Develop Reference

How to change the title of fragment when press back?

I have 3 fragments, Home, Menu and orders they can be loaded by bottomnavigtioview items and the title shown by it as well
once navigate from Home to Orders then if you want to go back to Home From Orders the title still "Orders"
public boolean onNavigationItemSelected(#NonNull MenuItem item) {
Fragment fragment;
switch (item.getItemId()) {
case R.id.navigation_home:
toolbar.setTitle(getResources().getString(R.string.title_home));
fragment = new HomeFragment();
loadFragment(fragment);
return true;
case R.id.navigation_menu:
toolbar.setTitle(getResources().getString(R.string.fragment_title_menu));
fragment = new ProductFragment();
loadFragment(fragment);
return true;
case R.id.navigation_orders:
toolbar.setTitle(getResources().getString(R.string.title_orders));
fragment = new OrdersFragment();
loadFragment(fragment);
return true;
}
return false;
}
};
private void loadFragment(Fragment fragment) {
// load fragment
FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
transaction.replace(R.id.frame_container, fragment);
transaction.addToBackStack(null);
transaction.commit();
}
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
context = this;
navigation = findViewById(R.id.navigation);
navigation.setOnNavigationItemSelectedListener(mOnNavigationItemSelectedListener);
// attaching bottom sheet behaviour - hide / show on scroll
CoordinatorLayout.LayoutParams layoutParams = (CoordinatorLayout.LayoutParams) navigation.getLayoutParams();
layoutParams.setBehavior(new BottomNavigationBehavior());
toolbar.setTitle(getResources().getString(R.string.title_home));
Fragment f = HomeFragment.newInstance();
getSupportFragmentManager().beginTransaction()
.replace(R.id.frame_container, f)
.commit();
}`
I have Also Tried this but its not working
`
fragmentmanger.addOnBackStackChangedListener -> public void onBackStackChanged() {
}`

Instead of calling toolbar.setTitle in your onNavigationItemSelected method, move it to onCreateView of each fragment. When you navigate back to a Fragment, onCreateView is executed again.

It worked for me when calling it in onResume like this in each fragment:
if(getActivity()!=null) {
((MainActivity)getActivity()).setActionBarTitle
(context.getResources().getString(R.string.YOUR_TITLE));
this is the function setActionBarTitle in MainActivity
public void setActionBarTitle(String title) {
toolbar.setTitle(title);
}

RecyclerView not displayed after changing fragment

I have the following situation: an activity with three fragments that I switch between them, in the fragment A for example I fetch some data, save it into an array and I set a recycler view using that array. Then I go to some other fragment, B, and when turning back to A the recycler view is not displayed anymore.
How can I solve this situation? I tried to put in the onResume method of the fragment mAdapter.notifyDataSetChanged() but it didn't worked.
How I swap the fragments:
mMainNav.setOnNavigationItemSelectedListener(new BottomNavigationView.OnNavigationItemSelectedListener() {
#Override
public boolean onNavigationItemSelected(#NonNull MenuItem item) {
switch (item.getItemId()){
case R.id.navigation_home:
setFragment(homeFragment);
return true;
case R.id.navigation_search:
setFragment(searchFragment);
return true;
case R.id.navigation_notifications:
setFragment(notificationsFragment);
return true;
}
return false;
}
});
private void setFragment(Fragment fragment) {
FragmentTransaction fragmentTransaction = getFragmentManager().beginTransaction();
fragmentTransaction.replace(R.id.main_frame, fragment);
fragmentTransaction.commit();
}

Adding back button to fragment

I have a bottom navigation bar that contains 4 fragments and when a tab is selected a new instance of that fragment is loaded.
private BottomNavigationView.OnNavigationItemSelectedListener mOnNavigationItemSelectedListener
= new BottomNavigationView.OnNavigationItemSelectedListener() {
#Override
public boolean onNavigationItemSelected(#NonNull MenuItem item) {
Fragment fragment = null;
switch (item.getItemId()) {
case R.id.navigation_home:
fragment = HomeFragment.newInstance();
break;
case R.id.navigation_cards:
fragment = CardsFragment.newInstance();
break;
case R.id.navigation_deals:
fragment = DealsFragment.newInstance();
break;
case R.id.navigation_settings:
fragment = SettingsFragment.newInstance();
break;
}
if (fragment != null) {
FragmentTransaction fragmentTransaction = getSupportFragmentManager().beginTransaction();
fragmentTransaction.replace(R.id.content, fragment);
fragmentTransaction.commit();
}
return true;
}
};
Now in my HomeFragment there is a RecyclerView that On Item Select it opens a new Fragment:
myViewHolder.cardView.setOnClickListener(view -> {
System.out.println("clicked");
Fragment fragment = new TargetDetailsFragment();
FragmentTransaction ft = ((AppCompatActivity) context).getSupportFragmentManager()
.beginTransaction();
ft.replace(R.id.content, fragment).addToBackStack(null);
ft.commit();
});
I want to add a back button to the TargetDetails Fragments that takes you back to the home page when selected and I attempted doing that by implementing OnBackStackChangedListener in the Main activity
#Override
public void onBackStackChanged() {
shouldDisplayHomeUp();
}
public void shouldDisplayHomeUp(){
//Enable Up button only if there are entries in the back stack
boolean canback = getSupportFragmentManager().getBackStackEntryCount()>0;
getSupportActionBar().setDisplayHomeAsUpEnabled(canback);
}
#Override
public boolean onSupportNavigateUp() {
//This method is called when the up button is pressed. Just the pop back stack.
getSupportFragmentManager().popBackStack();
return true;
}
}
but the problem is when I click on it its reloads the HomeFragment Again but I simply want it to go back to the saved instance of that Fragment

