Develop Reference

Why does pressing back from detail activity after landscape-to-portrait-switch show an empty screen?

Below is the MainActivity class that I'm using. The code checks to see if the phone is in landscape or portrait. If it's in portrait, it will show the main fragment in the main activity only (the main fragment is a static fragment in the main_activity.xml file). Then if a "Recipe" is clicked it will open a detail activity with its own fragment. If the phone is in landscape mode, it will show the main fragment and the detail fragment side by side. Everything works perfectly fine however when I follow the procedure below I get a white screen instead of the main activity:
Procedure:
Switch to landscape
Switch back to portrait
Choose an item and wait for the detail activity to open
Press back
Here instead of the main activity window I get a white screen
If I don't switch to landscape and just start with the portrait mode everything is fine. It seems like switching to landscape does something that causes the problem and I can't figure out what. Any tip on what's going on or where to look would be much appreciated.
public class MainActivity extends AppCompatActivity implements RecipesFragment.OnRecipeClickListener {
private String RECIPE_PARCEL_KEY;
private boolean mTwoPane;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
RECIPE_PARCEL_KEY = getString(R.string.ParcelKey_RecipeParcel);
if (findViewById(R.id.linearLayoutTwoPane) != null) {
mTwoPane = true;
if (savedInstanceState == null) {
RecipeFragment recipeFragment = new RecipeFragment();
FragmentManager fragmentManager = getSupportFragmentManager();
fragmentManager.beginTransaction()
.add(R.id.recipeFrameForTwoPane, recipeFragment)
.commit();
}
} else {
mTwoPane = false;
}
}
#Override
public void OnRecipeClick(Recipe recipe) {
if (mTwoPane) {
RecipeFragment recipeFragment = new RecipeFragment();
recipeFragment.setRecipe(recipe);
FragmentManager fragmentManager = getSupportFragmentManager();
fragmentManager.beginTransaction()
.replace(R.id.recipeFrameForTwoPane, recipeFragment)
.commit();
} else {
Class destinationClass = DetailActivity.class;
Intent intentToStartDetailActivity = new Intent(this, destinationClass);
intentToStartDetailActivity.putExtra(RECIPE_PARCEL_KEY, recipe);
startActivity(intentToStartDetailActivity);
}
}
}
EDIT:
Adding RecipeFragment's code below:
public class RecipeFragment extends Fragment {
private Recipe mRecipe;
#BindView(R.id.tv_recipeName) TextView recipeNameTextView;
public RecipeFragment(){
}
#Nullable
#Override
public View onCreateView(LayoutInflater inflater, #Nullable ViewGroup container, #Nullable Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.recipe_fragment,container,false);
ButterKnife.bind(this,view);
if(mRecipe!=null) {
recipeNameTextView.setText(mRecipe.getName());
}else{
recipeNameTextView.setText(getString(R.string.messageSelectARecipe));
}
return view;
}
public void setRecipe(Recipe recipe){
mRecipe = recipe;
}
}
EDIT:
