Develop Reference

Android Back Button with Fragments in Tabs

I am using tabs to switch between different lists in my app. When a user touches an item in a list, the following is the code to show and hide the detail. I am wondering how to add a back-button that goes back to the correct list it came from. I am replacing fragments so I don't know if the standard back button works in my case?
public class MainActivity extends AppCompatActivity implements
NavigationView.OnNavigationItemSelectedListener,
TabLayout.OnTabSelectedListener,
CustomerFragment.CustomerListListener,
CustomerDetailListener {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
ActionBar actionBar = getSupportActionBar();
actionBar.setHomeButtonEnabled(true);
actionBar.setDisplayHomeAsUpEnabled(true);
actionBar.setDisplayShowHomeEnabled(true);
}
public void onShowCustomerDetail(Customer customer){
HostFragment hostFragment = (HostFragment) customPagerAdapter.getItem(viewPager.getCurrentItem());
CustomerDetailFragment fragment = CustomerDetailFragment.newInstance(customer);
hostFragment.replaceFragment(fragment, true);
}
public void onCloseCustomerDetail() {
HostFragment hostFragment = (HostFragment) customPagerAdapter.getItem(viewPager.getCurrentItem());
CustomerFragment fragment = new CustomerFragment();
hostFragment.replaceFragment(fragment, true);
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
// just for testing. will do switch case here
onBackPressed();
}
#Override
public void onBackPressed() {
if (getFragmentManager().getBackStackEntryCount() > 0) {
getFragmentManager().popBackStack();
} else {
super.onBackPressed();
}
}
}
CustomPagerAdapter:
public class CustomPagerAdapter extends FragmentStatePagerAdapter {
private final List<String> tabTitles = new ArrayList<String>() {{
add("Messages");
add("Customers");
add("Jobs");
add("Maps");
}};
private List<Fragment> tabs = new ArrayList<>();
public CustomPagerAdapter(FragmentManager fragmentManager) {
super(fragmentManager);
initializeTabs();
}
private void initializeTabs() {
tabs.add(HostFragment.newInstance(new MessageFragment()));
tabs.add(HostFragment.newInstance(new CustomerFragment()));
tabs.add(HostFragment.newInstance(new JobFragment()));
tabs.add(HostFragment.newInstance(new MapFragment()));
}
#Override
public Fragment getItem(int position) {
return tabs.get(position);
}
#Override
public int getCount() {
return tabs.size();
}
#Override
public CharSequence getPageTitle(int position) {
return tabTitles.get(position);
}
}
HostFragment:
public class HostFragment extends BackStackFragment {
private Fragment fragment;
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
super.onCreateView(inflater, container, savedInstanceState);
View view = inflater.inflate(R.layout.fragment_host, container, false);
if (fragment != null) {
replaceFragment(fragment, false);
}
return view;
}
public void replaceFragment(Fragment fragment, boolean addToBackstack) {
if (addToBackstack) {
getChildFragmentManager().beginTransaction().replace(R.id.hosted_fragment, fragment).addToBackStack(null).commit();
} else {
getChildFragmentManager().beginTransaction().replace(R.id.hosted_fragment, fragment).commit();
}
}
public static HostFragment newInstance(Fragment fragment) {
HostFragment hostFragment = new HostFragment();
hostFragment.fragment = fragment;
return hostFragment;
}
}

Because of the way I set up my fragments inside tabs using Child Fragment Manager, I had to do this in my onBackPressed to make it work:
#Override
public void onBackPressed() {
HostFragment hostFragment = (HostFragment) customPagerAdapter.getItem(viewPager.getCurrentItem());
FragmentManager fm = hostFragment.getChildFragmentManager();
if (fm.getBackStackEntryCount() > 0) {
fm.popBackStack();
} else {
super.onBackPressed();
}
}

First of all you need to add fragments in backstack while using it
see below code for creating a fragment and adding inside it to backstack
public final static String TAG_FRAGMENT = "HostFragment"; // used inside every fragment
final HostFragment fragment = new HostFragment();
final FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
transaction.replace(R.id.fragment, fragment, TAG_FRAGMENT);
transaction.addToBackStack(TAG_FRAGMENT);
transaction.commit();
After that inside activity onBackPressed() you need to pop fragment every backpressed that you want.
#Override
public void onBackPressed() {
if (getFragmentManager().getBackStackEntryCount() > 0) {
getFragmentManager().popBackStack(); // pop fragment here
} else {
super.onBackPressed(); // after nothing is there default behavior of android works.
}
}

All you need to do is add the fragment to the back stack when you create your fragment. It would look something like this:
CustomerDetailFragment fragment=CustomerDetailFragment.newInstance(customer);
getFragmentManager().beginTransaction()
.addToBackStack("Fragment Tag")
.replace(R.id.yourContainer, fragment, "Fragment Tag")
.commit();
Once you have this, you can just use the home back button to pop the fragments off the stack. If you want to use a custom button to go back, you would have to implement your own popping of the stack, which would call getFragmentManager().popBackStack();

