I have got CardView with Views inside a RecyclerView. I have created adapter in which assets are attached to Views and everything works. Now, I would like to change these Views from my activity. Is it any simple way to do that?
public class MainActivity extends AppCompatActivity {
RecyclerView recyclerView;
private RecyclerView.LayoutManager layoutManager;
private List<Offer>offers;
TextView timer; //timer inside CardView
private void getViewReferences() {
recyclerView = (RecyclerView)findViewById(R.id.mainRecyclerView);
timer = (TextView)findViewById(R.id.timer);
}
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
getViewReferences();
layoutManager = new LinearLayoutManager(this);
recyclerView.setLayoutManager(layoutManager);
initializeData();
initializeAdapter();
timer.setText("13:16"); //NullPointerException here
}
private void initializeData(){
offers = new ArrayList<>();
offers.add(new Offer("godzina", R.drawable.zdj, 200));
offers.add(new Offer("godzina", R.drawable.zdj));
}
private void initializeAdapter() {
RecyclerViewAdapter adapter = new RecyclerViewAdapter(offers);
recyclerView.setAdapter(adapter);
}
}
So you don't want to change the Views but you want to update the text values of the views in your list.
You can't directly do that by trying to find the Views in the recyclerView and change the text. The adapter is responsible for giving values to your list. So you need to update the dataset in the adapter and call one of the notifyDataSetChanged methods on the adapter to update the recyclerView.
The big advantage of this design is that it places Views in Cache in order to reuse them multiple times without having to inflate and construct them again. This is a huge performance improvement.
You need to read the docs and some tutorials to understand the adapter design pattern better.
Related
What is the use of recyclerview.setLayoutManager() in this code?
Please elaborate it in detail.I know about recyclerview but i am confused on what is the use of setLayoutManager() here?
public class MainActivity extends AppCompatActivity {
public static final int NEW_WORD_ACTIVITY_REQUEST_CODE = 1;
private WordViewModel mWordViewModel;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Toolbar toolbar = findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
RecyclerView recyclerView = findViewById(R.id.recyclerview);
final WordListAdapter adapter = new WordListAdapter(this);
recyclerView.setAdapter(adapter);
recyclerView.setLayoutManager(new LinearLayoutManager(this));
More than a year late but the idea behind the setLayoutManager is to set the layout of the contents, i.e. list of repeating views in the recycler view. If you scroll down to the documentation here, it will tell you that there are several strategies for lists and grids so that should give you a clue. Furthermore, it tells you that without it, RecyclerView will not function i.e. there is no out of the box default.
So if you want e.g. to set the LinearLayoutto be horizontal (by default it is vertical) then you have to specify that.
LinearLayoutManager layoutManager
= new LinearLayoutManager(this, LinearLayoutManager.HORIZONTAL, false);
RecyclerView myItems = findViewById(R.id.my_recycler_view);
myItems.setLayoutManager(layoutManager);
I have a list of data to be displayed in a recycler view and that is working fine. Now I have another dynamic list of data to be displayed inside the parent recycler-view. So I tried using another recycler-view inside the parent recycler-view, that is not working fine. It will be good if I get some idea of using recycler-view inside another one. Thanks in advance..!
I have illustrated my problem with an example:
For eg: I have a parent recyclerView with five linearLayout and I have created a child recyclerView inside the Linearlayout with visibility GONE. Now when I click the first Linearlayout I am changing the visibility of child recyclerView for the first Linearlayout to VISIBLE and attaching a separate view to it and same concept for all the other Linearlayouts. What happens is when I click first, second, third and fourth linearLayout the child recyclerView is not displaying date which I pass to it, all those first, sec, third and fourth data are accumulated and displayed in the last (i.e) inside fifth linearLayout.
Here is my parent recyclerview code:
class CardAdapter extends RecyclerView.Adapter<CardAdapter.MyViewHolder>
{
RecyclerView insideCardRecyclerView,recyclerView;
List<String> monthsWeek = new ArrayList<>();
List<String> dealers = new ArrayList<>();
List<String> dealersList = new ArrayList<>();
List<String> date = new ArrayList<>();
HashSet<String> dealersListHash = new HashSet<>();
public CardAdapter(List<String> monthsWeek,List<String> dealers,List<String> date)
{
this.monthsWeek = monthsWeek;
this.dealers = dealers;
this.date = date;
}
public class MyViewHolder extends RecyclerView.ViewHolder
{
ProgressBar progressBar;
RecyclerView recyclerView;
TextView period;
LinearLayout linearLayoutParent,linearLayoutCardDetails;
public MyViewHolder(View view)
{
super(view);
linearLayoutParent = (LinearLayout) view.findViewById(R.id.card_view_linear_parent_layout);
linearLayoutCardDetails = (LinearLayout) view.findViewById(R.id.linear_card_layout_details);
period = (TextView) view.findViewById(R.id.period_summary_graph_card);
insideCardRecyclerView = (RecyclerView) view.findViewById(R.id.summary_graph_card_view_recycler_view);
}
}
#Override
public CardAdapter.MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType)
{
View itemView = LayoutInflater.from(getActivity())
.inflate(R.layout.summary_card_view,parent,false);
recyclerView = (RecyclerView) parent;
return new CardAdapter.MyViewHolder(itemView);
}
#Override
public void onBindViewHolder(final MyViewHolder holder, final int position)
{
holder.period.setText(monthsWeek.get(position));
holder.linearLayoutParent.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view)
{
if(searchClick)
{
for (String date1 : date)
{
if(Objects.equals(date1,monthsWeek.get(position)))
{
Log.e("Summary123 date..///", date1);
dealersList.add(dealers.get(date.indexOf(date1)));
}
}
searchClick = false;
holder.linearLayoutCardDetails.setVisibility(View.VISIBLE);
dealersListHash.addAll(dealersList);
dealersList.clear();
dealersList.addAll(dealersListHash);
//if the condition is true i am attaching another recyclerview inside this.
