Android Fragments (with WebView) - Activity gets Destroyed

Android Fragments (with WebView) - Activity gets Destroyed - android

I am using a Tab based Activity in my App and I want to implement a Fragment Stack with WebViews. In these WebViews I want to catch URL requests and replace the current WebView Fragment with a new one. Unfortunately I always get Activity was destroyed Exception but don't know why.
Can you please give me some hints how to fix this?
I use the following code (At the end of the code sample you will recognise the method handleUrlRequest where I want to replace the current Fragment):
public class FragmentStackSupport extends SherlockFragmentActivity {
int mStackLevel = 1;
public static int THEME = R.style.Theme_Sherlock_Light;
#Override
protected void onCreate(Bundle savedInstanceState) {
setTheme(THEME); //Used for theme switching in samples
super.onCreate(savedInstanceState);
setContentView(R.layout.fragment_stack);
if (savedInstanceState == null) {
// Do first time initialization -- add initial fragment.
Fragment newFragment = Web.newInstance(mStackLevel);
FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
ft.add(R.id.simple_fragment, newFragment).commit();
} else {
mStackLevel = savedInstanceState.getInt("level");
}
}
#Override
public void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
outState.putInt("level", mStackLevel);
}
public void addFragmentToStack() {
mStackLevel++;
// Instantiate a new fragment.
Fragment newFragment = Web.newInstance(mStackLevel);
// Add the fragment to the activity, pushing this transaction
// on to the back stack.
FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
ft.replace(R.id.simple_fragment, newFragment);
ft.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_OPEN);
ft.addToBackStack(null);
ft.commit();
}
public static class Web extends SherlockFragment {
int mNum;
/**
* Create a new instance of CountingFragment, providing "num"
* as an argument.
*/
static Web newInstance(int num) {
Web f = new Web();
// Supply num input as an argument.
Bundle args = new Bundle();
args.putInt("num", num);
f.setArguments(args);
return f;
}
/**
* When creating, retrieve this instance's number from its arguments.
*/
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
mNum = getArguments() != null ? getArguments().getInt("num") : 1;
}
/**
* The Fragment's UI is just a simple text view showing its
* instance number.
*/
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View v = inflater.inflate(R.layout.hello_world, container, false);
View wv = v.findViewById(R.id.webview);
WebView webView = ((WebView)wv);
webView.loadUrl("http://www.google.at");
webView.setWebViewClient(new MyWebViewClient());
return v;
}
}
public static class MyWebViewClient extends WebViewClient {
#Override
public boolean shouldOverrideUrlLoading(WebView view, String urlString) {
handleURLRequest("modal");
return false;
}
private void handleURLRequest(String transitionStyle){
// here I want to replace the Fragment with a new one.
}
}
}

Finally I got it. I passed the instance of Web through my WebViewClient where I handle the URL Request and want to do the Fragment Transaction.
There I call instanceOfWeb.getActivity().getSupportFragmentManager().beginTransaction() to init the Fragment Transaction.

Related

How to move from an activity to a fragment in Android?

May you assist by telling me the best way to moves from an activity to a fragment. This is what I have so far but it doesnt seem to work.
This is how I am calling the function(getCategory)
private void selectItem( int group, int usage)
{
if (!shown) return;
classificationGroup = group;
((DashboardActivity)getActivity()).getCallCategory(classificationGroup);
}
And in the activity I am trying to move to a fragment
public Fragment getCallCategory(int position) {
return new CallLogsFragment();
}

The standard pattern for creating fragments looks like this:
Inside your fragment class (make sure to import the android.support.v4.app.Fragment):
public class MyFragment extends Fragment {
public static final String TAG = "MyFragment";
private int position;
// You can add other parameters here
public static MyFragment newInstance(int position) {
Bundle args = new Bundle();
// Pass all the parameters to your bundle
args.putInt("pos", position);
MyFragment fragment = new MyFragment();
fragment.setArguments(args);
return fragment;
}
#Override
public void onCreate(#Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
this.position = getArguments().getInt("pos");
}
}
Inside your activity:
public class MainActivity extends AppCompatActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// Add your parameters
MyFragment fragment = MyFragment.newInstance(10);
// R.id.container - the id of a view that will hold your fragment; usually a FrameLayout
getSupportFragmentManager().beginTransaction()
.add(R.id.container, fragment, MyFragment.TAG)
.commit();
}
}
When you want to access public methods of your fragment instance, use FragmentManager#findFragmentByTag(String tag) to find your instance of fragment:
MyFragment fragment = (MyFragment) getSupportFragmentManager().findFragmentByTag(MyFragment.TAG);
if(fragment != null){
// Do something with fragment
}
For a more detailed explanation, I suggest you read the official docs on fragments: https://developer.android.com/guide/components/fragments.html

