Recyclerview is not displaying data when using generic adapter & viewholder

问题

In my android project, I created Generic RecyclerView's Adapter class & Viewholder class like below,

Adapter class,

public class BaseRecyclerViewAdapter extends RecyclerView.Adapter<BaseViewHolder> {

    private ItemClickListener itemClickListener;
    private List<? extends Object> objectArrayList;
    private int layout;
    private BaseViewHolder baseViewHolder;

    public BaseRecyclerViewAdapter(int layout, ItemClickListener itemClickListener, List<? extends Object> objectArrayList) {
        this.layout = layout;
        this.itemClickListener = itemClickListener;
        this.objectArrayList = objectArrayList;
    }

    public BaseRecyclerViewAdapter(BaseViewHolder baseViewHolder, int layout,
                                   ItemClickListener itemClickListener, List<? extends Object> objectArrayList) {
        this.baseViewHolder = baseViewHolder;
        this.layout = layout;
        this.itemClickListener = itemClickListener;
        this.objectArrayList = objectArrayList;
    }

    @NonNull
    @Override
    public BaseViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        View itemView = LayoutInflater.from(parent.getContext()).inflate(layout, parent, false);
        return new BaseViewHolder(itemView, itemClickListener);
    }

    @Override
    public void onBindViewHolder(@NonNull BaseViewHolder holder, int position) {

    }

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

ViewHolder class

public class BaseViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener, View.OnLongClickListener {

    private CardView cardView;
    private AppCompatImageView imgEdit;
    private AppCompatImageView imgDelete;
    private ItemClickListener itemClickListener;

    public BaseViewHolder(View itemView, ItemClickListener itemClickListener) {
        super(itemView);
        cardView = itemView.findViewById(R.id.cardView);
        imgEdit = itemView.findViewById(R.id.imgEdit);
        imgDelete = itemView.findViewById(R.id.imgDelete);
        imgDelete.setOnClickListener(this);
        cardView.setOnClickListener(this);
        cardView.setOnLongClickListener(this);
        this.itemClickListener = itemClickListener;
    }

    @Override
    public void onClick(View view) {
        if (view.getId() == cardView.getId()) {
            itemClickListener.onClick(view, getLayoutPosition(), ConstantCodes.ACTION_CLICK);
        } else if (view.getId() == imgDelete.getId()) {
            itemClickListener.onClick(view, getLayoutPosition(), ConstantCodes.ACTION_DELETE);
        } else if (view.getId() == imgEdit.getId()) {
            itemClickListener.onClick(view, getLayoutPosition(), ConstantCodes.ACTION_EDIT);
        }
    }

    @Override
    public boolean onLongClick(View view) {
        itemClickListener.onLongClick(view, getLayoutPosition());
        return false;
    }
}

Here is the way I implement the above adapter & viewholder in my activity class

private class DispatchViewHolder extends BaseViewHolder {
    AppCompatTextView txtInvoiceNo;
    AppCompatTextView txtVehicleNo;
    AppCompatTextView txtPartyName;
    AppCompatTextView txtNoOfBags;
    AppCompatTextView txtMaterialType;
    AppCompatTextView txtWeight;

    DispatchViewHolder(View itemView, ItemClickListener itemClickListener) {
        super(itemView, itemClickListener);
    }
}


private class DispatchMaterialAdapter extends BaseRecyclerViewAdapter {

    ItemClickListener itemClickListener;
    List<? extends Object> objectArrayList;

    DispatchMaterialAdapter(ItemClickListener itemClickListener, List<? extends Object> objectArrayList) {
        super(R.layout.dispatch_material_row, itemClickListener, objectArrayList);
        this.itemClickListener = itemClickListener;
        this.objectArrayList = objectArrayList;
    }

    @NonNull
    @Override
    public DispatchViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        View itemView = LayoutInflater.from(parent.getContext()).inflate(R.layout.dispatch_material_row, parent, false);
        return new DispatchViewHolder(itemView, itemClickListener);
    }

    @Override
    public void onBindViewHolder(@NonNull BaseViewHolder holder, int position) {
        try {
            DispatchViewHolder dispatchViewHolder = (DispatchViewHolder) holder;
            DispatchMaterialMd dispatchMaterialMd = (DispatchMaterialMd) objectArrayList.get(position);
            dispatchViewHolder.txtInvoiceNo.setText(dispatchMaterialMd.getInvoiceNo());
            dispatchViewHolder.txtVehicleNo.setText(dispatchMaterialMd.getVehicleNo());
            dispatchViewHolder.txtPartyName.setText(dispatchMaterialMd.getPartyName());
            dispatchViewHolder.txtNoOfBags.setText(dispatchMaterialMd.getNoOfBags());
            dispatchViewHolder.txtMaterialType.setText(dispatchMaterialMd.getMaterialType());
            dispatchViewHolder.txtWeight.setText(dispatchMaterialMd.getWeight());
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

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

I have data in my objectArrayList list. I can print it in console, but nothing is coming in recyclerview. In recyclerview, it is only displaying empty Textview.

