I have an array adapter and associated code that worked fine when in an activity. I'm migrating to using fragments and now it doesn't update. Using action bar tabs, if I go to my tab the first time the list populates and shows fine. If I go to a different tab and come back, the list is populated but the list view is empty.
If I add something to the list during the first visit, the list is updated fine. If I leave, come back, and add an item it does not show up. An item is added to the list by saving an image to the database and then calling refreshGallery().
#Override
public onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View v = inflater.inflate(R.layout.inspection_images, container, false);
mListView = (ListView) v.findViewById(R.id.inspection_images_list);
setInspectionImages(mInspection.getInspectionImages());
return v;
}
#Override
public void onResume() {
refreshGallery();
}
public void refreshGallery() {
mInspectionImages = mInspection.getInspectionImages();
setInspectionImages(mInspectionImages());
}
public void setInspectionImages(ArrayList<InspectionImage> images) {
if (null == mArrayAdapter) {
mArrayAdapter = new InspectionImageAdapter(getActivity().getApplicationContext(), R.layout.inspection_image_list_item, images);
mListView.setAdapter(mArrayAdapter);
}
else {
mArrayAdapter.clear();
addInspectionImagesToList(images);
}
}
public void addInspectionImagesToList(ArrayList<InpsectionImage> images) {
mArrayAdapter.addAll(images);
mArrayAdapter.notifyDataSetChanged();
}
Assuming you've implemented onTabSelected() as per the Android developers guide, i.e.:
public void onTabSelected(Tab tab, FragmentTransaction ft) {
// Check if the fragment is already initialized
if (mFragment == null) {
// If not, instantiate and add it to the activity
mFragment = Fragment.instantiate(mActivity, mClass.getName());
ft.add(android.R.id.content, mFragment, mTag);
} else {
// If it exists, simply attach it in order to show it
ft.attach(mFragment);
}
}
What happens when you show the fragment the first time:
in onTabSelected(), mFragment is null and a new one is instantiated
the created fragment is attached to mActivity
the fragment's onCreateView() is called, mListView is created, mArrayAdapter is created and populated and attached to mListView and mListView is returned
the list view items are visible and everything is dandy
What happens after you switched out to another tab then switched back to that same one:
in onTabSelected(), mFragment exists so only ft.attach(mFragment); is executed (on the same fragment as before, i.e. no new fragment is created)
the existing fragment is attached to mActivity once more
the fragment's onCreateView() is called (check the fragment lifecycle and what happens when a fragment is attached if you wonder why), a new mListView is created, setInspectionImages() is called and the old mArrayAdapter is present so it's populated but never attached to the new mListView
the mListView shown in the layout doesn't have any adapter attached, and all of your actions populate a now unrelated array adapter
For one thing you don't have to repopulate the adapter on each onResume(). Do it once at creation time (I would put it in onActivityCreated()) and just update it when necessary.
And then you don't need to check for the existence of mArrayAdapter, just create it every time in onActivityCreated().
If you want to keep your current design though, just be sure to nullify its reference when the list view disappears:
#Override
public void onDestroyView () {
mArrayAdapter = null;
mListView = null;
}
Related
I have implemented some fragments which are hosted by a single Activity (they're in the same activity). In one of these fragments (Let's say fragment A), I have a vertical recyclerview.
The problem is arises when I want to navigate from Fragment A to other fragments (Again, in the same activity). Suppose that I'm clicking the middle member of the list, then I navigate to the next fragment. When I want to back into the first fragment (Fragment A), it inflates the list from first. Seeming that it looses its position, however, using onSaveInstanceState() and also onCreateView(), I try to store and restore the selected item's position every time I quit or enter the fragment.
I think this issue may be originated from fragments' lifecycle which all are in one single activity. As this answer, mentioning :
In a Fragment, all of their lifecycle callbacks are directly tied to their parent Activity. So onSaveInstanceState gets called on the Fragment when its parent Activity has onSaveInstanceState called.
and that's why I emphasize on the "single" activity. How can we handle such situation?
I have debugged my program and onSaveInstanceState and onCreateView were not even called when they were supposed to. Below is my attempted code:
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
if(savedInstanceState!=null){
selectedItem = savedInstanceState.getInt(BUNDLE_KEY_SELECTED_ITEM);
}
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
if (savedInstanceState != null){
selectedItem = savedInstanceState.getInt(BUNDLE_KEY_SELECTED_ITEM);
}
myRecyclerView = (RecyclerView) v.findViewById(R.id.rv_mine);
// mData is a an ArrayList
myAdapter = new MyAdapter(mData, getContext(), this.selectedItem);
myLayoutManager = new LinearLayoutManager(getActivity());
myRecyclerView.setLayoutManager(myLayoutManager);
myRecyclerView.setAdapter(myAdapter);
return v;
}
#Override
public void onSaveInstanceState(Bundle outState) {
outState.putInt(BUNDLE_KEY_SELECTED_ITEM,selectedItem);
super.onSaveInstanceState(outState);
}
Well you can use .add() to add fragments to your activity than .replace(), Which preserves the state of the fragment within the activity, and if using replace function which will cause the onCreateView callback to trigger again.