Maintaining fragments instance state between transactions

From all the searches I have found on SO stating that you should save your instance state in the #Override public void onSaveInstanceState(Bundle outState)
However This is tightly coupled with the activities lifestyle.
How can I save the state of my listview in a fragment that gets swapped out with another fragment.
I have one main activity which all the fragments are loaded into.
I have tried this so far:
#Override
public void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
//Save adapter data so that when the fragment is returned to it can be resused.
ArrayList<CategoryMobileDto> categories = new ArrayList<CategoryMobileDto>();
for(int i=0; i < adapter.getCount();i++)
{
categories.add(adapter.getItem(i));
}
String persistData = new Gson().toJson(categories);
outState.putString("Categories", persistData);
}
and then in my OnCreate();
if(savedInstanceState!=null)
{
String data =savedInstanceState.getString("Categories");
Type collectionType = new TypeToken<ArrayList<CategoryMobileDto>>() {
}.getType();
adapter.addAll(gson.<Collection<CategoryMobileDto>>fromJson(data, collectionType));
adapter.notifyDataSetChanged();
}else{
// Make request to server
}
however savedInstanceState is always null. But this makes sense as my activity is not being destroyed and recreated.
This is how I transition from one fragment to another:
fragment.setArguments(args);
FragmentManager fragmentManager = getFragmentManager();
FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
fragmentTransaction.replace(R.id.container, fragment, "ProductListFragment");
fragmentTransaction.addToBackStack(null);
fragmentTransaction.commit();
Is there a way i can save the state of my listview when the fragment is removed and then restore it again when the fragment is popped from the back-stack?

Move this code from onCreate() to onActivityCreated() of Fragment
if(savedInstanceState!=null)
{
String data =savedInstanceState.getString("Categories");
Type collectionType = new TypeToken<ArrayList<CategoryMobileDto>>() {
}.getType();
adapter.addAll(gson.<Collection<CategoryMobileDto>>fromJson(data, collectionType));
adapter.notifyDataSetChanged();
}else{
// Make request to server
}
If you have any query please let me know.

You can use the Arguments with the Fragment(Only if you have the data to show in fragment before the fragment is loaded means attached). You can setArguments to a fragment which will be persisted when you go to another fragment by fragment transaction and when you come back, load the fragment from the getArguments function.
public void setArguments (Bundle args)
Added in API level 11
Supply the construction arguments for this fragment. This can only be called before the fragment has been attached to its activity; that is, you should call it immediately after constructing the fragment. The arguments supplied here will be retained across fragment destroy and creation.
public final Bundle getArguments ()
Added in API level 11
Return the arguments supplied when the fragment was instantiated, if any.
Please find the sample code below for passing data between fragments :
main.xml
<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="#+id/flContainer"
android:layout_width="match_parent"
android:layout_height="match_parent" >
</FrameLayout>
MainActivity.java
public class MainActivity extends Activity implements IFragContainer {
private static final String FRAG_TAG = "FragTag";
private FragBase mFrag;
private String dataToBePassedBack;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
changeFragment(FragA.class, "Data to Frag A");
}
#Override
public void changeFragment(Class<? extends FragBase> fragClass, String data) {
try {
FragmentTransaction ft = getFragmentManager().beginTransaction();
mFrag = fragClass.newInstance();
Bundle args = new Bundle();
args.putString("DATA", data);
mFrag.setArguments(args);
ft.replace(R.id.flContainer, mFrag, FRAG_TAG);
ft.addToBackStack(mFrag.toString());
ft.commit();
} catch (Exception e) {
e.printStackTrace();
}
}
#Override
public void onBackPressed() {
dataToBePassedBack = mFrag.getDataToPassBack();
FragmentManager mgr = getFragmentManager();
mgr.executePendingTransactions();
boolean doCheckAndExit = true;
for (int i = mgr.getBackStackEntryCount() - 1; i > 0; i--) {
BackStackEntry entry = mgr.getBackStackEntryAt(i);
if (!TextUtils.isEmpty(entry.getName())) {
mgr.popBackStackImmediate(entry.getId(),
FragmentManager.POP_BACK_STACK_INCLUSIVE);
doCheckAndExit = false;
break;
}
}
if (doCheckAndExit) {
finish();
} else {
mFrag = (FragBase) mgr.findFragmentByTag(FRAG_TAG);
}
}
#Override
public String getDataToBePassedBack() {
return dataToBePassedBack;
}
}
IFragContainer.java
public interface IFragContainer {
void changeFragment(Class<? extends FragBase> fragClass, String data);
String getDataToBePassedBack();
}
FragBase.java
public abstract class FragBase extends Fragment {
public String getDataToPassBack(){
return null;
}
}
FragA.java
public class FragA extends FragBase {
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
Button btn = new Button(getActivity());
final IFragContainer fragContainer = (IFragContainer) getActivity();
if (TextUtils.isEmpty(fragContainer.getDataToBePassedBack())) {
btn.setText(getArguments().getString("DATA"));
} else {
btn.setText(fragContainer.getDataToBePassedBack());
}
btn.setLayoutParams(new LayoutParams(LayoutParams.WRAP_CONTENT,
LayoutParams.WRAP_CONTENT));
btn.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
fragContainer.changeFragment(FragB.class, "Data to Frag B");
}
});
return btn;
}
}
FragB.java
public class FragB extends FragBase {
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
Button btn = new Button(getActivity());
btn.setText(getArguments().getString("DATA"));
btn.setLayoutParams(new LayoutParams(LayoutParams.WRAP_CONTENT,
LayoutParams.WRAP_CONTENT));
btn.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
getActivity().onBackPressed();
}
});
return btn;
}
#Override
public String getDataToPassBack() {
return "Data from Frag B to A";
}
}

