I want to have a fragment for each item in a listview, because I want to separate some logic out. I am using a view holder for each item. If the view doesn't exist, I create a new fragment and add it into the container.
holder.mMyFragment = new MyFragment(mActivity, this);
mActivity.getSupportFragmentManager().beginTransaction().add(R.id.my_container, holder.mMyFragment).commit();
Also for each item, I call holder.mMyFragment.setUi(dataSource, position) to set UI of the fragment based on the data source and position.
The problem I'm having is I initialize the UI elements of fragment in onCreateView method of the fragment class, but it's not called when I add the fragment to the item. So later when I call setUi() which uses some UI elements in fragment it complains a NullPointerException. Does anyone have a suggestion? Thanks!
"THERE IS A SOLUTION" for this.
The issue is, you cannot add fragment directly to the container(FrameLayout) with same "id" in listview as you have done in the above code.
The trick is, create listview(Recyclerview) of "LinearLayout". Then dynamically create FrameLayout in adapter and assign different id's for each. Inflate Fragment to FrameLayout and this FrameLayout to LinearLayout.
#Override
protected void onBindBasicItemView(RecyclerView.ViewHolder holder, int position) {
if (holder instanceof VideoHomeViewHolder) {
VideoHomeViewHolder videoHomeViewHolder = (VideoHomeViewHolder) holder;
FrameLayout frameLayout = new FrameLayout(mContext);
frameLayout.setId(position+1); //since id cannot be zero
FragmentHelper.popBackStackAndReplace(mFragmentManager, frameLayout.getId(),
new ShowLatestVideosFragment(mShowLatestVideosItems.get(position)));
videoHomeViewHolder.linearLayout.addView(frameLayout);
}
}
I want to have a fragment for each item in a listview, because I want to separate some logic out.
You can't use fragment as list item views because the API doesn't allow you - View and Fragment aren't even related so there's no way you can use it like that. Make custom views and use adapter getViewTypeCount and getView to use different list item behavior.
Fragment are managed by Activity's FragmentManager or by other Fragments child FragmentManager; while list item views are managed by ListView & ListAdapter. You can use ListViews in Fragments, but not the other way around.
A simple way.
One problem:You should store add restore fragment state.
holder.mMyFragment = new MyFragment(mActivity, this);
int id = View.generateViewId();
findViewByTag("abc").setId(id);
mActivity.getSupportFragmentManager().beginTransaction().add(id, holder.mMyFragment).commit();
Hi I was facing the same problem and I found the way to do it.
My problem was similar to you:
"I want to have a fragment for each item in a listview, because I want to separate some logic out"
In my app I have to give the option to display custom items in vertical (listView) and horizontal (ViewPager) mode. Additionally I had to deal with 18 custom items and each one with different logic, so the best approach was reusing the fragments that I was using for ViewPager in ListView.
I got it but not in the way you were trying, I mean, I used my fragments like "ViewHolders":
Define fragment's widget like variables of class in each fragment.
Create a custom ArrayAdapter and override: getViewTypeCount(), getItemViewType(int position), getCount(), getItem(int position) getView(int position, View convertView, ViewGroup parent)
In getView I checked what kind of layout I needed before "inflate" the respective XML, create a fragment, assign widget from XML to fragment (with rootView.findViewById) and set "tag" with the new fragment.
What you can see at this point is that fragments in ListView never got attached to Activity but you got what you wanted: logic distributed in several parts and all benefits of ListView (reuse of rows, scroll, etc).
If you need I can post part of my code but you have to deal with "spanglish" ;).
UPDATED
All the problem is because when you create a Fragment to be used with ViewPager, usually all "layout and "setup" code is inside onCreateView method, I mean:
Get the view object you are going to use (View rootView = inflater.inflate(R.layout.fragment_question_horizontal_container, container, false);)
Get the widgets from above layout, define behaviors, fonts, etc: (answer = (EditText)rootView.findViewById(R.id.answer_question_text);)
Until this point there is nothing weird.
If you are going to use a fragment with the behavior described above you have to "emulate" the call to onCreateView, fill the data and attach it to the listView.
