Develop Reference

How to show a fragment inside a specific Fragment Container in Android

Whenever I want to change fragment depending on the item selected I use:
getSupportFragmentManager().beginTransaction().replace(R.id.fragment_container, fragment).commit();
But now I want to make it so that I can simply show the different fragments instead of creating new ones every time I re-select them, so I found .show instead of .replace, but the problem with .show is that I can not declare where I want that fragment to be shown... or perhaps I'm maybe doing it wrong:
getSupportFragmentManager().beginTransaction().show(fragment).commit();

If you want to use show/hide method, you need to add a fragment before this, as you can see the container is available here. I just showed an example of how to show or hide one fragment. If you have a lot of fragments you can for example save the list and then hide others in the loop. If interested, I added from below.
public void showFragment(Fragment fragment) {
FragmentTransaction fragmentTransaction = getSupportFragmentManager().beginTransaction();
if (fragment.isAdded()) {
fragmentTransaction.show(fragment);
} else {
fragmentTransaction.add(R.id.container, fragment);
}
fragmentTransaction.commit();
}
public void hideFragment(Fragment fragment) {
FragmentTransaction fragmentTransaction = getSupportFragmentManager().beginTransaction();
if (fragment.isAdded()) {
fragmentTransaction.hide(fragment);
}
fragmentTransaction.commit();
}
If there are many fragments
public class MainActivity extends AppCompatActivity {
HashMap<String, Fragment> fragments = new HashMap<>();
#Override
protected void onCreate(#Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
/*
* call this method when you want to add a new fragment
* Example: addFragment(new A(), "TAG_A")
* */
public void addFragment(Fragment fragment, String fragmentTag) {
FragmentTransaction fragmentTransaction = getSupportFragmentManager().beginTransaction();
/*Before add fragment we hide others*/
for (String fTag : fragments.keySet()) {
Fragment fragmentInStack = fragments.get(fTag);
if (fragmentInStack.isAdded() && !fragmentInStack.isHidden()) {
fragmentTransaction.hide(fragmentInStack);
}
}
if (!fragment.isAdded()) {
fragments.put(fragmentTag, fragment);
fragmentTransaction.add(R.id.container, fragment, fragmentTag);
} else {
fragmentTransaction.show(fragment);
}
fragmentTransaction.commit();
}
/*
* call this method when you want to show fragment which are on the list
* Example: We have current fragment C and you want to show fragment A, that to call showFragment("TAG_A")
* */
public void showFragment(String fragmentTag) {
FragmentTransaction fragmentTransaction = getSupportFragmentManager().beginTransaction();
/*hide others fragment besides the one we need to show*/
for (String fTag : fragments.keySet()) {
Fragment fragmentInStack = fragments.get(fTag);
if (!fTag.equals(fragmentTag) && fragmentInStack.isAdded()) {
fragmentTransaction.hide(fragmentInStack);
}
}
Fragment fragment = fragments.get(fragmentTag);
if (fragment != null && fragment.isAdded()) {
fragmentTransaction.show(fragment);
}
fragmentTransaction.commit();
}
}

FragmentTransaction hide/show doesn't work sometimes

I have an activity with bottom navigation tabs that are changing the fragments in it. When I click back and forth on those tabs, at some point it stops working. Code executes just fine as I put some logs in it. But the fragments aren't being switched.
Code is in kotlin but it's rather straight forward
fun showTabFragment(tag: String) {
val currentFragment: Fragment? = supportFragmentManager.fragments?.lastOrNull()
var fragment = supportFragmentManager.findFragmentByTag(tag)
val fragmentExists = fragment != null
if (fragment == null) {
when (tag) {
TAG_LOGBOOK -> fragment = LogbookFragment()
TAG_RECIPES -> fragment = RecipesFragment()
TAG_PROFILE -> fragment = ProfileFragment()
else -> fragment = MeetingPlacesFragment()
}
}
val transaction = supportFragmentManager.beginTransaction()
if (currentFragment != null) {
Log.i("jacek", "hiding " + currentFragment.javaClass.simpleName)
transaction.hide(currentFragment)
}
if (fragmentExists) {
Log.i("jacek", "showing " + fragment.javaClass.simpleName)
transaction.show(fragment)
} else {
Log.i("jacek", "adding " + fragment.javaClass.simpleName)
transaction.add(R.id.container, fragment, tag)
}
transaction.commit()
}
The fragments are quite heavy. I will try with some lightweight ones, but still that shouldn't be a problem in my opinion. Is there anything else I could try?
I'm using the latest support library - 25.2.0
Also I'm not interested in replacing the fragments as the point is to add crossfade animation without recreating them

