Develop Reference

(Android) NavigationBarView clear GridView

I have three fragment in NavigationBarView.
First fragment has gridview(gridview data is dynamic by network search).
But when I go to second fragment and back to first fragment, the gridview in first fragment is clear.
How can I prevent the gridview's data from being cleared?
Here my navigation code.
// in global variable
NavigationBarView navigationBarView;
FirstFragment firstFragment;
SecondFragment secondFragment;
ThirdFragment thirdFragment;
// ...
firstFragment = new FirstFragment();
secondFragment= new SecondFragment();
thirdFragment = new ThirdFragment();
getSupportFragmentManager().beginTransaction().replace(R.id.containers, firstFragment).commit();
navigationBarView = findViewById(R.id.bottom_navigationview);
navigationBarView.setKeepScreenOn(true);
navigationBarView.setOnItemSelectedListener(new NavigationBarView.OnItemSelectedListener() {
#Override
public boolean onNavigationItemSelected(#NonNull MenuItem item) {
switch(item.getItemId())
{
case R.id.menu_first:
getSupportFragmentManager().beginTransaction().replace(R.id.containers, firstFragment).commit();
return true;
case R.id.menu_second:
getSupportFragmentManager().beginTransaction().replace(R.id.containers, secondFragment).commit();
return true;
case R.id.menu_third:
getSupportFragmentManager().beginTransaction().replace(R.id.containers, thirdFragment).commit();
return true;
}
return false;
}
});

addToBackStack method when replacing one fragment by another:
getFragmentManager().beginTransaction().replace(R.id.content_frame, fragment).addToBackStack("my_fragment").commit();
and also use onbackpressed to back with state using back button
#Override
public void onBackPressed() {
if (getParentFragmentManager().getBackStackEntryCount() > 0) {
getParentFragmentManager().popBackStack();
} else {
super.onBackPressed();
}
}
use same popBackStack() to navigate from navigationbar also

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);
}

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().

How to keep fragments state like Instagram in Android?

I need to implement the UI of my app, like the Instagram one. I need to switch from different fragments, with the usage of the bottom navigation view, but I need to keep state of the fragments, like I left them. How Can I achieve this?
#Override
public boolean onNavigationItemSelected(#NonNull MenuItem item) {
item.setChecked(true);
switch (item.getItemId()) {
case R.id.action_formation:
if (homeFragment == null) {
homeFragment = new HomeFragment();
}
displayFragment(homeFragment);
break;
case R.id.action_result:
if (introResultFragment == null) {
introResultFragment = new IntroResultFragment();
}
displayFragment(introResultFragment);
break;
case R.id.action_market:
displayFragment(new MarketFragment());
break;
}
return false;
}
public void displayFragment(final Fragment fragment) {
FragmentManager fragmentManager = getFragmentManager();
FragmentTransaction fragmentTransaction = fragmentManager
.beginTransaction();
fragmentTransaction.replace(R.id.container, fragment, fragment.getClass().toString());
fragmentTransaction.commit();
}

It's been a long time but I want to offer my open source library in github which implements the same UX of Youtube and Instagram:
https://github.com/ZachBublil/ZNavigator
You got to add this dependency to your gradle:
compile 'com.zach.znavigator:znavigator:1.0.0'
The only thing you have to do is to pass the list of fragments you want to be in the BottomNavigationView:
public class SampleActivity extends NavigationActivity {
private BottomNavigationView navigationView;
#Override
protected void onCreate(#Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
navigationView = (BottomNavigationView) findViewById(R.id.navigationView);
LinkedHashMap<Integer, Fragment> rootFragments = new LinkedHashMap<>();
rootFragments.put(R.id.tab1, new FirstTab());
rootFragments.put(R.id.tab2,new SecondTab());
rootFragments.put(R.id.tab3, new ThirdTab());
init(rootFragments, R.id.container);
navigationView.setOnNavigationItemSelectedListener(this);
navigationView.setOnNavigationItemReselectedListener(this);
}
#Override
public void tabChanged(int id) {
navigationView.getMenu().findItem(id).setChecked(true);
}
}
If you want to open a new fragment as inner screen in one of the tabs you can do it by using ZNavigation class in the tab fragment:
ZNavigation.openChildFragment(getFragmentManager(),new ChildFragment());

just remember the active fragment, and use userVisiableHint to get active status in each fragment.
private Fragment currentFragment; // need to be init
private void switch2Fragment(Fragment target){
getFragmentManager().executePendingTransactions();
if(target.isAdded){
getFragmentManager().beginTransaction().hide(currentFragment).show(target).commit();
} else {
getFragmentManager().beginTransaction().hide(currentFragment).add(R.id.xxx, target).commit();
}
currentFragment.setUserVisibleHint(false);
currentFragment = target;
target.setUserVisibleHint(true);
}
private boolean isFragmentActive(Fragment target){
return target.getUserVisibleHint();
}