I followed #mt0s's advice and created different background colors for the fragments and activities and finally narrowed down the problem to a line in my recyclerview adapter code. My adapter code is below. Inside loadInBackground() on line URL url = new URL(getString(R.string.URL_RecipeJSON)); I get a Fragment RecipesFragment{96e9b6a} not attached to Activity exception. I don't understand why I'm getting this exception and what the best way to resolve this is. Have I placed the right code in the right fragment methods (ie OnCreate vs OnActivityCreated vs OnCreateView vs etc)?
public class RecipesFragment extends Fragment
implements RecipeAdapter.RecipeAdapterOnClickHandler,
LoaderManager.LoaderCallbacks<ArrayList<Recipe>> {
#BindView(R.id.rv_recipes) RecyclerView mRecyclerView;
private RecipeAdapter mRecipeAdapter;
private static final int LOADER_ID = 1000;
private static final String TAG = "RecipesFragment";
private OnRecipeClickListener mOnRecipeClickListener;
public RecipesFragment(){
}
public interface OnRecipeClickListener {
void OnRecipeClick(Recipe recipe);
}
#Nullable
#Override
public View onCreateView(LayoutInflater inflater, #Nullable ViewGroup container, Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.recipes_fragment, container, false);
ButterKnife.bind(this, view);
LinearLayoutManager layoutManager = new LinearLayoutManager(getActivity(), LinearLayoutManager.VERTICAL, false);
mRecyclerView.setLayoutManager(layoutManager);
mRecyclerView.setHasFixedSize(true);
mRecipeAdapter = new RecipeAdapter(this);
mRecyclerView.setAdapter(mRecipeAdapter);
return view;
}
#Override
public void onActivityCreated(#Nullable Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
}
#Override
public void onCreate(#Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
getLoaderManager().initLoader(LOADER_ID, null, this);
}
#Override
public void onPause() {
super.onPause();
}
#Override
public void onResume() {
super.onResume();
}
#Override
public void OnClick(Recipe recipe) {
mOnRecipeClickListener.OnRecipeClick(recipe);
}
#Override
public void onAttach(Context context) {
super.onAttach(context);
try{
mOnRecipeClickListener = (OnRecipeClickListener) context;
} catch (ClassCastException e){
Log.e(TAG, "onAttach: Host activity class must implement OnRecipeClickListener.");
}
}
#Override
public Loader<ArrayList<Recipe>> onCreateLoader(int i, Bundle bundle) {
return new AsyncTaskLoader<ArrayList<Recipe>>(getActivity()) {
#Override
protected void onStartLoading() {
super.onStartLoading();
forceLoad();
}
#Override
public ArrayList<Recipe> loadInBackground() {
String response;
ArrayList<Recipe> recipes = null;
try {
URL url = new URL(getString(R.string.URL_RecipeJSON)); //***I get an exception here***
response = NetworkUtils.getResponseFromHttpUrl(url, getActivity());
recipes = RecipeJsonUtils.getRecipeFromJson(getActivity(), response);
} catch (Exception e) {
Log.e(TAG, "loadInBackground: " + e.getMessage());
}
return recipes;
}
};
}
#Override
public void onLoadFinished(Loader<ArrayList<Recipe>> loader, ArrayList<Recipe> recipes) {
mRecipeAdapter.setRecipeData(recipes);
}
#Override
public void onLoaderReset(Loader<ArrayList<Recipe>> loader) {
}
}