I am using Android Studio and I created an Activity that contains a NavigationDrawerFragment.
One of the Fragments is loading the content of an SQLite database inside a ListView, using a custom ArrayAdapter with complex items.
My problem is that if I select another fragment in the drawer, then come back to this one, the onCreate() of the Fragment is called again, so is the onCreateView(), and the database is loaded once again.
How can I preserve everything without having to load the database nor populate the list again?
I don't have this problem when orientation changes, so I am a bit confused. Maybe it is because I have a layout for both Portrait and Landscape ?
here is the code of the onCreateView()
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
getActivity().getActionBar().show();
View view = inflater.inflate(R.layout.fragment_papers, container, false);
allItems = new ArrayList<ItemData>();
getAllItemsFromDB("");
mAdapter = new ItemsList(getActivity(), allItems, this, mDBApi);
// Set the adapter
mListView = (AbsListView) view.findViewById(R.id.list);
mListView.setAdapter(mAdapter);
// Set OnItemClickListener so we can be notified on item clicks
mListView.setOnItemClickListener(this);
mListView.setOnScrollListener(this);
return view;
}
and the getAllItemsFromDB() contains something like
public void getAllItemsFromDB(String query){
Cursor c = sqldb.rawQuery("SELECT * FROM 'Table' " + query, null);
while (c.moveToNext()) {
allItems.add(parseSQL(sqldb, c));
}
c.close();
}
Set your array list static
private static List<ItemData> allItems;
Then check it for null and initialise it only once
if(allItems == null) {
allItems = new ArrayList<ItemData>();
getAllItemsFromDB("");
}
may be ur loading frament everytime as
FragmentManager fragmentManager = getFragmentManager();
fragmentManager.beginTransaction().replace(R.id.content_frame, new UrFragment()).commit();
Don't do that, create instance of fragment and use it.
// update the main content by replacing fragments
Fragment fragment = new UrFragment();
FragmentManager fragmentManager = getFragmentManager();
fragmentManager.beginTransaction().replace(R.id.content_frame, fragment).commit();
Im having some problems when it comes to porting my app from the normal activity style to the fragment style. Im beginning to notice that when a fragment gets recreated, or popped from the backstack it loses its views. When I say that Im talking about a listview in particular. What im doing is im loading items into the listview, then rotating the screen. When it goes back through, it gets a nullpointerexception. I debug it and sure enough the listview is null. Here is the relevant code to the fragment
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup viewGroup, Bundle savedInstanceState) {
return inflater.inflate(R.layout.sg_question_frag, viewGroup, false);
}
#Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
list = (ListView)getActivity().findViewById(R.id.sgQuestionsList);
if (savedInstanceState != null) {
catId = savedInstanceState.getInt("catId");
catTitle = savedInstanceState.getString("catTitle");
}
populateList(catId, catTitle);
}
And here is how it is called (keep in mind there are a few other fragments that im working with as well)
#Override
public void onTopicSelected(int id, String catTitle) {
// TODO Auto-generated method stub
FragmentManager fm = this.getSupportFragmentManager();
SGQuestionFragment sgQuestFrag = (SGQuestionFragment) fm.findFragmentByTag("SgQuestionList");
FragmentTransaction ft = fm.beginTransaction();
//If the fragment isnt instantiated
if (sgQuestFrag == null) {
sgQuestFrag = new SGQuestionFragment();
sgQuestFrag.catId = id;
sgQuestFrag.catTitle = catTitle;
//Fragment isnt there, so we have to put it there
if (mDualPane) {
//TO-DO
//If we are not in dual pane view, then add the fragment to the second container
ft.add(R.id.sgQuestionContainer, sgQuestFrag,"SgQuestionList").commit();
} else {
ft.replace(R.id.singlePaneStudyGuide, sgQuestFrag, "SqQuestionList").addToBackStack(null).commit();
}
} else if (sgQuestFrag != null) {
if (sgQuestFrag.isVisible()) {
sgQuestFrag.updateList(id, catTitle);
} else {
sgQuestFrag.catId = id;
sgQuestFrag.catTitle = catTitle;
ft.replace(R.id.sgQuestionContainer, sgQuestFrag, "SgQuestionList");
ft.addToBackStack(null);
ft.commit();
sgQuestFrag.updateList(id, catTitle);
}
}
fm.executePendingTransactions();
}
What I would ultimately want it to do is to completely recreate the activity, forget the fragments and everything and just act like the activity was started in landscape mode or portrait mode. I dont really need the fragments there, I can recreate them progmatically with some saved variables
If you want to get a reference to a view from within a Fragment always look for that View in the View returned by the getView() method. In your case, at the time you look for the ListView the Fragment's view probably isn't yet attached to the activity so the reference will be null. So you use:
list = (ListView) getView().findViewById(R.id.sgQuestionsList);
I have a problem reloading an activity with tabs and fragments when I change the orientation of my device.