Write a fuction onBackpress()
#Override
public void onBackPressed() {
new AlertDialog.Builder(this)
.setTitle("Exit?")
.setMessage("Do you really want to exit?")
.setNegativeButton("No")
.setPositiveButton("Yes", new OnClickListener() {
public void onClick(DialogInterface arg0, int arg1) {
YourActivityname.super.onBackPressed();
}
}).create().show();
}

Android refresh a fragment list from its parent activity

I have a main activity which contains the action bar with 3 menu buttons in it.
I then have a fragment within this main activity which has a list.
I would like to be able to refresh the list in the fragment from the main activity, when one of the menu buttons is clicked, or preferably just removed all the rows from the list.
Any help is appreciated.
Thanks.
public class Favourite extends SherlockFragmentActivity {
ActionBar actionBar;
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.favourite);
actionBar = getSupportActionBar();
actionBar.setDisplayShowTitleEnabled(false);
BitmapDrawable bg = (BitmapDrawable)getResources().getDrawable(R.drawable.actionbar_bg);
bg.setTileModeX(TileMode.REPEAT);
getSupportActionBar().setBackgroundDrawable(bg);
getSupportActionBar().setIcon(R.drawable.favourite_title);
actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
ActionBar.Tab tabAll = actionBar.newTab();
ActionBar.Tab tabfavs = actionBar.newTab();
ActionBar.Tab tabhist = actionBar.newTab();
tabAll.setText("all");
tabfavs.setText("favs");
tabhist.setText("hist");
tabAll.setTabListener(new MyTabListener());
tabfavs.setTabListener(new MyTabListener());
tabhist.setTabListener(new MyTabListener());
actionBar.addTab(tabAll);
actionBar.addTab(tabfavs);
actionBar.addTab(tabhist);
try{
}
catch(Exception e)
{
}
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
MenuInflater inflater = getSupportMenuInflater();
inflater.inflate(R.menu.actionbar_itemlist_favourite, menu);
return true;
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
switch(item.getItemId()) {
case R.id.history:
break;
case R.id.favourite:
Intent favAct = new Intent(this, Favourite.class);
startActivity(favAct);
break;
case R.id.delete:
///I WANT TO BE ABLE TO REFRESH FRAGMENTLIST FROM HERE
}
return true;
}
}
class MyTabListener implements ActionBar.TabListener {
public void onTabSelected(Tab tab, FragmentTransaction ft) {
if(tab.getPosition()==0)
{
FavouriteAllWords frag = new FavouriteAllWords();
ft.replace(android.R.id.content, frag);
}
else if(tab.getPosition()==1)
{
FavouriteFavWords frag = new FavouriteFavWords();
ft.replace(android.R.id.content, frag);
}
else if(tab.getPosition()==2)
{
FavouriteHistWords frag = new FavouriteHistWords();
ft.replace(android.R.id.content, frag);
}
}
public void onTabUnselected(Tab tab, FragmentTransaction ft) {
// TODO Auto-generated method stub
}
public void onTabReselected(Tab tab, FragmentTransaction ft) {
// TODO Auto-generated method stub
}
}
////////////////////MY LIST FRAGMENT CLASS
public class FavouriteAllWords extends ListFragment {
ArrayAdapter<String> adapter;
List<String> stringOfFavWords;
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup group, Bundle saved)
{
adapter = new ArrayAdapter<String>(
inflater.getContext(), R.layout.row, stringOfFavWords);
setListAdapter(adapter);
return super.onCreateView(inflater, group, saved);
}
#Override
public void onActivityCreated (Bundle savedInstanceState)
{
super.onActivityCreated(savedInstanceState);
}
}

You can easily achieve this using INTERFACE
MainActivity.java
public class MainActivity extends Activity {
public FragmentRefreshListener getFragmentRefreshListener() {
return fragmentRefreshListener;
}
public void setFragmentRefreshListener(FragmentRefreshListener fragmentRefreshListener) {
this.fragmentRefreshListener = fragmentRefreshListener;
}
private FragmentRefreshListener fragmentRefreshListener;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Button b = (Button)findViewById(R.id.btnRefreshFragment);
b.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
if(getFragmentRefreshListener()!=null){
getFragmentRefreshListener().onRefresh();
}
}
});
}
public interface FragmentRefreshListener{
void onRefresh();
}
}
MyFragment.java
public class MyFragment extends Fragment {
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View v = null; // some view
/// Your Code
((MainActivity)getActivity()).setFragmentRefreshListener(new MainActivity.FragmentRefreshListener() {
#Override
public void onRefresh() {
// Refresh Your Fragment
}
});
return v;
}
}

Just make your update/refresh method public and call it from your Activity.
OR
Use LocalBroadcastManager or EventBus to send event from your Activity, and by subscribing to this event in a Fragment - react to it and call refresh/update method.

Your activity can call methods in the fragment by acquiring a reference to the Fragment.
(1) Provide a tag when you add your fragment.
transaction.add(R.id.fragment_container, myFragment, "myfragmentTag");
(2) In your hosting activity you can find the fragment and have access to it's methods.
FragmentManager fm = getSupportFragmentManager();
myFragment f = (myFragment) fm.findFragmentByTag("myfragmentTag");
f.refreshAdapter()
(3) refreshAdapter() could now call adapter.notifyDataSetChanged().
This is one of the recommended ways to communicate up to a fragment.
The interface implementation is mainly for communicating back to the activity.

