Add downloads to the deletion helper.

This adds a deletion service to delete files in the Downloads
folder. All of the files there are collected and offered to the
user to delete.

Bug: 28621781
Change-Id: I94431f9abc3a0afa2d07dbab763312c09e830aef

res/values/strings.xml

@@ -7589,4 +7589,13 @@
     <!-- Summary of how much backed up storage that photos and videos service can clear from the local device. [CHAR LIMIT=NONE]-->
     <string name="deletion_helper_photos_summary"><xliff:g id="used" example="1.2GB">%1$s</xliff:g>, older than <xliff:g id="days">%2$d</xliff:g> days</string>
 
+    <!-- Preference title for the downloads deletion service. [CHAR LIMIT=40]-->
+    <string name="deletion_helper_downloads_title">Downloads (<xliff:g id="numItems" example="67">%1$d</xliff:g>)</string>
+
+    <!-- Summary of how much stale data can be cleared from the local download folder. [CHAR LIMIT=NONE]-->
+    <string name="deletion_helper_downloads_summary"><xliff:g id="used" example="1.2GB">%1$s</xliff:g>, last modified <xliff:g id="days">%2$s</xliff:g></string>
+
+    <!-- Summary for when when there is nothing in the downloads folder to clear. [CHAR LIMIT=NONE]-->
+    <string name="deletion_helper_downloads_summary_empty"><xliff:g id="used" example="1.2GB">%1$s</xliff:g></string>
+
 </resources>

res/xml/deletion_helper_list.xml

@@ -20,6 +20,9 @@
     <com.android.settings.PhotosDeletionPreference
         android:key="delete_photos" />
 
+    <com.android.settings.deletionhelper.DownloadsDeletionPreference
+        android:key="delete_downloads" />
+
     <PreferenceCategory
         android:key="apps_group"
         android:title="@string/deletion_helper_apps_title" />

src/com/android/settings/DeletionPreference.java

@@ -0,0 +1,117 @@
+/*
+ * Copyright (C) 2016 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 com.android.settings;
+
+import android.content.Context;
+import android.content.res.Resources;
+import android.graphics.drawable.Drawable;
+import android.support.v7.preference.Preference;
+import android.support.v7.preference.Preference.OnPreferenceChangeListener;
+import android.support.v7.preference.CheckBoxPreference;
+import android.support.v7.preference.PreferenceViewHolder;
+import android.util.AttributeSet;
+import android.util.TypedValue;
+import android.text.format.Formatter;
+import android.widget.TextView;
+import com.android.settings.deletionhelper.DeletionType;
+
+/**
+ * Preference to handle the deletion of various data types in the Deletion Helper.
+ */
+public abstract class DeletionPreference extends CheckBoxPreference implements
+        DeletionType.FreeableChangedListener, OnPreferenceChangeListener {
+    private DeletionType.FreeableChangedListener mListener;
+    private boolean mChecked;
+    private long mFreeableBytes;
+    private int mFreeableItems;
+    private DeletionType mDeletionService;
+
+    public DeletionPreference(Context context, AttributeSet attrs) {
+        super(context, attrs);
+        setOnPreferenceChangeListener(this);
+    }
+
+    @Override
+    public void onBindViewHolder(PreferenceViewHolder holder) {
+        super.onBindViewHolder(holder);
+        final TextView titleView = (TextView) holder.findViewById(android.R.id.title);
+        if (titleView != null) {
+            titleView.setTextColor(getTintColor(getContext()));
+        }
+    }
+
+    /**
+     * Returns the number of bytes which can be cleared by the deletion service.
+     * @return The number of bytes.
+     */
+    public long getFreeableBytes() {
+        return mChecked ? mFreeableBytes : 0;
+    }
+
+    /**
+     * Register a listener to be called back on when the freeable bytes have changed.
+     * @param listener The callback listener.
+     */
+    public void registerFreeableChangedListener(DeletionType.FreeableChangedListener listener) {
+        mListener = listener;
+    }
+
+    /**
+     * Registers a deletion service to update the preference's information.
+     * @param deletionService A photo/video deletion service.
+     */
+    public void registerDeletionService(DeletionType deletionService) {
+        mDeletionService = deletionService;
+        if (mDeletionService != null) {
+            mDeletionService.registerFreeableChangedListener(this);
+        }
+    }
+
+    /**
+     * Returns the deletion service powering the preference.
+     * @return The deletion service.
+     */
+    public DeletionType getDeletionService() {
+        return mDeletionService;
+    }
+
+    @Override
+    public void onFreeableChanged(int numItems, long freeableBytes) {
+        mFreeableItems = numItems;
+        mFreeableBytes = freeableBytes;
+        maybeUpdateListener();
+    }
+
+    @Override
+    public boolean onPreferenceChange(Preference preference, Object newValue) {
+        mChecked = (boolean) newValue;
+        maybeUpdateListener();
+        return true;
+    }
+
+    private int getTintColor(Context context) {
+        TypedValue value = new TypedValue();
+        context.getTheme().resolveAttribute(android.R.attr.colorAccent, value, true);
+        return context.getColor(value.resourceId);
+    }
+
+    private void maybeUpdateListener() {
+        if (mListener != null) {
+            mListener.onFreeableChanged(mFreeableItems, getFreeableBytes());
+        }
+    }
+}

