/*
 * Copyright (C) 2007 The Android Open Source Project
 *
 * 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.
 */

package android.widget;

import android.annotation.WorkerThread;
import android.app.IServiceConnection;
import android.appwidget.AppWidgetHostView;
import android.appwidget.AppWidgetManager;
import android.content.ComponentName;
import android.content.Context;
import android.content.Intent;
import android.content.ServiceConnection;
import android.content.pm.ApplicationInfo;
import android.os.Handler;
import android.os.HandlerThread;
import android.os.IBinder;
import android.os.Looper;
import android.os.Message;
import android.os.RemoteException;
import android.util.Log;
import android.util.SparseArray;
import android.util.SparseBooleanArray;
import android.util.SparseIntArray;
import android.view.LayoutInflater;
import android.view.View;
import android.view.View.MeasureSpec;
import android.view.ViewGroup;
import android.widget.RemoteViews.OnClickHandler;

import com.android.internal.widget.IRemoteViewsFactory;

import java.lang.ref.WeakReference;
import java.util.Arrays;
import java.util.HashMap;
import java.util.LinkedList;
import java.util.concurrent.Executor;

An adapter to a RemoteViewsService which fetches and caches RemoteViews to be later inflated as child views. The adapter runs in the host process, typically a Launcher app. It makes a service connection to the RemoteViewsService running in the AppWidgetsProvider's process. This connection is made on a background thread (and proxied via the platform to get the bind permissions) and all interaction with the service is done on the background thread. On first bind, the adapter will load can cache the RemoteViews locally. Afterwards the connection is only made when new RemoteViews are required. 
@hide
/**
 * An adapter to a RemoteViewsService which fetches and caches RemoteViews to be later inflated as
 * child views.
 *
 * The adapter runs in the host process, typically a Launcher app.
 *
 * It makes a service connection to the {@link RemoteViewsService} running in the
 * AppWidgetsProvider's process. This connection is made on a background thread (and proxied via
 * the platform to get the bind permissions) and all interaction with the service is done on the
 * background thread.
 *
 * On first bind, the adapter will load can cache the RemoteViews locally. Afterwards the
 * connection is only made when new RemoteViews are required.
 * @hide
 */
public class RemoteViewsAdapter extends BaseAdapter implements Handler.Callback {

    private static final String TAG = "RemoteViewsAdapter";

    // The max number of items in the cache
    private static final int DEFAULT_CACHE_SIZE = 40;
    // The delay (in millis) to wait until attempting to unbind from a service after a request.
    // This ensures that we don't stay continually bound to the service and that it can be destroyed
    // if we need the memory elsewhere in the system.
    private static final int UNBIND_SERVICE_DELAY = 5000;

    // Default height for the default loading view, in case we cannot get inflate the first view
    private static final int DEFAULT_LOADING_VIEW_HEIGHT = 50;

    // We cache the FixedSizeRemoteViewsCaches across orientation. These are the related data
    // structures;
    private static final HashMap<RemoteViewsCacheKey, FixedSizeRemoteViewsCache>
            sCachedRemoteViewsCaches = new HashMap<>();
    private static final HashMap<RemoteViewsCacheKey, Runnable>
            sRemoteViewsCacheRemoveRunnables = new HashMap<>();

    private static HandlerThread sCacheRemovalThread;
    private static Handler sCacheRemovalQueue;

    // We keep the cache around for a duration after onSaveInstanceState for use on re-inflation.
    // If a new RemoteViewsAdapter with the same intent / widget id isn't constructed within this
    // duration, the cache is dropped.
    private static final int REMOTE_VIEWS_CACHE_DURATION = 5000;

    private final Context mContext;
    private final Intent mIntent;
    private final int mAppWidgetId;
    private final Executor mAsyncViewLoadExecutor;

    private OnClickHandler mRemoteViewsOnClickHandler;
    private final FixedSizeRemoteViewsCache mCache;
    private int mVisibleWindowLowerBound;
    private int mVisibleWindowUpperBound;

    // The set of requested views that are to be notified when the associated RemoteViews are
    // loaded.
    private RemoteViewsFrameLayoutRefSet mRequestedViews;

    private final HandlerThread mWorkerThread;
    // items may be interrupted within the normally processed queues
    private final Handler mMainHandler;
    private final RemoteServiceHandler mServiceHandler;
    private final RemoteAdapterConnectionCallback mCallback;

    // Used to indicate to the AdapterView that it can use this Adapter immediately after
    // construction (happens when we have a cached FixedSizeRemoteViewsCache).
    private boolean mDataReady = false;

    
USed to dedupe RemoteViews.mApplication so that we do not hold on to multiple copies of the same ApplicationInfo object. /**
     * USed to dedupe {@link RemoteViews#mApplication} so that we do not hold on to
     * multiple copies of the same ApplicationInfo object.
     */
    private ApplicationInfo mLastRemoteViewAppInfo;

    
An interface for the RemoteAdapter to notify other classes when adapters
are actually connected to/disconnected from their actual services.
/**
     * An interface for the RemoteAdapter to notify other classes when adapters
     * are actually connected to/disconnected from their actual services.
     */
    public interface RemoteAdapterConnectionCallback {
        
Returns:
whether the adapter was set or not./**
         * @return whether the adapter was set or not.
         */
        boolean onRemoteAdapterConnected();

        void onRemoteAdapterDisconnected();

        
This defers a notifyDataSetChanged on the pending RemoteViewsAdapter if it has not
connected yet.
/**
         * This defers a notifyDataSetChanged on the pending RemoteViewsAdapter if it has not
         * connected yet.
         */
        void deferNotifyDataSetChanged();

        void setRemoteViewsAdapter(Intent intent, boolean isAsync);
    }

    public static class AsyncRemoteAdapterAction implements Runnable {

        private final RemoteAdapterConnectionCallback mCallback;
        private final Intent mIntent;

        public AsyncRemoteAdapterAction(RemoteAdapterConnectionCallback callback, Intent intent) {
            mCallback = callback;
            mIntent = intent;
        }