cardAdapterList = new CardAdapterList(dealersList);
LinearLayoutManager mLayoutManager1 = new LinearLayoutManager(getActivity(), LinearLayoutManager.VERTICAL,true);
mLayoutManager1.setReverseLayout(false);
insideCardRecyclerView.setLayoutManager(mLayoutManager1);
insideCardRecyclerView.setItemAnimator(new DefaultItemAnimator());
insideCardRecyclerView.setAdapter(cardAdapterList);
}
else
{
searchClick = true;
holder.linearLayoutCardDetails.setVisibility(View.GONE);
}
}
});
}
#Override
public int getItemCount() {
return monthsWeek.size();
}
}
I've been in trouble sometimes with RecyclerView when multiple lists are needed to be shown in a single page of the application. Its not a very good idea actually to have multiple lists in a single layout but however, the idea of having a ScrollView and the lists inside that ScrollView is even worse.
I had to implement a ListView inside a ScrollView once and yes it was not a very good experience. Firstly, my list was not scrolling at all. Then I had to add some code to disable the scrolling when the touch is detected inside the list. It was not a very good idea of solving the actual problem. I had another problem of having a fixed height of the ListView. In case of list items with dynamic heights, the solution failed.
Having two lists in the layout, one after one is not a good idea either. As the first list need to have a fixed height.
So, after searching for suggestions about how can I implement two lists in a single layout file, I found most of the developers suggests of having a single list with a header and footer if necessary. Later, I could manage to show two lists in a single RecyclerView using my custom Adapter. I thought I should save some of my code for future use and hence, you see this note.
You can refer this sample code.
i hope that you could help me.
i want to use a expandablerecyclerview but i dont need to expand a list of other elements like the lib says
library example
I just need that the item expand and show more info of the item inside the recycler
You can use advanced recyclerview's expandable future
public class ExpandableWithHeaderFooterExampleActivity extends AppCompatActivity {
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_demo_minimal);
OnListItemClickMessageListener clickListener = new OnListItemClickMessageListener() {
#Override
public void onItemClicked(String message) {
View container = findViewById(R.id.container);
Snackbar.make(container, message, Snackbar.LENGTH_SHORT).show();
}
};
RecyclerView recyclerView = findViewById(R.id.recycler_view);
// Setup expandable feature and RecyclerView
RecyclerViewExpandableItemManager expMgr = new RecyclerViewExpandableItemManager(null);
// Create wrapped adapter: MyItemAdapter -> expMgr.createWrappedAdapter -> MyHeaderFooterAdapter
RecyclerView.Adapter adapter;
adapter = new SimpleDemoExpandableItemAdapter(expMgr, clickListener);
adapter = expMgr.createWrappedAdapter(adapter);
adapter = new DemoHeaderFooterAdapter(adapter, clickListener);
recyclerView.setAdapter(adapter);
recyclerView.setLayoutManager(new LinearLayoutManager(this));
// NOTE: need to disable change animations to ripple effect work properly
((SimpleItemAnimator) recyclerView.getItemAnimator()).setSupportsChangeAnimations(false);
expMgr.attachRecyclerView(recyclerView);
}
}
I have a recyclerview inside a fragment and that fragment is inside a view pager.
notifydatasetchanged() is not working even though the same code works in other projects of mine. The only difference I can see is that it is inside a view pager now?.
This is how notify the change:
public void updateRecyler(){
// Clear the current array
alarmsFromSP.clear();
// Update the array (This is working the array size is changing)
alarmsFromSP.addAll(AlarmCollection.getAlarms(getActivity()));
// Notify the change
adapter.notifyDataSetChanged();
}
I create the recylerview in oncreate like this:
public class FragmentAllAlarms extends Fragment {
// Arraylist of the alarm data from the strings
ArrayList<Alarm> alarmsFromSP;
tabRefreshReceiver r;
RecyclerView rv;
AlarmsAdapter adapter;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View v = inflater.inflate(R.layout.fragment_all_alarms, container, false);
// Recycler
rv = (RecyclerView) v.findViewById(R.id.mainAlarmRecyclerView);
rv.setLayoutManager(new LinearLayoutManager(getActivity()));
// Get saved data for alarms from the shared preferences string
alarmsFromSP = AlarmCollection.getAlarms(getActivity());
System.out.println("StringIs"+alarmsFromSP.size());
// Adapter
adapter = new AlarmsAdapter(getActivity(), alarmsFromSP);
rv.setAdapter(adapter);
Is it possible I am losing reference to the array or is it somthing to do with the viewpager?