src/com/android/settings/PhotosDeletionPreference.java

@@ -19,107 +19,36 @@ package com.android.settings;
 import android.content.Context;
 import android.content.res.Resources;
 import android.graphics.drawable.Drawable;
-import android.support.v7.preference.Preference;
-import android.support.v7.preference.Preference.OnPreferenceChangeListener;
-import android.support.v7.preference.CheckBoxPreference;
-import android.support.v7.preference.PreferenceViewHolder;
 import android.util.AttributeSet;
-import android.util.TypedValue;
 import android.text.format.Formatter;
-import android.widget.TextView;
-import com.android.settings.deletionhelper.DeletionType;
 
 /**
  * Preference to handle the deletion of photos and videos in the Deletion Helper.
  */
-public class PhotosDeletionPreference extends CheckBoxPreference implements
-        DeletionType.FreeableChangedListener, OnPreferenceChangeListener {
+public class PhotosDeletionPreference extends DeletionPreference {
     // TODO(b/28560570): Remove this dummy value.
     private static final int FAKE_DAYS_TO_KEEP = 30;
-    private DeletionType.FreeableChangedListener mListener;
-    private boolean mChecked;
-    private long mFreeableBytes;
-    private int mFreeableItems;
-    private DeletionType mDeletionService;
 
     public PhotosDeletionPreference(Context context, AttributeSet attrs) {
         super(context, attrs);
         setIcon(getIcon(context));
-        updatePreferenceText();
-        setOnPreferenceChangeListener(this);
-    }
-
-    @Override
-    public void onBindViewHolder(PreferenceViewHolder holder) {
-        super.onBindViewHolder(holder);
-        final TextView titleView = (TextView) holder.findViewById(android.R.id.title);
-        if (titleView != null) {
-            titleView.setTextColor(getTintColor(getContext()));
-        }
-    }
-
-    /**
-     * Get the tint color for the preference's icon and text.
-     * @param context UI context to get the theme.
-     * @return The tint color.
-     */
-    public int getTintColor(Context context) {
-        TypedValue value = new TypedValue();
-        context.getTheme().resolveAttribute(android.R.attr.colorAccent, value, true);
-        return context.getColor(value.resourceId);
+        updatePreferenceText(0, 0);
     }
 
