How to call scrollToPosition(position) inside recyclerView's adapter?

Question

I have a setOnClick listener inside my onBindViewHolder

@Override
public void onBindViewHolder(final RecyclerView.ViewHolder holder, final int position) {
       ((ViewHolder) holder).txtType.setText(object.text);
       ((ViewHolder) holder).checkBox.setOnClickListener(new View.OnClickListener() {
                    @Override
                    public void onClick(View v) { 
                        Toast.makeText(mContext, ""+position, Toast.LENGTH_SHORT).show();                           
                      //???.scrolltoPosition(position+1);
                    }
                });

on click, I would be scrolling the viewport to the next recycler view item. I've done this inside my MainActivity java by recyclerView.scrollToPosition(position); . But inside Adapter Class on onBindViewHolder, I have no idea how to call my recyclerView on the Main Java Class.

How should I do this?

edit: For simplification purposes, I revised this previous code, because I have used a multiview adapter for my recycler. Here is the multiview adapter:

public class MultiViewTypeAdapter extends RecyclerView.Adapter {

private ArrayList<InstructionModel>dataSet;
Context mContext;
int total_types;
private LinearLayoutManager manager;

public MultiViewTypeAdapter(LinearLayoutManager manager)
{
    this.manager=manager;
}


public static class SimpleTextViewHolder extends RecyclerView.ViewHolder {

    TextView txtType;
    CardView cardView;
    CheckBox checkBox;

    public SimpleTextViewHolder(View itemView) {
        super(itemView);

        this.txtType = (TextView) itemView.findViewById(R.id.type);
        this.cardView = (CardView) itemView.findViewById(R.id.card_view);
        this.checkBox = (CheckBox) itemView.findViewById(R.id.checkBox);

    }
}
public static class TimeTextViewHolder extends RecyclerView.ViewHolder {

    TextView txtType;
    CardView cardView;
    CheckBox checkBox;

    public TimeTextViewHolder(View itemView) {
        super(itemView);

        this.txtType = (TextView) itemView.findViewById(R.id.type);
        this.cardView = (CardView) itemView.findViewById(R.id.card_view);
        this.checkBox = (CheckBox) itemView.findViewById(R.id.checkBox);
    }
}




public MultiViewTypeAdapter(ArrayList<InstructionModel> data, Context context) {
    this.dataSet = data;
    this.mContext = context;
    total_types = dataSet.size();
}

@Override
public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {

    View view;
    switch (viewType) {
        case InstructionModel.SIMPLE_TYPE:
            view = LayoutInflater.from(parent.getContext()).inflate(R.layout.simple, parent, false);
            return new SimpleTextViewHolder(view);
        case InstructionModel.TIME_TYPE:
            view = LayoutInflater.from(parent.getContext()).inflate(R.layout.time, parent, false);
            return new TimeTextViewHolder(view);
    }
    return null;
}

@Override
public int getItemViewType(int position) {

    switch (dataSet.get(position).type) {
        case 0:
            return InstructionModel.SIMPLE_TYPE;
        case 1:
            return InstructionModel.TIME_TYPE;
        default:    return -1;
    }
}

@Override
public void onBindViewHolder(final RecyclerView.ViewHolder holder, final int listPosition) {

    InstructionModel object = dataSet.get(listPosition);
    if (object != null) {
        switch (object.type) {

            case InstructionModel.SIMPLE_TYPE:

                ((SimpleTextViewHolder) holder).txtType.setText(object.text);
                break;
            case InstructionModel.TIME_TYPE:
                ((TimeTextViewHolder) holder).txtType.setText(object.text);

                break;
        }
    }



}

@Override
public int getItemCount() {
    return dataSet.size();
}

PS If you see some random useless stuff, I was trying something.

Answer 1

Pass the LayoutManger with constuctor

 class Adapter extends RecyclerView.Adapter<Adapter.ViewHolder> {
            private LinearLayoutManager manager;

            public Adapter(LinearLayoutManager manager)
            {
                this.manager=manager;
            }


        @Override
        public void onBindViewHolder(final RecyclerView.ViewHolder holder, final int position) {
           ((ViewHolder) holder).txtType.setText(object.text);
           ((ViewHolder) holder).checkBox.setOnClickListener(new View.OnClickListener() {
                        @Override
                        public void onClick(View v) { 
                            Toast.makeText(mContext, ""+position, Toast.LENGTH_SHORT).show();                           
                          manager.scrollToPosition(position+1);
                        }
                    });
    }

Answer 2

我觉得你应该定义一个接口来通知你的父RecyclerView做滚动操作，把RecyclerView放到ViewHodler里面操作，导致耦合

Answer 3

You can pass a listener object in the constructor which implements by Fragment OR Activity.

/**
 * item click interface of adapter
 */
public interface MultiViewTypeAdapterListener {
    void onScroll(int position)
}  

This interface implements by Fragment OR Activity

/**
     * On Scroll Implement Method from adapter listener.
     *
     * @param position
     */
    @Override
    public void onScroll(int position) {
        // Here you can call that method 
        recyclerview.scrolltoPosition(position)
    }

Then you pass this listener in the constructor of the adapter.

private void buildRecyclerView() {
  multiViewTypeAdapter = new MultiViewTypeAdapter(this);
  recyclerView.setAdapter(multiViewTypeAdapter);
}

In the constructor, you can assign like this

 private MultiViewTypeAdapterListener mMultiViewTypeAdapterListener;
 public OfferAdapter(MultiViewTypeAdapterListener mMultiViewTypeAdapterListener) {
        this.mMultiViewTypeAdapterListener = mMultiViewTypeAdapterListener
        }
    }

Now you can use this listener by setting click listener on anyViwe like this

((ViewHolder) holder).checkBox.setOnClickListener(new View.OnClickListener() {
                    @Override
                    public void onClick(View v) { 
                        Toast.makeText(mContext, ""+position, Toast.LENGTH_SHORT).show();                           
                      //???.scrolltoPosition(position+1);
                        mMultiViewTypeAdapterListener.onScroll(position+1);
                    }
                });

It returns to call the method of onItemClick which implements this method.

Answer 4

  private int getScrollRange() {
        int scrollRange = 0;
        if (parent.getChildCount() > 0) {
            View child = parent.getChildAt(0);
            scrollRange = Math.max(0,
                    child.getHeight() - (parent.getHeight()));
        }
        return scrollRange;
    }

ScrollView parent=findViewById(R.id.scroll_Recipe_Detail);
parent.scrollTo(0,getScrollRange());

Answer 5

if you want to scroll on new items added, you must override "onItemsAdded". Here is how I did it:

recyclerView.apply {
        setHasFixedSize(true)
        layoutManager = MyLinearLayoutManager(this@MainActivity)
        ...
}

private class MyLinearLayoutManager(private val context: Context) :
    LinearLayoutManager(context) {

    // Force new items appear at the top
    override fun onItemsAdded(recyclerView: RecyclerView, positionStart: Int, itemCount: Int) {
        super.onItemsAdded(recyclerView, positionStart, itemCount)

        scrollToPosition(findLastVisibleItemPosition())
    }
}