Biraj Zalavadia's answer is 100% right, you will call nay fragment methods from using interface....
this interface methods is running without error...
use this in MainActivity above oncreate
private FragmentRefreshListener fragmentRefreshListener;
public FragmentRefreshListener getFragmentRefreshListener() {
return fragmentRefreshListener;
}
public void setFragmentRefreshListener(
FragmentRefreshListener fragmentRefreshListener) {
this.fragmentRefreshListener = fragmentRefreshListener;
}
inside of Activity
private void refreshcall(String result2) {
// TODO Auto-generated method stub
if (getFragmentRefreshListener() != null) {
getFragmentRefreshListener().onRefresh(result2);
}
}
and put this in needed Fragment
private FragmentRefreshListener fragmentRefreshListener;
public FragmentRefreshListener getFragmentRefreshListener() {
return fragmentRefreshListener;
}
public void setFragmentRefreshListener(
FragmentRefreshListener fragmentRefreshListener) {
this.fragmentRefreshListener = fragmentRefreshListener;
}

Communicating with Other Fragments
http://developer.android.com/training/basics/fragments/communicating.html
This can also be used to communicate between an Activity and a Fragment.

When you click on ActionBar any Button then call interface to refresh the ListFragment. Because in java interface is used for inter-communication.

In Kotlin
Get the list of Support Fragment from the activity and check Instance and then call fragment function
val fragments = supportFragmentManager.fragments
for (fragment in fragments) {
if (fragment is HomeCategoriesFragment) {
fragment.updateAdapter() // Define function in Fragment
}
}

Android - save/restore fragment state

I have an Activity in which I go through several fragments. In every fragment I have several views (EditText, ListView, Map, etc).
How can I save the instance of the fragment that is shown at that moment? I need it to work when the activity is onPause() --> onResume(). Also I need it to work when I return from another fragment (pop from backstack).
From the main Activity I call the first fragment, then from the the fragment I call the next one.
Code for my Activity:
public class Activity_Main extends FragmentActivity{
public static Fragment_1 fragment_1;
public static Fragment_2 fragment_2;
public static Fragment_3 fragment_3;
public static FragmentManager fragmentManager;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
fragment_1 = new Fragment_1();
fragment_2 = new Fragment_2();
fragment_3 = new Fragment_3();
fragmentManager = getSupportFragmentManager();
FragmentTransaction transaction_1 = fragmentManager.beginTransaction();
transaction_1.replace(R.id.content_frame, fragment_1);
transaction_1.commit();
}}
Then here is the code for one of my fragments:
public class Fragment_1 extends Fragment {
private EditText title;
private Button go_next;
#Override
public View onCreateView(final LayoutInflater inflater,
ViewGroup container, Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_1,
container, false);
title = (EditText) rootView.findViewById(R.id.title);
go_next = (Button) rootView.findViewById(R.id.go_next);
image.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
FragmentTransaction transaction_2 = Activity_Main.fragmentManager
.beginTransaction();
transaction_2.replace(R.id.content_frame,
Activity_Main.fragment_2);
transaction_2.addToBackStack(null);
transaction_2.commit();
});
}}
I have searched a lot of information but nothing clear. Can somebody give a clear solution and an example, please ?

When a fragment is moved to the backstack, it isn't destroyed. All the instance variables remain there. So this is the place to save your data. In onActivityCreated you check the following conditions:
Is the bundle != null? If yes, that's where the data is saved (probably orientation change).
Is there data saved in instance variables? If yes, restore your state from them (or maybe do nothing, because everything is as it should be).
Otherwise your fragment is shown for the first time, create everything anew.
Edit: Here's an example
public class ExampleFragment extends Fragment {
private List<String> myData;
#Override
public void onSaveInstanceState(final Bundle outState) {
super.onSaveInstanceState(outState);
outState.putSerializable("list", (Serializable) myData);
}
#Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
if (savedInstanceState != null) {
//probably orientation change
myData = (List<String>) savedInstanceState.getSerializable("list");
} else {
if (myData != null) {
//returning from backstack, data is fine, do nothing
} else {
//newly created, compute data
myData = computeData();
}
}
}
}

Android fragment has some advantages and some disadvantages.
The most disadvantage of the fragment is that when you want to use a fragment you create it ones.
When you use it, onCreateView of the fragment is called for each time. If you want to keep state of the components in the fragment you must save fragment state and yout must load its state in the next shown.
This make fragment view a bit slow and weird.
I have found a solution and I have used this solution: "Everything is great. Every body can try".
When first time onCreateView is being run, create view as a global variable. When second time you call this fragment onCreateView is called again you can return this global view. The fragment component state will be kept.
View view;
#Override
public View onCreateView(LayoutInflater inflater,
#Nullable ViewGroup container, #Nullable Bundle savedInstanceState) {
setActionBar(null);
if (view != null) {
if ((ViewGroup)view.getParent() != null)
((ViewGroup)view.getParent()).removeView(view);
return view;
}
view = inflater.inflate(R.layout.mylayout, container, false);
}

Try this :
#Override
protected void onPause() {
super.onPause();
if (getSupportFragmentManager().findFragmentByTag("MyFragment") != null)
getSupportFragmentManager().findFragmentByTag("MyFragment").setRetainInstance(true);
}
#Override
protected void onResume() {
super.onResume();
if (getSupportFragmentManager().findFragmentByTag("MyFragment") != null)
getSupportFragmentManager().findFragmentByTag("MyFragment").getRetainInstance();
}
Hope this will help.
Also you can write this to activity tag in menifest file :
android:configChanges="orientation|screenSize"
Good luck !!!