I finally figured out the problem and the solution. The problem is that onStartLoading() in the AsyncTaskLoader anonymous class in RecipesFragment class gets called every time the fragment is resumed whether the enclosing Loader is called or not. This causes the problem. I need to have control over when onStartLoading() is being called and I only want it to be called if and only if the enclosing Loader is being initialized or restarted. As such, I destroyed the loader in onPause() of the fragment and restarted it in onResume(). Hence, I added the following code to the RecipesFragment class:
#Override
public void onPause() {
super.onPause();
getLoaderManager().destroyLoader(LOADER_ID);
}
#Override
public void onResume() {
super.onResume();
getLoaderManager().restartLoader(LOADER_ID, null, this);
}
I also removed initLoader() from onCreate(). This way, every time the fragment is resumed (or created) onStartLoading() will be called. I tried this and it solves my problem.

When you switch from the landscape to portrait or the opposite the Android OS destroy your activity and recreate it again. this what probably trigger your problem

"Already executed" error (Retrofit2 and Android)

First of all, I have 2 fragments and they show different json values(2 links). If I change fragment(.replace()), that fragment get values with retrofit and show it. It works well but other fragment is deleted with values. After change fragment, it downloads again so I change structure. I want to take 2 json objects once so I get json objects in mainactivity and fragments get these with methods. They work well in first opening but if i open a fragment second time, it gives this error. How can I solve it?
java.lang.IllegalStateException: Already executed.
at retrofit2.OkHttpCall.enqueue(OkHttpCall.java:84)
Code is very long, i will show main structure.
MainActivity.java
public class MainActivity extends AppCompatActivity
{
private Call<Restaurant[]> restaurantCall;
private Call<Dining[]> diningCall;
#Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
//Restaurant Json value
RestaurantInterface restaurantInterface = RetroClient.getClient().create(RestaurantInterface.class);
restaurantCall = restaurantInterface.getJsonValues();
//Dininghall Json value
DiningInterface diningInterface = RetroClient.getClient().create(DiningInterface.class);
diningCall = diningInterface.getJsonValues();
}
public Call<Restaurant[]> RestaurantJson()
{
return this.restaurantCall;
}
public Call<Dining[]> DiningJson()
{
return this.diningCall;
}
}
RestaurantFragment.java (Other fragment has same structure)
public class RestFragment extends Fragment
{
#Nullable
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
{
View view = inflater.inflate(R.layout.fragment_rest, container, false);
Call<Restaurant[]> call = ((MainActivity) getActivity()).RestaurantJson();
call.enqueue(new Callback<Restaurant[]>()
{
.
.

Summing up, in order to avoid the "Already executed" exception, clone the call:
public Call<Restaurant[]> RestaurantJson()
{
return this.restaurantCall.clone();
}
public Call<Dining[]> DiningJson()
{
return this.diningCall.clone();
}
If you want to execute the call in the activity and not in the fragment as you are actually doing, then you need to call enqueue(new Callbak(... in your activity.
So you need something like this:
public class RestFragment extends Fragment {
#Nullable
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment_rest, container, false);
((MainActivity) getActivity()).RestaurantJson(this);
}
public void onResponse(Response<T> response) {
//your fragment code on response
}
...
}
public class MainActivity extends AppCompatActivity {
public void RestaurantJson(final RestFragment fragment)
{
RestaurantInterface restaurantInterface = RetroClient.getClient().create(RestaurantInterface.class);
restaurantCall = restaurantInterface.getJsonValues();
restaurantCall.enqueue(new Callback<Restaurant[]>() {
#Override
public void onResponse(Call<T> call, Response<T> response) {
...
fragment.onResponse(response);
}
}
...
}
The same for your DiningFragment and your dining call...