        @Override
        public void run() {
            mCallback.setRemoteViewsAdapter(mIntent, true);
        }
    }

    static final int MSG_REQUEST_BIND = 1;
    static final int MSG_NOTIFY_DATA_SET_CHANGED = 2;
    static final int MSG_LOAD_NEXT_ITEM = 3;
    static final int MSG_UNBIND_SERVICE = 4;

    private static final int MSG_MAIN_HANDLER_COMMIT_METADATA = 1;
    private static final int MSG_MAIN_HANDLER_SUPER_NOTIFY_DATA_SET_CHANGED = 2;
    private static final int MSG_MAIN_HANDLER_REMOTE_ADAPTER_CONNECTED = 3;
    private static final int MSG_MAIN_HANDLER_REMOTE_ADAPTER_DISCONNECTED = 4;
    private static final int MSG_MAIN_HANDLER_REMOTE_VIEWS_LOADED = 5;

    
Handler for various interactions with the RemoteViewsService. /**
     * Handler for various interactions with the {@link RemoteViewsService}.
     */
    private static class RemoteServiceHandler extends Handler implements ServiceConnection {

        private final WeakReference<RemoteViewsAdapter> mAdapter;
        private final Context mContext;

        private IRemoteViewsFactory mRemoteViewsFactory;

        // The last call to notifyDataSetChanged didn't succeed, try again on next service bind.
        private boolean mNotifyDataSetChangedPending = false;
        private boolean mBindRequested = false;

        RemoteServiceHandler(Looper workerLooper, RemoteViewsAdapter adapter, Context context) {
            super(workerLooper);
            mAdapter = new WeakReference<>(adapter);
            mContext = context;
        }

        @Override
        public void onServiceConnected(ComponentName name, IBinder service) {
            // This is called on the same thread.
            mRemoteViewsFactory = IRemoteViewsFactory.Stub.asInterface(service);
            enqueueDeferredUnbindServiceMessage();

            RemoteViewsAdapter adapter = mAdapter.get();
            if (adapter == null) {
                return;
            }

            if (mNotifyDataSetChangedPending) {
                mNotifyDataSetChangedPending = false;
                Message msg = Message.obtain(this, MSG_NOTIFY_DATA_SET_CHANGED);
                handleMessage(msg);
                msg.recycle();
            } else {
                if (!sendNotifyDataSetChange(false)) {
                    return;
                }

                // Request meta data so that we have up to date data when calling back to
                // the remote adapter callback
                adapter.updateTemporaryMetaData(mRemoteViewsFactory);
                adapter.mMainHandler.sendEmptyMessage(MSG_MAIN_HANDLER_COMMIT_METADATA);
                adapter.mMainHandler.sendEmptyMessage(MSG_MAIN_HANDLER_REMOTE_ADAPTER_CONNECTED);
            }
        }

        @Override
        public void onServiceDisconnected(ComponentName name) {
            mRemoteViewsFactory = null;
            RemoteViewsAdapter adapter = mAdapter.get();
            if (adapter != null) {
                adapter.mMainHandler.sendEmptyMessage(MSG_MAIN_HANDLER_REMOTE_ADAPTER_DISCONNECTED);
            }
        }

        @Override
        public void handleMessage(Message msg) {
            RemoteViewsAdapter adapter = mAdapter.get();

            switch (msg.what) {
                case MSG_REQUEST_BIND: {
                    if (adapter == null || mRemoteViewsFactory != null) {
                        enqueueDeferredUnbindServiceMessage();
                    }
                    if (mBindRequested) {
                        return;
                    }
                    int flags = Context.BIND_AUTO_CREATE
                            | Context.BIND_FOREGROUND_SERVICE_WHILE_AWAKE;
                    final IServiceConnection sd = mContext.getServiceDispatcher(this, this, flags);
                    Intent intent = (Intent) msg.obj;
                    int appWidgetId = msg.arg1;
                    mBindRequested = AppWidgetManager.getInstance(mContext)
                            .bindRemoteViewsService(mContext, appWidgetId, intent, sd, flags);
                    return;
                }
                case MSG_NOTIFY_DATA_SET_CHANGED: {
                    enqueueDeferredUnbindServiceMessage();
                    if (adapter == null) {
                        return;
                    }
                    if (mRemoteViewsFactory == null) {
                        mNotifyDataSetChangedPending = true;
                        adapter.requestBindService();
                        return;
                    }
                    if (!sendNotifyDataSetChange(true)) {
                        return;
                    }

                    // Flush the cache so that we can reload new items from the service
                    synchronized (adapter.mCache) {
                        adapter.mCache.reset();
                    }

                    // Re-request the new metadata (only after the notification to the factory)
                    adapter.updateTemporaryMetaData(mRemoteViewsFactory);
                    int newCount;
                    int[] visibleWindow;
                    synchronized (adapter.mCache.getTemporaryMetaData()) {
                        newCount = adapter.mCache.getTemporaryMetaData().count;
                        visibleWindow = adapter.getVisibleWindow(newCount);
                    }

                    // Pre-load (our best guess of) the views which are currently visible in the
                    // AdapterView. This mitigates flashing and flickering of loading views when a
                    // widget notifies that its data has changed.
                    for (int position : visibleWindow) {
                        // Because temporary meta data is only ever modified from this thread
                        // (ie. mWorkerThread), it is safe to assume that count is a valid
                        // representation.
                        if (position < newCount) {
                            adapter.updateRemoteViews(mRemoteViewsFactory, position, false);
                        }
                    }