Here is my code that I have used for the ViewPager, the idea is to see if the current page number is 0 than to proceed super.onBackPressed(); otherwise go to the previous fragment:
#Override
public void onBackPressed() {
if(vpPager.getCurrentItem()!=0) {
vpPager.setCurrentItem(vpPager.getCurrentItem()-1, true);
} else {
super.onBackPressed();
}
}

By adding below code in your Activity.
The fragment back stack can be managed.
#Override
public void onBackPressed() {
int count = getFragmentManager().getBackStackEntryCount();
if (count == 0) {
super.onBackPressed();
//additional code
} else {
getFragmentManager().popBackStack();
}
}

Hello #Bolu Okunaiya i think you should try this it will help you to manage backstack to desired fragment without loading same fragment again.
For Stop loading previous fragment you should use "add" instead of "replace" with your FragmentTransaction

Inside your MainActivity
#Override
public void onBackStackChanged() {
//shouldDisplayHomeUp();
Fragment currentFragment = getActivity().getFragmentManager()
.findFragmentById(R.id.fragment_container);
if (currentFragment instanceof TargetDetails) {
Log.v(TAG, "your current fragment is TargetDetails");
popBackStackImmediate(); //<<<< immediate parent fragment will open,which is your HomeFragement
}
}
To use popBackStackImmediate() you need to *replace FragmentA with FragmentB and use addToBackstack() before commit().

Handle back-press inside of Fragments irrespective of navigation route

My app has a navigation drawer with three items linking to three fragments A, B and C
when I click on the back button from any of the Fragments, the app exits.I solved this by declaring these constants in my base activity:
public static boolean IS_FRAGMENT_A = false;
public static boolean IS_FRAGMENT_B = false;
public static boolean IS_FRAGMENT C = false;
and then in the selectView method I did this:
private void displayView(int position) {
IS_FRAGMENT_A = false;
IS_FRAGMENT_B = false;
IS_FRAGMENT_C = false;
// update the main content by replacing fragments
Fragment fragment = null;
switch (position) {
case 0:
fragment = new FragmentA();
IS_FRAGMENT_A = true;
break;
case 1:
fragment = new FragmentB();
IS_FRAGMENT_B = true;
break;
case 2:
fragment = new FragmentC();
IS_FRAGMENT_C = true;
break;
default:
break;
}
And in the overriden onBackPressed() method I did this
public void onBackPressed() {
if (IS_FRAGMENT_A) {
finish();
} else {
displayView(0);
}
}
This works fine when am navigating to these fragments from the navigation drawer.However, when I go to any of the fragments through an ActionBar button, the onBackPressed method does not work.
In Fragment A, I have an ActionBar button that takes me to Fragment B:
public boolean onOptionsItemSelected(MenuItem menuItem) {
int id = menuItem.getItemId();
switch (id) {
case R.id.action_new:
Fragment fragmentB = new FragmentB();
FragmentManager fragmentManager = getFragmentManager();
FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
fragmentTransaction.replace(R.id.frame_container, fragmentB);
fragmentTransaction.addToBackStack(null);
fragmentTransaction.commit();
return true;
default:
return super.onOptionsItemSelected(menuItem);
}
}
When I press the back button from FragmentB after navigating to it via this method the app exits, unlike when I navigate to it through the navigation drawer.
I have tried adding this to the onCreate() method of FragmentB with no luck:
BaseActivity.IS_FRAGMENT_B = true;
My question is, how do I make the back button work in all fragments irrespective of how I got there?

Get previous fragment back

Here is my code snippet:
I want to create a new fragment initially, but if the fragment is already created the i want to show the previous fragment;
But every time a new fragment is initialise.
#Override
protected void onCreate(Bundle savedInstanceState) {
.
.
showFragment(FRAGMENT_ADD_DETAILS);
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
case android.R.id.home:
if(currentFragment==FRAGMENT_ADD_DETAILS){
finish();
}else{
showFragment(FRAGMENT_ADD_DETAILS);
}
break;
case R.id.menu_action_next:
showFragment(FRAGMENT_INVITE_FRIENDS);
break;
}
return super.onOptionsItemSelected(item);
}
#Override
public boolean onPrepareOptionsMenu(Menu menu) {
return super.onPrepareOptionsMenu(menu);
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
.
.
return true;
}
private void showFragment(int fragmentType) {
Log.d(TAG,"showFragment : "+fragmentType);
FragmentManager fragmentManager = getFragmentManager();
Fragment prevFragment = fragmentManager.findFragmentByTag(String.valueOf(fragmentType));
FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
if (prevFragment == null) { //create a fresh instance of fragment
Log.d(TAG,"Initialize new fragment");
Fragment newFragment;
if (fragmentType == FRAGMENT_ADD_DETAILS) {
newFragment = new NewDetailsFragment();
} else {
newFragment = new NewInviteFragment();
}
fragmentTransaction.replace(R.id.ant_container_layout, newFragment);
fragmentTransaction.addToBackStack(String.valueOf(fragmentType));
} else {//just reuse the previous fragment
Log.d(TAG,"Re-Using previous fragment");
fragmentTransaction.replace(R.id.ant_container_layout, prevFragment);
}
fragmentTransaction.commit();
}
Please Help!

You never add any tags to your fragments, so you cannot find them by using findFragmentByTag().
When you replace a fragment, instead of
fragmentTransaction.replace(R.id.ant_container_layout, newFragment);
use the overloaded method that accepts a tag:
fragmentTransaction.replace(R.id.ant_container_layout, newFragment, String.valueOf(fragmentType));
You try to restore your fragments in onCreate() of your activity but it seems that you haven't retained your fragments. They are thus destroyed together with the activity and when the activity is created again, new fragments are created.