I'm probably not seeing the solution.
Here is the brief description of what I have:
SignInActivity(AppCompatActivity) - handle the Firebase authentication, on success calls the method:
private void onAuthSuccess(FirebaseUser user) {
// Go to MainActivity
startActivity(new Intent(SignInActivity.this, MainActivity.class));
finish();
}
MainActivity(AppCompatActivity) - handle the menus for the application, this menu in particular are fragments with buttons. When a button is clicked I change the fragment that contains other buttons. Something like this:
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
if (savedInstanceState == null) {
getSupportFragmentManager()
.beginTransaction()
.setCustomAnimations(R.anim.slide_in_up, R.anim.slide_out_left)
.replace(R.id.fragmentContent, MainMenuFragment.newInstance())
.commitNow();
}
getSupportFragmentManager().addOnBackStackChangedListener(new
FragmentManager.OnBackStackChangedListener() {
#Override
public void onBackStackChanged() {
int stackHeight = getSupportFragmentManager().getBackStackEntryCount();
getSupportActionBar().setHomeButtonEnabled(stackHeight > 0);
getSupportActionBar().setDisplayHomeAsUpEnabled(stackHeight > 0);
}
});
}
public void replaceFragments(Class fragmentClass, boolean isBack) {
Fragment fragment = null;
FragmentManager fm = getSupportFragmentManager();
FragmentTransaction ft = fm.beginTransaction();
if (isBack) {
ft.setCustomAnimations(R.anim.slide_in_left, R.anim.slide_out_right);
} else {
ft.setCustomAnimations(R.anim.slide_in_right, R.anim.slide_out_left, R.anim.slide_in_left, R.anim.slide_out_right);
}
try {
fragment = (Fragment) fragmentClass.newInstance();
} catch (Exception e) {
fragment = null;
e.printStackTrace();
}
if (fragment != null) {
ft.replace(R.id.fragmentContent, fragment);
ft.addToBackStack(fragmentClass.getName());
ft.commit();
}
}
MainMenuFragment(Fragment) - First set of options, several buttons on top of each other. Depending on the button clicked will call MainActivity.replaceFragment passing the next Fragment to go.
public class MainMenuFragment extends Fragment {
private static final String TAG = "MainMenuFragment";
public static MainMenuFragment newInstance() {
return new MainMenuFragment();
}
public MainMenuFragment() {
// Required empty public constructor
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
View view = inflater.inflate(R.layout.fragment_main_menu, container, false);
final Button btnAssets = view.findViewById(R.id.btnAssets);
final Button btnAudit = view.findViewById(R.id.btnAudit);
btnAssets.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
Log.i(TAG, "BtnAssets_onClick");
((MainActivity)getActivity()).replaceFragments(AssetMenuFragment.class);
}
});
btnAudit.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
Log.i(TAG, "BtnAudit_onClick");
((MainActivity)getActivity()).replaceFragments(AuditMenuFragment.class);
}
});
return view;
}
}
The AssetMenuFragment and the AuditMenuFragment are pretty much the same as the MainMenu, only the text for the buttons and some layout details changes.
When I'm using the app I first signIn, which leads me to the MainActivity, which loads the MainMenuFragment on onCreate. There I'm presented with two buttons, one to go to the AssetMenuFragment and the other to go to the AuditMenuFragment, they replace the fragment with their according layouts.
If I click the Asset button, once the fragment is replaced, because of:
getSupportActionBar().setHomeButtonEnabled(stackHeight > 0);
getSupportActionBar().setDisplayHomeAsUpEnabled(stackHeight > 0);
I'm presented with the back arrow to go back to MainMenuFragment. Everything works as expected.
Now the problem! If I'm in this AssetMenuFragment, with my beautiful back arrow showing on the ActionBar and decided to click the "Square" button on the device, which is probably run the onPause and onStop, and them click on the app again, which will run the onCreate and onStart again, my back arrow disappears, because now int stackHeight = getSupportFragmentManager().getBackStackEntryCount(); is zero.
How can I save my stack and restore it later so I can press back on the AssetMenuFragment and go back to MainMenuFragment.
It is a lot to read, but I'll appreciate the help, thanks!

In the end I knew it had to be something simple.
Both checks are correct.
getSupportActionBar().setHomeButtonEnabled(stackHeight > 0);
getSupportActionBar().setDisplayHomeAsUpEnabled(stackHeight > 0);
The problem was that I didn't check for them on onCreate, only on the getSupportFragmentManager().addOnBackStackChangedListener event.
Here is the MainActivity now:
private ActionBar actionBar;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
if (savedInstanceState == null) {
getSupportFragmentManager()
.beginTransaction()
.setCustomAnimations(R.anim.slide_in_right, R.anim.slide_out_left)
.replace(R.id.fragmentContent, MainMenuFragment.newInstance())
.commitNow();
}
actionBar = getSupportActionBar();
updateActionBarBackButton();
getSupportFragmentManager().addOnBackStackChangedListener(new
FragmentManager.OnBackStackChangedListener() {
#Override
public void onBackStackChanged() {
updateActionBarBackButton();
}
});
}
private void updateActionBarBackButton() {
int stackHeight = getSupportFragmentManager().getBackStackEntryCount();
getSupportActionBar().setHomeButtonEnabled(stackHeight > 0);
getSupportActionBar().setDisplayHomeAsUpEnabled(stackHeight > 0);
}