In order to save the Fragment state you need to implement onSaveInstanceState():
"Also like an activity, you can retain the state of a fragment using a Bundle, in case the activity's process is killed and you need to restore the fragment state when the activity is recreated. You can save the state during the fragment's onSaveInstanceState() callback and restore it during either onCreate(), onCreateView(), or onActivityCreated(). For more information about saving state, see the Activities document."
http://developer.android.com/guide/components/fragments.html#Lifecycle

As stated here: Why use Fragment#setRetainInstance(boolean)?
you can also use fragments method setRetainInstance(true) like this:
public class MyFragment extends Fragment {
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// keep the fragment and all its data across screen rotation
setRetainInstance(true);
}
}

You can get current Fragment from fragmentManager. And if there are non of them in fragment manager you can create Fragment_1
public class MainActivity extends FragmentActivity {
public static Fragment_1 fragment_1;
public static Fragment_2 fragment_2;
public static Fragment_3 fragment_3;
public static FragmentManager fragmentManager;
#Override
protected void onCreate(Bundle arg0) {
super.onCreate(arg0);
setContentView(R.layout.main);
fragment_1 = (Fragment_1) fragmentManager.findFragmentByTag("fragment1");
fragment_2 =(Fragment_2) fragmentManager.findFragmentByTag("fragment2");
fragment_3 = (Fragment_3) fragmentManager.findFragmentByTag("fragment3");
if(fragment_1==null && fragment_2==null && fragment_3==null){
fragment_1 = new Fragment_1();
fragmentManager.beginTransaction().replace(R.id.content_frame, fragment_1, "fragment1").commit();
}
}
}
also you can use setRetainInstance to true what it will do it ignore onDestroy() method in fragment and your application going to back ground and os kill your application to allocate more memory you will need to save all data you need in onSaveInstanceState bundle
public class Fragment_1 extends Fragment {
private EditText title;
private Button go_next;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setRetainInstance(true); //Will ignore onDestroy Method (Nested Fragments no need this if parent have it)
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
onRestoreInstanceStae(savedInstanceState);
return super.onCreateView(inflater, container, savedInstanceState);
}
//Here you can restore saved data in onSaveInstanceState Bundle
private void onRestoreInstanceState(Bundle savedInstanceState){
if(savedInstanceState!=null){
String SomeText = savedInstanceState.getString("title");
}
}
//Here you Save your data
#Override
public void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
outState.putString("title", "Some Text");
}
}