Understanding animation fragment and animation view together

I right understanding that it is impossible to simultaneously perform the animation of the fragment and view.
I try to run view animation and fragment at the same time
private void startAnim(){
mShowDarkOverlay = ObjectAnimator.ofFloat(mBackDarkOverlay, "alpha", 0f, 1f);
mShowDarkOverlay.setDuration(100);
mShowDarkOverlay.setStartDelay(0);
mShowDarkOverlay.start();
getSupportFragmentManager().beginTransaction()
.setCustomAnimations(android.R.anim.fade_in,R.anim.paddle_fade_out)
.replace(R.id.fragment_container, new MyFragment())
.commit();
}
But I only see the animation fragment.
I understand that the animation on the view runs in the main thread, and when it starts the animation of the fragments, the animation view is interrupted.
Is that right? Cannot be performed immediately animation view and fragment ?
UPDATE
I created test project. github
Open application - press button(add item) in action bar (waiting 3 seconds)- click button "2".
And we see the result. Animation View does not begin until you create the fragment.
Fragment blocks the main thread?
In my case the fragment need 2-3 seconds to be created.
I want to change the background and at the same time to change the fragment. Is this possible?

public class FragmentCustomAnimationSupport extends FragmentActivity {
int mStackLevel = 1;
private TextView mTestAnimationView;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.fragment_stack);
mTestAnimationView = (TextView) findViewById(R.id.title);
// Watch for button clicks.
Button button = (Button)findViewById(R.id.new_fragment);
button.setOnClickListener(new OnClickListener() {
public void onClick(View v) {
addFragmentToStack();
}
});
if (savedInstanceState == null) {
// Do first time initialization -- add initial fragment.
Fragment newFragment = CountingFragment.newInstance(mStackLevel);
FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
ft.add(R.id.simple_fragment, newFragment).commit();
} else {
mStackLevel = savedInstanceState.getInt("level");
}
}
#Override
public void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
outState.putInt("level", mStackLevel);
}
void addFragmentToStack() {
mStackLevel++;
Animator animator = ObjectAnimator.ofFloat(mTestAnimationView, "alpha", 0f, 1f);
animator.setDuration(300);
animator.start();
// Instantiate a new fragment.
Fragment newFragment = CountingFragment.newInstance(mStackLevel);
// Add the fragment to the activity, pushing this transaction
// on to the back stack.
FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
ft.setCustomAnimations(R.anim.fragment_slide_left_enter,
R.anim.fragment_slide_left_exit,
R.anim.fragment_slide_right_enter,
R.anim.fragment_slide_right_exit);
ft.replace(R.id.simple_fragment, newFragment);
ft.addToBackStack(null);
ft.commit();
}
public static class CountingFragment extends Fragment {
int mNum;
/**
* Create a new instance of CountingFragment, providing "num"
* as an argument.
*/
static CountingFragment newInstance(int num) {
CountingFragment f = new CountingFragment();
// Supply num input as an argument.
Bundle args = new Bundle();
args.putInt("num", num);
f.setArguments(args);
return f;
}
/**
* When creating, retrieve this instance's number from its arguments.
*/
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
mNum = getArguments() != null ? getArguments().getInt("num") : 1;
}
/**
* The Fragment's UI is just a simple text view showing its
* instance number.
*/
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View v = inflater.inflate(R.layout.hello_world, container, false);
View tv = v.findViewById(R.id.text);
((TextView)tv).setText("Fragment #" + mNum);
tv.setBackgroundDrawable(getResources().getDrawable(android.R.drawable.gallery_thumb));
return v;
}
}
}
I tried in SupportV4Demo, code above, animation of view and fragment played together. mTestAnimationView was a textView layouted above the fragment container(R.id.simple_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){
}
}