Back button from activity is removing fragment

I am trying to retain the state of Fragment. I have MotherActivity in which I have FragmentOne,FragmentTwo,FragmentThree and inside from FragmentTwo I am calling another activity ChildActivity. Problem is that When I am pressing back button in ChildActivity it is refreshing MotherActivity and not keeping the state of my FragmentTwo instead it is showing me FragmentOne which come first time.
I only want when I am pressing BackButton from ChildActivity, on container FragmentTwo should be there:
MainAcitivity:
public class MotherActivity extends FragmentActivity {
AHBottomNavigation bottomNavigation;
Fragment selectedFragment = null;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
bottomNavigation = (AHBottomNavigation) findViewById(R.id.navigation);
bottomNavigation.addItem(item1);
bottomNavigation.addItem(item2);
bottomNavigation.addItem(item3);
bottomNavigation.setOnTabSelectedListener(new AHBottomNavigation.OnTabSelectedListener() {
#Override
public boolean onTabSelected(int position, boolean wasSelected) {
if (position == 0) {
selectedFragment = FragmentOne.newInstance(bottomNavigation);
} else if (position == 1) {
selectedFragment = FragmentTwo.newInstance(bottomNavigation);
} else if (position == 2) {
selectedFragment = FragmentThree.newInstance(bottomNavigation);
}
android.app.FragmentManager fragmentManager = getFragmentManager();
android.app.FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
fragmentTransaction.replace(R.id.frame_layout,selectedFragment);
fragmentTransaction.commit();
return true;
}
});
}
#Override
protected void onStart() {
super.onStart();
android.app.FragmentManager fragmentManager = getFragmentManager();
android.app.FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
fragmentTransaction.replace(R.id.frame_layout, FragmentOne.newInstance(bottomNavigation));
fragmentTransaction.commit();
}
public void setNotification(){
bottomNavigation.setNotification("1", 1);
}
#Override
protected void onSaveInstanceState(Bundle outState) {
//No call for super().
}
#Override
public void onBackPressed() {
Intent intent = new Intent();
setResult(113, intent);
finish();
return;
}
}
FragmentTwo from where I am calling childActivity:
public class FragmentTwo extends Fragment {
public static AHBottomNavigation bottomNavigation1;
Card_detail_Adapter_Footer searchabledapter;
public static boolean showAddress = false;
Fragment selectedFragment;
public static FragmentTwo newInstance(AHBottomNavigation bottomNavigation) {
FragmentTwo fragment = new FragmentTwo();
bottomNavigation1 = bottomNavigation;
showNotificationCounter(3);
return fragment;
}
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment_cart, container, false);
if(showAddress == true){
showAddress = false;
// From here I am calling ChildActivity
Intent intent = new Intent(getActivity(), ChildActivity.class);
startActivity(intent);
}
return view;
}
}
In ChildActivity simply calling onBackPressed()

The problem is with the onStart() method of your MotherActivity.java because when you open another activity from FragmentTwo, your MotherActivity onStop() gets called. When you press back button from ChildActivity onStart() of MotherActivity called which is replacing FragmentTwo from FragmentOne by committing transaction.
Please have a look at https://developer.android.com/guide/components/activities/activity-lifecycle.html

Put code from onStart() method into onCreate() method and check if configuration been changed:
if (savedInstanceState == null) {
android.app.FragmentManager fragmentManager = getFragmentManager();
android.app.FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
fragmentTransaction.add(R.id.frame_layout, FragmentOne.newInstance(bottomNavigation));
fragmentTransaction.commit();
}