cannot restore view pager fragment state

i have a view pager with 3 fragments. i use retrofit rest api to populate each of my fragments for the first time. What i would like to achieve is when the user swipes back either in first or third fragment(those 2 fragment are being being destroyed by the view pager) to restore the data(saved in an array list) and not make a rest api call again. What i have done is to save the array list of downloaded data in onSaveInstanceState() and successfully retrieve it when the user swipes back to one of the 2 above fragments only FOR THE 1 FIRST TIME. The problem is when i navigate back to either one of the 2 fragments the specific bundle key where the array list was saved contains null value.
CompletedSurveysFragment(the third fragment):
public class CompletedSurveysFragment extends Fragment implements SAMVCView {
private static final String debugTag = CompletedSurveysFragment.class.getSimpleName();
private View view;
private RecyclerView completedSurveysRcV;
private SAMVCPresenterImpl SAMVCpresenterImpl;
private SurveysRcvAdapter surveysRcvAdapter;
private List<SurveyData> data;
public CompletedSurveysFragment() {}
public static CompletedSurveysFragment newInstance() {
return new CompletedSurveysFragment();
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
Log.e(debugTag, "onCreateView");
if ( view == null ) view = inflater.inflate(R.layout.fragment_completedsurveys, container, false);
completedSurveysRcV = (RecyclerView) view.findViewById(R.id.completedSurveysRcV);
return view;
}
// TODO: 21/6/2016 configure Limit and offset values
#Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
Log.e(debugTag, "onActivityCreated " + savedInstanceState);
LinearLayoutManager linearLayoutManager = new LinearLayoutManager(getActivity());
completedSurveysRcV.setHasFixedSize(true);
completedSurveysRcV.setLayoutManager(linearLayoutManager);
completedSurveysRcV.addItemDecoration(new DividerItemDecoration(ContextCompat.getDrawable(getActivity(), R.drawable.divider)));
if (savedInstanceState == null) {
SAMVCpresenterImpl = new SAMVCPresenterImpl(this);
SAMVCpresenterImpl.getSurveysBasedOnSpecificFirmId(new AllSurveysBody(getResources().getString(R.string.list_surveys), LoginActivity.getSessionPrefs(getActivity()).getInt(getResources().getString(R.string.firm_id), 0), getResources().getString(R.string.completed), 8, 0));
surveysRcvAdapter = new SurveysRcvAdapter(null, completedSurveysRcV);
completedSurveysRcV.setAdapter(surveysRcvAdapter);
} else {
//Log.e(debugTag, savedInstanceState.+"");
if (savedInstanceState.getParcelableArrayList("data") != null) {
Log.e(debugTag, "here "+ savedInstanceState);
surveysRcvAdapter = new SurveysRcvAdapter(savedInstanceState.<SurveyData>getParcelableArrayList("data"), completedSurveysRcV);
completedSurveysRcV.setAdapter(surveysRcvAdapter);
surveysRcvAdapter.notifyDataSetChanged();
}
//Log.e(debugTag, getArguments().getParcelableArrayList("data")+"");
}
}
#Override
public void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
outState.putParcelableArrayList("data", (ArrayList<? extends Parcelable>) this.data);
Log.e(debugTag, "CompletedFragment onSaveInstanceState "+ outState);
}
#Override
public void onSuccessSurveysFetched(List<SurveyData> data) {
this.data = data;
surveysRcvAdapter = new SurveysRcvAdapter(data, completedSurveysRcV);
completedSurveysRcV.setAdapter(surveysRcvAdapter);
surveysRcvAdapter.notifyDataSetChanged();
}
#Override
public void onFailure() {
}
}
View pager adapter:
public class SurveysPagerAdapter extends FragmentStatePagerAdapter {
private static final String debugTag = SurveysPagerAdapter.class.getSimpleName();
private List<SurveyData> data;
String[] tabText;
public SurveysPagerAdapter(FragmentManager fragmentManager, String[] tabText) {
super(fragmentManager);
this.tabText = tabText;
}
#Override
public Fragment getItem(int position) {
Log.e("SurveysPagerAdapter", position+"");
switch (position) {
case 0:
return CompletedSurveysFragment.newInstance();
case 1:
return OngoingSurveysFragment.newInstance();
case 2:
return PendingSurveysFragment.newInstance();
default:
return null;
}
}
#Override
public CharSequence getPageTitle(int position) {
return tabText[position];
}
#Override
public int getCount() {
return 3;
}
}

Your issue is that you're always returning a new instance of your fragment. Instead of calling CompletedSurveysFragment.newInstance(); (and your other Fragments) every time user swipes, create an array of fragments and retrieve it this way:
...
Fragment [] pages = new Fragment[getCount()];
...
#Override
public Fragment getItem(int position) {
Log.e("SurveysPagerAdapter", position+"");
switch (position) {
case 0:
if(pages[position] == null)
pages[position] = CompletedSurveysFragment.newInstance();
return pages[position];
...
}
Then, you can fetch and cache your data in onCreate() and retrieve it later in onResume() in your respective fragments.

I think onPause() and onResume() won't work. Fragments are tied to their parent activity so since you browse through fragments parent activity is on an onResume() status. What I suggest you to do is to use singleton objects to fetch and store your data. Each fragment can keep a reference to the respective object and have instant access to the data you need. There is plenty of info about singleton pattern and how it works.