Following way, implement recyclerview,

layoutManager = new LinearLayoutManager(this);
dispatchMaterialAdapter =
                new DispatchMaterialAdapter(itemClickListener, dispatchMaterialMds);
            recycleListDetail.setLayoutManager(layoutManager);
            recycleListDetail.setAdapter(dispatchMaterialAdapter);

dispatchMaterialMds is an arraylist of model class which is filled from the database's data.

Can you please help me, why my data is not getting displayed ?

回答1:

You made BaseViewHolder that did the inflation then redone it in the DispatchViewHolder not sure if this will solve the problem but there was repeated code.

private class DispatchViewHolder extends BaseViewHolder {
    AppCompatTextView txtInvoiceNo;
    AppCompatTextView txtVehicleNo;
    AppCompatTextView txtPartyName;
    AppCompatTextView txtNoOfBags;
    AppCompatTextView txtMaterialType;
    AppCompatTextView txtWeight;

    DispatchViewHolder(View itemView, ItemClickListener itemClickListener) {
        super(itemView, itemClickListener);
    }
}


private class DispatchMaterialAdapter extends BaseRecyclerViewAdapter {

    ItemClickListener itemClickListener;
    List<? extends Object> objectArrayList;

    DispatchMaterialAdapter(ItemClickListener itemClickListener, List<? extends Object> objectArrayList) {
        super(R.layout.dispatch_material_row, itemClickListener, objectArrayList);
        this.itemClickListener = itemClickListener;
        this.objectArrayList = objectArrayList;
    }

@Override
public DispatchViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
    View itemView = LayoutInflater.from(parent.getContext()).inflate(R.layout.dispatch_material_row, parent, false);
    return new DispatchViewHolder(itemView, itemClickListener);
}
@Override
public void onBindViewHolder(@NonNull BaseViewHolder holder, int position) {
    try {
        DispatchViewHolder dispatchViewHolder = (DispatchViewHolder) holder;
        DispatchMaterialMd dispatchMaterialMd = (DispatchMaterialMd) objectArrayList.get(position);
        dispatchViewHolder.txtInvoiceNo.setText(dispatchMaterialMd.getInvoiceNo());
        dispatchViewHolder.txtVehicleNo.setText(dispatchMaterialMd.getVehicleNo());
        dispatchViewHolder.txtPartyName.setText(dispatchMaterialMd.getPartyName());
        dispatchViewHolder.txtNoOfBags.setText(dispatchMaterialMd.getNoOfBags());
        dispatchViewHolder.txtMaterialType.setText(dispatchMaterialMd.getMaterialType());
        dispatchViewHolder.txtWeight.setText(dispatchMaterialMd.getWeight());
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

In the DispatchViewHolder:

AppCompatTextView txtInvoiceNo;
AppCompatTextView txtVehicleNo;
AppCompatTextView txtPartyName;
AppCompatTextView txtNoOfBags;
AppCompatTextView txtMaterialType;
AppCompatTextView txtWeight;
DispatchViewHolder(View itemView, ItemClickListener itemClickListener) {
    super(itemView, itemClickListener);
    //Initiliazation of new view?
}

回答2:

make change in set adapter code like below.

        recycleListDetail.setLayoutManager(new LinearLayoutManager(this));
    dispatchMaterialAdapter =
            new DispatchMaterialAdapter(itemClickListener, dispatchMaterialMds);
    recycleListDetail.setLayoutManager(layoutManager);
    recycleListDetail.setAdapter(dispatchMaterialAdapter);
    dispatchMaterialAdapter.notifyDataSetChanged();

and also check your adapter in bind view get the arraylist value and check arraylist type in getting and passing to adapter that same or not.

回答3:

above discussion i am make demo for recycler view and is wroking using simple string array.. Adapter class.

public class RecyclerViewAdpater extends RecyclerView.Adapter { List mStringList=new ArrayList<>();// hear you can pass any pojo class object. Context mContext;

public RecyclerViewAdpater(List<String> mStringList, Context mContext) {
    this.mStringList = mStringList;
    this.mContext = mContext;
}

@Override
public ItemViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
   View view= LayoutInflater.from(parent.getContext()).inflate(R.layout.activity_main,parent,false);
    return new ItemViewHolder(view);
}

@Override
public void onBindViewHolder(ItemViewHolder holder, int position) {
    String data=mStringList.get(position); // if you pass object of class then create that class object.
    holder.textView.setText(data);
 }

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

public class ItemViewHolder extends RecyclerView.ViewHolder {
    TextView textView;
    public ItemViewHolder(View itemView) {
        super(itemView);
        textView=itemView.findViewById(R.id.timeData);
    }
}

}

then implement activity like below code put in onCreate view method ...

 recyclerViewAdpater=new RecyclerViewAdpater(mStingList,this);
    mRvData.setLayoutManager(new LinearLayoutManager(this));
    mRvData.setAdapter(recyclerViewAdpater);
    chatAdapter.notifyDataSetChanged();

回答4:

Please try this

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

来源：https://stackoverflow.com/questions/49379746/recyclerview-is-not-displaying-data-when-using-generic-adapter-viewholder