                    // Propagate the notification back to the base adapter
                    adapter.mMainHandler.sendEmptyMessage(MSG_MAIN_HANDLER_COMMIT_METADATA);
                    adapter.mMainHandler.sendEmptyMessage(
                            MSG_MAIN_HANDLER_SUPER_NOTIFY_DATA_SET_CHANGED);
                    return;
                }

                case MSG_LOAD_NEXT_ITEM: {
                    if (adapter == null || mRemoteViewsFactory == null) {
                        return;
                    }
                    removeMessages(MSG_UNBIND_SERVICE);
                    // Get the next index to load
                    final int position = adapter.mCache.getNextIndexToLoad();
                    if (position > -1) {
                        // Load the item, and notify any existing RemoteViewsFrameLayouts
                        adapter.updateRemoteViews(mRemoteViewsFactory, position, true);

                        // Queue up for the next one to load
                        sendEmptyMessage(MSG_LOAD_NEXT_ITEM);
                    } else {
                        // No more items to load, so queue unbind
                        enqueueDeferredUnbindServiceMessage();
                    }
                    return;
                }
                case MSG_UNBIND_SERVICE: {
                    unbindNow();
                    return;
                }
            }
        }

        protected void unbindNow() {
            if (mBindRequested) {
                mBindRequested = false;
                mContext.unbindService(this);
            }
            mRemoteViewsFactory = null;
        }

        private boolean sendNotifyDataSetChange(boolean always) {
            try {
                if (always || !mRemoteViewsFactory.isCreated()) {
                    mRemoteViewsFactory.onDataSetChanged();
                }
                return true;
            } catch (RemoteException | RuntimeException e) {
                Log.e(TAG, "Error in updateNotifyDataSetChanged(): " + e.getMessage());
                return false;
            }
        }

        private void enqueueDeferredUnbindServiceMessage() {
            removeMessages(MSG_UNBIND_SERVICE);
            sendEmptyMessageDelayed(MSG_UNBIND_SERVICE, UNBIND_SERVICE_DELAY);
        }
    }

    
A FrameLayout which contains a loading view, and manages the re/applying of RemoteViews when
they are loaded.
/**
     * A FrameLayout which contains a loading view, and manages the re/applying of RemoteViews when
     * they are loaded.
     */
    static class RemoteViewsFrameLayout extends AppWidgetHostView {
        private final FixedSizeRemoteViewsCache mCache;

        public int cacheIndex = -1;

        public RemoteViewsFrameLayout(Context context, FixedSizeRemoteViewsCache cache) {
            super(context);
            mCache = cache;
        }

        
Updates this RemoteViewsFrameLayout depending on the view that was loaded.
Params:
view – the RemoteViews that was loaded. If null, the RemoteViews was not loaded
            successfully.
forceApplyAsync – when true, the host will always try to inflate the view
                       asynchronously (for eg, when we are already showing the loading
                       view)/**
         * Updates this RemoteViewsFrameLayout depending on the view that was loaded.
         * @param view the RemoteViews that was loaded. If null, the RemoteViews was not loaded
         *             successfully.
         * @param forceApplyAsync when true, the host will always try to inflate the view
         *                        asynchronously (for eg, when we are already showing the loading
         *                        view)
         */
        public void onRemoteViewsLoaded(RemoteViews view, OnClickHandler handler,
                boolean forceApplyAsync) {
            setOnClickHandler(handler);
            applyRemoteViews(view, forceApplyAsync || ((view != null) && view.prefersAsyncApply()));
        }

        
Creates a default loading view. Uses the size of the first row as a guide for the
size of the loading view.
/**
         * Creates a default loading view. Uses the size of the first row as a guide for the
         * size of the loading view.
         */
        @Override
        protected View getDefaultView() {
            int viewHeight = mCache.getMetaData().getLoadingTemplate(getContext()).defaultHeight;
            // Compose the loading view text
            TextView loadingTextView = (TextView) LayoutInflater.from(getContext()).inflate(
                    com.android.internal.R.layout.remote_views_adapter_default_loading_view,
                    this, false);
            loadingTextView.setHeight(viewHeight);
            return loadingTextView;
        }

        @Override
        protected Context getRemoteContext() {
            return null;
        }

        @Override
        protected View getErrorView() {
            // Use the default loading view as the error view.
            return getDefaultView();
        }
    }

    
Stores the references of all the RemoteViewsFrameLayouts that have been returned by the
adapter that have not yet had their RemoteViews loaded.
/**
     * Stores the references of all the RemoteViewsFrameLayouts that have been returned by the
     * adapter that have not yet had their RemoteViews loaded.
     */
    private class RemoteViewsFrameLayoutRefSet
            extends SparseArray<LinkedList<RemoteViewsFrameLayout>> {

        
Adds a new reference to a RemoteViewsFrameLayout returned by the adapter.
/**
         * Adds a new reference to a RemoteViewsFrameLayout returned by the adapter.
         */
        public void add(int position, RemoteViewsFrameLayout layout) {
            LinkedList<RemoteViewsFrameLayout> refs = get(position);

            // Create the list if necessary
            if (refs == null) {
                refs = new LinkedList<>();
                put(position, refs);
            }

            // Add the references to the list
            layout.cacheIndex = position;
            refs.add(layout);
        }

        
Notifies each of the RemoteViewsFrameLayouts associated with a particular position that
the associated RemoteViews has loaded.
/**
         * Notifies each of the RemoteViewsFrameLayouts associated with a particular position that
         * the associated RemoteViews has loaded.
         */
        public void notifyOnRemoteViewsLoaded(int position, RemoteViews view) {
            if (view == null) return;

            // Remove this set from the original mapping
            final LinkedList<RemoteViewsFrameLayout> refs = removeReturnOld(position);
            if (refs != null) {
                // Notify all the references for that position of the newly loaded RemoteViews
                for (final RemoteViewsFrameLayout ref : refs) {
                    ref.onRemoteViewsLoaded(view, mRemoteViewsOnClickHandler, true);
                }
            }
        }

        
We need to remove views from this set if they have been recycled by the AdapterView.
/**
         * We need to remove views from this set if they have been recycled by the AdapterView.
         */
        public void removeView(RemoteViewsFrameLayout rvfl) {
            if (rvfl.cacheIndex < 0) {
                return;
            }
            final LinkedList<RemoteViewsFrameLayout> refs = get(rvfl.cacheIndex);
            if (refs != null) {
                refs.remove(rvfl);
            }
            rvfl.cacheIndex = -1;
        }
    }