The reason this is happening is because onSaveInstanceState only occurs when the parent activity is closed. Since the parent activity of your viewpager is still active when you switch between your fragments, onSaveInstanceState will not be called.
To get the data to save like you are intending, what I would likely do instead is save the data in onPause() and retrieve the data in onResume().
EDIT
According to the docs you need to put the call to super.onSaveInstanceState(savedInstanceState); after you modify the Bundle.
#Override
public void onSaveInstanceState(Bundle savedInstanceState) {
// Save the user's current game state
savedInstanceState.putInt(STATE_SCORE, mCurrentScore);
savedInstanceState.putInt(STATE_LEVEL, mCurrentLevel);
// Always call the superclass so it can save the view hierarchy state
super.onSaveInstanceState(savedInstanceState);
}

Parcelable from activity to fragment

I am new to parcelable and I am trying to pass data from an Activity (MainActivity) to a fragment (MainFragment) but I`m struggle to get this right.
I made a class (InfoBean) with all the (parcelable) data. When I send the data from the MainActivity, the data from bean.newTheme (2131296447) is there but as soon as I try to retrieve in the Fragment, the value is 0!
Could someone pls have a look, what I`m doing wrong? Thank you for your help.
Send data (MainActivity):
public class MainActivity extends AppCompatActivity implements NavigationView.OnNavigationItemSelectedListener {
InfoBean bean = new InfoBean();
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
SecureSharedPreferences theme = SecureSharedPreferences.getInstance(this, "MyPrefsFile");
int newTheme = theme.getInt("themeCustom", 0);
bean.newTheme = newTheme;
Bundle bundle = new Bundle();
bundle.putInt("theme", bean.newTheme); // debug shows value 2131296447
MainFragment mf = new MainFragment();
mf.setArguments(bundle);
//
}
}
Retrieve data (MainFragment):
public class MainFragment extends Fragment {
InfoBean bean = new InfoBean();
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
//
Bundle bundle = this.getArguments(); // Debugging shows 0!
if (bundle != null) {
bean.newTheme = bundle.getInt("theme");
}
if (bean.newTheme == 2131296447) { // White Theme
mCardView1.setBackgroundColor(Color.parseColor("#E8EBED"));
} else { // Dark Theme
mCardView1.setBackgroundColor(Color.parseColor("#282929"));
relLay.setBackgroundColor(Color.parseColor("#1B1C1C"));
}
return rootView;
}
}
InfoBean.class:
public class InfoBean implements Parcelable {
public int newTheme;
public int THEME_DARK = R.style.DarkTheme;
public int THEME_LIGHT = R.style.LightTheme;
#Override
public int describeContents() {
return 0;
}
#Override
public void writeToParcel(Parcel dest, int flags) {
dest.writeInt(this.newTheme);
dest.writeInt(this.THEME_DARK);
dest.writeInt(this.THEME_LIGHT);
}
public InfoBean() {
}
protected InfoBean(Parcel in) {
this.newTheme = in.readInt();
this.THEME_DARK = in.readInt();
this.THEME_LIGHT = in.readInt();
}
public static final Parcelable.Creator<InfoBean> CREATOR = new Parcelable.Creator<InfoBean>() {
#Override
public InfoBean createFromParcel(Parcel source) {
return new InfoBean(source);
}
#Override
public InfoBean[] newArray(int size) {
return new InfoBean[size];
}
};
}

If you have embedded fragment in your XML you can't use the setArguments() like that in your program. It is better to use dynamic fragment creation.
There is a brief example in android developer website which can guide you: http://developer.android.com/reference/android/app/Fragment.html there is also another implementation when you have embedded fragments and how to process arguments with that.
There is also another resource here which may help you:
Set arguments of fragment from activity

In your activity, you are using .putInt("theme" .....) but in the fragment you call .getParcelable("theme"). You're getting 0 because you're attempting to get two different data types.