I'm not quite sure if this question is still bothering you, since it has been several months. But I would like to share how I dealt with this.
Here is the source code:
int FLAG = 0;
private View rootView;
private LinearLayout parentView;
/**
* The fragment argument representing the section number for this fragment.
*/
private static final String ARG_SECTION_NUMBER = "section_number";
/**
* Returns a new instance of this fragment for the given section number.
*/
public static Fragment2 newInstance(Bundle bundle) {
Fragment2 fragment = new Fragment2();
Bundle args = bundle;
fragment.setArguments(args);
return fragment;
}
public Fragment2() {
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
super.onCreateView(inflater, container, savedInstanceState);
Log.e("onCreateView","onCreateView");
if(FLAG!=12321){
rootView = inflater.inflate(R.layout.fragment_create_new_album, container, false);
changeFLAG(12321);
}
parentView=new LinearLayout(getActivity());
parentView.addView(rootView);
return parentView;
}
/* (non-Javadoc)
* #see android.support.v4.app.Fragment#onDestroy()
*/
#Override
public void onDestroy() {
// TODO Auto-generated method stub
super.onDestroy();
Log.e("onDestroy","onDestroy");
}
/* (non-Javadoc)
* #see android.support.v4.app.Fragment#onStart()
*/
#Override
public void onStart() {
// TODO Auto-generated method stub
super.onStart();
Log.e("onstart","onstart");
}
/* (non-Javadoc)
* #see android.support.v4.app.Fragment#onStop()
*/
#Override
public void onStop() {
// TODO Auto-generated method stub
super.onStop();
if(false){
Bundle savedInstance=getArguments();
LinearLayout viewParent;
viewParent= (LinearLayout) rootView.getParent();
viewParent.removeView(rootView);
}
parentView.removeView(rootView);
Log.e("onStop","onstop");
}
#Override
public void onPause() {
super.onPause();
Log.e("onpause","onpause");
}
#Override
public void onResume() {
super.onResume();
Log.e("onResume","onResume");
}
And here is the MainActivity:
/**
* Fragment managing the behaviors, interactions and presentation of the
* navigation drawer.
*/
private NavigationDrawerFragment mNavigationDrawerFragment;
/**
* Used to store the last screen title. For use in
* {#link #restoreActionBar()}.
*/
public static boolean fragment2InstanceExists=false;
public static Fragment2 fragment2=null;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);
setContentView(R.layout.activity_main);
mNavigationDrawerFragment = (NavigationDrawerFragment) getSupportFragmentManager()
.findFragmentById(R.id.navigation_drawer);
mTitle = getTitle();
// Set up the drawer.
mNavigationDrawerFragment.setUp(R.id.navigation_drawer,
(DrawerLayout) findViewById(R.id.drawer_layout));
}
#Override
public void onNavigationDrawerItemSelected(int position) {
// update the main content by replacing fragments
FragmentManager fragmentManager = getSupportFragmentManager();
FragmentTransaction fragmentTransaction=fragmentManager.beginTransaction();
switch(position){
case 0:
fragmentTransaction.addToBackStack(null);
fragmentTransaction.replace(R.id.container, Fragment1.newInstance(position+1)).commit();
break;
case 1:
Bundle bundle=new Bundle();
bundle.putInt("source_of_create",CommonMethods.CREATE_FROM_ACTIVITY);
if(!fragment2InstanceExists){
fragment2=Fragment2.newInstance(bundle);
fragment2InstanceExists=true;
}
fragmentTransaction.addToBackStack(null);
fragmentTransaction.replace(R.id.container, fragment2).commit();
break;
case 2:
fragmentTransaction.addToBackStack(null);
fragmentTransaction.replace(R.id.container, FolderExplorerFragment.newInstance(position+1)).commit();
break;
default:
break;
}
}
The parentView is the keypoint.
Normally, when onCreateView, we just use return rootView. But now, I add rootView to parentView, and then return parentView. To prevent "The specified child already has a parent. You must call removeView() on the ..." error, we need to call parentView.removeView(rootView), or the method I supplied is useless.
I also would like to share how I found it. Firstly, I set up a boolean to indicate if the instance exists. When the instance exists, the rootView will not be inflated again. But then, logcat gave the child already has a parent thing, so I decided to use another parent as a intermediate Parent View. That's how it works.
Hope it's helpful to you.

If you using bottombar and insted of viewpager you want to set custom fragment replacement logic with retrieve previously save state you can do using below code
String current_frag_tag = null;
String prev_frag_tag = null;
#Override
public void onTabSelected(TabLayout.Tab tab) {
switch (tab.getPosition()) {
case 0:
replaceFragment(new Fragment1(), "Fragment1");
break;
case 1:
replaceFragment(new Fragment2(), "Fragment2");
break;
case 2:
replaceFragment(new Fragment3(), "Fragment3");
break;
case 3:
replaceFragment(new Fragment4(), "Fragment4");
break;
default:
replaceFragment(new Fragment1(), "Fragment1");
break;
}
public void replaceFragment(Fragment fragment, String tag) {
if (current_frag_tag != null) {
prev_frag_tag = current_frag_tag;
}
current_frag_tag = tag;
FragmentManager manager = null;
try {
manager = requireActivity().getSupportFragmentManager();
FragmentTransaction ft = manager.beginTransaction();
if (manager.findFragmentByTag(current_frag_tag) == null) { // No fragment in backStack with same tag..
ft.add(R.id.viewpagerLayout, fragment, current_frag_tag);
if (prev_frag_tag != null) {
try {
ft.hide(Objects.requireNonNull(manager.findFragmentByTag(prev_frag_tag)));
} catch (NullPointerException e) {
e.printStackTrace();
}
}
// ft.show(manager.findFragmentByTag(current_frag_tag));
ft.addToBackStack(current_frag_tag);
ft.commit();
} else {
try {
ft.hide(Objects.requireNonNull(manager.findFragmentByTag(prev_frag_tag)))
.show(Objects.requireNonNull(manager.findFragmentByTag(current_frag_tag))).commit();
} catch (NullPointerException e) {
e.printStackTrace();
}
}
} catch (Exception e) {
e.printStackTrace();
}
}
Inside Child Fragments you can access fragment is visible or not using below method
note: you have to implement below method in child fragment
#Override
public void onHiddenChanged(boolean hidden) {
super.onHiddenChanged(hidden);
try {
if(hidden){
adapter.getFragment(mainVideoBinding.viewPagerVideoMain.getCurrentItem()).onPause();
}else{
adapter.getFragment(mainVideoBinding.viewPagerVideoMain.getCurrentItem()).onResume();
}
}catch (Exception e){
}
}