    
The meta-data associated with the cache in it's current state.
/**
     * The meta-data associated with the cache in it's current state.
     */
    private static class RemoteViewsMetaData {
        int count;
        int viewTypeCount;
        boolean hasStableIds;

        // Used to determine how to construct loading views.  If a loading view is not specified
        // by the user, then we try and load the first view, and use its height as the height for
        // the default loading view.
        LoadingViewTemplate loadingTemplate;

        // A mapping from type id to a set of unique type ids
        private final SparseIntArray mTypeIdIndexMap = new SparseIntArray();

        public RemoteViewsMetaData() {
            reset();
        }

        public void set(RemoteViewsMetaData d) {
            synchronized (d) {
                count = d.count;
                viewTypeCount = d.viewTypeCount;
                hasStableIds = d.hasStableIds;
                loadingTemplate = d.loadingTemplate;
            }
        }

        public void reset() {
            count = 0;

            // by default there is at least one dummy view type
            viewTypeCount = 1;
            hasStableIds = true;
            loadingTemplate = null;
            mTypeIdIndexMap.clear();
        }

        public int getMappedViewType(int typeId) {
            int mappedTypeId = mTypeIdIndexMap.get(typeId, -1);
            if (mappedTypeId == -1) {
                // We +1 because the loading view always has view type id of 0
                mappedTypeId = mTypeIdIndexMap.size() + 1;
                mTypeIdIndexMap.put(typeId, mappedTypeId);
            }
            return mappedTypeId;
        }

        public boolean isViewTypeInRange(int typeId) {
            int mappedType = getMappedViewType(typeId);
            return (mappedType < viewTypeCount);
        }

        public synchronized LoadingViewTemplate getLoadingTemplate(Context context) {
            if (loadingTemplate == null) {
                loadingTemplate = new LoadingViewTemplate(null, context);
            }
            return loadingTemplate;
        }
    }

    
The meta-data associated with a single item in the cache.
/**
     * The meta-data associated with a single item in the cache.
     */
    private static class RemoteViewsIndexMetaData {
        int typeId;
        long itemId;

        public RemoteViewsIndexMetaData(RemoteViews v, long itemId) {
            set(v, itemId);
        }

        public void set(RemoteViews v, long id) {
            itemId = id;
            if (v != null) {
                typeId = v.getLayoutId();
            } else {
                typeId = 0;
            }
        }
    }

    /**
     *
     */
    private static class FixedSizeRemoteViewsCache {

        // The meta data related to all the RemoteViews, ie. count, is stable, etc.
        // The meta data objects are made final so that they can be locked on independently
        // of the FixedSizeRemoteViewsCache. If we ever lock on both meta data objects, it is in
        // the order mTemporaryMetaData followed by mMetaData.
        private final RemoteViewsMetaData mMetaData = new RemoteViewsMetaData();
        private final RemoteViewsMetaData mTemporaryMetaData = new RemoteViewsMetaData();

        // The cache/mapping of position to RemoteViewsMetaData.  This set is guaranteed to be
        // greater than or equal to the set of RemoteViews.
        // Note: The reason that we keep this separate from the RemoteViews cache below is that this
        // we still need to be able to access the mapping of position to meta data, without keeping
        // the heavy RemoteViews around.  The RemoteViews cache is trimmed to fixed constraints wrt.
        // memory and size, but this metadata cache will retain information until the data at the
        // position is guaranteed as not being necessary any more (usually on notifyDataSetChanged).
        private final SparseArray<RemoteViewsIndexMetaData> mIndexMetaData = new SparseArray<>();

        // The cache of actual RemoteViews, which may be pruned if the cache gets too large, or uses
        // too much memory.
        private final SparseArray<RemoteViews> mIndexRemoteViews = new SparseArray<>();

        // An array of indices to load, Indices which are explicitly requested are set to true,
        // and those determined by the preloading algorithm to prefetch are set to false.
        private final SparseBooleanArray mIndicesToLoad = new SparseBooleanArray();

        // We keep a reference of the last requested index to determine which item to prune the
        // farthest items from when we hit the memory limit
        private int mLastRequestedIndex;


        // The lower and upper bounds of the preloaded range
        private int mPreloadLowerBound;
        private int mPreloadUpperBound;

        // The bounds of this fixed cache, we will try and fill as many items into the cache up to
        // the maxCount number of items, or the maxSize memory usage.
        // The maxCountSlack is used to determine if a new position in the cache to be loaded is
        // sufficiently ouside the old set, prompting a shifting of the "window" of items to be
        // preloaded.
        private final int mMaxCount;
        private final int mMaxCountSlack;
        private static final float sMaxCountSlackPercent = 0.75f;
        private static final int sMaxMemoryLimitInBytes = 2 * 1024 * 1024;

        public FixedSizeRemoteViewsCache(int maxCacheSize) {
            mMaxCount = maxCacheSize;
            mMaxCountSlack = Math.round(sMaxCountSlackPercent * (mMaxCount / 2));
            mPreloadLowerBound = 0;
            mPreloadUpperBound = -1;
            mLastRequestedIndex = -1;
        }

        public void insert(int position, RemoteViews v, long itemId, int[] visibleWindow) {
            // Trim the cache if we go beyond the count
            if (mIndexRemoteViews.size() >= mMaxCount) {
                mIndexRemoteViews.remove(getFarthestPositionFrom(position, visibleWindow));
            }

            // Trim the cache if we go beyond the available memory size constraints
            int pruneFromPosition = (mLastRequestedIndex > -1) ? mLastRequestedIndex : position;
            while (getRemoteViewsBitmapMemoryUsage() >= sMaxMemoryLimitInBytes) {
                // Note: This is currently the most naive mechanism for deciding what to prune when
                // we hit the memory limit.  In the future, we may want to calculate which index to
                // remove based on both its position as well as it's current memory usage, as well
                // as whether it was directly requested vs. whether it was preloaded by our caching
                // mechanism.
                int trimIndex = getFarthestPositionFrom(pruneFromPosition, visibleWindow);

