如何在Recycler视图中自动更新商品数据？

Question

Let's say there's an RecyclerView consisting of CardView in it,in each card ie item there are two TextView one is for name of the device and another is for the rssi level ,so when user refreshes the the data then only rssi will get refresh rather whole list get refresh.

I have got the data in the RecyclerView but it get's repeated rather than updating it.

Model class:-

import android.support.annotation.NonNull;

public class RepeaterModel implements Comparable,Cloneable{

    public String macdev;
    public int rssi ;
    public int imageid;

    public RepeaterModel(String macdev, int rssi, int imageid) {
        this.macdev = macdev;
        this.rssi = rssi;
        this.imageid = imageid;
    }

    public String getMacdev() {
        return macdev;
    }

    public void setMacdev(String macdev) {
        this.macdev = macdev;
    }

    public int getRssi() {
        return rssi;
    }

    public void setRssi(int rssi) {
        this.rssi = rssi;
    }

    public int getImageid() {
        return imageid;
    }

    public void setImageid(int imageid) {
        this.imageid = imageid;
    }



    @Override
    public int compareTo(@NonNull Object o) {
        RepeaterModel compare =(RepeaterModel)o;
        if(compare.getMacdev().equals(this.macdev) && compare.getImageid()==this.imageid && compare.getRssi()==this.rssi)
        {
            return 0;
        }
        return 1;
    }

    @Override
    public RepeaterModel clone()
    {
        RepeaterModel clone;
        try {
            clone = (RepeaterModel) super.clone();

        } catch (CloneNotSupportedException e) {
            throw new RuntimeException(e); //should not happen
        }

        return clone;

    }
}

Device Adapter class:-

public class ReapeaterDeviceAdapter extends RecyclerView.Adapter<ReapeaterDeviceAdapter.CryptoViewHolder> {

    private ArrayList<RepeaterModel> data;

    public class CryptoViewHolder extends RecyclerView.ViewHolder {

        private TextView mName, mPrice;

        public CryptoViewHolder(View itemView) {
            super(itemView);
            mName = itemView.findViewById(R.id.txtName);
            mPrice = itemView.findViewById(R.id.txtPrice);
        }
    }

    public ReapeaterDeviceAdapter(ArrayList<RepeaterModel> data) {
        this.data = data;
    }

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

    @Override
    public void onBindViewHolder(CryptoViewHolder holder, int position) {
        holder.mName.setText(data.get(position).macdev);
        holder.mPrice.setText(String.valueOf(data.get(position).rssi));
    }

    @Override
    public void onBindViewHolder(CryptoViewHolder holder, int position, List<Object> payloads) {

        if (payloads.isEmpty()) {
            super.onBindViewHolder(holder, position, payloads);
        } else {
            Bundle o = (Bundle) payloads.get(0);

            for (String key : o.keySet()) {
                if (key.equals("price")) {
                    holder.mName.setText(data.get(position).macdev);
                    holder.mPrice.setText(String.valueOf(data.get(position).rssi));
                    holder.mPrice.setTextColor(Color.GREEN);
                    this.notifyItemChanged(position);
                }
            }
        }
    }

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

    public ArrayList<RepeaterModel> getData() {
        return data;
    }

    public void setData(ArrayList<RepeaterModel> newData) {

        DiffUtil.DiffResult diffResult = DiffUtil.calculateDiff(new MyDiffUtilCallBack(newData, data));
        diffResult.dispatchUpdatesTo(this);
        data.clear();
        this.data.addAll(newData);
        //this.notifyDataSetChanged();
    }
}

DiffUtilCallback class:-

public class MyDiffUtilCallBack extends DiffUtil.Callback {
    ArrayList<RepeaterModel> newList;
    ArrayList<RepeaterModel> oldList;

    public MyDiffUtilCallBack(ArrayList<RepeaterModel> newList, ArrayList<RepeaterModel> oldList) {
        this.newList = newList;
        this.oldList = oldList;
    }

    @Override
    public int getOldListSize() {
        return oldList != null ? oldList.size() : 0;
    }

    @Override
    public int getNewListSize() {
        return newList != null ? newList.size() : 0;
    }

    @Override
    public boolean areItemsTheSame(int oldItemPosition, int newItemPosition) {
        return newList.get(newItemPosition).getMacdev()==oldList.get(oldItemPosition).getMacdev() ;
    }

    @Override
    public boolean areContentsTheSame(int oldItemPosition, int newItemPosition) {
        int result = newList.get(newItemPosition).compareTo(oldList.get(oldItemPosition));
        return result == 0;
    }

    @Nullable
    @Override
    public Object getChangePayload(int oldItemPosition, int newItemPosition) {

        RepeaterModel newModel = newList.get(newItemPosition);
        RepeaterModel oldModel = oldList.get(oldItemPosition);

        Bundle diff = new Bundle();
        if(newModel.getMacdev().equals(oldModel.getMacdev()) ) {
            if (newModel.rssi != (oldModel.rssi)) {
                diff.putInt("price", newModel.rssi);
            }
            if (diff.size() == 0) {
                return null;
            }
        }
        return diff;
        //return super.getChangePayload(oldItemPosition, newItemPosition);
    }
}

Answer 1

Lets say your adapter has a private field mItems and a public method that looks like this

public void setItems(List<YourClass> items){
    mItems= items;
    notifyDataSetChanged();
}

Calling this method would refresh your recycler view. Alternatively, you can simply notify your adapter like this:

yourAdapterInstance.notifyDataSetChanged();

Answer 2

The implementation of DiffCallback is not working correctly:

@Override
public boolean areItemsTheSame(int oldItemPosition, int newItemPosition) {
    return newList.get(newItemPosition).getMacdev()==oldList.get(oldItemPosition).getMacdev() ;
}

to use equals method instead of '=='

    @Override
    public boolean areItemsTheSame(int oldItemPosition, int newItemPosition) {
        return newList.get(newItemPosition).getMacdev().equals(oldList.get(oldItemPosition).getMacdev()) ;
    }

Also, remove this.notifyItemChanged(position); from method public void onBindViewHolder(CryptoViewHolder holder, int position, List<Object> payloads) { also you need to update list before dispatching update.

public void setData(ArrayList<RepeaterModel> newData) {

    DiffUtil.DiffResult diffResult = DiffUtil.calculateDiff(new 
    MyDiffUtilCallBack(newData, data));

    data.clear();
    this.data.addAll(newData);
    diffResult.dispatchUpdatesTo(this);
}

PS: the code may be not working correctly, changing the color to Color GREEN may affect "non updated" item du to recycling. It is better to change the RepeaterModel by adding the edited/updated information to model.

Answer 3

You should set adapter ie recylerview.setAdapter(adapter) only once.And at any other place where you are changing the data in the Arraylist use adapter.notifyDatasetChanged() to refresh list. It will refresh only the changes not the whole list.

Source: https://medium.com/@suragch/updating-data-in-an-android-recyclerview-842e56adbfd8

Answer 4

Instead of notifyDatasetChanged, you should use notifyItemChanged() with an customized object.

Create data class say UpdateRecord with 2 members

data class UpdateRecord(val _name : String? , val _rssi :String?)

when rssi changes, call Adapter's

notifyItemChange(position, UpdateRecord(null, newRssi))

You will receive call onBindViewHolder(position, payload), the first object in payload is the UpdateRecord object. Check and do

val updateRecord = payload[0] as UpdateRecord
if (updateRecord._name != null) {
  // update name text view
}
if (updateRecord._rssi != null) {
  // update rssi text view
}

This is the partial update mechanism in RecyclerView, which updates only what is changed.