You need to reuse the same instance of a fragment that you wanted to hide or show.
private fun replaceFragment(fragment: Fragment) {
supportFragmentManager.beginTransaction().apply {
if (fragment.isAdded) {
show(fragment)
} else {
add(R.id.fmFragmentContainer, fragment)
}
supportFragmentManager.fragments.forEach {
if (it != fragment && it.isAdded) {
hide(it)
}
}
}.commit()
}

#Ali's answer is good, yet imagine if you have 5 fragments. This is another way to show/hide your fragments:
// in BaseFragment
public abstract String getTAG();
//in FragmentA, FragmentB and FragmentC
public String getTAG(){
return TAG;
}
//Activity containing the fragments
//android.support.v4.app.Fragment;
private FragmentA fragmentA; //inherited BaseFragment
private FragmentB fragmentB; //inherited BaseFragment
private FragmentC fragmentC; //inherited BaseFragment
private ConcurrentHashMap<String,BaseFragment> mapOfAddedFragments = new ConcurrentHashMap<>();
/**
* Displays fragment A
*/
private void displayFragmentA() {
displayFragment(fragmentA)
}
/**
* Displays fragment B
*/
private void displayFragmentB() {
displayFragment(fragmentB)
}
/**
* Displays fragment C
*/
private void displayFragmentC() {
displayFragment(fragmentC)
}
/**
* Loads a fragment using show a fragment
* #param fragment
*/
private void displayFragment(BaseFragment fragment){
if(!mapOfAddedFragments.containsKey(fragment.getTAG()))
mapOfAddedFragments.put(fragment.getTAG(), fragment);
showFragment(fragment.getTAG(), R.id.containerBody);
}
/**
* Displays a fragment and hides all the other ones
* #param fragmentTag is the tag of the fragment we want to display
*/
private void showFragment(String fragmentTag, #IdRes int containerViewId){
FragmentTransaction ft = this.getSupportFragmentManager().beginTransaction();
BaseFragment fragment = null;
fragment = mapOfAddedFragments.get(fragmentTag);
if(fragment != null) {
if (fragment.isAdded())
ft.show(fragment);
else { //fragment needs to be added to the frame container
ft.add(containerViewId, fragment, fragment.getTAG());
}
}
else //the chosen fragment doesn't exist
return;
//we hide the other fragments
for (ConcurrentHashMap.Entry<String, BaseFragment> entry : mapOfAddedFragments.entrySet()){
if(!entry.getKey().equals(fragmentTag)){
BaseFragment fragmentTemp = entry.getValue();
// Hide the other fragments
if(fragmentTemp != null)
if(fragmentTemp.isAdded())
ft.hide(fragmentTemp);
}
}
//commit changes
ft.commit();
}
And to instantiate them you can do this in the onCreate() method of your activity:
//don't forget to get the .TAG elsewhere before using them here
//never call them directly
private void instantiateFragments(Bundle inState) {
if (inState != null) {
fragmentA = inState.containsKey(FragmentA.TAG) ?
(FragmentA) getSupportFragmentManager().getFragment(inState, FragmentA.TAG):
FragmentA.newInstance(FragmentA.TAG,"0");
fragmentB = inState.containsKey(FragmentB.TAG) ?
(FragmentB) getSupportFragmentManager().getFragment(inState, FragmentB.TAG):
FragmentB.newInstance(FragmentB.TAG,"1");
fragmentc = inState.containsKey(FragmentC.TAG) ?
(FragmentC) getSupportFragmentManager().getFragment(inState, FragmentC.TAG):
FragmentC.newInstance(FragmentC.TAG,"2");
}
else{
fragmentA = FragmentA.newInstance(FragmentA.TAG,"0");
fragmentB = FragmentB.newInstance(FragmentB.TAG,"1");
fragmentc = FragmentC.newInstance(FragmentC.TAG,"2");
}
}
Edit according to Shujaat Ali Khan's question:
The BaseFragment extends support4 fragment:
public abstract class BaseFragment extends Fragment {
public abstract String getTAG();
//whatever we can add to be inherited
}
FragmentA for example:
public class FragmentA extends BaseFragment {
// Store instance variables
private static final String ARG_PARAM1 = "param1";
private static final String ARG_PARAM2 = "param2";
private String mParam1;
private String mParam2;
public static final String TAG = "FragmentA";
// newInstance constructor for creating fragment with arguments
public static FragmentA newInstance(String param1, String param2) {
FragmentA fragment = new FragmentA();
Bundle args = new Bundle();
args.putString(ARG_PARAM1, param1);
args.putString(ARG_PARAM2, param2);
fragment.setArguments(args);
return fragment;
}
// Store instance variables based on arguments passed
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
if (getArguments() != null) {
mParam1 = getArguments().getString(ARG_PARAM1);
mParam2 = getArguments().getString(ARG_PARAM2);
}
}
// Inflate the view for the fragment based on layout XML
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragmentA, container, false);
return view;
}
//other lifecycle methods
#Override
public String getTAG() {
return TAG;
}
}
Finally the R.id.containerBody is the id of a FrameLayout containing the fragments in the activity containing these fragments.