                // Need to check that this is a valid index, to cover the case where you have only
                // a single view in the cache, but it's larger than the max memory limit
                if (trimIndex < 0) {
                    break;
                }

                mIndexRemoteViews.remove(trimIndex);
            }

            // Update the metadata cache
            final RemoteViewsIndexMetaData metaData = mIndexMetaData.get(position);
            if (metaData != null) {
                metaData.set(v, itemId);
            } else {
                mIndexMetaData.put(position, new RemoteViewsIndexMetaData(v, itemId));
            }
            mIndexRemoteViews.put(position, v);
        }

        public RemoteViewsMetaData getMetaData() {
            return mMetaData;
        }
        public RemoteViewsMetaData getTemporaryMetaData() {
            return mTemporaryMetaData;
        }
        public RemoteViews getRemoteViewsAt(int position) {
            return mIndexRemoteViews.get(position);
        }
        public RemoteViewsIndexMetaData getMetaDataAt(int position) {
            return mIndexMetaData.get(position);
        }

        public void commitTemporaryMetaData() {
            synchronized (mTemporaryMetaData) {
                synchronized (mMetaData) {
                    mMetaData.set(mTemporaryMetaData);
                }
            }
        }

        private int getRemoteViewsBitmapMemoryUsage() {
            // Calculate the memory usage of all the RemoteViews bitmaps being cached
            int mem = 0;
            for (int i = mIndexRemoteViews.size() - 1; i >= 0; i--) {
                final RemoteViews v = mIndexRemoteViews.valueAt(i);
                if (v != null) {
                    mem += v.estimateMemoryUsage();
                }
            }
            return mem;
        }

        private int getFarthestPositionFrom(int pos, int[] visibleWindow) {
            // Find the index farthest away and remove that
            int maxDist = 0;
            int maxDistIndex = -1;
            int maxDistNotVisible = 0;
            int maxDistIndexNotVisible = -1;
            for (int i = mIndexRemoteViews.size() - 1; i >= 0; i--) {
                int index = mIndexRemoteViews.keyAt(i);
                int dist = Math.abs(index-pos);
                if (dist > maxDistNotVisible && Arrays.binarySearch(visibleWindow, index) < 0) {
                    // maxDistNotVisible/maxDistIndexNotVisible will store the index of the
                    // farthest non-visible position
                    maxDistIndexNotVisible = index;
                    maxDistNotVisible = dist;
                }
                if (dist >= maxDist) {
                    // maxDist/maxDistIndex will store the index of the farthest position
                    // regardless of whether it is visible or not
                    maxDistIndex = index;
                    maxDist = dist;
                }
            }
            if (maxDistIndexNotVisible > -1) {
                return maxDistIndexNotVisible;
            }
            return maxDistIndex;
        }

        public void queueRequestedPositionToLoad(int position) {
            mLastRequestedIndex = position;
            synchronized (mIndicesToLoad) {
                mIndicesToLoad.put(position, true);
            }
        }
        public boolean queuePositionsToBePreloadedFromRequestedPosition(int position) {
            // Check if we need to preload any items
            if (mPreloadLowerBound <= position && position <= mPreloadUpperBound) {
                int center = (mPreloadUpperBound + mPreloadLowerBound) / 2;
                if (Math.abs(position - center) < mMaxCountSlack) {
                    return false;
                }
            }

            int count;
            synchronized (mMetaData) {
                count = mMetaData.count;
            }
            synchronized (mIndicesToLoad) {
                // Remove all indices which have not been previously requested.
                for (int i = mIndicesToLoad.size() - 1; i >= 0; i--) {
                    if (!mIndicesToLoad.valueAt(i)) {
                        mIndicesToLoad.removeAt(i);
                    }
                }

                // Add all the preload indices
                int halfMaxCount = mMaxCount / 2;
                mPreloadLowerBound = position - halfMaxCount;
                mPreloadUpperBound = position + halfMaxCount;
                int effectiveLowerBound = Math.max(0, mPreloadLowerBound);
                int effectiveUpperBound = Math.min(mPreloadUpperBound, count - 1);
                for (int i = effectiveLowerBound; i <= effectiveUpperBound; ++i) {
                    if (mIndexRemoteViews.indexOfKey(i) < 0 && !mIndicesToLoad.get(i)) {
                        // If the index has not been requested, and has not been loaded.
                        mIndicesToLoad.put(i, false);
                    }
                }
            }
            return true;
        }
        
Returns the next index to load /** Returns the next index to load */
        public int getNextIndexToLoad() {
            // We try and prioritize items that have been requested directly, instead
            // of items that are loaded as a result of the caching mechanism
            synchronized (mIndicesToLoad) {
                // Prioritize requested indices to be loaded first
                int index = mIndicesToLoad.indexOfValue(true);
                if (index < 0) {
                    // Otherwise, preload other indices as necessary
                    index = mIndicesToLoad.indexOfValue(false);
                }
                if (index < 0) {
                    return -1;
                } else {
                    int key = mIndicesToLoad.keyAt(index);
                    mIndicesToLoad.removeAt(index);
                    return key;
                }
            }
        }

        public boolean containsRemoteViewAt(int position) {
            return mIndexRemoteViews.indexOfKey(position) >= 0;
        }
        public boolean containsMetaDataAt(int position) {
            return mIndexMetaData.indexOfKey(position) >= 0;
        }

        public void reset() {
            // Note: We do not try and reset the meta data, since that information is still used by
            // collection views to validate it's own contents (and will be re-requested if the data
            // is invalidated through the notifyDataSetChanged() flow).