Here's the situation:
I have an activity which has 3 tabs in the action bar. Each tab loads a different fragment in a FrameLayout in main view. Everything works fine if I don't change the orientation of the device. But when I do that Android tries to initialize the currently selected fragment twice which produce the following error:
E/AndroidRuntime(2022): Caused by: android.view.InflateException: Binary XML file line #39: Error inflating class fragment
Here's the sequence of steps that produce the error:
I load the activity, select tab nr 2. and change the orientation of the device.
Android destroys the activity and the instance of the fragment loaded by tab nr 2 (from now on, 'Fragment 2'). Then it proceeds to create new instances of the activity and the fragment.
Inside Activity.onCreate() I add the first tab to the action bar. When I do that, this tab gets automatically selected. It may represent a problem in the future, but I don't mind about that now. onTabSelected gets called and a new instance of the first fragment is created and loaded (see code below).
I add all the other tabs without any event being triggered, which is fine.
I call ActionBar.selectTab(myTab) to select Tab nr 2.
onTabUnselected() gets called for the first tab, and then onTabSelected() for the second tab. This sequence replaces the current fragment for an instance of Fragment 2 (see code below).
Next, Fragment.onCreateView() is called on Fragment 2 instance and the fragment layout gets inflated.
Here is the problem. Android Calls onCreate() and then onCreateView() on the fragment instance ONCE AGAIN, which produces the exception when I try to inflate (a second time) the layout.
Obviously the problem is Android is initializing the fragment twice, but I don't know why.
I tried NOT selecting the second tab when I reaload the activity but the second fragment gets initialized anyway and it is not shown (since I didn't select its tab).
I found this question: Android Fragments recreated on orientation change
The user asks basically the same I do, but I don't like the chosen answer (it's only a workaroud). There must be some way to get this working without the android:configChanges trick.
In case it's not clear, what I want to know how whether to prevent the recreation of the fragment or to avoid the double initialization of it. It would be nice to know why is this happening also. :P
Here is the relevant code:
public class MyActivity extends Activity implements ActionBar.TabListener {
private static final String TAG_FRAGMENT_1 = "frag1";
private static final String TAG_FRAGMENT_2 = "frag2";
private static final String TAG_FRAGMENT_3 = "frag3";
Fragment frag1;
Fragment frag2;
Fragment frag3;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// my_layout contains a FragmentLayout inside
setContentView(R.layout.my_layout);
// Get a reference to the fragments created automatically by Android
// when reloading the activity
FragmentManager fm = getFragmentManager();
this.frag1 = fm.findFragmentByTag(MyActivity.TAG_FRAGMENT_1);
this.frag2 = fm.findFragmentByTag(MyActivity.TAG_FRAGMENT_2);
this.frag3 = fm.findFragmentByTag(MyActivity.TAG_FRAGMENT_3)
ActionBar actionBar = getActionBar();
// snip...
// This triggers onTabSelected for the first tab
actionBar.addTab(actionBar.newTab()
.setText("Tab1").setTabListener(this)
.setTag(MyActivity.TAG_FRAGMENT_1));
actionBar.addTab(actionBar.newTab()
.setText("Tab2").setTabListener(this)
.setTag(MyActivity.TAG_FRAGMENT_2));
actionBar.addTab(actionBar.newTab()
.setText("Tab3").setTabListener(this)
.setTag(MyActivity.TAG_FRAGMENT_3));
Tab t = null;
// here I get a reference to the tab that must be selected
// snip...