The problem here is even though you're hiding "current" fragment, there are other fragments loaded in the memory and that gives inconsistent behaviour.
You should be able to fix this by hiding all the fragment except the fragment you want to show.
Thanks to this answer. Show hide fragment in android
eg:
private FragmentA fragmentA;
private FragmentB fragmentB;
private FragmentC fragmentC;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
fragmentA = FragmentA.newInstance();
fragmentB = FragmentB.newInstance();
fragmentC = FragmentC.newInstance();
}
protected void displayFragmentA() {
FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
if (fragmentA.isAdded()) {
ft.show(fragmentA);
} else {
ft.add(R.id.fragement_container, fragmentA);
}
if (fragmentB.isAdded()) { ft.hide(fragmentB); }
if (fragmentC.isAdded()) { ft.hide(fragmentC); }
ft.commit();
}
Similarly you will have to write functions for displayFragmentB() and displayFragmentC()

Fragments stack Android

Imagine one activity with 3 fragments: starts showing the first one, select a menu option and go to the second one, select another option and go to the 3rd fragment and select again the first option an return to the second one.
f1 -> f2 -> f3 -> f2
When I press back I want the app returns to fragment 3 and when I press back again it should return to fragment 1 and if press back again, close the app.
Something like if the fragment exists, move it to top of the stack and if not, create it.
Thank you!

Here is solution I came up over time.
The idea is following, you need to keep a stack data structure and whenever you add a fragment add it to stack as well, then override onBackPress method and check if stack is not empty then replace your fragment container with new fragment from top of the stack when it is empty do super.onbackpress
So here is a parent class for all kind of fragment based navigation.
public abstract class FragmentsStackActivity extends BaseActivity {
public static final String TAG_BUNDLE = "bundle_tag";
protected final Bundle fragmentArgs = new Bundle();
protected Stack<Fragment> fragments = new Stack<>();
abstract protected void setupFragments();
public void setFragmentArguments(Fragment fragment, Bundle arguments){
if(!fragments.isEmpty() && fragments.peek()!=fragment){
fragment.setArguments(arguments);
}
}
public void setFragmentFromStack() {
if(!fragments.isEmpty()) {
Fragment fragment = fragments.peek();
final Fragment oldFragment = getSupportFragmentManager().findFragmentById(R.id.fragment_container);
if (oldFragment == null || oldFragment != fragment) {
getFragmentManager().popBackStack(null, FragmentManager.POP_BACK_STACK_INCLUSIVE);
final FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
//transaction.setCustomAnimations(R.anim.animator_left_right_in, R.anim.animator_left_right_in);
transaction.replace(R.id.fragment_container, fragment).commit();
}
}else {
finish();
}
}
#Override
protected void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
//TODO need to save fragment stack
}
}
example of an activity that extends this class
public class LoginActivity extends FragmentsStackActivity{
private final MyFragment1 fragment1 = new MyFragment1();
private final MyFragment2 fragment2 = new MyFragment2();
private final User mUser = new User();
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_login);
setupFragments();
setFragmentFromStack();
}
#Override
protected void setupFragments() {
fragments.add(fragment2);
//fragment2.setNotifier(this); // I use notifiers listener but you can choose whatever convenient for you
Bundle fragmentArgs = new Bundle();
fragmentArgs.putBoolean(Constants.TAG_LOGIN, true);
fragmentArgs.putParcelable(User.TAG, mUser);
fragmentArgs.putInt(Constants.TYPE, getIntent().getIntExtra(Constants.TYPE, 0));
fragment2.setArguments(fragmentArgs);
//fragment1.setNotifier(this); // I use notifiers listener but you can choose whatever convenient for you
}
// this method teals with handling messages from fragments in order to provide navigation
// when some actions taken inside the fragment, you can implement your own version
public void onReceiveMessage(String tag, Bundle bundle) {
switch (tag) {
case MyFragment2.TAG_BACK:
case MyFragment1.TAG_BACK:
fragments.pop();
setFragmentFromStack();
break;
case MyFragment2.TAG_NEXT:
fragment1.setArguments(bundle);
fragments.add(fragment1);
setFragmentFromStack();
break;
case MyFragment1.TAG_NEXT:
goToWelcomeScreen(bundle);
finish();
break;
}
}
private void goToWelcomeScreen(Bundle bundle){
}
}