            mPreloadLowerBound = 0;
            mPreloadUpperBound = -1;
            mLastRequestedIndex = -1;
            mIndexRemoteViews.clear();
            mIndexMetaData.clear();
            synchronized (mIndicesToLoad) {
                mIndicesToLoad.clear();
            }
        }
    }

    static class RemoteViewsCacheKey {
        final Intent.FilterComparison filter;
        final int widgetId;

        RemoteViewsCacheKey(Intent.FilterComparison filter, int widgetId) {
            this.filter = filter;
            this.widgetId = widgetId;
        }

        @Override
        public boolean equals(Object o) {
            if (!(o instanceof RemoteViewsCacheKey)) {
                return false;
            }
            RemoteViewsCacheKey other = (RemoteViewsCacheKey) o;
            return other.filter.equals(filter) && other.widgetId == widgetId;
        }

        @Override
        public int hashCode() {
            return (filter == null ? 0 : filter.hashCode()) ^ (widgetId << 2);
        }
    }

    public RemoteViewsAdapter(Context context, Intent intent,
            RemoteAdapterConnectionCallback callback, boolean useAsyncLoader) {
        mContext = context;
        mIntent = intent;

        if (mIntent == null) {
            throw new IllegalArgumentException("Non-null Intent must be specified.");
        }

        mAppWidgetId = intent.getIntExtra(RemoteViews.EXTRA_REMOTEADAPTER_APPWIDGET_ID, -1);
        mRequestedViews = new RemoteViewsFrameLayoutRefSet();

        // Strip the previously injected app widget id from service intent
        if (intent.hasExtra(RemoteViews.EXTRA_REMOTEADAPTER_APPWIDGET_ID)) {
            intent.removeExtra(RemoteViews.EXTRA_REMOTEADAPTER_APPWIDGET_ID);
        }

        // Initialize the worker thread
        mWorkerThread = new HandlerThread("RemoteViewsCache-loader");
        mWorkerThread.start();
        mMainHandler = new Handler(Looper.myLooper(), this);
        mServiceHandler = new RemoteServiceHandler(mWorkerThread.getLooper(), this,
                context.getApplicationContext());
        mAsyncViewLoadExecutor = useAsyncLoader ? new HandlerThreadExecutor(mWorkerThread) : null;
        mCallback = callback;

        if (sCacheRemovalThread == null) {
            sCacheRemovalThread = new HandlerThread("RemoteViewsAdapter-cachePruner");
            sCacheRemovalThread.start();
            sCacheRemovalQueue = new Handler(sCacheRemovalThread.getLooper());
        }

        RemoteViewsCacheKey key = new RemoteViewsCacheKey(new Intent.FilterComparison(mIntent),
                mAppWidgetId);

        synchronized(sCachedRemoteViewsCaches) {
            if (sCachedRemoteViewsCaches.containsKey(key)) {
                mCache = sCachedRemoteViewsCaches.get(key);
                synchronized (mCache.mMetaData) {
                    if (mCache.mMetaData.count > 0) {
                        // As a precautionary measure, we verify that the meta data indicates a
                        // non-zero count before declaring that data is ready.
                        mDataReady = true;
                    }
                }
            } else {
                mCache = new FixedSizeRemoteViewsCache(DEFAULT_CACHE_SIZE);
            }
            if (!mDataReady) {
                requestBindService();
            }
        }
    }

    @Override
    protected void finalize() throws Throwable {
        try {
            mServiceHandler.unbindNow();
            mWorkerThread.quit();
        } finally {
            super.finalize();
        }
    }

    public boolean isDataReady() {
        return mDataReady;
    }

    public void setRemoteViewsOnClickHandler(OnClickHandler handler) {
        mRemoteViewsOnClickHandler = handler;
    }

    public void saveRemoteViewsCache() {
        final RemoteViewsCacheKey key = new RemoteViewsCacheKey(
                new Intent.FilterComparison(mIntent), mAppWidgetId);

        synchronized(sCachedRemoteViewsCaches) {
            // If we already have a remove runnable posted for this key, remove it.
            if (sRemoteViewsCacheRemoveRunnables.containsKey(key)) {
                sCacheRemovalQueue.removeCallbacks(sRemoteViewsCacheRemoveRunnables.get(key));
                sRemoteViewsCacheRemoveRunnables.remove(key);
            }

            int metaDataCount = 0;
            int numRemoteViewsCached = 0;
            synchronized (mCache.mMetaData) {
                metaDataCount = mCache.mMetaData.count;
            }
            synchronized (mCache) {
                numRemoteViewsCached = mCache.mIndexRemoteViews.size();
            }
            if (metaDataCount > 0 && numRemoteViewsCached > 0) {
                sCachedRemoteViewsCaches.put(key, mCache);
            }

            Runnable r = () -> {
                synchronized (sCachedRemoteViewsCaches) {
                    if (sCachedRemoteViewsCaches.containsKey(key)) {
                        sCachedRemoteViewsCaches.remove(key);
                    }
                    if (sRemoteViewsCacheRemoveRunnables.containsKey(key)) {
                        sRemoteViewsCacheRemoveRunnables.remove(key);
                    }
                }
            };
            sRemoteViewsCacheRemoveRunnables.put(key, r);
            sCacheRemovalQueue.postDelayed(r, REMOTE_VIEWS_CACHE_DURATION);
        }
    }

    @WorkerThread
    private void updateTemporaryMetaData(IRemoteViewsFactory factory) {
        try {
            // get the properties/first view (so that we can use it to
            // measure our dummy views)
            boolean hasStableIds = factory.hasStableIds();
            int viewTypeCount = factory.getViewTypeCount();
            int count = factory.getCount();
            LoadingViewTemplate loadingTemplate =
                    new LoadingViewTemplate(factory.getLoadingView(), mContext);
            if ((count > 0) && (loadingTemplate.remoteViews == null)) {
                RemoteViews firstView = factory.getViewAt(0);
                if (firstView != null) {
                    loadingTemplate.loadFirstViewHeight(firstView, mContext,
                            new HandlerThreadExecutor(mWorkerThread));
                }
            }
            final RemoteViewsMetaData tmpMetaData = mCache.getTemporaryMetaData();
            synchronized (tmpMetaData) {
                tmpMetaData.hasStableIds = hasStableIds;
                // We +1 because the base view type is the loading view
                tmpMetaData.viewTypeCount = viewTypeCount + 1;
                tmpMetaData.count = count;
                tmpMetaData.loadingTemplate = loadingTemplate;
            }
        } catch (RemoteException | RuntimeException e) {
            Log.e("RemoteViewsAdapter", "Error in updateMetaData: " + e.getMessage());