// This triggers onTabUnselected/onTabSelected
ab.selectTab(t);
}
#Override
protected void onDestroy() {
// Not sure if this is necessary
this.frag1 = null;
this.frag2 = null;
this.frag3 = null;
super.onDestroy();
}
#Override
public void onTabSelected(Tab tab, FragmentTransaction ft) {
Fragment curFrag = getFragmentInstanceForTag(tab.getTag().toString());
if (curFrag == null) {
curFrag = createFragmentInstanceForTag(tab.getTag().toString());
if(curFrag == null) {
// snip...
return;
}
}
ft.replace(R.id.fragment_container, curFrag, tab.getTag().toString());
}
#Override
public void onTabUnselected(Tab tab, FragmentTransaction ft)
{
Fragment curFrag = getFragmentInstanceForTag(tab.getTag().toString());
if (curFrag == null) {
// snip...
return;
}
ft.remove(curFrag);
}
private Fragment getFragmentInstanceForTag(String tag)
{
// Returns this.frag1, this.frag2 or this.frag3
// depending on which tag was passed as parameter
}
private Fragment createFragmentInstanceForTag(String tag)
{
// Returns a new instance of the fragment requested by tag
// and assigns it to this.frag1, this.frag2 or this.frag3
}
}
The code for the Fragment is irrelevant, it just returns an inflated view on onCreateView() method override.
I got a simple answer for that:
Just add setRetainInstance(true); to the Fragment's onAttach(Activity activity) or onActivityCreated(Bundle savedInstanceState).
These two are call-backs in the Fragment Class.
So basically, what setRetainInstance(true) does is:
It maintains the state of your fragment as it is, when it goes through:
onPause();
onStop();
It maintains the instance of the Fragment no matter what the Activity goes through.
The problem with it could be, if there are too many Fragments, it may put a strain on the System.
Hope it helps.
#Override
public void onAttach(Activity activity) {
super.onAttach(activity);
setRetainInstance(true);
}
Open for Correction as always. Regards, Edward Quixote.
It seems that, when the screen is rotated and the app restarted, it is recreating each Fragment by calling the default constructor for the Fragment's class.
I have encountered the same issue and used the following workaround:
in the fragment's onCreateView begining of:
if (mView != null) {
// Log.w(TAG, "Fragment initialized again");
((ViewGroup) mView.getParent()).removeView(mView);
return mView;
}
// normal onCreateView
mView = inflater.inflate(R.layout...)
I think this is a fool proof way to avoid re-inflating of the root view of the fragment:
private WeakReference<View> mRootView;
private LayoutInflater mInflater;
/**
* inflate the fragment layout , or use a previous one if already stored <br/>
* WARNING: do not use in any function other than onCreateView
* */
private View inflateRootView() {
View rootView = mRootView == null ? null : mRootView.get();
if (rootView != null) {
final ViewParent parent = rootView.getParent();
if (parent != null && parent instanceof ViewGroup)
((ViewGroup) parent).removeView(rootView);
return rootView;
}
rootView = mFadingHelper.createView(mInflater);
mRootView = new WeakReference<View>(rootView);
return rootView;
}
#Override
public View onCreateView(final LayoutInflater inflater, final ViewGroup container, final Bundle savedInstanceState) {
mInflater=inflater!=null?inflater:LayoutInflater.from(getActivity());
final View view = inflateRootView();
... //update your data on the views if needed
}
add
android:configChanges="orientation|screenSize"
in the manifest file
To protect activity recreate try to add configChanges in your Activity tag (in manifest), like:
android:configChanges="keyboardHidden|orientation|screenSize"
My code was a little different, but I believe our problem is the same.
In the onTabSelected I didn't use replace, I use add when is the first time creating the fragment and attach if isn't. In the onTabUnselected I use detach.
The problem is that when the view is destroyed, my Fragment was attached to the FragmentManager and never destroyed. To solve that I implemented on the onSaveInstanceBundle to detach the fragment from the FragmentManager.
The code was something like that:
FragmentTransition ft = getSupportFragmentManager().begin();
ft.detach(myFragment);
ft.commit();
In the first try I put that code in the onDestroy, but I get a exception telling me that I couldn't do it after the onSaveInstanceBundle, so I moved the code to the onSaveInstanceBundle and everything worked.
Sorry but the place where I work don't allow me to put the code here on StackOverflow. This is what I remember from the code. Feel free to edit the answer to add the code.
I think you are facing what I faced. I had a thread downloader for json which starts in onCreate() , each time I changed the orientation the thread is called and download is fired. I fixed this using onSaveInstance() and onRestoreInstance() to pass the json response in a list, in combination of checking if the list is not empty, so the extra download is not needed.
I hope this gives you a hint.