     /**
      * Updates the title and summary of the preference with fresh information.
      */
-    public void updatePreferenceText() {
+    public void updatePreferenceText(int items, long bytes) {
         Context context = getContext();
-        setTitle(context.getString(R.string.deletion_helper_photos_title,
-                mFreeableItems));
+        setTitle(context.getString(R.string.deletion_helper_photos_title, items));
         setSummary(context.getString(R.string.deletion_helper_photos_summary,
-                Formatter.formatFileSize(context, mFreeableBytes), FAKE_DAYS_TO_KEEP));
-    }
-
-    /**
-     * Returns the number of bytes which can be cleared by the deletion service.
-     * @return The number of bytes.
-     */
-    public long getFreeableBytes() {
-        return mChecked ? mFreeableBytes : 0;
-    }
-
-    /**
-     * Register a listener to be called back on when the freeable bytes have changed.
-     * @param listener The callback listener.
-     */
-    public void registerFreeableChangedListener(DeletionType.FreeableChangedListener listener) {
-        mListener = listener;
-    }
-
-    /**
-     * Registers a deletion service to update the preference's information.
-     * @param deletionService A photo/video deletion service.
-     */
-    public void registerDeletionService(DeletionType deletionService) {
-        mDeletionService = deletionService;
-        if (mDeletionService != null) {
-            mDeletionService.registerFreeableChangedListener(this);
-        }
+                Formatter.formatFileSize(context, bytes), FAKE_DAYS_TO_KEEP));
     }
 
     @Override
-    public void onFreeableChanged(int numItems, long freeableBytes) {
-        mFreeableItems = numItems;
-        mFreeableBytes = freeableBytes;
-        updatePreferenceText();
-        maybeUpdateListener();
-    }
-
-    @Override
-    public boolean onPreferenceChange(Preference preference, Object newValue) {
-        mChecked = (boolean) newValue;
-        maybeUpdateListener();
-        return true;
+    public void onFreeableChanged(int items, long bytes) {
+        super.onFreeableChanged(items, bytes);
+        updatePreferenceText(items, bytes);
     }
 
     private Drawable getIcon(Context context) {
@@ -134,10 +63,4 @@ public class PhotosDeletionPreference extends CheckBoxPreference implements
         }
         return iconDrawable;
     }
-
-    private void maybeUpdateListener() {
-        if (mListener != null) {
-            mListener.onFreeableChanged(mFreeableItems, getFreeableBytes());
-        }
-    }
 }

src/com/android/settings/deletionhelper/DeletionHelperFragment.java

@@ -25,6 +25,7 @@ import android.util.ArraySet;
 import android.util.Log;
 import android.view.View;
 import android.widget.Button;
+import com.android.settings.deletionhelper.DownloadsDeletionPreference;
 import com.android.settings.PhotosDeletionPreference;
 import com.android.settings.SettingsPreferenceFragment;
 import com.android.settings.R;
@@ -54,10 +55,14 @@ public class DeletionHelperFragment extends SettingsPreferenceFragment implement
 
     private static final String KEY_APPS_GROUP = "apps_group";
     private static final String KEY_PHOTOS_VIDEOS_PREFERENCE = "delete_photos";
+    private static final String KEY_DOWNLOADS_PREFERENCE = "delete_downloads";
+
+    private static final int DOWNLOADS_LOADER_ID = 1;
 
     private Button mCancel, mFree;
     private PreferenceGroup mApps;
     private PhotosDeletionPreference mPhotoPreference;
+    private DownloadsDeletionPreference mDownloadsPreference;
 
     private ApplicationsState mState;
     private Session mSession;
@@ -67,6 +72,7 @@ public class DeletionHelperFragment extends SettingsPreferenceFragment implement
     private boolean mHasReceivedAppEntries, mHasReceivedBridgeCallback, mFinishedLoading;
     private DeletionHelperFeatureProvider mProvider;
     private DeletionType mPhotoVideoDeletion;
+    private DownloadsDeletionType mDownloadsDeletion;
 