How to handle bottom navigation perfectly with back pressed

I am working on a bottom navigation bar, but I am not getting perfectly bottom navigation bar.
My MainActivity class:
public class MainActivity extends AppCompatActivity {
private static final String SELECTED_ITEM = "selected_item";
private BottomNavigationView bottomNavigationView;
private Toolbar toolbar;
private MenuItem menuItemSelected;
private int mMenuItemSelected;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
bottomNavigationView = (BottomNavigationView) findViewById(R.id.bottom_navigation);
bottomNavigationView.setOnNavigationItemSelectedListener(new BottomNavigationView.OnNavigationItemSelectedListener() {
#Override
public boolean onNavigationItemSelected(#NonNull MenuItem item) {
selectFragment(item);
return true;
}
});
//Always load first fragment as default
FragmentTransaction fragmentTransaction = getSupportFragmentManager().beginTransaction();
fragmentTransaction.replace(R.id.frameLayout, new AnnouncementFragment());
fragmentTransaction.commit();
if (savedInstanceState != null) {
mMenuItemSelected = savedInstanceState.getInt(SELECTED_ITEM, 0);
menuItemSelected = bottomNavigationView.getMenu().findItem(mMenuItemSelected);
} else {
menuItemSelected = bottomNavigationView.getMenu().getItem(0);
}
selectFragment(menuItemSelected);
}
private void selectFragment(MenuItem item) {
Fragment fragment = null;
Class fragmentClass;
switch (item.getItemId()) {
case R.id.action_announcement:
fragmentClass = AnnouncementFragment.class;
break;
case R.id.action_menu:
fragmentClass = MenuFragment.class;
break;
case R.id.action_menu_reports:
fragmentClass = ReportFragment.class;
break;
case R.id.action_setting:
fragmentClass = SettingFragment.class;
break;
default:
fragmentClass = AnnouncementFragment.class;
}
try {
fragment = (Fragment) fragmentClass.newInstance();
} catch (Exception e) {
e.printStackTrace();
}
FragmentManager fragmentManager = getSupportFragmentManager();
fragmentManager.beginTransaction().replace(R.id.frameLayout, fragment).commit();
}
#Override
protected void onSaveInstanceState(Bundle outState) {
outState.putInt(SELECTED_ITEM, mMenuItemSelected);
super.onSaveInstanceState(outState);
}
And my back pressed also not working properly:
#Override
public void onBackPressed() {
MenuItem homeItem = bottomNavigationView.getMenu().getItem(0);
if (mMenuItemSelected != homeItem.getItemId()) {
selectFragment(homeItem);
} else {
super.onBackPressed();
}
}
How should I do that because bottom menu has uneven distribution on bar. How to properly maintain the menu space without uneven distribution.
Here I am attaching my result which I obtain on AVD

According to the guidelines for Material Design
On Android, the Back button does not navigate between bottom
navigation bar views.
EDIT: Material Design link no longer mentions back button behavior.
Pressing the back button you can quit the application, which is the default behavior, such as in Google Photo...
FragmentManager fragmentManager = getFragmentManager();
FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
fragmentTransaction.replace(R.id.content, fragment);
// note: there is NOT a addToBackStack call
fragmentTransaction.commit();
...or lead the user to the home section and then, if pushed again, at the exit.
Personally I find this last pattern much better.
To get it without override onBackPressed you need to identify the home fragment and differentiate it from all the others
navigation = (BottomNavigationView) findViewById(R.id.navigation);
navigation.setOnNavigationItemSelectedListener(new BottomNavigationView.OnNavigationItemSelectedListener() {
#Override
public boolean onNavigationItemSelected(#NonNull MenuItem item) {
switch (item.getItemId()) {
case R.id.navigation_home:
viewFragment(new HomeFragment(), FRAGMENT_HOME);
return true;
case R.id.navigation_page_1:
viewFragment(new OneFragment(), FRAGMENT_OTHER);
return true;
case R.id.navigation_page_2:
viewFragment(new TwoFragment(), FRAGMENT_OTHER);
return true;
}
return false;
}
});
What you have to do now is write the viewfragment method that have to:
Know how many fragments there are in the stack before the commit
If the fragment is not "home type", save it to the stack before
the commit
Add an OnBackStackChangedListener that when the stack decreases,
(i.e. when I pressed back ), delete all the fragments that are
not "home type" (POP_BACK_STACK_INCLUSIVE) , bringing us to the home fragment
Below the full method with comments
private void viewFragment(Fragment fragment, String name){
final FragmentManager fragmentManager = getFragmentManager();
FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
fragmentTransaction.replace(R.id.content, fragment);
// 1. Know how many fragments there are in the stack
final int count = fragmentManager.getBackStackEntryCount();
// 2. If the fragment is **not** "home type", save it to the stack
if( name.equals( FRAGMENT_OTHER) ) {
fragmentTransaction.addToBackStack(name);
}
// Commit !
fragmentTransaction.commit();
// 3. After the commit, if the fragment is not an "home type" the back stack is changed, triggering the
// OnBackStackChanged callback
fragmentManager.addOnBackStackChangedListener(new FragmentManager.OnBackStackChangedListener() {
#Override
public void onBackStackChanged() {
// If the stack decreases it means I clicked the back button
if( fragmentManager.getBackStackEntryCount() <= count){
// pop all the fragment and remove the listener
fragmentManager.popBackStack(FRAGMENT_OTHER, POP_BACK_STACK_INCLUSIVE);
fragmentManager.removeOnBackStackChangedListener(this);
// set the home button selected
navigation.getMenu().getItem(0).setChecked(true);
}
}
});
}

Try this
#Override
public void onBackPressed() {
BottomNavigationView bottomNavigationView = (BottomNavigationView) findViewById(R.id.navigation);
int seletedItemId = bottomNavigationView.getSelectedItemId();
if (R.id.home != seletedItemId) {
setHomeItem(MainActivity.this);
} else {
super.onBackPressed();
}
}
public static void setHomeItem(Activity activity) {
BottomNavigationView bottomNavigationView = (BottomNavigationView)
activity.findViewById(R.id.navigation);
bottomNavigationView.setSelectedItemId(R.id.home);
}