I solved this problem by using below code.
private void loadFragment(){
LogUtil.l(TAG,"loadFragment",true);
fm = getSupportFragmentManager();
Fragment hf = fm.findFragmentByTag("HOME");
Fragment sf = fm.findFragmentByTag("SETTING");
if(hf==null) {
homeFragment = getHomeFragment();// new HomeFragment();
settingsFragment = getSettingsFragment();// new Fragment();
fm.beginTransaction().add(R.id.fm_place, settingsFragment, "SETTING").hide(settingsFragment).commit();
fm.beginTransaction().add(R.id.fm_place, homeFragment, "HOME").commit();
activeFragment = homeFragment;
}else{
homeFragment = hf;
settingsFragment = sf;
activeFragment = sf;
}
}
Initiate this method in OnCreate();
EDIT
So it seems that my Fragment is retained in the FragmentManager which tries to reinitialize it. Still not sure why it isn't destroyed with the Activity. As for the loading message, this is displayed when the ListView does not have an adapter set. I however, set the adapter items in onCreate and onResume so I'm not sure why this loading screen is showing. Still open to any explanations of this behavior
Original
I'm playing around with fragments and noticed a weird error that is popping up when I change the orientation of the screen. This error should not be happening though because all the data is recreated in the onCreate when the screen orientation is changed. Also, the fragment onResume() is called twice after the rotation. Here's my steps for creating the error and how the debugger is hitting the functions.
Activity: onCreate()
Activity: onResume()
Fragment: onResume()
Rotate Screen
Activity: onCreate()
Activity: onResume()
Fragment: onResume() (items are null even though Activity.onResume() set them)
Fragment: onResume() (items are not null, why is this being called twice?)
After this last fragment onResume is hit, the tablet displays a "Loading..." message and icon. Why is the data not displayed in the list any more? My suspicions are that the onCreate is creating a second fragment. The first fragment looses its data because of the orientation destroying the views, the second fragment gets the data and the loading screen is the first fragment with no data items and the second fragment is hidden. I may be wrong. Why aren't the fragments all destroyed when the screen is rotated like the Activity? Please do not critique the code unless its to solve this specific issue. I'm not actually making an app, I'm experimenting with fragment functionality. Thanks!
Main Activity
private ArrayList<Object> items = new ArrayList<Object>();
private MyListFragment mylistFragment;
public MainActivity() {
items.add("Hello");
items.add("World");
items.add("Goodbye");
}
/** Called when the activity is first created. */
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
FragmentManager fm = getFragmentManager();
FragmentTransaction ft = fm.beginTransaction();
mylistFragment = new MyListFragment();
mylistFragment.setItems(items);
ft.add(R.id.container, mylistFragment);
ft.commit();
}
#Override
public void onResume() {
super.onResume();
mylistFragment.setItems(items);
mylistFragment.getListView().setOnItemClickListener(new OnItemClickListener() {
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
Toast.makeText(MainActivity.this, ((TextView)view).getText(), Toast.LENGTH_LONG).show();
}
});
}
List Fragment
private List<Object> items = null;
private Boolean isSet = false;
#Override
public void onResume() {
super.onResume();
if( !isSet && items != null) {
setListAdapter(new ArrayAdapter<Object>(getActivity(), R.layout.item, items));
isSet = true;
}
}
public void setItems(List<Object> items) {
this.items = items;
if( this.isResumed() ) {
setListAdapter(new ArrayAdapter<Object>(getActivity(), R.layout.item, items));
isSet = true;
} else {
isSet = false;
}
}
The FragmentManager will automatically recreate the Fragment for me. However, the data inside them needs to be reinitialized. Therefore my code was creating a second fragment. The loading screen was because the first fragment no longer had its adapter of items and the second fragment was hidden. What a headache, I almost think the FragmentManager should destroy the Fragments so you can recreate them with the data they hold.
I believe this is why in the various demos via Diane and other google examples... they typically have some way of helping hte initialization via a static method... and setArguments.
IIRC, the fragment creation stuff will call the default constructor to create, but only knows about populating with appropriate data via setArguments. In the example on the android development blog... the id was being passed from the listactivity, to the details fragment. After setParams is called, the fragmentManager should be able to reanimate it.
Documentation seems to be sparse on the subject and I'd like to be doing things right, so if you guys have feedback, I'd appreciate it.
It seems that using FragmentActivity from the support library saves and restores instance automatically. Therefore, only do your fragment transactions if savedInstanceState is null.
For example, in your FragmentActivity's onCreate(), do the following:
if(savedInstanceState == null){
FragmentManager fragmentManager = getSupportFragmentManager();
fragmentManager.beginTransaction()
.replace(R.id.fragment_container, mFragment).commit(); //mFragment is your own defined fragment
}