     @Override
     public void onCreate(Bundle savedInstanceState) {
@@ -80,11 +86,14 @@ public class DeletionHelperFragment extends SettingsPreferenceFragment implement
         addPreferencesFromResource(R.xml.deletion_helper_list);
         mApps = (PreferenceGroup) findPreference(KEY_APPS_GROUP);
         mPhotoPreference = (PhotosDeletionPreference) findPreference(KEY_PHOTOS_VIDEOS_PREFERENCE);
+        mDownloadsPreference =
+                (DownloadsDeletionPreference) findPreference(KEY_DOWNLOADS_PREFERENCE);
         mProvider =
                 FeatureFactory.getFactory(app).getDeletionHelperFeatureProvider();
         if (mProvider != null) {
             mPhotoVideoDeletion = mProvider.createPhotoVideoDeletionType();
         }
+        mDownloadsDeletion = new DownloadsDeletionType(getActivity());
 
         if (savedInstanceState != null) {
             mHasReceivedAppEntries =
@@ -117,6 +126,9 @@ public class DeletionHelperFragment extends SettingsPreferenceFragment implement
                 if (mPhotoPreference != null && mPhotoPreference.isChecked()) {
                     mPhotoVideoDeletion.clearFreeableData();
                 }
+                if (mDownloadsPreference != null && mDownloadsPreference.isChecked()) {
+                    mDownloadsDeletion.clearFreeableData();
+                }
 
                 ArraySet<String> apps = new ArraySet<>();
                 for (AppEntry entry : mAppEntries) {
@@ -153,6 +165,9 @@ public class DeletionHelperFragment extends SettingsPreferenceFragment implement
             mPhotoPreference.registerFreeableChangedListener(this);
             mPhotoPreference.registerDeletionService(mPhotoVideoDeletion);
         }
+
+        mDownloadsPreference.registerFreeableChangedListener(this);
+        mDownloadsPreference.registerDeletionService(mDownloadsDeletion);
     }
 
     @Override
@@ -172,6 +187,10 @@ public class DeletionHelperFragment extends SettingsPreferenceFragment implement
         if (mPhotoVideoDeletion != null) {
             mPhotoVideoDeletion.onResume();
         }
+        if (mDownloadsDeletion != null) {
+            mDownloadsDeletion.onResume();
+            getLoaderManager().initLoader(DOWNLOADS_LOADER_ID, new Bundle(), mDownloadsDeletion);
+        }
     }
 
 
@@ -193,6 +212,9 @@ public class DeletionHelperFragment extends SettingsPreferenceFragment implement
         if (mPhotoVideoDeletion != null) {
             mPhotoVideoDeletion.onPause();
         }
+        if (mDownloadsDeletion != null) {
+            mDownloadsDeletion.onPause();
+        }
     }
 
     private void rebuild() {
@@ -211,7 +233,8 @@ public class DeletionHelperFragment extends SettingsPreferenceFragment implement
         for (int i = 0; i < entryCount; i++) {
             AppEntry entry = apps.get(i);
             final String packageName = entry.label;
-            AppDeletionPreference preference = (AppDeletionPreference) getCachedPreference(entry.label);
+            AppDeletionPreference preference =
+                    (AppDeletionPreference) getCachedPreference(entry.label);
             if (preference == null) {
                 preference = new AppDeletionPreference(getActivity(), entry,
                         mState);
@@ -322,6 +345,9 @@ public class DeletionHelperFragment extends SettingsPreferenceFragment implement
         if (mPhotoPreference != null) {
             freeableSpace += mPhotoPreference.getFreeableBytes();
         }
+        if (mDownloadsPreference != null) {
+            freeableSpace += mDownloadsPreference.getFreeableBytes();
+        }
         return freeableSpace;
     }
 }