#Override
public void onBackPressed() {
BottomNavigationView mBottomNavigationView = findViewById(R.id.navigation);
if (mBottomNavigationView.getSelectedItemId() == R.id.navigation_home)
{
super.onBackPressed();
finish();
}
else
{
mBottomNavigationView.setSelectedItemId(R.id.navigation_home);
}
}

This is maybe a little late but I think the best way to do it is as simple as this.
#Override
public void onBackPressed() {
if (mBottomNavigationView.getSelectedItemId() == R.id.action_home) {
super.onBackPressed();
} else {
mBottomNavigationView.setSelectedItemId(R.id.action_home);
}
}
I hope it helps and happy coding :)

onBackPressed did not worked for me. So this I used.
#Override
protected void onResume() {
super.onResume();
bottomNavigationView.getMenu().getItem(0).setChecked(true);
}

The best way is: when in home button the app is closed and when in another button back in home button.
Below I put my code :
first i'm load home button in navigation View :
private void loadFragment(Fragment fragment) {
Toast.makeText(this, "load", Toast.LENGTH_SHORT).show();
FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
transaction.replace(R.id.frame_container, fragment, TAG_FRAGMENT);
transaction.commit();
}
and remember dont call addToBackStack() .
and then handle the situation by onBackPressed() :
#Override
public void onBackPressed() {
if (navigation.getSelectedItemId() == R.id.bottomAkhbar) {
super.onBackPressed();
} else {
navigation.setSelectedItemId(R.id.bottomAkhbar);
}
}

I had the same problem so I solved my problem using this method:
In my main activity, I have a bottom nav bar and a nav drawer, I need to sync items in my drawer and bottom nav:
I created a method for my main fragment and the others:
my main fragment replacer:
public void MainFragmentChanger(final Fragment fragment, final String TAG){
if (main_page_fragment != null){
fragmentTransaction = myFragmentManager.beginTransaction();
fragmentTransaction.remove(main_page_fragment).commit();
}
if (main_drawer.isDrawerOpen()){
main_drawer.closeDrawer();
}
new Handler().post(new Runnable() {
#Override
public void run() {
main_page_fragment = fragment;
main_page_fragment.setRetainInstance(true);
fragmentTransaction = myFragmentManager.beginTransaction();
fragmentTransaction.replace(R.id.main_container, main_page_fragment,TAG);
fragmentTransaction.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_FADE);
fragmentTransaction.commitAllowingStateLoss();
}
});
}
and this is for my other fragment replacer:
public void changeBottomFragment(final Fragment fragment, final String TAG){
if (main_drawer.isDrawerOpen()){
main_drawer.closeDrawer();
}
new Handler().post(new Runnable() {
#Override
public void run() {
main_page_fragment = fragment;
main_page_fragment.setRetainInstance(true);
fragmentTransaction = myFragmentManager.beginTransaction();
fragmentTransaction.replace(R.id.main_container, main_page_fragment);
fragmentTransaction.addToBackStack(null);
fragmentTransaction.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_FADE);
fragmentTransaction.commitAllowingStateLoss();
}
});
}
so after that, I need to sync items in both drawer and bar:
Note I use material navigation drawer by Mike Penz, and com.ashokvarma.bottomnavigation.BottomNavigationBar for nav bar.
here is the method for that purpose:
public void changeNavAndBarStats(String tag){
if (tag == "flash"){
bottomNavigationBar.selectTab(2,false);
main_drawer.setSelection(flashcards.getIdentifier(),false);
}else if (tag == "dic"){
bottomNavigationBar.selectTab(3,false);
main_drawer.setSelection(dictionary.getIdentifier(),false);
}else if (tag == "Home"){
bottomNavigationBar.selectTab(0,false);
main_drawer.setSelection(home.getIdentifier(),false);
}
}
So I call my fragments Like this:
MainFragmentChanger(new MainPageFragment(),"Home");
bottomNavigationBar.selectTab(0,false);
changeBottomFragment(new FlashCardFragment(),"flash");
bottomNavigationBar.selectTab(2,false);
changeBottomFragment(new TranslateFragment(),"dic");
bottomNavigationBar.selectTab(3,false);
At the end I call changeNavAndBarStatus in my fragment's onResume method:
((MainPageActivity)getContext()).changeNavAndBarStats("flash");
That's it! you are good to go!

Try this to achieve the following:
on back press:
from home fragment exit the app.
from other fragments goto home fragment.
//On Back Press if we are at a Fragment other than the Home Fragment it will navigate back to the
// Home Fragment. From Home Fragment it will exit the App.
#Override
public void onBackPressed() {
int backStackEntryCount = getSupportFragmentManager().getBackStackEntryCount();
if (backStackEntryCount == 0) {
super.onBackPressed();
} else {
goHome();
}
}
public void goHome() {
//Following code will set the icon of the bottom navigation to active
final BottomNavigationView mBottomNav = findViewById(R.id.nav_view);
MenuItem homeItem = mBottomNav.getMenu().getItem(0);
mBottomNav.setSelectedItemId(homeItem.getItemId());
getSupportFragmentManager().popBackStackImmediate();
//To delete all entries from back stack immediately one by one.
int backStackEntry = getSupportFragmentManager().getBackStackEntryCount();
for (int i = 0; i < backStackEntry; i++) {
getSupportFragmentManager().popBackStackImmediate();
}
//To navigate to the Home Fragment
final HomeFragment homeFragment = new HomeFragment();
FragmentTransaction myFragmentTransaction = getSupportFragmentManager().beginTransaction();
myFragmentTransaction.replace(R.id.nav_host_fragment, homeFragment, "HomeFrag Tag");
myFragmentTransaction.commit();
}