savedInstanceState is always null in fragments

Below is my code:
public class MyListFragmentActivity extends FragmentActivity{
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
System.out.println("DEBUG : MLFA onCreate");
if (savedInstanceState == null) {
getSupportFragmentManager().beginTransaction().replace(fragmentID, new MyListFragment())
.replace(detailFragmentID, new MyDetailFragment()).commit();
}
}
#Override
protected void onRestart() {
FragmentTransaction fragmentTransaction = getSupportFragmentManager().beginTransaction();
Fragment prevFrag = getSupportFragmentManager().findFragmentById(detailFragmentID);
if (prevFrag != null) {
fragmentTransaction.remove(prevFrag);
getSupportFragmentManager().beginTransaction().replace(detailFragmentID, new MyDetailFragment()).commitAllowingStateLoss();
} else {
getSupportFragmentManager().beginTransaction().replace(detailFragmentID, new MyDetailFragment()).commitAllowingStateLoss();
}
}
MyListFragment
public class MyListFragment extends Fragment{
//When we click on each item in list view call detail fragment to relad its layout
OnItemClickListener onItemClickListener = new OnItemClickListener() {
/** Getting the fragmenttransaction object, which can be used to add, remove or replace a fragment */
FragmentTransaction fragmentTransaction = getFragmentManager().beginTransaction();
/** Getting the existing detailed fragment object, if it already exists.
* The fragment object is retrieved by its tag name
* */
Fragment prevFrag = getFragmentManager().findFragmentById(detailFragmentID);
/** Remove the existing detailed fragment object if it exists */
if (prevFrag != null) {
fragmentTransaction.remove(prevFrag);
MyDetailFragment mydetailFragment = new MyDetailFragment();
fragmentTransaction.replace(detailFragmentID, mydetailFragment);
fragmentTransaction.addToBackStack(null);
fragmentTransaction.show(getFragmentManager().findFragmentById(detailFragmentID));
fragmentTransaction.commit();
}
}
MyDetailFragment
public class MyDetailFragment extends Fragment{
#Override
public void onCreate(Bundle savedInstanceState) {
setRetainInstance(true);
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
if (savedInstanceState != null) {
// it is not entering the inside here
}
#Override
public void onSaveInstanceState(Bundle savedInstanceState) {
super.onSaveInstanceState(savedInstanceState);
// saving some values
}
When i title my device after me setting the setRetainInstance(true); the savedInstanceState is always null , so how can i get my saved values here ?
Why so? What am i doing wrong here and how to fix this ?

I think that you loose your instanceState because you alway create a new Fragment instance in your onRestart() method.
Try it this way:
#Override
protected void onRestart() {
Fragment prevFrag = getSupportFragmentManager().findFragmentById(detailFragmentID);
if (prevFrag == null || !(prevFrag instanceof MyDetailFragment)) {
getSupportFragmentManager().beginTransaction().replace(detailFragmentID, new MyDetailFragment());
}
}
This way you only attach a new instance of your Fragment only if there's no another valid Fragment of the same type.
Note that setRetainInstance(true); prevents the FragmentManager to destroy your Fragment instance when a configuration change happens.
So it has no sense to manually destroy your Fragment (by calling .remove(...)) and then init a new one with .replace(..., new MyDetailFragment()). This is why you always get an empty savedInstanceState: you are in a new instance, so no previous saved states!
Also remember that calling .commitAllowingStateLoss() on a FragmentTransaction allows the Fragment Manager it to avoid saving the savedInstanceState, so you should use it only if you really know what you're doing.
Have a nice day! :)

According to Android:
onSaveInstanceState() will be called by default for a view if and only it has an id.
The default implementation takes care of most of the UI per-instance state for you by calling onSaveInstanceState() on each view in the hierarchy that has an id, and by saving the id of the currently focused view (all of which is restored by the default implementation of onRestoreInstanceState(Bundle)).

Develop Reference

The Android operating system is a mobile operating system that was developed by Google (GOOGL?) to be primarily used for touchscreen devices, cell phones, and tablets.

Android Fragments (with WebView) - Activity gets Destroyed - android

Finally I got it. I passed the instance of Web through my WebViewClient where I handle the URL Request and want to do the Fragment Transaction. There I call instanceOfWeb.getActivity().getSupportFragmentManager().beginTransaction() to init the Fragment Transaction.

Related

How to move from an activity to a fragment in Android?

Maintaining fragments instance state between transactions

Understanding animation fragment and animation view together

Android - save/restore fragment state

savedInstanceState is always null in fragments

Categories

Resources