Here is the trick: split the code in onCreateView in some methods that doesn't care about who's calling them. An example of my onCreateView:
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_pregunta_horizontal_container, container, false);
addAnswerLayout(rootView, R.layout.fragment_pregunta_texto, getActivity());
setUpComponents(rootView);
//those 2 methods are about my app logic so I'm not going to talk much about them
setUpQuestionState(savedInstanceState);
readSavedAnswer();
return rootView;
}
public void addAnswerLayout(View rootView, int optionId, Context context) {
mContext = context;
RelativeLayout relativeLayout = (RelativeLayout)rootView.findViewById(R.id.pregunta_container);
LayoutInflater inflater = ((Activity)mContext).getLayoutInflater();
View newView = inflater.inflate(optionId, relativeLayout, false);
relativeLayout.addView(newView);
}
public void setUpComponents(View rootView) {
//next line: some heritage that you can ignore
super.setUpComponents(rootView);
respuesta = (EditText)rootView.findViewById(R.id.pregunta_respuesta_texto);
respuesta.setTypeface(UiHelper.getInstance(getActivity()).typeface);
respuesta.setTextColor(mContext.getResources().getColor(R.color.drs_gris));
...
}
Now let's go to the CustomArrayAdapter for list view:
Define your customArrayAdapter something like this: PreguntasVerticalArrayAdapter extends ArrayAdapter<Pregunta> where "Pregunta" is a generic Fragment with the logic from above.
Override getViewTypeCount(), getItemViewType(int position), getCount(), getItem(int position) getView(int position, View convertView, ViewGroup parent).
The getView follow the same behavior: get the object for the given position in params, reuse a "viewholder" and fill the data. Here my getView:
#Override
public View getView(int position, View convertView, ViewGroup parent) {
View rowView = convertView;
Pregunta pregunta = mData.get(position);
if (rowView == null)
rowView = createQuestionUI(pregunta, parent, position);
fillDataInRow((PreguntaUI)rowView.getTag(), pregunta, position);
return rowView;
}
private View createPreguntaUI(Pregunta pregunta, ViewGroup parent, int position) {
View rootView = null;
LayoutInflater inflater = (mPreguntasVerticalFragment.getActivity()).getLayoutInflater();
//you can ignore this part of the code ralted to Bundle.
Bundle args = new Bundle();
args.putLong(PreguntaUI.PREGUNTAUI_ID, pregunta.getIdpregunta());
args.putInt(PreguntaUI.PREGUNTAUI_INDEX, position);
args.putInt(PreguntaUI.PREGUNTAUI_TOTAL_QUESTIONS, getCount());
//internal method of "pregunta" to know what kind of question it is.
String tipo = pregunta.getTipo();
if (tipo.equalsIgnoreCase(PreguntaType.TEXT.toString())) {
rootView = inflater.inflate(R.layout.fragment_pregunta_vertical_container, parent, false);
Pregunta_texto pregunta_texto = new Pregunta_texto();
pregunta_texto.setArguments(args);
//LOOK AT THIS POINT!!!: I'm calling the same methods that I called in onCreateView fragment's method.
pregunta_texto.addAnswerLayout(rootView, R.layout.fragment_pregunta_texto,
mPreguntasVerticalFragment.getActivity());
pregunta_texto.setUpComponents(rootView);
pregunta_texto.setUpQuestionState(null);
pregunta_texto.readSavedAnswer();
//I'm adding the fragment to reuse it when I can
rootView.setTag(pregunta_texto);
}
else if ...
return rootView;
}
That is all... at this point, if you have enough experience dealing with CustomArrayAdapters and Fragments you probably got it! :D
From the Android Documentation : "A Fragment represents a behavior or a portion of user interface in an Activity. You can combine multiple fragments in a single activity to build a multi-pane UI and reuse a fragment in multiple activities."
For your activity, do you want to add 2 fragments where the first one displays a listView (= ListFragment and the other one is in the right and is shown only when the user clicks on an item (from the first fragment or listView) ?
Instead of using ListFragment, you can use RecyclerView, Android has documentation on that:
https://developer.android.com/training/basics/fragments/creating.html#AddInLayout
Related
I've seen all the related questions, and tried their answers. I have a ListView inside a fragment and it's onItemClick method is called when inside one activity, but not called when in another one. Everything else is the same. I've tried:
Changing android:clickable explicitly.
Changing android:focusable and android:focusableInTouchMode explicitly.
Calling listView.setItemsCanFocus.
Adding android:descendantFocusability="blocksDescendants" attribute both on fragment and activity root.
Still, it's not working. It's the same fragment with same adapter, which doesn't have conditionals about being in which activity. However, in one activity it works perfectly, and in another, onItemClick is not called. I'm on ICS. Why would this happen?
