Slice background worker with Wi-Fi Slice

Test: manual

Change-Id: Ic4fdc5713f511ff80f03728c99c68fda3d0cab02

src/com/android/settings/slices/CustomSliceable.java

@@ -89,6 +89,16 @@ public interface CustomSliceable {
         return null;
     }
 
+    /**
+     * Settings Slices which can represent component lists that are updatable by the
+     * {@link SliceBackgroundWorker} returned here.
+     *
+     * @return a {@link SliceBackgroundWorker} for fetching the list of results in the background.
+     */
+    default SliceBackgroundWorker getBackgroundWorker() {
+        return null;
+    }
+
     /**
      * Standardize the intents returned to indicate actions by the Slice.
      * <p>

src/com/android/settings/slices/SettingsSliceProvider.java

@@ -28,6 +28,7 @@ import android.os.StrictMode;
 import android.provider.Settings;
 import android.provider.SettingsSlicesContract;
 import android.text.TextUtils;
+import android.util.ArrayMap;
 import android.util.ArraySet;
 import android.util.KeyValueListParser;
 import android.util.Log;
@@ -131,6 +132,8 @@ public class SettingsSliceProvider extends SliceProvider {
 
     final Set<Uri> mRegisteredUris = new ArraySet<>();
 
+    final Map<Uri, SliceBackgroundWorker> mWorkerMap = new ArrayMap<>();
+
     public SettingsSliceProvider() {
         super(READ_SEARCH_INDEXABLES);
     }
@@ -165,6 +168,7 @@ public class SettingsSliceProvider extends SliceProvider {
             if (filter != null) {
                 registerIntentToUri(filter, sliceUri);
             }
+            startBackgroundWorker(sliceable);
             return;
         }
 
@@ -191,6 +195,7 @@ public class SettingsSliceProvider extends SliceProvider {
             SliceBroadcastRelay.unregisterReceivers(getContext(), sliceUri);
             mRegisteredUris.remove(sliceUri);
         }
+        stopBackgroundWorker(sliceUri);
         mSliceDataCache.remove(sliceUri);
     }
 
@@ -348,6 +353,31 @@ public class SettingsSliceProvider extends SliceProvider {
         }
     }
 
+    private void startBackgroundWorker(CustomSliceable sliceable) {
+        final SliceBackgroundWorker worker = sliceable.getBackgroundWorker();
+        if (worker == null) {
+            return;
+        }
+
+        final Uri uri = sliceable.getUri();
+        Log.d(TAG, "Starting background worker for: " + uri);
+        if (mWorkerMap.containsKey(uri)) {
+            return;
+        }
+
+        mWorkerMap.put(uri, worker);
+        worker.onSlicePinned();
+    }
+
+    private void stopBackgroundWorker(Uri uri) {
+        final SliceBackgroundWorker worker = mWorkerMap.get(uri);
+        if (worker != null) {
+            Log.d(TAG, "Stopping background worker for: " + uri);
+            worker.onSliceUnpinned();
+            mWorkerMap.remove(uri);
+        }
+    }
+
     private List<Uri> buildUrisFromKeys(List<String> keys, String authority) {
         final List<Uri> descendants = new ArrayList<>();
 

src/com/android/settings/slices/SliceBackgroundWorker.java

@@ -0,0 +1,85 @@
+/*
+ * Copyright (C) 2018 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.slices;
+
+import android.content.ContentResolver;
+import android.net.Uri;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * The Slice background worker is used to make Settings Slices be able to work with data that is
+ * changing continuously, e.g. available Wi-Fi networks.
+ *
+ * The background worker will be started at {@link SettingsSliceProvider#onSlicePinned(Uri)}, and be
+ * stopped at {@link SettingsSliceProvider#onSliceUnpinned(Uri)}.
+ *
+ * {@link SliceBackgroundWorker} caches the results, uses the cache to compare if there is any data
+ * changed, and then notifies the Slice {@link Uri} to update.
+ */
+public abstract class SliceBackgroundWorker<E> {
+
+    private final ContentResolver mContentResolver;
+    private final Uri mUri;
+
+    private List<E> mCachedResults;
+
+    protected SliceBackgroundWorker(ContentResolver cr, Uri uri) {
+        mContentResolver = cr;
+        mUri = uri;
+    }
+
+    /**
+     * Called when the Slice is pinned. This is the place to register callbacks or initialize scan
+     * tasks.
+     */
+    protected abstract void onSlicePinned();
+
+    /**
+     * Called when the Slice is unpinned. This is the place to unregister callbacks or perform any
+     * final cleanup.
+     */
+    protected abstract void onSliceUnpinned();
+
+    /**
+     * @return a {@link List} of cached results
+     */
+    public final List<E> getResults() {
+        return mCachedResults == null ? null : new ArrayList<>(mCachedResults);
+    }
+
+    /**
+     * Update the results when data changes
+     */
+    protected final void updateResults(List<E> results) {
+        boolean needNotify = false;
+
+        if (results == null) {
+            if (mCachedResults != null) {
+                needNotify = true;
+            }
+        } else {
+            needNotify = !results.equals(mCachedResults);
+        }
+
+        if (needNotify) {
+            mCachedResults = results;
+            mContentResolver.notifyChange(mUri, null);
+        }
+    }
+}