Develop Reference

how to save android recycler view state (scroll position) in an activity with two fragments

I am new to Android and, as a first step, am building an app, for running in a handset, with an activity in which I put two fragments. The first fragment has a recycler view of items that are supposed to represent article titles. When I click on one, the second fragment opens and shows the title (in a text view) and the content (in another text view) of the article (for the moment, for simplicity, I put the article title as fake titles and I have a setting for which the content is not shown but it is shown the title in the content text view too).
I want to save the scroll position of the recycler view.
When I scroll down, having on top of the screen an article title different from the first, I choose an article and my second fragment opens with the expected contents, and that's ok. When I rotate to landscape, the same fragment contains the same content, ok. So:
1) when I press the back button from the landscape, returning to the first fragment, I get the same setting for the recycler view, ok;
2) when I rotate again to portrait, remaining on the second fragment, it is ok too. Now, if I press the back button to return to the first fragment, to the list of articles, the recycler view is NOT set to start with the item I initially scrolled to. What can I do?
I have this code in the first fragment, the one containing the recycler view:
#Override
public void onSaveInstanceState(Bundle state) {
int lastFirstVisiblePosition = ((LinearLayoutManager) recyclerView.getLayoutManager()).findFirstCompletelyVisibleItemPosition();
state.putInt(Articles.RECYCLER_POSITION_KEY, lastFirstVisiblePosition);
super.onSaveInstanceState(state);
}
#Override
public void onActivityCreated(Bundle state) {
super.onActivityCreated(state);
if (state != null) {
int lastFirstVisiblePosition = state.getInt(Articles.RECYCLER_POSITION_KEY);
((LinearLayoutManager) recyclerView.getLayoutManager()).scrollToPosition(lastFirstVisiblePosition);
}
}
What am I missing? Thanks.
[EDIT] In my listener is this, for invoking the second fragment:
ArticleReaderFrag newFragment = new ArticleReaderFrag();
Bundle args = new Bundle();
args.putString(NEW_FRAG_TITLE_KEY, item);
args.putString(NEW_FRAG_BODY_KEY, itemb);
newFragment.setArguments(args);
FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
transaction.replace(R.id.main_activity, newFragment);
transaction.addToBackStack(null);
transaction.commit();

Reuse Fragment
When the Activity launches for the first time create a new instance of Fragment and use a TAG to save it with FragmentManager. When the activity gets recreated after orientation change. Retreive the old instance using the Tag.
Here is a sample code which you should have in your activity.
#Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.first_activity);
fragmentManager = getSupportFragmentManager();
if(savedInstanceState==null) {
userFragment = UserNameFragment.newInstance();
fragmentManager.beginTransaction().add(R.id.profile, userFragment, "TAG").commit();
}
else {
userFragment = fragmentManager.findFragmentByTag("TAG");
}
}
How to save scroll position?
That happens by default. Read this answer for more detail.
EDIT
I believe this is your method
public createSecondFragment(int position){
ArticleReaderFrag newFragment = new ArticleReaderFrag();
Bundle args = new Bundle();
args.putString(NEW_FRAG_TITLE_KEY, item);
args.putString(NEW_FRAG_BODY_KEY, itemb);
newFragment.setArguments(args);
FragmentTransaction transaction =
getSupportFragmentManager().beginTransaction();
transaction.replace(R.id.main_activity, newFragment);
transaction.addToBackStack(null);
transaction.commit();
}
Save the position of on rotation and use that position to load the specific fragment.
Call the method when the activity is recreated after orientation change
#Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.first_activity);
if(savedInstanceState!=null) {
int lastSavedPosition = // Your logic
createSecondFragment(lastSavedPosition )
}
}

Is it possible to keep all fragments in running state on using BottomNavigationView, even those which are not visible on the screen?

I am trying to use BottomNavigatioView in my MainActivity and when on clicking a tab in the bottom navigation, the new fragment replaces the previous one, which takes the previous one to the onDestroyView state.
How can we make all the fragments in the onResume state, regardless of whether they are or not visible on the FrameLayout.