src/com/android/settings/deletionhelper/DownloadsDeletionPreference.java

@@ -0,0 +1,60 @@
+/*
+ * Copyright (C) 2016 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 com.android.settings.deletionhelper;
+
+import android.content.Context;
+import android.text.format.DateUtils;
+import android.util.AttributeSet;
+import android.text.format.Formatter;
+import com.android.settings.DeletionPreference;
+import com.android.settings.R;
+
+/**
+ * Preference to handle the deletion of photos and videos in the Deletion Helper.
+ */
+public class DownloadsDeletionPreference extends DeletionPreference {
+    public DownloadsDeletionPreference(Context context, AttributeSet attrs) {
+        super(context, attrs);
+        updatePreferenceText(0, 0, Long.MAX_VALUE);
+    }
+
+    @Override
+    public void onFreeableChanged(int numItems, long freeableBytes) {
+        super.onFreeableChanged(numItems, freeableBytes);
+        DownloadsDeletionType deletionService = (DownloadsDeletionType) getDeletionService();
+        updatePreferenceText(numItems, freeableBytes, deletionService.getMostRecentLastModified());
+    }
+
+    private void updatePreferenceText(int items, long bytes, long mostRecent) {
+        Context context = getContext();
+        setTitle(context.getString(R.string.deletion_helper_downloads_title,
+                items));
+        // If there are no files to clear, show the empty text instead.
+        if (mostRecent < Long.MAX_VALUE) {
+            setSummary(context.getString(R.string.deletion_helper_downloads_summary,
+                    Formatter.formatFileSize(context, bytes),
+                    DateUtils.getRelativeTimeSpanString(mostRecent,
+                            System.currentTimeMillis(),
+                            DateUtils.DAY_IN_MILLIS,
+                            DateUtils.FORMAT_ABBREV_RELATIVE)));
+        } else {
+            setSummary(context.getString(R.string.deletion_helper_downloads_summary_empty,
+                    Formatter.formatFileSize(context, bytes)));
+        }
+    }
+
+}

src/com/android/settings/deletionhelper/DownloadsDeletionType.java

@@ -0,0 +1,109 @@
+/*
+ * Copyright (C) 2016 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 com.android.settings.deletionhelper;
+
+import android.app.LoaderManager.LoaderCallbacks;
+import android.content.Context;
+import android.content.Loader;
+import android.os.AsyncTask;
+import android.os.Bundle;
+import android.os.Environment;
+import com.android.settings.deletionhelper.FetchDownloadsLoader.DownloadsResult;
+
+import java.io.File;
+import java.util.ArrayList;
+
+/**
+ * The DownloadsDeletionType provides stale download file information to the
+ * {@link DownloadsDeletionPreference}.
+ */
+public class DownloadsDeletionType implements DeletionType, LoaderCallbacks<DownloadsResult> {
+    private int mItems;
+    private long mBytes;
+    private long mMostRecent;
+    private FreeableChangedListener mListener;
+    private FetchDownloadsLoader mTask;
+    private ArrayList<File> mFiles;
+    private Context mContext;
+
+    public DownloadsDeletionType(Context context) {
+        mContext = context;
+    }
+
+    @Override
+    public void registerFreeableChangedListener(FreeableChangedListener listener) {
+        mListener = listener;
+        if (mFiles != null) {
+            maybeUpdateListener();
+        }
+    }
+
+    @Override
+    public void onResume() {
+    }
+
+    @Override
+    public void onPause() {
+    }
+
+    @Override
+    public void clearFreeableData() {
+        if (mFiles != null) {
+            AsyncTask.execute(new Runnable() {
+                @Override
+                public void run() {
+                    for (File file : mFiles) {
+                        file.delete();
+                    }
+                }
+            });
+        }
+    }
+
+    @Override
+    public Loader<DownloadsResult> onCreateLoader(int id, Bundle args) {
+        return new FetchDownloadsLoader(mContext,
+                Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS));
+    }
+
+    @Override
+    public void onLoadFinished(Loader<DownloadsResult> loader, DownloadsResult data) {
+        mMostRecent = data.youngestLastModified;
+        mFiles = data.files;
+        mBytes = data.totalSize;
+        mItems = mFiles.size();
+        maybeUpdateListener();
+    }
+
+    @Override
+    public void onLoaderReset(Loader<DownloadsResult> loader) {
+    }
+
+    /**
+     * Returns the most recent last modified time for any clearable file.
+     * @return The last modified time.
+     */
+    public long getMostRecentLastModified() {
+        return mMostRecent;
+    }
+
+    private void maybeUpdateListener() {
+        if (mListener != null) {
+            mListener.onFreeableChanged(mItems, mBytes);
+        }
+    }
+}