Update
Since you have your fragment embedded in xml, you can't pass values to fragment class. To that you need to make it excute through java code and remove that xml. Make fragment Transaction then it will work
Update
You should try retrieving values in onCreate method of fragment.
#overide
protect void onCreate(bundle onSavedInstance){
if (savedInstance != null) {
bean.newTheme = bundle.getInt("theme");
}
}
Try this
if (bundle != null) {
bean.newTheme = bundle.getInt("theme");
}
instead of
if (bundle != null) {
bean.newTheme = bundle.getParcelable("theme");
}

Restore savedInstanceState before Fragments onCreate method

I made a test application so I can learn how to save the InstanceState.
Now we have a Main Fragment Activity and two Tab Fragments. I have a variable in the Main Activity that it's value sat in the onCreate method.. and I would like to share it with the fragments.
So I created a public method in the Main Activity to call it inside the fragments when I need the value of that variable. ((TMainActivity) getActivity()).getTestString()
The problem is when the device is rotated I got the default value of the string and not the saved value.
And that's obviously because onRestoreInstanceState is called after the onCreate of the fragments.
Now, how can I work that out?
TMainActivity.java
public class TMainActivity extends FragmentActivity {
final private static String TAG = "TMainActivity";
final private static String EXTRA_TEST = "MAIN_KEY";
private CollectionPagerAdapter mCollectionPagerAdapter;
private ViewPager mainPager;
private String test = "Default";
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Log.v(TAG, "onCreate() Before test= " + test);
if (savedInstanceState == null) {
test = "New";
} else {
test = savedInstanceState.getString(EXTRA_TEST) + " - Restored";
}
Log.v(TAG, "onCreate() After test= " + test);
mainPager = (ViewPager) findViewById(R.id.main_pager);
mCollectionPagerAdapter = new CollectionPagerAdapter(getSupportFragmentManager());
mainPager.setAdapter(mCollectionPagerAdapter);
}
#Override
protected void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
Log.v(TAG, "onSaveInstanceState()");
outState.putString(EXTRA_TEST, test);
}
#Override
protected void onRestoreInstanceState(Bundle savedInstanceState) {
super.onRestoreInstanceState(savedInstanceState);
Log.v(TAG, "onRestoreInstanceState()");
Log.v(TAG, "onRestoreInstanceState() savedInstanceState=" + (savedInstanceState != null));
test = savedInstanceState.getString(EXTRA_TEST);
}
public String getTestString() {
return test;
}
private class CollectionPagerAdapter extends FragmentStatePagerAdapter {
public CollectionPagerAdapter(FragmentManager fm) {
super(fm);
}
#Override
public Fragment getItem(int i) {
Fragment fragment = null;
switch (i) {
case 0:
fragment = new Tab1Fragment();
break;
case 1:
fragment = new Tab2Fragment();
break;
}
return fragment;
}
#Override
public int getCount() {
return 2;
}
#Override
public CharSequence getPageTitle(int position) {
return "OBJECT " + (position + 1);
}
}
}
Tab1Fragment.java
public class Tab1Fragment extends Fragment {
final private static String TAG = "Tab1Fragment";
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
Log.v(TAG, "onCreate()");
Log.v(TAG, "getTestString()=" + ((TMainActivity) getActivity()).getTestString());
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_main_tab1, container, false);
return rootView;
}
}
Tab2Fragment.java
public class Tab2Fragment extends Fragment {
final private static String TAG = "Tab2Fragment";
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
Log.v(TAG, "onCreate()");
Log.v(TAG, "getTestString()=" + ((TMainActivity) getActivity()).getTestString());
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_main_tab2, container, false);
return rootView;
}
}

I just had the same problem. First is called onCreate in the Activity and in this method you have already available that Bundle with your data. That means that you can restore the Activity and then use the data in onCreateView of the Fragment which is called later.
Basically you do not override the onRestoreInstanceState() method, but rename it and call it from onCreate in your Activity. The reason not to override that method is because it would be called 2 times—from onCreate by you and then as a part of the Activity life-cycle. That would reset the value if it was changed in the Fragment.
In your case you can just move
Log.v(TAG, "getTestString()=" + ((TMainActivity) getActivity()).getTestString());
from onCreate to onCreateView.
This not a good solution when you're restoring large amount of data. Your UI thread would get stuck on restoring the Activity. But in such a case you can restore just some part of the data that is needed in the Fragment and the rest restore in onRestoreInstanceState.