Android backstack functioning for fragments

I have written a code where I try to navigate in between fragments 1, 2 ,3 ,4. The navigation is like: 1->2->3->4->2.
Each fragment has a button whose onClickListener calls the method in interface which is implemented by the mainactivity, wherein position is passed as parameter.
e.g. onClick on the button in 4th fragment calls the method wherein I pass the position parameter as '2' to call the second fragment.
Now, I have added the transaction 1->2 to the backstack, Using a backstack name "second". When, I try to go from 4>2, I use the function popBackStackImmediate("second", 0). But, the boolean response is false and nothing is popped from the stack.
My questions are :
Why is popBackStackImmediate returning false?
What is the use of second parameter in the same function i.e flag ?
When we add the transaction in the backstack, the transaction is saved and not the fragment. So, where is the fragment object getting saved actually as the backstack saves the transaction?
The MainActivity in my code is :
`
public class MainActivity extends AppCompatActivity implements Frag1.OnFragmentInteractionListener, Frag2.OnFragmentInteractionListener, Frag3.OnFragmentInteractionListener, Frag4.OnFragmentInteractionListener {
LinearLayout layout;
Frag1 frag1;
Frag2 frag2;
Frag3 frag3;
Frag4 frag4;
android.support.v4.app.FragmentTransaction transaction;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Log.i("I", "Main Act");
layout = (LinearLayout) findViewById(R.id.frag);
frag1 = Frag1.newInstance();
transaction = getSupportFragmentManager().beginTransaction();
// Replace whatever is in the fragment_container view with this fragment,
// and add the transaction to the back stack so the user can navigate back
transaction.add(R.id.frag, frag1, "first");
// frag1 = Frag1.newInstance();
// transaction.add(R.id.frag, frag1, "first1");
// transaction.add(R.id.frag, frag2, "second");
// transaction.add(R.id.frag, frag2, "second");
// transaction.add(R.id.frag, frag3, "third");
// Commit the transaction
// transaction.add(R.id.frag, frag3, "third");
// transaction.replace(R.id.frag, frag2, "second");
transaction.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);
}
// Fragment to activity interface implementation
#Override
public void onFragmentInteraction(int pos) {
if (pos == 2) {
// Fragment f = getSupportFragmentManager().findFragmentByTag("second");
FragmentManager manager = getSupportFragmentManager();
boolean isAvail = manager.popBackStackImmediate("second", 0);
if (isAvail) {
// frag2 = (Frag2) f;
Log.i("MainAct", "Instance of 2 yes");
}else{
transaction = getSupportFragmentManager().beginTransaction();
frag2 = Frag2.newInstance();
Log.i("MainAct", "Instance of 2 No");
transaction.replace(R.id.frag, frag2, "second");
transaction.addToBackStack("second");
transaction.commit();
}
} else if (pos == 3) {
Fragment f = getSupportFragmentManager().findFragmentByTag("third");
transaction = getSupportFragmentManager().beginTransaction();
if (f instanceof Frag3) {
frag3 = (Frag3) f;
Log.i("MainAct", "Instance of 3 yes");
}else{
frag3 = Frag3.newInstance();
Log.i("MainAct", "Instance of 3 No");
}
transaction.replace(R.id.frag, frag3, "third");
transaction.commit();
}
else if (pos == 4) {
Fragment f = getSupportFragmentManager().findFragmentByTag("four");
transaction = getSupportFragmentManager().beginTransaction();
if (f instanceof Frag3) {
frag4 = (Frag4) f;
Log.i("MainAct", "Instance of 4 yes");
}else{
frag4 = Frag4.newInstance();
Log.i("MainAct", "Instance of 4 No");
}
transaction.replace(R.id.frag, frag4, "four");
transaction.commit();
}
}
}`

You are trying to call popBackStackImmediate("second", 0); instead replace the fragment.
Try this,
Create Interface PageTraveller and implement in MainActivity
public interface PageTraveller {
public void openPage(int pageNo);
}
override the method openPage()
#Override
public void openPage(int pageNo) {
android.support.v4.app.Fragment fragment;
switch (pageNo){
case 1:
fragment = getSupportFragmentManager().findFragmentByTag("fragmentOne");
fragmentManager.beginTransaction().replace(R.id.pageContainer,fragment).addToBackStack("fragmentOne").commit();
break;
case 2:
fragment = getSupportFragmentManager().findFragmentByTag("fragmentTwo");
if (fragment instanceof FragmentTwo)
fragmentTwo = (FragmentTwo)fragment;
else
fragmentTwo = new FragmentTwo();
fragmentManager.beginTransaction().replace(R.id.pageContainer,fragmentTwo).addToBackStack("fragmentTwo").commit();
break;
case 3:
fragment = getSupportFragmentManager().findFragmentByTag("fragmentThree");
if (fragment instanceof FragmentTwo)
fragmentThree = (FragmentThree)fragment;
else
fragmentThree = new FragmentThree();
fragmentManager.beginTransaction().replace(R.id.pageContainer,fragmentThree).addToBackStack("fragmentThree").commit();
break;
case 4:
fragment = getSupportFragmentManager().findFragmentByTag("fragmentFour");
if (fragment instanceof FragmentTwo)
fragmentFour = (FragmentFour)fragment;
else
fragmentFour = new FragmentFour();
fragmentManager.beginTransaction().replace(R.id.pageContainer,fragmentFour).addToBackStack("fragmentFour").commit();
break;
}
}
Create First fragment FragmentOne
public class FragmentOne extends Fragment{
PageTraveller pageTraveller;
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View viewOne = inflater.inflate(R.layout.fragment_one,null);
Button btnOne = (Button)viewOne.findViewById(R.id.text1);
btnOne.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
pageTraveller.openPage(2);
}
});
return viewOne;
}
#Override
public void onAttach(Context context) {
super.onAttach(context);
pageTraveller = (PageTraveller) context;
}
}
in XML fragment_one add
<Button
android:id="#+id/btnOne"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textSize="40dp"
android:layout_gravity="center|center_horizontal|center_vertical"
android:text="Fragment 1"/>
Create FragmentTwo, FragmentThree, FragmentFour same way as above.
but in your FragmentFour call pageTraveller.openPage(2);
For more reference try 1. go back to the previous fragment in the backstack
Fragments official Android Developer website
Its work for me, try it may help you.