src/com/android/settings/deletionhelper/FetchDownloadsLoader.java

@@ -0,0 +1,96 @@
+/*
+ * Copyright (C) 2016 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 com.android.settings.deletionhelper;
+
+import android.content.Context;
+import android.support.annotation.VisibleForTesting;
+import com.android.settings.utils.AsyncLoader;
+
+import java.io.File;
+import java.util.ArrayList;
+
+/**
+ * FetchDownloadsLoader is an asynchronous task which returns files in the Downloads
+ * directory which have not been modified in longer than 90 days.
+ */
+public class FetchDownloadsLoader extends
+        AsyncLoader<FetchDownloadsLoader.DownloadsResult> {
+    private File mDirectory;
+
+    /**
+     * Sets up a FetchDownloadsLoader in any directory.
+     * @param directory The directory to look into.
+     */
+    public FetchDownloadsLoader(Context context, File directory) {
+        super(context);
+        mDirectory = directory;
+    }
+
+    @Override
+    protected void onDiscardResult(DownloadsResult result) {}
+
+    @Override
+    public DownloadsResult loadInBackground() {
+        return collectFiles(mDirectory);
+    }
+
+    @VisibleForTesting
+    static DownloadsResult collectFiles(File dir) {
+        return collectFiles(dir, new DownloadsResult());
+    }
+
+    private static DownloadsResult collectFiles(File dir, DownloadsResult result) {
+        File downloadFiles[] = dir.listFiles();
+        if (downloadFiles == null) {
+        }
+        if (downloadFiles != null && downloadFiles.length > 0) {
+            for (File currentFile : downloadFiles) {
+                if (currentFile.isDirectory()) {
+                    collectFiles(currentFile, result);
+                } else {
+                    if (currentFile.lastModified() < result.youngestLastModified) {
+                        result.youngestLastModified = currentFile.lastModified();
+                    }
+                    result.files.add(currentFile);
+                    result.totalSize += currentFile.length();
+                }
+            }
+        }
+
+        return result;
+    }
+
+    /**
+     * The DownloadsResult is the result of a {@link FetchDownloadsLoader} with the files
+     * and the amount of space they use.
+     */
+    public static class DownloadsResult {
+        public long totalSize;
+        public long youngestLastModified;
+        public ArrayList<File> files;
+
+        public DownloadsResult() {
+            this(0, Long.MAX_VALUE, new ArrayList<File>());
+        }
+
+        public DownloadsResult(long totalSize, long youngestLastModified, ArrayList<File> files) {
+            this.totalSize = totalSize;
+            this.youngestLastModified = youngestLastModified;
+            this.files = files;
+        }
+    }
+}