I have been stuck with this for two days now any help is greatly appreciated.
Thanks in advance
make sure that updateRecyler() is called,
and try to change adapter.notifyDataSetChanged(); to rv.getAdapter().notifyDataSetChanged();
this worked for me once.
I have faced the same problem, then I found a temporary solution, instead of using notifyDataSetChanged() use
recyclerView.setAdapter(adapter);
recyclerView.scrollToPosition(postion);
I am trying to use RecyclerView to create a chat application. I am using a LinearLayoutManager with setReverseLayout(true).
When I am scrolled all the way to the bottom (which is the dataset start = newest message) and a new message is inserted into the dataset, the item appears at the bottom of the list as expected (the view is scrolled up to make room for the new item).
The problem I have is when I have scrolled up to see the older messages. When a new message is inserted to the beginning of the dataset, the view is scrolled up by approximately one message height, even though that message isn't even rendered since it's out of the viewport's range.
How can I keep the scrolling behavior, when the view is scrolled to the bottom, but disable it when I have scrolled to the older messages?
UPDATE:
I also made a small app, where this problem is reproduced:
https://github.com/ehehhh/RecyclerViewProblem
UPDATE 2: I committed the fix that worked to the repo I made as well.
Relevant code (hopefully):
compile 'com.android.support:recyclerview-v7:24.2.0'
XML:
<android.support.v7.widget.RecyclerView
android:layout_width="match_parent"
android:layout_height="match_parent"
android:clipToPadding="false"
android:paddingBottom="8dp"
android:paddingTop="8dp"
app:layout_behavior="#string/appbar_scrolling_view_behavior"/>
RecyclerView init code:
layoutManager = new LinearLayoutManager(context);
layoutManager.setOrientation(LinearLayoutManager.VERTICAL);
layoutManager.setReverseLayout(true);
recyclerView.setLayoutManager(layoutManager);
recyclerView.setScrollContainer(true);
recyclerView.setLayoutAnimation(null);
recyclerView.setItemAnimator(null);
adapter = new ChatAdapter(...);
recyclerView.setAdapter(adapter);
Adapter:
public class ChatAdapter extends RecyclerView.Adapter<ChatViewHolder> {
private List<MessageWrapper> dataset;
public ChatAdapter(List<MessageWrapper> dataset, ...) {
this.dataset = dataset;
setHasStableIds(true);
}
...
#Override
public long getItemId(int position) {
return dataset.get(position).getId();
}
#Override
public int getItemCount() {
return dataset.size();
}
public void datasetChanged(List<MessageWrapper> dataset) {
this.dataset = dataset;
notifyDataSetChanged();
}
}
When a new item is added to the dataset, I just call the datasetChanged method in the adapter.
in Recycler view using notifyDataSetChanged is redundant if you know the items changed
you can use
notifyItemInserted(position)
in this particular case what worked was
notifyItemInserted(0);
or
notifyItemRangeInserted(positionStart, newItems.size() - 1)
this will only rebind the views in this range
check
https://developer.android.com/reference/android/support/v7/widget/RecyclerView.Adapter.html#notifyItemInserted(int)
I had a similar issue. I was making chat application, and my RecyclerView was always displaying rows from the top, and I wanted it to go to the bottom to display last inserted message. This is what worked for me, recyclerView.scrollToPosition(messages.size()-1) added in ChildEventListener:
public class MainActivity extends AppCompatActivity {
private RecyclerView recyclerView;
private MessageAdapter mMessageAdapter;
private List<Message> messages;
private FirebaseDatabase mFirebaseDatabase;
private DatabaseReference mMessagesDatabaseRef;
....
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mFirebaseDatabase = FirebaseDatabase.getInstance();
mMessagesDatabaseRef = mFirebaseDatabase.getReference().child("messages");
recyclerView = (RecyclerView) findViewById(R.id.recycler_view);
// Initialize message ListView and its adapter
messages = new ArrayList<>();
mMessageAdapter = new MessageAdapter(messages);
RecyclerView.LayoutManager mLayoutManager = new LinearLayoutManager(getApplicationContext());
recyclerView.setLayoutManager(mLayoutManager);
recyclerView.setAdapter(mMessageAdapter);
.....
mMessagesDatabaseRef.addChildEventListener(new ChildEventListener() {
#Override
public void onChildAdded(DataSnapshot dataSnapshot, String s) {
messages.add(dataSnapshot.getValue(Message.class));
recyclerView.scrollToPosition(messages.size()-1);
mMessageAdapter.notifyDataSetChanged();
}
......
});
}
}