You can try this /
its worked for me
public class MainActivity extends BaseActivity {
private HomeFragment homeFragment = new HomeFragment();
private CartFragment cartFragment = new CartFragment();
private ProfileFragment profileFragment = new ProfileFragment();
private BottomNavigationView bottomNavigationView;
#Override
protected void onCreate(#Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
if (savedInstanceState == null){
setContentView(R.layout.activity_main);
bottomNavigationView = findViewById(R.id.bottom_nav);
bottomNavigationView.setSelectedItemId(R.id.btnHome);
FragmentTransaction homeFm = getSupportFragmentManager().beginTransaction();
homeFm.replace(R.id.fragment_container, homeFragment);
homeFm.commit();
setupView();
}
}
private void setupView() {
bottomNavigationView.setOnNavigationItemSelectedListener(item -> {
{
switch (item.getItemId()) {
case R.id.btnHome:
loadFragment(homeFragment);
return true;
case R.id.btnCart:
loadFragment(cartFragment);
return true;
case R.id.btnProfile:
loadFragment(profileFragment);
return true;
}
return false;
}
});
}
private void loadFragment(Fragment fragment) {
FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
transaction.replace(R.id.fragment_container, fragment);
transaction.addToBackStack(null);
transaction.commit();
}
#Override
public void onBackPressed() {
if (bottomNavigationView.getSelectedItemId() == R.id.btnHome)
{
finish();
}
else
{
bottomNavigationView.setSelectedItemId(R.id.btnHome);
}
}}

Use addToBackStack Method when calling a fragment like this,
getSupportFragmentManager().beginTransaction().addToBackStack(null).add(R.id.content_home_nav,newFragment).commit();
Use this code in your onBackPressed Method
if (getSupportFragmentManager().getBackStackEntryCount() > 0 ){
getFragmentManager().popBackStack();
} else {
super.onBackPressed();
}

For your requirement you would be working with fragments on navigation for this you can use Tablayout with view pager and make bottom navigation.
<android.support.design.widget.TabLayout
android:id="#+id/tab_layout"
android:layout_width="match_parent"
android:layout_height="60dp"></android.support.design.widget.TabLayout>
and then setup viewpager with tab layout and add icon to tablayout in your activity
tabLayout = (TabLayout) findViewById(R.id.tab_layout);
viewPager = (ViewPager) findViewById(R.id.controller_pager);
viewPager.setAdapter(new ViewPagerAdapter(getSupportFragmentManager()));
viewPager.setOffscreenPageLimit(4);
tabLayout.setupWithViewPager(viewPager);
tabLayout.getTabAt(0).setIcon(R.drawable.selector_home);
tabLayout.getTabAt(1).setIcon(R.drawable.selector_contact);
tabLayout.getTabAt(2).setIcon(R.drawable.selector_profile);
tabLayout.getTabAt(3).setIcon(R.drawable.selector_settings);
now handle all things on the click of tablayout and it will work fine
tabLayout.addOnTabSelectedListener(this);

I was facing the same problem but after doing this I got the solution
First Paste this code in your main activity (where you are using Bottom navigation bar)
BottomNavigationView bottomNavigationView = (BottomNavigationView) findViewById(R.id.navigation);
BottomNavigationViewHelper.disableShiftMode(bottomNavigationView);
And then create a class named BottomNavigationViewHelper and paste the following code.
public class BottomNavigationViewHelper {
public static void disableShiftMode(BottomNavigationView view) {
BottomNavigationMenuView menuView = (BottomNavigationMenuView) view.getChildAt(0);
try {
Field shiftingMode = menuView.getClass().getDeclaredField("mShiftingMode");
shiftingMode.setAccessible(true);
shiftingMode.setBoolean(menuView, false);
shiftingMode.setAccessible(false);
for (int i = 0; i < menuView.getChildCount(); i++) {
BottomNavigationItemView item = (BottomNavigationItemView) menuView.getChildAt(i);
//noinspection RestrictedApi
item.setShiftingMode(false);
// set once again checked value, so view will be updated
//noinspection RestrictedApi
item.setChecked(item.getItemData().isChecked());
}
} catch (NoSuchFieldException e) {
Log.e("BNVHelper", "Unable to get shift mode field", e);
} catch (IllegalAccessException e) {
Log.e("BNVHelper", "Unable to change value of shift mode", e);
}
}
}
Hope It helps