Switching Fragments in Master/Detail Flow

I am attempting to create an app which has a Master/Detail flow using Fragments. Selecting an item will open a detail fragment which may then which to "open" another fragment and add it to the back stack.
I have renamed classes to help illustrate what they do.
public class ListOfDetails extends FragmentActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
...
}
//Callback method indicating that an item with the given ID was selected.
public void onItemSelected(String id) {
// Performing logic to determine what fragment to start omitted
if (ifTwoPanes()) {
Fragment fragment = new DetailFragmentType1();
getSupportFragmentManager().beginTransaction().replace(R.id.aContainer, fragment).commit();
} else {
Intent newIntent = new Intent(this, SinglePaneFragmentWrapper.class);
newIntent.putExtra("id", id);
startActivity(newIntent);
}
}
// My attempt at making it possible to change displayed fragment from within fragments
public void changeDetailFragment(Fragment fragment) {
FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
transaction.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_OPEN);
transaction.addToBackStack(null);
transaction.replace(R.id.aContainer, fragment);
transaction.commit();
}
}
An example of one of the detail fragments. There are many different Fragments that may be created in different circumstances.
public class DetailFragmentType1 extends Fragment {
private ListOfDetails parent;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
Activity a = getActivity();
if (a instanceof ListOfDetails) {
parent = (ListOfDetails) a;
}
}
#Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
Button aButton = (Button) getActivity().findViewById(R.id.aButton);
aButton.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
parent.changeDetailFragment(new SubDetailFragment());
}
});
}
}
When on phone, a wrapper activity is used to hold the fragment
public class SinglePaneFragmentWrapper extends FragmentActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// Duplicate logic must be performed to start fragment
// Performing logic to determine what fragment to start omitted
String id = getIntent().getStringExtra("id");
if(id == "DetailFragmentType1") {
Fragment fragment = new DetailFragmentType1();
getSupportFragmentManager().beginTransaction().replace(R.id.aContainer, fragment).commit();
} else {
...
}
}
}
What is the proper way to change the fragment that is open in the detail pane in this circumstance? My method feels like a hack when using two panes and doesn't even work when using only one pane because getParent() from SinglePaneFragmentWrapper returns null, making me unable to call parent.changeDetailFragment().
This is a complicated question, hopefully I explained it well. Let me know if I missed something. Thanks

There are lots of opinions around this and lots of ways of doing it. I think in this case the problem is "who is responsible for changing the fragment?" on the surface it seems that a listener on the button is the obvious place, but then the fragment shouldn't know what it is hosted in (a symptom of that is getting an undesirable result like null from getParent()).
In your case I would suggest you implement a "listener" interface in the parent and "notify" from the fragment.. when the parent is notified, it changes the fragment. This way the fragment is not changing itself (so doesn't need to know how).. so.. for your case..
Add a new interface:
public interface FragmentChangeListener {
void onFragmentChangeRequested(Fragment newFragment);
}
Implement the interface in your ListOfDetails activity
public class ListOfDetails extends FragmentActivity implements FragmentChangeListener {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
...
}
//Callback method indicating that an item with the given ID was selected.
public void onItemSelected(String id) {
// Performing logic to determine what fragment to start omitted
if (ifTwoPanes()) {
Fragment fragment = new DetailFragmentType1();
getSupportFragmentManager().beginTransaction().replace(R.id.aContainer, fragment).commit();
} else {
Intent newIntent = new Intent(this, SinglePaneFragmentWrapper.class);
newIntent.putExtra("id", id);
startActivity(newIntent);
}
}
// My attempt at making it possible to change displayed fragment from within fragments
public void changeDetailFragment(Fragment fragment) {
FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
transaction.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_OPEN);
transaction.addToBackStack(null);
transaction.replace(R.id.aContainer, fragment);
transaction.commit();
}
// This is the interface implementation that will be called by your fragments
void onFragmentChangeRequested(Fragment newFragment) {
changeDetailFragment(newFragment);
}
}
Added listener to detail fragment
public class DetailFragmentType1 extends Fragment {
private FragmentChangeListener fragmentChangeListener;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// Actually you might not have an activity here.. you should probably be
// doing this in onAttach
//Activity a = getActivity();
//if (a instanceof ListOfDetails) {
// parent = (ListOfDetails) a;
//}
}
#Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
Button aButton = (Button) getActivity().findViewById(R.id.aButton);
aButton.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
// parent.changeDetailFragment(new SubDetailFragment());
notifyFragmentChange(new SubDetailFragment());
}
});
}
#Override
public void onAttach(Activity activity) {
// This is called when the fragment is attached to an activity..
if (activity instanceof FragmentChangeListener) {
fragmentChangeListener = (FragmentChangeListener) activity;
} else {
// Find your bugs early by making them clear when you can...
if (BuildConfig.DEBUG) {
throw new IllegalArgumentException("Fragment hosts must implement FragmentChangeListener");
}
}
}
private void notifyFragmentChange(Fragment newFragment) {
FragmentChangeListener listener = fragmentChangeListener;
if (listener != null) {
listener.onFragmentChangeRequested(newFragment);
}
}
}
And implement the same interface to your single pane activity...
public class SinglePaneFragmentWrapper extends FragmentActivity implements FragmentChangeListener {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// Duplicate logic must be performed to start fragment
// Performing logic to determine what fragment to start omitted
String id = getIntent().getStringExtra("id");
if(id == "DetailFragmentType1") {
Fragment fragment = new DetailFragmentType1();
getSupportFragmentManager().beginTransaction().replace(R.id.aContainer, fragment).commit();
} else {
...
}
}
// My attempt at making it possible to change displayed fragment from within fragments
public void changeDetailFragment(Fragment fragment) {
FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
transaction.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_OPEN);
transaction.addToBackStack(null);
transaction.replace(R.id.aContainer, fragment);
transaction.commit();
}
// This is the interface implementation that will be called by your fragments
void onFragmentChangeRequested(Fragment newFragment) {
changeDetailFragment(newFragment);
}
}
Note the similarity between your single pane and your multi-pane activities.. this suggests that you could either put all of the duplicated code (changefragment etc) into a single activity that they both extend or that in maybe they are the same activities with different layouts...
I hope that helps, Good luck.
Regards,
CJ

