CODEWITHSUNDEEP
androidandroid-recyclerview
B. Tsai
B. Tsai

Reputation: 549

Android recyclerView findViewHolderForAdapterPosition returns null

I want to click an item in recyclerView programmatically, I found a way do that:

recyclerView.findViewHolderForAdapterPosition(0).itemView.performClick();

but it doesn't work for me, the findViewHolderForAdapterPosition just returns null.

Did I miss something in my code?

HistoryListAdapter:

public class HistoryListAdapter extends RecyclerView.Adapter<HistoryListAdapter.ViewHolder> {
private static ArrayList<RecordItem> recordItems;
private static FragmentActivity activity;
private static RecordList recordList;

public HistoryListAdapter(ArrayList<RecordItem> recordItems, FragmentActivity FA, RecordList FRL) {
    this.recordItems = recordItems;
    this.activity = FA;
    this.recordList = FRL;
}

@Override
public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
    // create a new view
    View itemLayoutView = LayoutInflater.from(parent.getContext()).inflate(R.layout.recorditem, parent, false);
    return new ViewHolder(itemLayoutView);
}

@Override
public void onBindViewHolder(final ViewHolder viewHolder, final int position) {
    // TextView setText ...
}

// Return the size of the itemsData (invoked by the layout manager)
@Override
public int getItemCount() {
    return recordItems.size();
}

// inner class to hold a reference to each item of RecyclerView
public static class ViewHolder extends RecyclerView.ViewHolder{
    public TextView result, datetime;

    public ViewHolder(View itemLayoutView) {
        super(itemLayoutView);
        itemLayoutView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if (activity != null) {
                    // do something...
                }
            }
        });
        result = (TextView) itemLayoutView.findViewById(R.id.result);
        heartrate = (TextView) itemLayoutView.findViewById(R.id.heartrate);
        datetime = (TextView) itemLayoutView.findViewById(R.id.datetime);
    }
}
}

RecordList:

RecyclerView listView = (RecyclerView) layoutView.findViewById(R.id.listView);
HistoryListAdapter listadapter = new HistoryListAdapter(itemsToShow, getActivity(), RecordList.this);
listView.swapAdapter(listadapter, false);
listView.findViewHolderForAdapterPosition(0).itemView.performClick();

I omitted some code, But it should not affect the overall structure of my code.

Upvotes: 33

Views: 30921

Answers (6)

Alejandro Lagos
Alejandro Lagos

Reputation: 179

I know that is very late, but maybe is helpful for other people in the Kotlin era:

 binding.recycler.post {
     val view = binding.recycler.findViewHolderForAdapterPosition(position)?.itemView?.performClick()
 }

Upvotes: 5

Seachal
Seachal

Reputation: 27

you can do this:

postAndNotifyAdapter(new Handler(),mRecyclerView);



protected void postAndNotifyAdapter(final Handler handler, final RecyclerView recyclerView) {
    handler.post(new Runnable() {
        @Override
        public void run() {
            if ( recyclerView.findViewHolderForLayoutPosition(0)!=null) {
                // This will call first item by calling "performClick()" of view.
                recyclerView.findViewHolderForLayoutPosition(0).itemView.performClick();
            } else {
                //   
                postAndNotifyAdapter(handler, recyclerView);
            }
        }
    });
}

Upvotes: 1

sommer
sommer

Reputation: 1

I wouldnt recommend using post delay. Although it works the timing is arbitrary.

Using OnPreDrawListener on the recyclerview, timing will be aligned with the next draw cycle and visible items are accessible.

Upvotes: 0

Dharmaraj
Dharmaraj

Reputation: 1306

you can do this:

   listView.postDelayed(new Runnable()
            {
                @Override
                public void run()
                {
                    if(listView.findViewHolderForAdapterPosition(0)!=null )
                    {

                        listView.findViewHolderForAdapterPosition(0).itemView.performClick();
                    }
                }
            },50);

Upvotes: 29

Айкол Койкелов
Айкол Койкелов

Reputation: 9

Hey I've solved the problem this way: 

public class MyAdapter extends RecyclerView.Adapter<MyAdapter.ViewHolder> {

private TextView mTotalSum;
protected int mSum;
protected ArrayList<BasketRVAdapter.ViewHolder> mViewHolders;

public BasketRVAdapter(JSONArray recyclerItems, Context context, TextView totalSum) {
    super(recyclerItems, context);
    mTotalSum = totalSum;
    mViewHolders = new ArrayList<>();
}