Try this.
getSupportFragmentManager().addOnBackStackChangedListener(new FragmentManager.OnBackStackChangedListener() {
#Override
public void onBackStackChanged() {
// Gets the previous global stack count
int previousStackCount = mPreviousStackCount;
// Gets a FragmentManager instance
FragmentManager localFragmentManager = getSupportFragmentManager();
// Sets the current back stack count
int currentStackCount = localFragmentManager.getBackStackEntryCount();
// Re-sets the global stack count to be the current count
mPreviousStackCount = currentStackCount;
boolean popping = currentStackCount < previousStackCount;
if(popping){
bottomNavigationView.getMenu().getItem(0).setChecked(true);
}
}
});

Please try this solution.
I have made changes in your code given in question.
I have assumed that on back pressing first time your app will come back to home fragment (in your case Announcement fragment) and if you back press again, the app will close.
This flow will also reflect in bottom navigation bar.
public class MainActivity extends AppCompatActivity {
private static final String BACK_STACK_ROOT_TAG = "root_home_fragment";
private static final String SELECTED_ITEM = "selected_item";
private Fragment fragment;
private FragmentManager fragmentManager;
private BottomNavigationView bottomNavigationView;
private Toolbar toolbar;
private MenuItem menuItemSelected;
private int mMenuItemSelected;
private BottomNavigationView.OnNavigationItemSelectedListener mOnNavigationItemSelectedListener
= new BottomNavigationView.OnNavigationItemSelectedListener() {
#Override
public boolean onNavigationItemSelected(#NonNull MenuItem item) {
boolean selected = false;
switch (item.getItemId()) {
case R.id.action_announcement:
fragment = AnnouncementFragment.newInstance();
selected = true;
break;
case R.id.action_menu:
fragment = MenuFragment.newInstance();
selected = true;
break;
case R.id.action_menu_reports:
fragment = ReportFragment.newInstance();
selected = true;
break;
case R.id.action_setting:
fragment = SettingFragment.newInstance();
selected = true;
}
if(fragment !=null){
fragmentManager = getFragmentManager();
switch (item.getItemId()) {
case R.id.action_announcement:
// Pop every fragment from backstack including home fragment.
fragmentManager.popBackStack(BACK_STACK_ROOT_TAG, FragmentManager.POP_BACK_STACK_INCLUSIVE);
fragmentManager.beginTransaction()
.replace(R.id.content, fragment)
.addToBackStack(BACK_STACK_ROOT_TAG)
.commit();
break;
default:
fragmentManager.beginTransaction()
.replace(R.id.content, fragment)
.addToBackStack(null)
.commit();
break;
}
}
return selected;
}
};
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
bottomNavigationView = (BottomNavigationView) findViewById(R.id.bottom_navigation);
bottomNavigationView.setOnNavigationItemSelectedListener(mOnNavigationItemSelectedListener);
//Always load first fragment as default
bottomNavigationView.setSelectedItemId(R.id.action_announcement);
if (savedInstanceState != null) {
mMenuItemSelected = savedInstanceState.getInt(SELECTED_ITEM, 0);
menuItemSelected = bottomNavigationView.getMenu().findItem(mMenuItemSelected);
} else {
menuItemSelected = bottomNavigationView.getMenu().getItem(0);
}
}
#Override
protected void onSaveInstanceState(Bundle outState) {
outState.putInt(SELECTED_ITEM, mMenuItemSelected);
super.onSaveInstanceState(outState);
}
public void onBackPressed() {
int count = getFragmentManager().getBackStackEntryCount();
if(count >1){
// We have lots of fragment on backstack to be popped.
// Pop till the root fragment.
getFragmentManager().popBackStack(BACK_STACK_ROOT_TAG, FragmentManager.POP_BACK_STACK_INCLUSIVE);
bottomNavigationView.setSelectedItemId(R.id.action_announcement);
}
else{
// Close the application when we are on home fragment.
supportFinishAfterTransition();
}
}
}

Most time when you, press back button, old fragment in the back stack,
are recalled. therefore the system call this onCreateView() method
there add this code
val bottomNav = activity?.findViewById<BottomNavigationView>(R.id.activity_main_bottom_navigation)
bottomNav?.selectedItemId = R.id.the_id_of_the_icon__that_represent_the_fragment

I did this after trying all and everything and at last it worked -_- .I have pasted this 2 override method in my each and every activity that i am surfing through my bottom navigation.
#Override
protected void onResume() {
super.onResume();
bottomNavigationView = (BottomNavigationView) findViewById(R.id.bottom_navigation_Menu_name);
bottomNavigationView.getMenu().getItem(Menu_item_position).setChecked(true);
}
#Override
protected void onRestart() {
super.onRestart();
bottomNavigationView = (BottomNavigationView) findViewById(R.id.bottom_navigation_Menu_name);
bottomNavigationView.getMenu().getItem(Menu_item_position).setChecked(true);
}