You can save the state of fragment and can restore it on onCreateView()
Bundle savedState;
public onCreateView(...){
..........
if(savedState != null){
String hello = savedState.getString("hello");
}
..........
}
#Override
public void onDestroyView(){
super.onDestroyView();
savedState.putString("hello", "Say hello");
}

Android Navigation Drawer wrong toolbar title onResume

I have a Navigation Drawer in the main activity of my app. On the onCreate method of the activity I initialize one of the fragments like this :
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
if (savedInstanceState == null) {
MenuItem menuItem = navigationView.getMenu().findItem(R.id.menu_history);
openFragment(menuItem);
}
public void openFragment(MenuItem menuItem){
Fragment newFragment = null;
switch (menuItem.getItemId()){
case R.id.menu_history :
newFragment = new HistoryFragment();
break;
//.....
}
if (newFragment != null){
//Replace content frame in activity_main.xml with newFragment
getSupportFragmentManager().beginTransaction()
.replace(R.id.content_frame, newFragment)
.commit();
menuItem.setChecked(true);
getSupportActionBar().setTitle(menuItem.getTitle());
}
drawerLayout.closeDrawers();
}
This all works well, the fragment appears on startup with the title on the toolbar being "History". But when the app goes into onPause and then onResume the toolbar title switches from "History" to the app name. I suspect this is an issue with onResume not opening the fragment / returning to its previous state correctly, because when I added the following lines to onResume the issue stopped:
#Override
protected void onResume() {
super.onResume();
MenuItem menuItem = navigationView.getMenu().findItem(R.id.menu_history);
openFragment(menuItem);
}
That solution seems to fix it but that means it has to reload the fragment with the animations every time the app is resumed, which isn't optimal. Any ideas on how to fix this?
If it helps, to recreate the issue I found useful to make the app split screen, because it always calls onResume. Thanks.

Inside your openFragment() method, you write:
getSupportActionBar().setTitle(menuItem.getTitle());
This is the only thing that changes your toolbar's title.
Note that this code has nothing to do with your Fragments, per se. When your activity is destroyed and recreated, the active Fragment will be successfully (automatically) destroyed and recreated by the FragmentManager... but your openFragment() method won't run again and so nothing will update your toolbar's title.
There are numerous ways you could solve this. Probably the right thing to do is update your toolbar's title from within one of your Fragment's lifecycle methods.
Edit: A reasonable place to update your toolbar's title would be in your fragment's onActivityCreated() method. This will run both when the fragment is first added and during recreation. Something like:
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
((AppCompatActivity) getActivity()).getSupportActionBar().setTitle("hello world");
}

If you do not want to re-create the fragment each time, you should use saveInstanceState like mentioned here: https://stackoverflow.com/a/17135346/1505074

Android keep selected fragment state / loaded url after orientation change,

I am new to fragments and have a lot of problems understanding and working with them. I will try to describe my problem step by step:
I start with a list
after selecting an item i start an activity with a dynamic url in a webview
If portrait, only the webview is showed, if landscape the list is presented next to it
In landscape when i select another item, it is showd in the webview (check the code)
Problem: When i turn back now to portrait the first selected item is showd instead of the last one.
How can i update the activity so it will keep the last opened url after orientation change?
if (fragment==null || ! fragment.isInLayout()) {
Intent intent = new Intent(this.getActivity(), DetailViewActivity.class);
intent.putExtra("link", urlforwebview);
startActivity(intent);
} else {
DetailView detailFragment =
(DetailView)
getFragmentManager().findFragmentById(R.id.detailfragment);
detailFragment.changeWebviewURL(urlforwebview);
}
FIX:
Added this to my detailfragment:
#Override
public void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
outState.putString("currentUrl", url);
}
#Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
if (savedInstanceState != null) {
// Restore last state for checked position.
url = savedInstanceState.getString("currentUrl", "");
changeWebviewURL(url);
}
}

Have a look at : onSaveInstanceState.
http://developer.android.com/reference/android/app/Activity.html#onSaveInstanceState(android.os.Bundle)
This answer here can help you: android fragment- How to save states of views in a fragment when another fragment is pushed on top of it

Getting back to a fragment keeping its previous state

I am an old Android programmer, but I used to use only Activities and I'm quite new with Fragments.
I've created an application with a menu bar (4 buttons) that, when clicked, are supposed to load each one a different Fragment above the menu bar.
The problem is that each time I click on one of the menu bar buttons, it reloads entirely the fragment and I would like it to show the Fragment on its previous state (just like the device Back button does).
How can I do such a thing?
Call from the main activity:
Fragment my_fragment = new MyFragment();
FragmentManager fragment_manager = getSupportFragmentManager();
FragmentTransaction fragment_transaction = fragment_manager.beginTransaction();
fragment_transaction.replace(R.id.fragment_container, my_fragment);
fragment_transaction.addToBackStack(null);
fragment_transaction.commit();
and most my MyFragment process code is in the function
onActivityCreated

You also can use onSaveInstanceState method as in activities,to restore data use Bundle savedInstanceState object, for example
#Override
public void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
outState.putInt("test", 1);
}
#Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
if (savedInstanceState != null) {
int testValue = savedInstanceState.getInt("test", 0);
}
}
http://developer.android.com/guide/components/fragments.html