Develop Reference

How to use main actvitiy floating action button from fragments in single activity?

I'm using BottomAppbar with floating action button in single activity.The Fab has different responsibility in different fragment.
HomeFragment -> adds new item
AddProblemFragment ->saves item(also icon changes)
DetailsFragment -> adds items to selected collections(also icon changes)
I have tried to use listener between activity and fragments. Icon and position changes perfectly but I couldn't handle calling methods that in fragments when clicked.
To solve clicking problem I'm getting fab reference from activity with
fab = requireActivity().findViewById(R.id.fab) in each fragment (in onViewCreated).
So, problem is after orientation changes gives
java.lang.NullPointerException: requireActivity().findViewById(R.id.fab) must not be null
Is there way to avoid getting this error after orientation changes? or Which lifecycle should choose to initialize fab?
Is it possible to initialize fab in BaseFragment and use it because almost each fragment have fab?
The Code Snippets:
//Each fragment same approach
private lateinit var fab:FloatingActionButton
override fun onViewCreated(view:View,savedInstanceState:Bundle?){
fab = requireActivity().findViewById(R.id.fab_btn_add)
fab.setImageResource(R.drawable.ic_related_icon)
fab.setOnClickListener {
//calls method
}

First you need to create an interface for you fab click listener for Example:
interface FabClickCallback {
void onFabClick()
}
and on your activity,
You Need create an instance from this Callback
private FabClickCallback fabCallback;
and you want create new method inside your Activity called for Example:
public void handleFabClickListener(FabClickCallback callback){
// TODO Here put callback
this.fabCallback = callback;
}
and you want trigger this callback when user click on Fab Button like This:
fab.setOnClickListener ( view -> {
if (this.fabCallback != null ) {
this.fabCallback.onFabClick();
}
});
finally on Each Fragment you want handle Fab Click you want call this function and pass your actual fab click code :
((YourActivity) requireActivity()).handleFabClickListener(this);
and your fragment must implements FabClickCallback interface

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

recyclerview open activity with navbar on click item

I'm new android developper. In my application I have a main activity with toolbar, that contains a title, and a recycler view.
The recycler view contains some items. I want to open a activity on click on them. My code is able to open the activity but the toolbar disappear.
I open the activity like this:
public VHolder(final View itemView){
super(itemView);
title = ((TextView) itemView.findViewById(R.id.articleTitle));
itemView.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
Intent intent = new Intent(itemView.getContext(), ArticleActivity.class);
intent.putExtra("title", currentNews.title);
intent.putExtra("content", currentNews.htmlContent);
itemView.getContext().startActivity(intent);
}
});
}
Have you any ideas and advices ?
Sorry about my poor english ;).

You are doing everything in the correct way. The problem is that toolbar is just another widget on your Activity and cannot be shared between multiple activities. So you should add toolbar view to the layout of the Activity which you are starting (ArticleActivity).
As another option you can show Fragment over RecyclerView instead of starting new Activity. Similar to this: how to open a different fragment on recyclerview OnClick

I have found the cause of my problem of toolbar. The opened activity (ArticleActivity) not extends "AppCompatActivity" like the main activity but, "Activity".

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();
}

Subactivity onClick Firing in Parent Class

I am having some trouble with the onClick handler in a sub activity of an ActivityGroup.
I am launching a StoreActivity using:
Intent storeIntent = new Intent(this, StoreActivity.class);
storeIntent.putExtra(StoreActivity.INTENT_STORE_ID, storeId);
View newVeiw = getLocalActivityManager().startActivity("StoreActivity", storeIntent).getDecorView();
setContentView(newVeiw);
Log.e("DEBUG", "current activity: " + getLocalActivityManager().getCurrentActivity().toString());
In the StoreActivity layout I have a button which defines an onClick method. For some reason however, it is trying to call this in the parent class that launched StoreActivity. Am I doing something wrong when launching the activity? The output of Log.e above says that StoreActivity is the current activity so I am a bit lost as to why this is happening. I can get around this by defining an onClickListener for the button in code in StoreActvity but I would like to avoid that if possible.

I think this is because you are calling setContentView from the parent activity instead of the subactivity. Why don't you just start the activity in the intent instead and set the content view in the new activity? It would be much simpler.
Try this:
Intent storeIntent = new Intent(this, StoreActivity.class);
storeIntent.putExtra(StoreActivity.INTENT_STORE_ID, storeId);
startActivity(storeIntent);
and then in StoreActivity.java do:
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
View newVeiw = getLocalActivityManager().startActivity("StoreActivity", storeIntent).getDecorView();
setContentView(newView); //not sure if this would work, would probably be easier to put your xml layout file in here.
}

Ok I have solved this. The problem was unrelated to any of this code. I had a common base class to my activities and in that I had accidentally made the inflater a singleton. This meant that all inflated layouts belonged to the first class that created that singleton instance which happened to be the class that was incorrectly receiving the onClick event. Removing that singleton resolved this.