Late answer but here it goes.
Let's say you have a BottomNavigation inside MainActivity with 4 Fragments.
FragmentA
FragmentB
FragmentC
FragmentD
If your are adding each fragment to backstack like so:
With kotlin:
main_bottom_navigation.setOnNavigationItemSelectedListener { item ->
var fragment: Fragment? = null
when (item.itemId) {
R.id.nav_a -> fragment = FragmentA()
R.id.nav_b -> fragment = FragmentB()
R.id.nav_c -> fragment = FragmentC()
R.id.nav_d -> fragment = FragmentD()
}
supportFragmentManager
.beginTransaction()
.setCustomAnimations(R.anim.abc_fade_in, R.anim.abc_fade_out)
.replace(R.id.home_content, fragment!!)
.addToBackStack(fragment.tag)
.commit()
true
}
You dont really need to override onBackPressed() inside the MainActivity but explicitly cast on each fragment and assigning the BottomNavigation like this:
FragmentA.kt
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
(activity as MainActivity).main_bottom_navigation.menu.getItem(0).isChecked = true
}
FragmentB.kt
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
(activity as MainActivity).main_bottom_navigation.menu.getItem(1).isChecked = true
}
FragmentC.kt
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
(activity as MainActivity).main_bottom_navigation.menu.getItem(2).isChecked = true
}
FragmentD.kt
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
(activity as MainActivity).main_bottom_navigation.menu.getItem(3).isChecked = true
}
Like this the fragment backstack will properly pop and even exit application when it reaches 0.

This is what I did to handle back press in the activity:
#Override
public void onBackPressed() {
super.onBackPressed();
if(homeFragment.isVisible()){
navView.setSelectedItemId(R.id.nav_home);
}
if(searchFragment.isVisible()){
navView.setSelectedItemId(R.id.nav_search);
}
if(myProfileFragment.isVisible()){
navView.setSelectedItemId(R.id.nav_profile);
}
}

this code is work for me:
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
OneSignal.startInit(this)
.inFocusDisplaying(OneSignal.OSInFocusDisplayOption.Notification)
.unsubscribeWhenNotificationsAreDisabled(true)
.init();
bottomNavigationView = findViewById(R.id.bottomNav);
frameLayout = findViewById(R.id.main_frame);
homeFragment = new HomeFragment();
aboutUsFragment = new AboutUsFragment();
recipesFragment = new RecipesFragment();
knowledgeFragment = new KnowledgeFragment();
contactFragment = new ContactFragment();
loadFragment(homeFragment);
bottomNavigationView.setOnNavigationItemSelectedListener(new BottomNavigationView.OnNavigationItemSelectedListener() {
#Override
public boolean onNavigationItemSelected(#NonNull MenuItem menuItem) {
switch (menuItem.getItemId()) {
case R.id.home:
//mManiNav.setItemBackgroundResource(R.color.blue);
loadFragment(homeFragment);
return true;
case R.id.deposit:
// mManiNav.setItemBackgroundResource(R.color.colorAccent);
loadFragment(recipesFragment);
return true;
case R.id.exchange:
//mManiNav.setItemBackgroundResource(R.color.colorPrimary);
loadFragment(knowledgeFragment);
return true;
case R.id.profile:
// mManiNav.setItemBackgroundResource(R.color.light_blue);
loadFragment(aboutUsFragment);
return true;
case R.id.payout:
// mManiNav.setItemBackgroundResource(R.color.light_blue);
loadFragment(contactFragment);
return true;
default:
return false;
}
}
});
}
Here the load fragment class:
private void loadFragment(Fragment fragment) {
FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
transaction.replace(R.id.main_frame, fragment);
transaction.addToBackStack(null);
transaction.commit();
}
Here is the popBackStackTillEntry method:
enter code here public void popBackStackTillEntry(int entryIndex) {
if (getSupportFragmentManager() == null) {
return;
}
if (getSupportFragmentManager().getBackStackEntryCount() <= entryIndex) {
return;
}
FragmentManager.BackStackEntry entry = getSupportFragmentManager().getBackStackEntryAt(
entryIndex);
if (entry != null) {
getSupportFragmentManager().popBackStackImmediate(entry.getId(),
FragmentManager.POP_BACK_STACK_INCLUSIVE);
}
}
Here is the backpress method:
boolean doubleBackToExitPressedOnce = false;
#Override
public void onBackPressed() {
if (doubleBackToExitPressedOnce) {
popBackStackTillEntry(0);
moveTaskToBack(true);
System.exit(0);
return;
}
this.doubleBackToExitPressedOnce = true;
loadFragment(new HomeFragment());
new Handler().postDelayed(new Runnable() {
#Override
public void run() {
doubleBackToExitPressedOnce=false;
}
}, 2000);
}

This is a simple and complete working code in Kotlin.
class MainActivity : AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
bottomNavigationView = findViewById(R.id.bottom_navigation)
bottomNavigationView.setOnItemSelectedListener {menuItem ->
when(menuItem.itemId){
R.id.navBottom_menu_1 -> nextFragment(Fragment_1())
R.id.navBottom_menu_2 -> nextFragment(Fragment_2())
R.id.navBottom_menu_3 -> nextFragment(Fragment_3())
R.id.navBottom_menu_4 -> nextFragment(Fragment_4())
else ->false
}
}
}
fun nextFragment(fm:Fragment): Boolean {
supportFragmentManager.beginTransaction().replace(R.id.linearLayout_rootFragment, fm).commit()
return true
}
fun isMenuChecked(itemIndex:Int):Boolean{
return bottomNavigationView.menu.getItem(itemIndex).isChecked
}
fun setMenuItemChecked(itemIndex:Int){
bottomNavigationView.menu.getItem(itemIndex).isChecked = true
}
override fun onBackPressed() {
when(true){
isMenuChecked(3) -> {nextFragment(Fragment_3()) ; setMenuItemChecked(2) }
isMenuChecked(2) -> {nextFragment(Fragment_2()) ; setMenuItemChecked(1) }
isMenuChecked(1) -> {nextFragment(Fragment_1()) ; setMenuItemChecked(0) }
else -> super.onBackPressed()
}
}
}