UPDATE:
Here is the relevant code in my fragment:
dataSource = (ArrayList<Map<String, Object>>) task.getResult();
FeedAdapter adapter = new FeedAdapter(getActivity(), dataSource, getUser());
ListView list = (ListView) rootView.findViewById(R.id.listView);
list.setItemsCanFocus(true);
//just trying these
list.setOnItemClickListener(self);
list.setAdapter(adapter);
adapter.notifyDataSetChanged();
if (dataSource.size() == 0) {
noPostsLabel.setVisibility(View.VISIBLE);
}
And in my adapter:
public View getView(int position, View convertView, ViewGroup parent) {
View view;
final Map<String, Object> post = objects.get(position);
LayoutInflater inflater = LayoutInflater.from(getContext());
if (convertView == null || convertView.getId() == R.id.headerRoot) {
view = inflater.inflate(R.layout.list_item_post_layout, parent, false);
} else {
view = convertView;
}
view.setClickable(false); //just trying these two now, they weren't here originally
view.setFocusable(false);
//populate
view.setTag(post);
[...] //populate the cell. very long code, redacted.
return view;
}
UPDATE 2:
I've also realized some cells are also not selectable in my "working" activity too, when they have a visible HorizontalScrollView within the cell (I have file attaching feature and it's only visible when there are files. Otherwise, it's in GONE visibility state). I have no idea why it's causing such trouble.
UPDATE 3:
I've also found out that views inside the cell are responsive. It's just the cell view itself which is not taking input.
UPDATE 4:
I've ended up moving the tap handler logic to the cell layout itself, instead of relying on list view's handler. I know it's not a good practice but I had to meet a deadline. Besides, it's working pretty smooth now. I'm not closing/answering the question as the technical problem is still present and I haven't found a real solution to it. I've just used a workaround to meet my project deadline.
I am not sure of your problem and I don't see the full code to debug.
I'll submit a sample code which normally should work in a Fragment.
#Override
public void onViewCreated(View view, Bundle savedInstanceState) {
ListView list = (ListView) view.findViewById(R.id.listView);
list.setOnItemClickListener(new AdapterView.OnItemClickListener() {
#Override
public void onItemClick(AdapterView<?> parent, View view, int positi on, long id) {
Log.d(TAG, "onItemClick");
}
});
Notes:
I don't use root or any other cached object. I use the view parameter for calling findViewById().
I don't know self also. Instead I instantiated a new view or AdapterView.
Have you tried setting callbacks for the fragments? That's the way Android recommends it. You can check out - https://developer.android.com/training/basics/fragments/communicating.html#Deliver
Inside the dialogFragment I have viewPager with two pages. Every page contains a custom adapter. One adapter with list of spinners, other adapter with list of EditTexts. ViewPager adds adapters fine.
public class PageFragment extends Fragment {
...
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.pagefragment_newprod, null);
LinearLayout ll=(LinearLayout) view.findViewById(R.id.tvLL);
ListView listView=new ListView(getActivity());
ll.addView(listView);
if (pageNumber==0){
dropDownAdapter=new DropDownAdapter(getActivity(), fillListAdapter);
listView.setAdapter(dropDownAdapter);
} else if (pageNumber==1){
boxAdapter = new BoxAdapter(getActivity(), filledFields);
listView.setAdapter(boxAdapter);
}
return view;
}
}
But it works to slow! Current Adapter (I mean at the curren page) create views every milisecond! Look at this:
public class BoxAdapter extends BaseAdapter{
...
#Override
public View getView(final int position, View convertView, ViewGroup parent) {
if (view == null) {
view = lInflater.inflate(R.layout.addproduct_item, parent, false);
}
Log.d(LOG_TAG, "====As I said every milisecond...======");
EditText editText = (EditText) view.findViewById(R.id.addProductEditText);
editText.setText(p.value);
return view;
}
}
Even when I focused the EditText this Log.d write messages every milisecond!
Besides that, adapter at the next page works too. I have other Log.d at the other adapter getView and it works when I used different page's adapter!
Please help me to understand what is wrong...(
The question has already been solved in the comments. The solution for the OP was apparently to remove complex fragments and their adapter. However, I also had complex fragments in a tab layout with a ViewPager, and the following solution fixed the slow paging problem:
viewPager.setOffscreenPageLimit(2);
The 2 will keep two pages away from the current page in memory. This was enough for me because I had three tabs. Be careful about keeping too many pages in memory, though. See the documentation.
I have a listview that is populated via an adapter. I need one of the items (which are just bits of text) in the listview to have a different background compared to the others (to mark it as the currently selected one).
I have all of the background logic, I just need a way to say listview.setBackgroundById(int position)
or something like that.
How do I do this?