You can implement this with the help of the following code:
// transaction.replace(R.id.detailFragment, frag1);
Transaction.remove(null).add(frag1) // frag1 on view
// transaction.replace(R.id.detailFragment, frag2).addToBackStack(null);
Transaction.remove(frag1).add(frag2).addToBackStack(null) // frag2 on view
// transaction.replace(R.id.detailFragment, frag3);
Transaction.remove(frag2).add(frag3) // frag3 on view
And for better understanding, have a ook at the following snippet:
// Works with either the framework FragmentManager or the
// support package FragmentManager (getSupportFragmentManager).
getSupportFragmentManager().beginTransaction()
.add(detailFragment, "detail")
// Add this transaction to the back stack
.addToBackStack()
.commit();
getSupportFragmentManager().addOnBackStackChangedListener(
new FragmentManager.OnBackStackChangedListener() {
public void onBackStackChanged() {
// Update your UI here.
}
});
have a look here http://developer.android.com/training/implementing-navigation/temporal.html

Add and remove fragment null pointer

I have two fragments that are in the main activity and i want to refresh them when something occurs.
Now the code works for second fragment, but won't work for the first, and i am not sure why.
I have been looking at the code for about an hour, and i can't seem to find a reason.
Here is the code
public class MainActivity extends FragmentActivity {
Fragment frag,frag2;
FragmentManager fm;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
String screen = getString(R.string.screen_type);
/*
* Get a reference to fragment manager
* Wire the container to represent fragment
*/
fm = getSupportFragmentManager();
frag = fm.findFragmentById(R.id.container);
if(screen.equals("large")){
frag2 = fm.findFragmentById(R.id.containerDetails);
loadFragments(frag,frag2,fm);
}
/*Loads the fragment into the activity*/
else
loadFragment(frag,fm);
}
private void loadFragments(Fragment frag, Fragment frag2, FragmentManager fm) {
if(frag == null && frag2 == null){
frag = new DisplayFragment();
frag2 = new DetailsFragment();
fm.beginTransaction().add(R.id.container,frag).add(R.id.containerDetails, frag2).commit();
}
}
private void loadFragment(Fragment frag, FragmentManager fm) {
if(frag == null){
frag = new DisplayFragment();
fm.beginTransaction().add(R.id.container,frag).commit();
}
}
public void updateDetails(int position) {
// Reload current fragment
if(frag2!=null)fm.beginTransaction().remove(frag2).commit();
frag2 = new DetailsFragment();
Bundle b = new Bundle();
b.putInt("Id",position);
frag2.setArguments(b);
fm.beginTransaction().add(R.id.containerDetails, frag2).commit();
}
public void updateDisplay() {
// Reload current fragment
if(frag!=null)fm.beginTransaction().remove(frag).commit(); //THIS IS ALWAYS NULL FOR SOME REASON
frag = new DisplayFragment();
fm.beginTransaction().add(R.id.container, frag).commit();
}
public void refreshDetails() {
// Reload current fragment
if(frag2!=null)fm.beginTransaction().remove(frag2).commit();
frag2 = new DetailsFragment();
fm.beginTransaction().add(R.id.containerDetails, frag2).commit();
}
}
The first fragment is always null, and it doesn't get removed, instead another fragment is pasted over that, and creates a mess.

