Develop Reference

How to start a fragment from a RecyclerView Adapter which is inside another fragment?

I have a tab view with two fragments. Those two fragments contain a recycler view with cards.
Each card in both fragments had a button.
Clicking on fragment 1's button should open the fragment 2 as a separate page and vice-versa.
I am struggling to find a method to implement this without making every too complex and tightly coupled.
This is fragment one with its own Adapter.
And this is fragment two:
Clicking on that SELECT DONOR button in Donees page should open donor fragment in a new page where the user will be able to assign a donor for the selected donee.
So I have two needs here
1) To start a fragment from a fragment
2) To Keep track from which Donee the new donor page was opened so that I can assign a donor for that specific donee.
I hope this is understandable.
so far I have tried LocalBroadcast and FragmentManager but its hard to keep track of what I'm doing with the code.
Can you guys suggest a better technique to achieve this ?

the easiest solution would probably be, starting a new activity, passing something like an ID, name or something to the intent on an Button click.
Context.startActivity(new Intent(Context, YourAssigneeActivity.class)
.putExtra("ID",id));

So I assume that you do not switch to the other tab when you click a button on one tab. Therefore the fragment should fill the whole screen.
With this assumption in mind you most likely have to switch the Activity. This can be dones easily with an Intent:
Intent intent = new Intent(getActivity(), ActivityB.class)
intent.putExtra("KEY", <your required data to transfer>);
getActivity().startActivityForResult(intent);
Note that when you use putExtra() don't forget that you need to implement Parcelable in those objects (explained here)
To get to know which item was clicked you can use the following pattern (pseudocode - I personally think it's really clean):
FragmentA implements YourAdapter.callback {
onItemClicked(<YourObject> item) {
<starting new activity as described above>
}
}
class YourAdapter extends RecyclerView.Adapter {
Callback mCallback;
YourAdapter(Context context, otherStuff) {
mCallback = (Callback) context;
}
interface Callback {
onItemClicked(<YourObject> item)
}
YourViewHolder implements View.OnClickListener {
onClick(View v) {
mCallback.onItemClicked(<YourObject> item)
}
}
}
Once you are in your Activity, you can set the Fragment in onCreate() of your Activity. In the Activity retrieve the data with getIntent() in the onCreate before creating the Fragment. Then you can put your data in the Fragment with setArguments(<Bundle>). In the Fragment in the onCreateview() retrieve it with getArguments().
I know this is kind of conmplicated. A better solution would be to just switch to an Activity and forget about the Fragment. This would remove one layer of complexity.
If you directly go from Fragment to Fragment you can ignore the Activity part but the rest should stay the same.
Hope this was the answer you were looking for!
Edit: Note that mCallback = (Callback) context is null if the Activity is not implementing Callback

overiding default back navigation within activity with multiple fragments

So i have a working solution, it seems not to be ideal but just need to confirm - so i have an activity with 3 fragments showing one at a time - i need to block the default back operation for two of those fragments so that when the back button is pressed nothing happens(for now, still developing).
So what i did was that i used an interface
//top of activity snippet
public class StudyKitActivity extends AppCompatActivity implements OnStudyKitBackListener{
private int fragment_id;
.
.
.
.
//interface method
#Override
public void onBackChanged(int fragment_id) {
this.fragment_id = fragment_id;
}
to set a variable on the activity
when i am changing the current fragment in the activity e.g set 1 for fragment A, 2 for fragment B and 3 for fragment C, so this is code snippet within fragment 2 when moving to fragment 3 -
onStudyKitBackListener.onBackChanged(3);
StudyKitResultFragment studyKitResultFragment = StudyKitResultFragment.getInstance(examResult);
getActivity().getSupportFragmentManager().beginTransaction().replace(R.id.frame_container, studyKitResultFragment).addToBackStack("exam_result").commit();
and i did an overwrite in my activity's onBackpressed to check the value of that variable and either execute the default OnBackPressed or do nothing like so -
#Override
public void onBackPressed() {
if(this.fragment_id==2||this.fragment_id==3){
}
else{
super.onBackPressed();
}
}
i came up with this cos other solutions like setting a tag and trying to get the fragment's tag or by checking current fragments id did not work for me, this is working like i expected but i have not seen it anywhere just want to know if there is an alternate solution.

