CursorRecyclerViewAdapter

CursorRecyclerViewAdapter.java

/*
 * Copyright (C) 2014 [email protected]
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 */
 
import android.content.Context;
import android.database.Cursor;
import android.database.DataSetObserver;
import android.support.v7.widget.RecyclerView;

/**
 * Created by skyfishjy on 10/31/14.
 */
 
public abstract class CursorRecyclerViewAdapter<VH extends RecyclerView.ViewHolder> extends RecyclerView.Adapter<VH> {

    private Context mContext;

    private Cursor mCursor;

    private boolean mDataValid;

    private int mRowIdColumn;

    private DataSetObserver mDataSetObserver;

    public CursorRecyclerViewAdapter(Context context, Cursor cursor) {
        mContext = context;
        mCursor = cursor;
        mDataValid = cursor != null;
        mRowIdColumn = mDataValid ? mCursor.getColumnIndex("_id") : -1;
        mDataSetObserver = new NotifyingDataSetObserver();
        if (mCursor != null) {
            mCursor.registerDataSetObserver(mDataSetObserver);
        }
    }

    public Cursor getCursor() {
        return mCursor;
    }

    @Override
    public int getItemCount() {
        if (mDataValid && mCursor != null) {
            return mCursor.getCount();
        }
        return 0;
    }

    @Override
    public long getItemId(int position) {
        if (mDataValid && mCursor != null && mCursor.moveToPosition(position)) {
            return mCursor.getLong(mRowIdColumn);
        }
        return 0;
    }

    @Override
    public void setHasStableIds(boolean hasStableIds) {
        super.setHasStableIds(true);
    }

    public abstract void onBindViewHolder(VH viewHolder, Cursor cursor);

    @Override
    public void onBindViewHolder(VH viewHolder, int position) {
        if (!mDataValid) {
            throw new IllegalStateException("this should only be called when the cursor is valid");
        }
        if (!mCursor.moveToPosition(position)) {
            throw new IllegalStateException("couldn't move cursor to position " + position);
        }
        onBindViewHolder(viewHolder, mCursor);
    }

    /**
     * Change the underlying cursor to a new cursor. If there is an existing cursor it will be
     * closed.
     */
    public void changeCursor(Cursor cursor) {
        Cursor old = swapCursor(cursor);
        if (old != null) {
            old.close();
        }
    }

    /**
     * Swap in a new Cursor, returning the old Cursor.  Unlike
     * {@link #changeCursor(Cursor)}, the returned old Cursor is <em>not</em>
     * closed.
     */
    public Cursor swapCursor(Cursor newCursor) {
        if (newCursor == mCursor) {
            return null;
        }
        final Cursor oldCursor = mCursor;
        if (oldCursor != null && mDataSetObserver != null) {
            oldCursor.unregisterDataSetObserver(mDataSetObserver);
        }
        mCursor = newCursor;
        if (mCursor != null) {
            if (mDataSetObserver != null) {
                mCursor.registerDataSetObserver(mDataSetObserver);
            }
            mRowIdColumn = newCursor.getColumnIndexOrThrow("_id");
            mDataValid = true;
            notifyDataSetChanged();
        } else {
            mRowIdColumn = -1;
            mDataValid = false;
            notifyDataSetChanged();
            //There is no notifyDataSetInvalidated() method in RecyclerView.Adapter
        }
        return oldCursor;
    }

    private class NotifyingDataSetObserver extends DataSetObserver {
        @Override
        public void onChanged() {
            super.onChanged();
            mDataValid = true;
            notifyDataSetChanged();
        }

        @Override
        public void onInvalidated() {
            super.onInvalidated();
            mDataValid = false;
            notifyDataSetChanged();
            //There is no notifyDataSetInvalidated() method in RecyclerView.Adapter
        }
    }
}

MyListCursorAdapter.java

import android.content.Context;
import android.database.Cursor;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.TextView;
import java.util.List;

/**
 * Created by skyfishjy on 10/31/14.
 */
public class MyListCursorAdapter extends CursorRecyclerViewAdapter<MyListCursorAdapter.ViewHolder>{

    public MyListCursorAdapter(Context context,Cursor cursor){
       super(context,cursor);
    }

    public static class ViewHolder extends RecyclerView.ViewHolder {
        public TextView mTextView;
        public ViewHolder(View view) {
            super(view);
            mTextView = view.findViewById(R.id.text);
        }
    }

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

    @Override
    public void onBindViewHolder(ViewHolder viewHolder, Cursor cursor) {
        MyListItem myListItem = MyListItem.fromCursor(cursor);
        viewHolder.mTextView.setText(myListItem.getName());
    }
}

MyListItem.java

public class MyListItem{
  private String name;
  
  public void setName(String name){
    this.name=name;
  }
  public String getName(){
    return name;
  }
  
  public static MyListItem fromCursor(Cursor cursor) {
    //TODO return your MyListItem from cursor.
  }
}

android.support.v7.util.AsyncListUtil can also be simple to implement.

Hello, first of all many thanks for sharing this code! Can you help me with a problem please? I have an Activity with a RecyclerView that uses an AsyncTaskLoader to load data from the database and update MyListCursorAdapter with cursor. All works fine until I delete a row from the database using ContentProvider, the adapter don't refresh and the RecyclerView that continue to show the item I deleted with a ContextMenu.
Any idea?

@skyfishjy
thanks for the example
@PRosenb
Thanks for the help. Now everything works fine ))

Thank you so much for this code! The example usage was also incredibly helpful.

I wonder if we can notifyChanged just for certain range, maybe we can have a lastBindIdx and compare idx within 10 item. It will make the animation work properly.

Thank you so much for this code!

Hi! Can you help me to update my adapter with yours?

Me too