Try using replace() method rather than add()

android fragment state restored only on back button , not when i select a fragment randomly from listview

Hi i have a listview sidebar and i am displaying fragments based on user selection in listview.
This is how i am replacing fragments
public void switchFragment(Fragment fragment, boolean addBackStack) {
try {
FragmentManager manager = getSupportFragmentManager();
FragmentTransaction ft = manager.beginTransaction();
ft.replace(R.id.content, fragment);
currentFragment = fragment;
//if (addBackStack)
ft.addToBackStack(null);
ft.commit();
} catch (Exception e) {
}
}
This is my sample fragment code.Now when i replace fragments i am saving instance state in onpause and restoring it in onresume but it only works when i press back button. When i manually navigate back to fragment from listview ,fragment state is not restored.Why?
public class Fragment1 extends BaseFragment {
int currentFragmentInd = 1;
private Button startButton;
private Button endButton;
private long savedStartTime;
private TextView setStartText;
private TextView setEndText;
private String starttime;
private String endtime;
public int getIndex() {
MyApplication.getApplication().setCurrentChild(0);
MyApplication.getApplication().setCurrentGroup(0);
return currentFragmentInd;
}
#Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
if (savedInstanceState !=null)
{
}
}
#Override
public void onResume() {
super.onResume();
setStartText= (TextView)getActivity().findViewById(R.id.MAtextView2);
setEndText= (TextView)getActivity().findViewById(R.id.MAtextView3);
setEndText.setText(endtime);
setStartText.setText(starttime);
}
#Override
public void onPause() {
super.onPause();
setStartText= (TextView)getActivity().findViewById(R.id.MAtextView2);
setEndText= (TextView)getActivity().findViewById(R.id.MAtextView3);
starttime=setStartText.getText().toString();
endtime=setEndText.getText().toString();
}
#Override
public void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
}
FrameLayout frameLayout;
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View contentView = inflater.inflate(R.layout.layout1, null, false);
((MainActivity) getActivity()).openList(0, 0);
if (savedInstanceState == null) {
}
startButton= (Button) contentView.findViewById(R.id.button);
endButton= (Button) contentView.findViewById(R.id.button2);
endButton.setEnabled(false);
setStartText= (TextView)contentView.findViewById(R.id.MAtextView2);
setEndText= (TextView)contentView.findViewById(R.id.MAtextView3);
startButton.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
Time now = new Time();
now.setToNow();
}
});
endButton.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
Time now = new Time();
now.setToNow();
setEndText.setText(now.hour+" : "+now.minute);
}
});
return contentView;
}
}

Late replay but might help somebody else.
This happens because when you click a listview item you create a new inctance of that fragment.
"I assume the fragment you send to switchFragment(Fragment fragment), is created using a 'new' keyword."
Therefore this new instance of a fragment doesnt hold your old data.
This is how I solved this. There are probably better ways, but since nobody replied, I will give my solution.
When you replace the fragment (ft.replace, fragment), give a string reference to that transaction: -ft.replace(R.id.content, fragment, "FRAGMENT_NAME");
When you add the fragment to the backstack with addToBackStack(null); put the name of your fragment where you have null.: -ft.addToBackStack("FRAGMENT_NAME");
Create a method which tells you if that fragment has already been created, and therefore exists in the back stack.:
public boolean isTagInBackStack(String tag){
Log.i(TAG, "isTagInBackStack() Start");
int x;
boolean toReturn = false;
int backStackCount = getSupportFragmentManager().getBackStackEntryCount();
Log.i(TAG, "backStackCount = " + backStackCount);
for (x = 0; x < backStackCount; x++){
Log.i(TAG, "Iter = " + x +" "+ getSupportFragmentManager().getBackStackEntryAt(x).getName());
if (tag == getSupportFragmentManager().getBackStackEntryAt(x).getName()){
toReturn = true;
}
}
Log.i(TAG, "isTagInBackStack() End, toReturn = " + toReturn);
return toReturn;
}
Now before you create a new instance of that fragment check in the backstack if a backstack item named "FRAGMENT_NAME" exists.
if it exists, use that item (fragment) instead of creating a new one.
if (isTagInBackStack("FRAGMENT_NAME")){
Log.i(TAG, "Tag is in BackStack!!!! frag is = " + getSupportFragmentManager().findFragmentByTag("FRAGMENT_NAME"));
FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
transaction.replace(R.id.main_activity_container, getSupportFragmentManager().findFragmentByTag("FRAGMENT_NAME"));
transaction.addToBackStack("FRAGMENT_NAME");
transaction.commit();
}else{
Create the fragment (this happens the first time.
}