Viewpager update and backstack

I have a view pager with 2 scrolling pages in my app. at first I populate it with two fragments.
In first fragment I have a button. clicking the button new adapter is created and view pager is populated with two different fragments. at the moment when I press back I exit from the app instead I want to restore previous state of the view pager. please help
For the first time:
ViewPagerAdapter pagerAdapter = new ViewPagerAdapter(getSupportFragmentManager(),nBank);
mViewpager.invalidate();
mViewpager.setAdapter(pagerAdapter);
Second time:
public void onListItemPressed(Currency objectCurrency) {
// TODO Auto-generated method stub
DetailPagerAdapter detaluriadapteri = new DetailPagerAdapter(getSupportFragmentManager());
mViewpager.setAdapter(detaluriadapteri);
}

One solution could be to implement onBackPressed:
#Override public void onBackPressed() {
if (mViewpager != null && mViewpager.getAdapter() instanceof DetailPagerAdapter) {
ViewPagerAdapter pagerAdapter = new ViewPagerAdapter(getSupportFragmentManager(),nBank);
mViewpager.invalidate();
mViewpager.setAdapter(pagerAdapter);
} else {
super.onBackPressed();
}
}
Though, I think it would be better to start a new activity using DetailPagerAdapter when onListItemPressed is called. This way the default behavior of android would be to navigate back to your main activity on backpress, currently your main activity could be getting too much responsibility. Thus, having a self contained activity handling the details part would also be easier to maintain as it might need different tabs, actionbar menu items, etc..
Could also be a Fragment containing a the details viewpager but I have had trouble implementing this myself. Should be possible though and my trouble might be caused by some of the libraries I use.

after configuration change fragment from backstack is now sharing the FrameLayout?

Problems with app:
When orientation changes the app is experiencing these problems:
Both FragmentA and FragmentC now occupy the FrameLayout container.
What works: Everything works as I want it to...prior to rotating the screen.
Activity description in brief:
EditActivity Purpose: edit collection and item fields.
Fragments this activity programmatically creates:
FragmentA - fragment for editing collection fields
FragmentB - ListFragment of items in collection
FragmentC - fragment for editing item fields.
Initial layout: FragmentA sits atop FragmentB, each in their own FrameLayouts.
When user clicks FragmentB's listview item: replace FragmentA with FragmentC to allow user to edit that item's fields. Now FragmentC sits atop FragmentB.
This seems like a very simple notion: the top portion of the activity is for editing either properties of the collection as a whole or a single item from the collection. I don't feel I have done anything wondrous with the layout so I'm a fair bit perplexed that a simple rotation of the phone (emulator) causes these problems that I am having such a dastardly time trying to fix.
Why the Android Fragment Guide example doesn't work for me: their example is much like what I am doing but their detail fragment is either being opened in a new activity or in its own Frame within the current activity, they don't do any swapping of fragments so I cannot glean how they would use the onSaveIstanceState to preserve the fragments that are visible and then use that information in onCreate to recreate the UI that was there prior to orientation change.
EDIT: took out one problem by caving and putting the listfragment in the XML, this solved the perpetual spinning "loading..." problem.