This needs to be as simple as possible, 'cause all of the other things done in the Activity are currently working perfectly. :)
As asked, this is my Adapter that I'm using:
public class SampleAdapter extends ArrayAdapter<SampleItem> {
private String title;
public SampleAdapter(Context context) {
super(context, 0);
}
public View getView(final int position, View convertView, ViewGroup parent) {
if (convertView == null) {
convertView = LayoutInflater.from(getContext()).inflate(R.layout.row_station, null);
}
TextView title = (TextView)convertView.findViewById(R.id.station_name);
font.setFont(title, 2, getActivity());
title.setText(getItem(position).title);
RelativeLayout info = (RelativeLayout)convertView.findViewById(R.id.info_relative_button);
info.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
MainActivity.setCurrentTab(41);
MainActivity.setBackDisabled(true);
Log.e("current tab:",String.valueOf(MainActivity.getCurrentTab()));
Fragment fragment = new StationInfo();
FragmentManager fragmentManager = getFragmentManager();
fragmentManager.beginTransaction().replace(R.id.content_frame, fragment).commit();
UserManager.getInstance().setStationId(getItem(position).id);
}
});
return convertView;
}
}
The SampleItem has 2 String fields, title and id, it's very simple.
You need to use a custom list adapter and have it return views with your desired background. Create a class extending ListAdapter or any of the existing SimpleAdapter etc and override getView to inflate a suitable view for your element, and add any logic you need to set the background of that view.
There is no way to tell the listview itself to decorate some of its elements by id or position.
Update: I just noticed you added the list adapter code.
Since you are already implementing getView, to change the background of your element simply call convertView.setBackgroundColor, or have two different views inflated depending on the situation.
(BTW it's really bad practice to call static methods on your activity like in your onClickListener.)
In ListView adapter:
#Override
public View getView(int position, View view, ViewGroup viewGroup) {
if(view==null)
....
//for example every even list item to be grey, every odd to be white
if(((position+1)%2)==0)
view.setBackgroundColor(mContext.getResources().getColor(R.color.grey));
else view.setBackgroundColor(mContext.getResources().getColor(android.R.color.white));
Hope you get an idea...
If I want to reuse a Fragment inside my ArrayAdapter, is that inefficient?
That is, in my ArrayAdapter, my getView() would look like this:
public View getView(final int position, View convertView, ViewGroup parent) {
UserFragment userFragment = new UserFragment();
return userFragment.getView();
}
I ask, because normally in the getView() method, it looks something like this:
public View getView(final int position, View convertView, ViewGroup parent) {
View view = convertView;
if (view == null) {
LayoutInflater inflater = (LayoutInflater) getContext()
.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
view = inflater.inflate(R.layout.user, null);
...//do stuff
}
Is it inefficient to create a Fragment each time the getView() is called?
First, Fragment has its own life cycle, like Activity's onCreate, onDestory, etc.
So if you do UserFragment userFragment = new UserFragment() in getView(), every time you scroll the ListView, a lot of different Fragment's instances will be created and scroll-out ones will be GC. This costs a lot.
Second, you are not reusing views. Each Fragment's instance has its own view structure, so userFragment.getView() will return a brand new View each time.
Basically, it is not recommended to use Fragment inside ListView. Use convertView is more efficient.
A Fragment is managed by a FragmentManager (through FragmentTransactions) owned by an Activity. Or you can have Fragments in Fragments.
A ListView manages its own views separately and also is recycling these views so when you scroll you'll get in convertView the view that you should use.
Bottom-line is: fragments reside ONLY in activities or in other fragments, while Views (ListView is a descendant of View) stay in Fragments or in Activities.
So: Is it inefficient to create a Fragment each time the getView() is called?. I see no reason why you should do this. In fact, it would be 1000 times more helpful to make push-ups instead of using Fragments in Views. There is not a single good technical article where somebody discusses these.
I write a Android application using ViewPager. And now, I have a confusion when use ViewPager.
When I use the code below to inflate a view from a layout xml file and add it into viewpager.
public Object instantiateItem(ViewGroup container, int position) {
View view = View.inflate(ShareTasksActivity.this, R.layout.item_internal_advertisement, null);
container.addView(view);
return view;
}
But When I use code below, the viewpager will show nothing.
public Object instantiateItem(ViewGroup container, int position) {
View view = View.inflate(ShareTasksActivity.this, R.layout.item_internal_advertisement, container);
return view;
}
I think the two snippets do the same thing, but the results are different. I don't know why. Can anyone help me ? Thank you !
Actually, these snippets are doing slightly different things:
Inflates view and add it to the container;
Just inflates view;
The issue here is the following:
call to View.inflate(ShareTasksActivity.this, R.layout.item_internal_advertisement, container); is equal to the following one: LayoutInflater.from(ShareTasksActivity.this).inflate(R.layout.item_internal_advertisement, container, false); (checkout its source). The same time instantiateItem() documentation mentions:
The adapter is responsible for adding the view to the container given
here
So, second variant doesn't work at all because it is not adding view to the container.
However, first variant per mine understanding also has an issue: layout parameters You might provide for top level view R.layout.item_internal_advertisement will not be applied if You provide null parent view.