Android activity demonstrating having progress bars within RecyclerView elements and how these progress bars can be updated from an Asynchronous task.

MainActivity.java

package com.hedgehoglab.progressrecyclerviewsample;

import android.os.AsyncTask;
import android.os.Bundle;
import android.support.annotation.NonNull;
import android.support.annotation.Nullable;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.util.Log;
import android.util.SparseArray;
import android.view.LayoutInflater;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.ViewGroup;
import android.widget.ProgressBar;
import android.widget.TextView;
import java.lang.ref.WeakReference;
import java.util.ArrayList;
import java.util.List;

/**
 * 	This class handles hosting {@link ProgressBar} views within {@link RecyclerView} items, by default
 * 	if a {@link android.support.v7.widget.RecyclerView.ViewHolder} is designated as a listener and passed
 * 	to another thread then as this ViewHolder is recycled the listener is also recycled. This means
 * 	that when the thread calls back to the ViewHolder it is acting on the recycled cell (e.g. start
 * 	task on progress bar one, scroll down, and progress bar 20 might be updating when on screen).
 *
 * 	This class demonstrates attaching and detaching the ViewHolder listener as the ViewHolder is being
 * 	bound and recycled respectively, ensuring that the task is only updating the desired ViewHolder.
 */
public class MainActivity extends AppCompatActivity {
	private static final String TAG = MainActivity.class.getSimpleName();

	private static final int NUM_OF_ITEMS = 50;

	private SparseArray<WaitingTask> mWaitingTaskSparseArray = new SparseArray<>();

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);

		RecyclerView recyclerView = (RecyclerView) findViewById(R.id.main_recyclerview);
		LinearLayoutManager llm = new LinearLayoutManager(MainActivity.this, LinearLayoutManager.VERTICAL, false);
		recyclerView.setLayoutManager(llm);

		ProgressAdapter progressAdapter = new ProgressAdapter();
		recyclerView.setAdapter(progressAdapter);

		List<ProgressObject> progressObjects = new ArrayList<>();
		for (int i = 0; i < NUM_OF_ITEMS; i++) {
			progressObjects.add(new ProgressObject(i, "Position " + i, 0));
		}
		progressAdapter.updateProgressObjects(progressObjects);
	}

	private interface WaitingListener {
		void onProgressUpdated(int progress);
	}

	private class ProgressAdapter extends RecyclerView.Adapter<ProgressViewHolder> {
		private List<ProgressObject> mProgressObjectList = new ArrayList<>();

		void updateProgressObjects(@NonNull List<ProgressObject> progressObjects) {
			mProgressObjectList = progressObjects;
			notifyDataSetChanged();
		}

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

		@Override
		public void onBindViewHolder(ProgressViewHolder holder, int position) {
			holder.bind(mProgressObjectList.get(position));
		}

		/**
		 * If a task has been created for the {@link ProgressObject} for this {@link ProgressViewHolder}
		 * then the listener is removed and the view is then recycled
		 * @param holder	{@link ProgressViewHolder} ViewHolder to recycle
		 */
		@Override
		public void onViewRecycled(ProgressViewHolder holder) {
			WaitingTask task = mWaitingTaskSparseArray.get(holder.getId());
			if (task != null) {
				task.updateListener(null);
			}
			super.onViewRecycled(holder);
		}

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

	private class ProgressViewHolder extends RecyclerView.ViewHolder implements WaitingListener {
		private ProgressBar mProgressBar;
		private TextView mProgressText;
		private int mId;

		ProgressViewHolder(View itemView) {
			super(itemView);
			mProgressBar = (ProgressBar) itemView.findViewById(R.id.viewholder_progress_bar);
			mProgressText = (TextView) itemView.findViewById(R.id.viewholder_progress_text);
		}

		/**
		 * When binding the {@link ProgressObject} to the ViewHolder, ensure that there is some form
		 * of ID held as a member variable to identify the task for this item, then update the
		 * progress bar to it's current value and if a task already exists for this data item, update
		 * the listener.
		 *
		 * @param progressObject	{@link ProgressObject} Data to be bound
		 */
		void bind(final ProgressObject progressObject) {
			mId = progressObject.getId();
			mProgressText.setText(progressObject.getTitle());
			mProgressBar.setProgress(progressObject.getProgress());

			WaitingTask task = mWaitingTaskSparseArray.get(mId);
			if (task != null) {
				task.updateListener(ProgressViewHolder.this);
			}

			itemView.setOnClickListener(new OnClickListener() {
				@Override
				public void onClick(View view) {
					// Create the task, set the listener, add to the task controller, and run
					WaitingTask task = new WaitingTask(progressObject, ProgressViewHolder.this);
					mWaitingTaskSparseArray.put(mId, task);
					task.execute();
				}
			});
		}

		@Override
		public void onProgressUpdated(int progress) {
			// Must be run on the UI thread, updates the progress bar to a new value via the callback
			mProgressBar.setProgress(progress);
		}

		public int getId() {
			return mId;
		}
	}

	private class WaitingTask extends AsyncTask<Void, Integer, Void> {
		private ProgressObject mProgressObject;
		private WeakReference<WaitingListener> mWaitingListenerWeakReference;

		WaitingTask(ProgressObject progressObject, WaitingListener waitingListener) {
			mProgressObject = progressObject;
			updateListener(waitingListener);
		}

		void updateListener(@Nullable WaitingListener waitingListener) {
			mWaitingListenerWeakReference = new WeakReference<>(waitingListener);
		}

		@Override
		protected Void doInBackground(Void... voids) {
			try {
				for (int i = 0; i <= 100; i++) {
					Thread.sleep(50);	// Random delay
					mProgressObject.setProgress(i);	// Update data set
					publishProgress(i);	// Inform UI of progress
				}
			} catch (InterruptedException ie) {
				Log.e(TAG, "Interrupted Exception: " + ie.getLocalizedMessage());
			}
			return null;
		}

		@Override
		protected void onProgressUpdate(Integer... values) {
			super.onProgressUpdate(values);
			if (mWaitingListenerWeakReference != null) {
				WaitingListener listener = mWaitingListenerWeakReference.get();
				if (listener != null) {
					listener.onProgressUpdated(values[0]);
				}
			}
		}
	}

	private class ProgressObject {
		private int mId;
		private String mTitle;
		private int mProgress;

		ProgressObject(int id, String title, int progress) {
			mId = id;
			mTitle = title;
			mProgress = progress;
		}

		int getId() {
			return mId;
		}

		void setId(int id) {
			mId = id;
		}

		String getTitle() {
			return mTitle;
		}

		void setTitle(String title) {
			mTitle = title;
		}

		int getProgress() {
			return mProgress;
		}

		void setProgress(int progress) {
			mProgress = progress;
		}
	}
}

Can you please post this on stackexchange? I wish I found this a long time a ago!