@Override
public RecyclerView.ViewHolder onCreateSwipeViewHolder(ViewGroup parent, int i) {
    View view = LayoutInflater.from(parent.getContext())
            .inflate(R.layout.view_basket_rv_item, parent, true);

    return new ViewHolder(view);
}

@Override
public void onBindSwipeViewHolder(final RecyclerView.ViewHolder viewHolder, int position) {
    final BasketRVAdapter.ViewHolder holder = (BasketRVAdapter.ViewHolder) viewHolder;

    JSONObject object;
    try {
        object = mRecyclerItems.getJSONObject(position);
        final int priceValue = object.getInt("price");
        final int quantityValue = object.getInt("quantity");

        holder.setId(object.getInt("id"));
        holder.title.setText(object.getString("title"));
        holder.price.setText(String.format(mContext.getString(R.string.price), priceValue));
        holder.quantity.setText(String.valueOf(quantityValue));
        holder.sum.setText(String.valueOf(priceValue * quantityValue));

        holder.quantity.addTextChangedListener(new TextWatcher() {
            @Override
            public void beforeTextChanged(CharSequence charSequence, int i, int i1, int i2) {

            }

            @Override
            public void onTextChanged(CharSequence charSequence, int i, int i1, int i2) {

            }

            @Override
            public void afterTextChanged(Editable editable) {
                String value = holder.quantity.getText().toString();

                if (value.equals("")) {
                    return;
                }

                if (value.equals("0")) {
                    Toast.makeText(mContext, R.string.null_value_error, Toast.LENGTH_SHORT).show();
                    return;
                }
                holder.sum.setText(String.valueOf(priceValue * Integer.valueOf(value)));
                setTotalSum();
            }

        });

        mViewHolders.add(holder);
        mSum += priceValue * quantityValue;

        if (position == getItemCount() - 1) {
            mTotalSum.setText(String.format(mContext.getString(R.string.total_sum), mSum));
        }
    } catch (JSONException e) {
        e.printStackTrace();
    }
}

@Override
public SwipeConfiguration onCreateSwipeConfiguration(Context context, int i) {
    return new SwipeConfiguration.Builder(context)
                                 .setLeftSwipeBehaviour(SwipeConfiguration.SwipeBehaviour.NORMAL_SWIPE)
                                 .setRightSwipeBehaviour(SwipeConfiguration.SwipeBehaviour.NO_SWIPE)
                                 .setLeftBackgroundColorResource(R.color.dt_basket_deleted)
                                 .setLeftUndoDescription(R.string.deleted)
                                 .setDescriptionTextColorResource(R.color.dt_white)
                                 .setLeftUndoable(true)
                                 .build();
}

@Override
public void onSwipe(int i, int i1, RecyclerView.ViewHolder holder) {
    try {
        if (i1 == SWIPE_LEFT) {
            remove(i);
            notifyItemRemoved(i);
            mViewHolders.remove(i);
            setTotalSum();
        }
    } catch (JSONException e) {
        e.printStackTrace();
    }
}

public int getSum() {
    return mSum;
}

public void setTotalSum() {
    int totalSum = 0;

    for (BasketRVAdapter.ViewHolder holder : mViewHolders) {
        totalSum += Integer.valueOf(holder.sum.getText().toString());
    }

    mSum = totalSum;
    mTotalSum.setText(String.format(mContext.getString(R.string.total_sum), totalSum));
}

public static class ViewHolder extends RecyclerView.ViewHolder {

    @Bind(R.id.trade_title)
    public TextView title;
    @Bind(R.id.trade_price)
    public TextView price;
    @Bind(R.id.trade_quantity)
    public EditText quantity;
    @Bind(R.id.sum)
    public TextView sum;

    private int mId;

    public ViewHolder(View itemView) {
        super(itemView);
        ButterKnife.bind(this, itemView);
    }

    public int getId() {
        return mId;
    }

    public void setId(int id) {
        mId = id;
    }
}}
  1. Added ArrayList mViewholders field inside class
  2. added each viewholder instance to mViewHolders arraylist inside onBindSwipeViewHolder method
  3. used mViewholders arraylist instead of findViewHolderForadapterposition method inside setTotalSum method

Upvotes: 0

Rami
Rami

Reputation: 7929

According to the official documentation:

if notifyDataSetChanged() has been called but the new layout has not been calculated yet, this method will return null since the new positions of views are unknown until the layout is calculated.

It's not safe to use findViewHolderForAdapterPosition().

While you call this method after listView.swapAdapter(listadapter, false); you'll always get a null as result because notifyDataSetChanged() will be called.

Upvotes: 31

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