This is how I solved my,
Wrap your main widget in WillPopScope() and set a function in the onWillpop: as this
Future<bool> _onBackpress() {
if (_currentpage != 0) {
setState(() {
_currentpage--;//decreases number of pages till the fisrt page
});
} else {
// a function to close the app
}
}

MainActivity to fragment and back to MainActivity on pressing back button

I have a Mainactivity which contains a Layout which is parent of 4 sub layout. on clicking on sub layout i am going to a new fragment replacing main layout. But i cant go back to MainActivity after pressing Back button
MainActivity.java
public class MainActivity extends AppCompatActivity {
RelativeLayout aboutUs;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
aboutUs = (RelativeLayout) findViewById(R.id.aboutUs);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
fab.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
.setAction("Action", null).show();
}
});
}
//click methods goes here
public void clickAboutUs(View view){
FragmentManager fragmentManager = getFragmentManager();
FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
FragmentAboutUs fragmentAboutUs = new FragmentAboutUs();
fragmentTransaction.replace(R.id.fragment_container,fragmentAboutUs);
fragmentTransaction.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_OPEN);
fragmentTransaction.addToBackStack(null);
fragmentTransaction.commit();
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_main, menu);
return true;
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
}
FragmentAboutUs.java
public class FragmentAboutUs extends Fragment
{
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.about_us, container,false);
return view;
}
}
How to go back to main page again after pressing back button from fragment.

Try Like this
public boolean popFragment() {
boolean isPop = false;
Fragment currentFragment = getSupportFragmentManager()
.findFragmentById(R.id.flContent);
if (getSupportFragmentManager().getBackStackEntryCount() > 0) {
isPop = true;
getSupportFragmentManager().popBackStackImmediate();
}
return isPop;
}
#Override
public void onBackPressed() {
if (!popFragment()) {
finish();
}
}
public void replaceFragment(Fragment fragment, boolean addToBackStack) {
FragmentTransaction transaction = getSupportFragmentManager()
.beginTransaction();
if (addToBackStack) {
transaction.addToBackStack(null);
} else {
getSupportFragmentManager().popBackStack(null,
FragmentManager.POP_BACK_STACK_INCLUSIVE);
}
transaction.replace(R.id.fragment_container, fragment);
transaction.commit();
getSupportFragmentManager().executePendingTransactions();
}
add above method is in your parent Activity
And Use like
FragmentAboutUs fragmentAboutUs = new FragmentAboutUs();
replaceFragment(fragmentAboutUs , true);

If you have one Activity and four fragments then set onBackPressed() as below in your MainActivity.
#Override
public void onBackPressed()
{
super.onBackPressed();
finish();
}
And in fragments:
#Override
public void onResume() {
super.onResume();
new PlayListFragment();
getView().setFocusableInTouchMode(true);
getView().requestFocus();
getView().setOnKeyListener(new View.OnKeyListener() {
#Override
public boolean onKey(View v, int keyCode, KeyEvent event) {
if (event.getAction() == KeyEvent.ACTION_UP && keyCode == KeyEvent.KEYCODE_BACK){
if(getFragmentManager().getBackStackEntryCount() > 0) {
getFragmentManager().popBackStack();
}
return true;
}
return false;
}
});
}

You can Override the onBackPressed of MainActivity
#Override
public void onBackPressed() {
if (getFragmentManager().getBackStackEntryCount() > 1) {
getFragmentManager().popBackStack();
} else {
super.onBackPressed();
}
}

Here is how it can be done in Xamarin:
Load fragment (I wrote helper method for that, but it's not necessary):
public void LoadFragment(Activity activity, Fragment fragment)
{
var backStateName = fragment.GetType().Name;
var fm = activity.FragmentManager;
var ft = fm.BeginTransaction();
ft.Replace(Resource.Id.mainContainer, fragment);
ft.AddToBackStack(backStateName);
ft.Commit();
}
Back button (in MainActivity):
public override void OnBackPressed()
{
if (isNavDrawerOpen()) drawerLayout.CloseDrawers();
else
{
var backStackEntryCount = FragmentManager.BackStackEntryCount;
if (backStackEntryCount == 1) Finish();
else if (backStackEntryCount > 1) FragmentManager.PopBackStack();
else base.OnBackPressed();
}
}
isNavDrawerOpen method:
bool isNavDrawerOpen()
{
return drawerLayout != null && drawerLayout.IsDrawerOpen(Android.Support.V4.View.GravityCompat.Start);
}