            // If we encounter a crash when updating, we should reset the metadata & cache
            // and trigger a notifyDataSetChanged to update the widget accordingly
            synchronized (mCache.getMetaData()) {
                mCache.getMetaData().reset();
            }
            synchronized (mCache) {
                mCache.reset();
            }
            mMainHandler.sendEmptyMessage(MSG_MAIN_HANDLER_SUPER_NOTIFY_DATA_SET_CHANGED);
        }
    }

    @WorkerThread
    private void updateRemoteViews(IRemoteViewsFactory factory, int position,
            boolean notifyWhenLoaded) {
        // Load the item information from the remote service
        final RemoteViews remoteViews;
        final long itemId;
        try {
            remoteViews = factory.getViewAt(position);
            itemId = factory.getItemId(position);

            if (remoteViews == null) {
                throw new RuntimeException("Null remoteViews");
            }
        } catch (RemoteException | RuntimeException e) {
            Log.e(TAG, "Error in updateRemoteViews(" + position + "): " + e.getMessage());

            // Return early to prevent additional work in re-centering the view cache, and
            // swapping from the loading view
            return;
        }

        if (remoteViews.mApplication != null) {
            // We keep track of last application info. This helps when all the remoteViews have
            // same applicationInfo, which should be the case for a typical adapter. But if every
            // view has different application info, there will not be any optimization.
            if (mLastRemoteViewAppInfo != null
                    && remoteViews.hasSameAppInfo(mLastRemoteViewAppInfo)) {
                // We should probably also update the remoteViews for nested ViewActions.
                // Hopefully, RemoteViews in an adapter would be less complicated.
                remoteViews.mApplication = mLastRemoteViewAppInfo;
            } else {
                mLastRemoteViewAppInfo = remoteViews.mApplication;
            }
        }

        int layoutId = remoteViews.getLayoutId();
        RemoteViewsMetaData metaData = mCache.getMetaData();
        boolean viewTypeInRange;
        int cacheCount;
        synchronized (metaData) {
            viewTypeInRange = metaData.isViewTypeInRange(layoutId);
            cacheCount = mCache.mMetaData.count;
        }
        synchronized (mCache) {
            if (viewTypeInRange) {
                int[] visibleWindow = getVisibleWindow(cacheCount);
                // Cache the RemoteViews we loaded
                mCache.insert(position, remoteViews, itemId, visibleWindow);

                if (notifyWhenLoaded) {
                    // Notify all the views that we have previously returned for this index that
                    // there is new data for it.
                    Message.obtain(mMainHandler, MSG_MAIN_HANDLER_REMOTE_VIEWS_LOADED, position, 0,
                            remoteViews).sendToTarget();
                }
            } else {
                // We need to log an error here, as the the view type count specified by the
                // factory is less than the number of view types returned. We don't return this
                // view to the AdapterView, as this will cause an exception in the hosting process,
                // which contains the associated AdapterView.
                Log.e(TAG, "Error: widget's RemoteViewsFactory returns more view types than " +
                        " indicated by getViewTypeCount() ");
            }
        }
    }

    public Intent getRemoteViewsServiceIntent() {
        return mIntent;
    }

    public int getCount() {
        final RemoteViewsMetaData metaData = mCache.getMetaData();
        synchronized (metaData) {
            return metaData.count;
        }
    }

    public Object getItem(int position) {
        // Disallow arbitrary object to be associated with an item for the time being
        return null;
    }

    public long getItemId(int position) {
        synchronized (mCache) {
            if (mCache.containsMetaDataAt(position)) {
                return mCache.getMetaDataAt(position).itemId;
            }
            return 0;
        }
    }

    public int getItemViewType(int position) {
        final int typeId;
        synchronized (mCache) {
            if (mCache.containsMetaDataAt(position)) {
                typeId = mCache.getMetaDataAt(position).typeId;
            } else {
                return 0;
            }
        }

        final RemoteViewsMetaData metaData = mCache.getMetaData();
        synchronized (metaData) {
            return metaData.getMappedViewType(typeId);
        }
    }

    
This method allows an AdapterView using this Adapter to provide information about which
views are currently being displayed. This allows for certain optimizations and preloading
which  wouldn't otherwise be possible.
/**
     * This method allows an AdapterView using this Adapter to provide information about which
     * views are currently being displayed. This allows for certain optimizations and preloading
     * which  wouldn't otherwise be possible.
     */
    public void setVisibleRangeHint(int lowerBound, int upperBound) {
        mVisibleWindowLowerBound = lowerBound;
        mVisibleWindowUpperBound = upperBound;
    }

    public View getView(int position, View convertView, ViewGroup parent) {
        // "Request" an index so that we can queue it for loading, initiate subsequent
        // preloading, etc.
        synchronized (mCache) {
            RemoteViews rv = mCache.getRemoteViewsAt(position);
            boolean isInCache = (rv != null);
            boolean hasNewItems = false;

            if (convertView != null && convertView instanceof RemoteViewsFrameLayout) {
                mRequestedViews.removeView((RemoteViewsFrameLayout) convertView);
            }

            if (!isInCache) {
                // Requesting bind service will trigger a super.notifyDataSetChanged(), which will
                // in turn trigger another request to getView()
                requestBindService();
            } else {
                // Queue up other indices to be preloaded based on this position
                hasNewItems = mCache.queuePositionsToBePreloadedFromRequestedPosition(position);
            }