Fragments onResume from back stack

I'm using the compatibility package to use Fragments with Android 2.2.
When using fragments, and adding transitions between them to the backstack, I'd like to achieve the same behavior of onResume of an activity, i.e., whenever a fragment is brought to "foreground" (visible to the user) after poping out of the backstack, I'd like some kind of callback to be activated within the fragment (to perform certain changes on a shared UI resource, for instance).
I saw that there is no built in callback within the fragment framework. is there s a good practice in order to achieve this?

For a lack of a better solution, I got this working for me:
Assume I have 1 activity (MyActivity) and few fragments that replaces each other (only one is visible at a time).
In MyActivity, add this listener:
getSupportFragmentManager().addOnBackStackChangedListener(getListener());
(As you can see I'm using the compatibility package).
getListener implementation:
private OnBackStackChangedListener getListener()
{
OnBackStackChangedListener result = new OnBackStackChangedListener()
{
public void onBackStackChanged()
{
FragmentManager manager = getSupportFragmentManager();
if (manager != null)
{
MyFragment currFrag = (MyFragment) manager.findFragmentById(R.id.fragmentItem);
currFrag.onFragmentResume();
}
}
};
return result;
}
MyFragment.onFragmentResume() will be called after a "Back" is pressed. few caveats though:
It assumes you added all
transactions to the backstack (using
FragmentTransaction.addToBackStack())
It will be activated upon each stack
change (you can store other stuff in
the back stack such as animation) so
you might get multiple calls for the
same instance of fragment.

I've changed the suggested solution a little bit. Works better for me like that:
private OnBackStackChangedListener getListener() {
OnBackStackChangedListener result = new OnBackStackChangedListener() {
public void onBackStackChanged() {
FragmentManager manager = getSupportFragmentManager();
if (manager != null) {
int backStackEntryCount = manager.getBackStackEntryCount();
if (backStackEntryCount == 0) {
finish();
}
Fragment fragment = manager.getFragments()
.get(backStackEntryCount - 1);
fragment.onResume();
}
}
};
return result;
}

After a popStackBack() you can use the following callback : onHiddenChanged(boolean hidden) within your fragment

The following section at Android Developers describes a communication mechanism Creating event callbacks to the activity. To quote a line from it:
A good way to do that is to define a callback interface inside the fragment and require that the host activity implement it. When the activity receives a callback through the interface, it can share the information with other fragments in the layout as necessary.
Edit:
The fragment has an onStart(...) which is invoked when the fragment is visible to the user. Similarly an onResume(...) when visible and actively running. These are tied to their activity counterparts.
In short: use onResume()

If a fragment is put on backstack, Android simply destroys its view. The fragment instance itself is not killed. A simple way to start should to to listen to the onViewCreated event, an put you "onResume()" logic there.
boolean fragmentAlreadyLoaded = false;
#Override
public void onViewCreated(View view, #Nullable Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onViewCreated(view, savedInstanceState);
if (savedInstanceState == null && !fragmentAlreadyLoaded) {
fragmentAlreadyLoaded = true;
// Code placed here will be executed once
}
//Code placed here will be executed even when the fragment comes from backstack
}

In my activity onCreate()
getSupportFragmentManager().addOnBackStackChangedListener(getListener());
Use this method to catch specific Fragment and call onResume()
private FragmentManager.OnBackStackChangedListener getListener()
{
FragmentManager.OnBackStackChangedListener result = new FragmentManager.OnBackStackChangedListener()
{
public void onBackStackChanged()
{
Fragment currentFragment = getSupportFragmentManager().findFragmentById(R.id.fragment_container);
if (currentFragment instanceof YOURFRAGMENT) {
currentFragment.onResume();
}
}
};
return result;
}