src/com/android/settings/utils/AsyncLoader.java

@@ -0,0 +1,109 @@
+/*
+ * Copyright (C) 2016 Google Inc.
+ * Licensed to 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 com.android.settings.utils;
+
+import android.content.AsyncTaskLoader;
+import android.content.Context;
+
+/**
+ * This class fills in some boilerplate for AsyncTaskLoader to actually load things.
+ *
+ * Subclasses need to implement {@link AsyncLoader#loadInBackground()} to perform the actual
+ * background task, and {@link AsyncLoader#onDiscardResult(T)} to clean up previously loaded
+ * results.
+ *
+ * This loader is based on the MailAsyncTaskLoader from the AOSP EmailUnified repo.
+ */
+public abstract class AsyncLoader<T> extends AsyncTaskLoader<T> {
+    private T mResult;
+
+    public AsyncLoader(final Context context) {
+        super(context);
+    }
+
+    @Override
+    protected void onStartLoading() {
+        if (mResult != null) {
+            deliverResult(mResult);
+        }
+
+        if (takeContentChanged() || mResult == null) {
+            forceLoad();
+        }
+    }
+
+    @Override
+    protected void onStopLoading() {
+        cancelLoad();
+    }
+
+    @Override
+    public void deliverResult(final T data) {
+        if (isReset()) {
+            if (data != null) {
+                onDiscardResult(data);
+            }
+            return;
+        }
+
+        final T oldResult = mResult;
+        mResult = data;
+
+        if (isStarted()) {
+            super.deliverResult(data);
+        }
+
+        if (oldResult != null && oldResult != mResult) {
+            onDiscardResult(oldResult);
+        }
+    }
+
+    @Override
+    protected void onReset() {
+        super.onReset();
+
+        onStopLoading();
+
+        if (mResult != null) {
+            onDiscardResult(mResult);
+        }
+        mResult = null;
+    }
+
+    @Override
+    public void onCanceled(final T data) {
+        super.onCanceled(data);
+
+        if (data != null) {
+            onDiscardResult(data);
+        }
+    }
+
+    /**
+     * Called when discarding the load results so subclasses can take care of clean-up or
+     * recycling tasks. This is not called if the same result (by way of pointer equality) is
+     * returned again by a subsequent call to loadInBackground, or if result is null.
+     *
+     * Note that this may be called concurrently with loadInBackground(), and in some circumstances
+     * may be called more than once for a given object.
+     *
+     * @param result The value returned from {@link AsyncLoader#loadInBackground()} which
+     *               is to be discarded.
+     */
+    protected abstract void onDiscardResult(final T result);
+}

tests/unit/src/com/android/settings/deletionhelper/FetchDownloadsLoaderTest.java

@@ -0,0 +1,90 @@
+/*
+ * Copyright (C) 2016 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 com.android.settings.deletionhelper;
+
+import com.android.settings.deletionhelper.FetchDownloadsLoader.DownloadsResult;
+
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.rules.TemporaryFolder;
+import org.junit.runners.JUnit4;
+
+import java.io.File;
+import java.io.FileWriter;
+
+import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertEquals;
+
+@RunWith(JUnit4.class)
+public class FetchDownloadsLoaderTest {
+    @Rule
+    public TemporaryFolder temporaryFolder = new TemporaryFolder();
+
+    @Test
+    public void testEmptyDirectory() throws Exception {
+        DownloadsResult result =
+                FetchDownloadsLoader.collectFiles(temporaryFolder.getRoot());
+        assertNotNull(result);
+        assertEquals(0, result.totalSize);
+        assertEquals(0, result.files.size());
+    }
+
+    @Test
+    public void testFilesInDirectory() throws Exception {
+        temporaryFolder.newFile();
+        temporaryFolder.newFile();
+
+        DownloadsResult result =
+                FetchDownloadsLoader.collectFiles(temporaryFolder.getRoot());
+        assertNotNull(result);
+        assertEquals(0, result.totalSize);
+        assertEquals(2, result.files.size());
+    }
+
+    @Test
+    public void testNestedDirectories() throws Exception {
+        File tempDir = temporaryFolder.newFolder();
+
+        File testFile = File.createTempFile("test", null, tempDir);
+        testFile.deleteOnExit();
+        DownloadsResult result =
+                FetchDownloadsLoader.collectFiles(temporaryFolder.getRoot());
+        assertNotNull(result);
+        assertEquals(0, result.totalSize);
+        assertEquals(1, result.files.size());
+    }
+
+    @Test
+    public void testSumFileSizes() throws Exception {
+        File first = temporaryFolder.newFile();
+        FileWriter fileWriter = new FileWriter(first);
+        fileWriter.write("test");
+        fileWriter.close();
+
+        File second = temporaryFolder.newFile();
+        fileWriter = new FileWriter(second);
+        fileWriter.write("test2");
+        fileWriter.close();
+
+        DownloadsResult result =
+                FetchDownloadsLoader.collectFiles(temporaryFolder.getRoot());
+        assertNotNull(result);
+        assertEquals(9, result.totalSize);
+        assertEquals(2, result.files.size());
+    }
+}