            final RemoteViewsFrameLayout layout;
            if (convertView instanceof RemoteViewsFrameLayout) {
                layout = (RemoteViewsFrameLayout) convertView;
            } else {
                layout = new RemoteViewsFrameLayout(parent.getContext(), mCache);
                layout.setExecutor(mAsyncViewLoadExecutor);
            }

            if (isInCache) {
                // Apply the view synchronously if possible, to avoid flickering
                layout.onRemoteViewsLoaded(rv, mRemoteViewsOnClickHandler, false);
                if (hasNewItems) {
                    mServiceHandler.sendEmptyMessage(MSG_LOAD_NEXT_ITEM);
                }
            } else {
                // If the views is not loaded, apply the loading view. If the loading view doesn't
                // exist, the layout will create a default view based on the firstView height.
                layout.onRemoteViewsLoaded(
                        mCache.getMetaData().getLoadingTemplate(mContext).remoteViews,
                        mRemoteViewsOnClickHandler,
                        false);
                mRequestedViews.add(position, layout);
                mCache.queueRequestedPositionToLoad(position);
                mServiceHandler.sendEmptyMessage(MSG_LOAD_NEXT_ITEM);
            }
            return layout;
        }
    }

    public int getViewTypeCount() {
        final RemoteViewsMetaData metaData = mCache.getMetaData();
        synchronized (metaData) {
            return metaData.viewTypeCount;
        }
    }

    public boolean hasStableIds() {
        final RemoteViewsMetaData metaData = mCache.getMetaData();
        synchronized (metaData) {
            return metaData.hasStableIds;
        }
    }

    public boolean isEmpty() {
        return getCount() <= 0;
    }

    
Returns a sorted array of all integers between lower and upper.
/**
     * Returns a sorted array of all integers between lower and upper.
     */
    private int[] getVisibleWindow(int count) {
        int lower = mVisibleWindowLowerBound;
        int upper = mVisibleWindowUpperBound;
        // In the case that the window is invalid or uninitialized, return an empty window.
        if ((lower == 0 && upper == 0) || lower < 0 || upper < 0) {
            return new int[0];
        }

        int[] window;
        if (lower <= upper) {
            window = new int[upper + 1 - lower];
            for (int i = lower, j = 0;  i <= upper; i++, j++){
                window[j] = i;
            }
        } else {
            // If the upper bound is less than the lower bound it means that the visible window
            // wraps around.
            count = Math.max(count, lower);
            window = new int[count - lower + upper + 1];
            int j = 0;
            // Add the entries in sorted order
            for (int i = 0; i <= upper; i++, j++) {
                window[j] = i;
            }
            for (int i = lower; i < count; i++, j++) {
                window[j] = i;
            }
        }
        return window;
    }

    public void notifyDataSetChanged() {
        mServiceHandler.removeMessages(MSG_UNBIND_SERVICE);
        mServiceHandler.sendEmptyMessage(MSG_NOTIFY_DATA_SET_CHANGED);
    }

    void superNotifyDataSetChanged() {
        super.notifyDataSetChanged();
    }

    @Override
    public boolean handleMessage(Message msg) {
        switch (msg.what) {
            case MSG_MAIN_HANDLER_COMMIT_METADATA: {
                mCache.commitTemporaryMetaData();
                return true;
            }
            case MSG_MAIN_HANDLER_SUPER_NOTIFY_DATA_SET_CHANGED: {
                superNotifyDataSetChanged();
                return true;
            }
            case MSG_MAIN_HANDLER_REMOTE_ADAPTER_CONNECTED: {
                if (mCallback != null) {
                    mCallback.onRemoteAdapterConnected();
                }
                return true;
            }
            case MSG_MAIN_HANDLER_REMOTE_ADAPTER_DISCONNECTED: {
                if (mCallback != null) {
                    mCallback.onRemoteAdapterDisconnected();
                }
                return true;
            }
            case MSG_MAIN_HANDLER_REMOTE_VIEWS_LOADED: {
                mRequestedViews.notifyOnRemoteViewsLoaded(msg.arg1, (RemoteViews) msg.obj);
                return true;
            }
        }
        return false;
    }

    private void requestBindService() {
        mServiceHandler.removeMessages(MSG_UNBIND_SERVICE);
        Message.obtain(mServiceHandler, MSG_REQUEST_BIND, mAppWidgetId, 0, mIntent).sendToTarget();
    }

    private static class HandlerThreadExecutor implements Executor {
        private final HandlerThread mThread;

        HandlerThreadExecutor(HandlerThread thread) {
            mThread = thread;
        }

        @Override
        public void execute(Runnable runnable) {
            if (Thread.currentThread().getId() == mThread.getId()) {
                runnable.run();
            } else {
                new Handler(mThread.getLooper()).post(runnable);
            }
        }
    }

    private static class LoadingViewTemplate {
        public final RemoteViews remoteViews;
        public int defaultHeight;

        LoadingViewTemplate(RemoteViews views, Context context) {
            remoteViews = views;

            float density = context.getResources().getDisplayMetrics().density;
            defaultHeight = Math.round(DEFAULT_LOADING_VIEW_HEIGHT * density);
        }

        public void loadFirstViewHeight(
                RemoteViews firstView, Context context, Executor executor) {
            // Inflate the first view on the worker thread
            firstView.applyAsync(context, new RemoteViewsFrameLayout(context, null), executor,
                    new RemoteViews.OnViewAppliedListener() {
                        @Override
                        public void onViewApplied(View v) {
                            try {
                                v.measure(
                                        MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED),
                                        MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED));
                                defaultHeight = v.getMeasuredHeight();
                            } catch (Exception e) {
                                onError(e);
                            }
                        }

                        @Override
                        public void onError(Exception e) {
                            // Do nothing. The default height will stay the same.
                            Log.w(TAG, "Error inflating first RemoteViews", e);
                        }
                    });
        }
    }
}