A little improved and wrapped into a manager solution.
Things to keep in mind. FragmentManager is not a singleton, it manages only Fragments within Activity, so in every activity it will be new. Also, this solution so far doesn't take ViewPager into account that calls setUserVisibleHint() method helping to control visiblity of Fragments.
Feel free to use following classes when dealing with this issue (uses Dagger2 injection). Call in Activity:
//inject FragmentBackstackStateManager instance to myFragmentBackstackStateManager
FragmentManager fragmentManager = getSupportFragmentManager();
myFragmentBackstackStateManager.apply(fragmentManager);
FragmentBackstackStateManager.java:
#Singleton
public class FragmentBackstackStateManager {
private FragmentManager fragmentManager;
#Inject
public FragmentBackstackStateManager() {
}
private BackstackCallback backstackCallbackImpl = new BackstackCallback() {
#Override
public void onFragmentPushed(Fragment parentFragment) {
parentFragment.onPause();
}
#Override
public void onFragmentPopped(Fragment parentFragment) {
parentFragment.onResume();
}
};
public FragmentBackstackChangeListenerImpl getListener() {
return new FragmentBackstackChangeListenerImpl(fragmentManager, backstackCallbackImpl);
}
public void apply(FragmentManager fragmentManager) {
this.fragmentManager = fragmentManager;
fragmentManager.addOnBackStackChangedListener(getListener());
}
}
FragmentBackstackChangeListenerImpl.java:
public class FragmentBackstackChangeListenerImpl implements FragmentManager.OnBackStackChangedListener {
private int lastBackStackEntryCount = 0;
private final FragmentManager fragmentManager;
private final BackstackCallback backstackChangeListener;
public FragmentBackstackChangeListenerImpl(FragmentManager fragmentManager, BackstackCallback backstackChangeListener) {
this.fragmentManager = fragmentManager;
this.backstackChangeListener = backstackChangeListener;
lastBackStackEntryCount = fragmentManager.getBackStackEntryCount();
}
private boolean wasPushed(int backStackEntryCount) {
return lastBackStackEntryCount < backStackEntryCount;
}
private boolean wasPopped(int backStackEntryCount) {
return lastBackStackEntryCount > backStackEntryCount;
}
private boolean haveFragments() {
List<Fragment> fragmentList = fragmentManager.getFragments();
return fragmentList != null && !fragmentList.isEmpty();
}
/**
* If we push a fragment to backstack then parent would be the one before => size - 2
* If we pop a fragment from backstack logically it should be the last fragment in the list, but in Android popping a fragment just makes list entry null keeping list size intact, thus it's also size - 2
*
* #return fragment that is parent to the one that is pushed to or popped from back stack
*/
private Fragment getParentFragment() {
List<Fragment> fragmentList = fragmentManager.getFragments();
return fragmentList.get(Math.max(0, fragmentList.size() - 2));
}
#Override
public void onBackStackChanged() {
int currentBackStackEntryCount = fragmentManager.getBackStackEntryCount();
if (haveFragments()) {
Fragment parentFragment = getParentFragment();
//will be null if was just popped and was last in the stack
if (parentFragment != null) {
if (wasPushed(currentBackStackEntryCount)) {
backstackChangeListener.onFragmentPushed(parentFragment);
} else if (wasPopped(currentBackStackEntryCount)) {
backstackChangeListener.onFragmentPopped(parentFragment);
}
}
}
lastBackStackEntryCount = currentBackStackEntryCount;
}
}
BackstackCallback.java:
public interface BackstackCallback {
void onFragmentPushed(Fragment parentFragment);
void onFragmentPopped(Fragment parentFragment);
}

This is the correct answer you can call onResume() providing the fragment is attached to the activity. Alternatively you can use onAttach and onDetach

onResume() for the fragment works fine...
public class listBook extends Fragment {
private String listbook_last_subtitle;
...
#Override
public void onCreate(Bundle savedInstanceState) {
String thisFragSubtitle = (String) getActivity().getActionBar().getSubtitle();
listbook_last_subtitle = thisFragSubtitle;
}
...
#Override
public void onResume(){
super.onResume();
getActivity().getActionBar().setSubtitle(listbook_last_subtitle);
}
...

public abstract class RootFragment extends Fragment implements OnBackPressListener {
#Override
public boolean onBackPressed() {
return new BackPressImpl(this).onBackPressed();
}
public abstract void OnRefreshUI();
}
public class BackPressImpl implements OnBackPressListener {
private Fragment parentFragment;
public BackPressImpl(Fragment parentFragment) {
this.parentFragment = parentFragment;
}
#Override
public boolean onBackPressed() {
((RootFragment) parentFragment).OnRefreshUI();
}
}
and final extent your Frament from RootFragment to see effect

My workaround is to get the current title of the actionbar in the Fragment before setting it to the new title. This way, once the Fragment is popped, I can change back to that title.
#Override
public void onResume() {
super.onResume();
// Get/Backup current title
mTitle = ((ActionBarActivity) getActivity()).getSupportActionBar()
.getTitle();
// Set new title
((ActionBarActivity) getActivity()).getSupportActionBar()
.setTitle(R.string.this_fragment_title);
}
#Override
public void onDestroy() {
// Set title back
((ActionBarActivity) getActivity()).getSupportActionBar()
.setTitle(mTitle);
super.onDestroy();
}

I have used enum FragmentTags to define all my fragment classes.
TAG_FOR_FRAGMENT_A(A.class),
TAG_FOR_FRAGMENT_B(B.class),
TAG_FOR_FRAGMENT_C(C.class)
pass FragmentTags.TAG_FOR_FRAGMENT_A.name() as fragment tag.
and now on
#Override
public void onBackPressed(){
FragmentManager fragmentManager = getFragmentManager();
Fragment current
= fragmentManager.findFragmentById(R.id.fragment_container);
FragmentTags fragmentTag = FragmentTags.valueOf(current.getTag());
switch(fragmentTag){
case TAG_FOR_FRAGMENT_A:
finish();
break;
case TAG_FOR_FRAGMENT_B:
fragmentManager.popBackStack();
break;
case default:
break;
}