Solved. Oh, the rabbit holes I traveled... At any rate, if you run into problems like this a couple of things to consider:
ultimately I didn't have to write any code in onSaveInstanceState(Bundle outState).
Ultimately I didn't have to make any considerations about handling the backstack in onSaveInstanceState or deal with it the activity's onCreate.
When first "adding" fragments programmatically to the FrameLayout, use replace instead of `add' - this was likely one of the roots of my troubles.
in onCreate check if savedInstanceState's bundle is null, if(savedInstanceState == null), and if it is then I know that the activity hasn't been torn down previously by a configuration change, so here I build fragments that should be displayed right at activity start up. Other fragments that are programmatically brought to life elsewhere (ie, later than the activity's onCreate()), they don't belong in the if, they belong in the else:
else onSaveInstanceState != null and I know there's only one reason this thing's not null, because the system made a bundle named outState in onSaveInstanceState(Bundle outState) and hucked it at the activity's onCreate method where I can now get my grubbies on it. So it is here that I know a couple of things:
for sure the fragments I created in the activity's onCreate are still a part of the activity (I didn't detach or destroy them), but, I cannot make that same claim for the fragments brought to life via a user's actions, those fragments may or may not be currently (at the time of orientation aka configuration change) attached to the activity.
This is a good place for an if-this-thing-is-attached clause. One of things I initially messed up on was I failed to give ALL of my programmatically added fragments a tag; give all programmatically added fragments tags. I can then find out if the savedInstanceState bundle contains that key with savedInstanceState.containsKey(MY_FRAG_TAG) and with getFragmentManager().findFragmentByTag(MY_FRAG_TAG)
So here's the activity's onCreate (simplified):
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_edit);
// ...omitted code...
if(savedInstanceState == null){
// create fragment for collection edit buttons
editCollection = FragmentA.newInstance(someVariable);
// programmatically add fragment to ViewGroup
getFragmentManager().beginTransaction().replace(R.id.edit_topFrame, editCollection, EDIT_COLLECTIONS_TAG).commit();
}
// else there be stuff inside the savedInstanceState bundle
else{
// fragments that will always be in the savedInstanceState bundle
editCollectionFragment = (FragmentA)getFragmentManager().findFragmentByTag(EDIT_COLLECTIONS_TAG);
// fragments that may not be in the bundle
if(savedInstanceState.containsKey(EDIT_ITEM_TAG)){
editItemFragment = (FragmentC)getFragmentManager().getFragment(savedInstanceState, EDIT_ITEM_TAG);
}
}
// This fragment is NOT programmatically added, ie, it is statically found in an XML file.
// Hence, the system will take care of preserving this fragment on configuration changes.
listFrag = (ListViewFragment)getFragmentManager().findFragmentById(R.id.ListFragment);
// create adapter
adapter = new EditCursorAdapter(this, null);
// set list fragment adapter
listFrag.setListAdapter(adapter);
// prepare the loader
getLoaderManager().initLoader(LOADER_ID, null, this);
}
And the Activity's listener for the list fragment, where FragmentC is swapped for FragmentA:
// listfragment listener
#Override
public void listFragListener(Cursor cursor) {
// checking backstack size
Log.d(TAG, SCOPE +"backstack size: "+getFragmentManager().getBackStackEntryCount());
// With each listview click there should be only one item in the backstack.
getFragmentManager().popBackStack();
// create new fragment
editItemFragment = FragmentC.newInstance(cursor);
// programmatically add new fragment
FragmentTransaction ft = getFragmentManager().beginTransaction();
ft.replace(R.id.edit_topFrame, editItemFragment, EDIT_ITEM_TAG);
ft.addToBackStack("pop all of these"); // was testing different ways of popping
ft.commit();
// interesting: this reports the same value as the first log in this method.
// ...clearly addToBackStack(null).commit() doesn't populate the backstack immediately?
Log.d(TAG, SCOPE +"backstack size: "+getFragmentManager().getBackStackEntryCount());
}
And onSaveInstanceState is naked as a jay bird:
#Override
protected void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
}
Summary: I have the activity functioning exactly as I want it to.
Now, if I had a bunch of added fragments then I might handle them in a more programmatic fashion rather than by hard coding the if(savedInstanceState.contains(*hard coded key*). This I tested a little bit but cannot attest to its efficacy, however for someone out there this might spark an idea of what you can do:
Make a private Set of added fragments:
// Collection of Frag Tags
private Set<String> AddedFragmentTagsSet = new HashSet<String>();
In onAttachFragment do something like:
#Override
public void onAttachFragment(Fragment fragment) {
super.onAttachFragment(fragment);
// logging which fragments get attached and when
Log.d(TAG, SCOPE +"attached fragment: " +fragment.toString());
// NOTE: XML frags have not frigg'n tags
// add attached fragment's tag to set of tags for attached fragments
AddedFragmentTagsSet.add(fragment.getTag());
// if a fragment has become detached remove its tag from the set
for(String tag : AddedFragmentTagsSet){
if(getFragmentManager().findFragmentByTag(tag).isDetached()){
AddedFragmentTagsSet.remove(tag);
}
Log.d(TAG, SCOPE +"contents of AddedFragmentTagsSet: " +tag);
}
}
Then in the activity's onCreate and within savedInstanceState clauses:
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_edit);
// ...omitted code...
if(savedInstanceState == null){
// create fragment for collection edit buttons
editCollection = FragmentA.newInstance(someVariable);
// programmatically add fragment to ViewGroup
getFragmentManager().beginTransaction().replace(R.id.edit_topFrame, editCollection, EDIT_COLLECTIONS_TAG).commit();
}
// else there be stuff inside the savedInstanceState bundle
else{
// fragments that will always be in the savedInstanceState bundle
editCollectionFragment = (FragmentA)getFragmentManager().findFragmentByTag(EDIT_COLLECTIONS_TAG);
//////////// find entries that are common to AddedFragmentTagsSet & savedInstanceState's set of keys ///////////
Set<String> commonKeys = savedInstanceState.keySet();
commonKeys.retainAll(AddedFragmentTagsSet);
for(String key : commonKeys){
editItemFragment = FragmentC)getFragmentManager().getFragment(savedInstanceState, key);
}
}
}
...but that is untested and presented merely to spark ideas; in trying to figure out what was wrong with my activity's handling of configuration changes I did stumble and fumble in this direction and think it might bear fruit for the right person; though ultimately, obviously, I found a simpler way to fix my issues this time around.

How do I call a method of a running child activity from a parent activity?

I am developing an android app which has 3 tabs, created in MainActivity.java. Every tab has its own activity. In those activities I have a method called "Refresh()" to update the listview in that tab.
When the user clicks on a button the method "refreshTab(View v)" is called.
// Tab refreshen
public void refreshTab (View v) {
Activity MyActivity = this.getCurrentActivity();
MyActivity.Refresh();
}
This is throwing "The Method Refresh() is undefined for the type Activity. However, "MyActivity" is filled with the tab activity.
How would I go about getting this to work?

You need to cast the activity to your type of activity. Right now you are trying to call the Android class activity, which does not have a "Refresh" function.

Your button handler is a little over-complicated (even though it's only two lines)...
Just do something like:
// Tab refreshen
public void refreshTab (View v) {
Refresh();
}
If the way you've defined your OnClickListener is directly inline (but still within your activity's class), you may need to add a little direction, where MyClassType is the name of your class that extends Activity:
// Tab refreshen
public void refreshTab (View v) {
MyClassType.this.Refresh();
}